Send failure event if we fail to handle a HTLC

[rust-lightning] / lightning / src / chain / channelmonitor.rs

// This file is Copyright its original authors, visible in version control
// history.
//
// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
// You may not use this file except in accordance with one or both of these
// licenses.

//! The logic to monitor for on-chain transactions and create the relevant claim responses lives
//! here.
//!
//! ChannelMonitor objects are generated by ChannelManager in response to relevant
//! messages/actions, and MUST be persisted to disk (and, preferably, remotely) before progress can
//! be made in responding to certain messages, see [`chain::Watch`] for more.
//!
//! Note that ChannelMonitors are an important part of the lightning trust model and a copy of the
//! latest ChannelMonitor must always be actively monitoring for chain updates (and no out-of-date
//! ChannelMonitors should do so). Thus, if you're building rust-lightning into an HSM or other
//! security-domain-separated system design, you should consider having multiple paths for
//! ChannelMonitors to get out of the HSM and onto monitoring devices.

use bitcoin::blockdata::block::BlockHeader;
use bitcoin::blockdata::transaction::{TxOut,Transaction};
use bitcoin::blockdata::script::{Script, Builder};
use bitcoin::blockdata::opcodes;

use bitcoin::hashes::Hash;
use bitcoin::hashes::sha256::Hash as Sha256;
use bitcoin::hash_types::{Txid, BlockHash, WPubkeyHash};

use bitcoin::secp256k1::{Secp256k1, ecdsa::Signature};
use bitcoin::secp256k1::{SecretKey, PublicKey};
use bitcoin::secp256k1;

use ln::{PaymentHash, PaymentPreimage};
use ln::msgs::DecodeError;
use ln::chan_utils;
use ln::chan_utils::{CounterpartyCommitmentSecrets, HTLCOutputInCommitment, HTLCType, ChannelTransactionParameters, HolderCommitmentTransaction};
use ln::channelmanager::HTLCSource;
use chain;
use chain::{BestBlock, WatchedOutput};
use chain::chaininterface::{BroadcasterInterface, FeeEstimator, LowerBoundedFeeEstimator};
use chain::transaction::{OutPoint, TransactionData};
use chain::keysinterface::{SpendableOutputDescriptor, StaticPaymentOutputDescriptor, DelayedPaymentOutputDescriptor, Sign, KeysInterface};
use chain::onchaintx::OnchainTxHandler;
use chain::package::{CounterpartyOfferedHTLCOutput, CounterpartyReceivedHTLCOutput, HolderFundingOutput, HolderHTLCOutput, PackageSolvingData, PackageTemplate, RevokedOutput, RevokedHTLCOutput};
use chain::Filter;
use util::logger::Logger;
use util::ser::{Readable, ReadableArgs, MaybeReadable, Writer, Writeable, U48, OptionDeserWrapper};
use util::byte_utils;
use util::events::Event;

use prelude::*;
use core::{cmp, mem};
use io::{self, Error};
use core::ops::Deref;
use sync::Mutex;

/// An update generated by the underlying Channel itself which contains some new information the
/// ChannelMonitor should be made aware of.
#[cfg_attr(any(test, fuzzing, feature = "_test_utils"), derive(PartialEq))]
#[derive(Clone)]
#[must_use]
pub struct ChannelMonitorUpdate {
        pub(crate) updates: Vec<ChannelMonitorUpdateStep>,
        /// The sequence number of this update. Updates *must* be replayed in-order according to this
        /// sequence number (and updates may panic if they are not). The update_id values are strictly
        /// increasing and increase by one for each new update, with one exception specified below.
        ///
        /// This sequence number is also used to track up to which points updates which returned
        /// ChannelMonitorUpdateErr::TemporaryFailure have been applied to all copies of a given
        /// ChannelMonitor when ChannelManager::channel_monitor_updated is called.
        ///
        /// The only instance where update_id values are not strictly increasing is the case where we
        /// allow post-force-close updates with a special update ID of [`CLOSED_CHANNEL_UPDATE_ID`]. See
        /// its docs for more details.
        pub update_id: u64,
}

/// If:
///    (1) a channel has been force closed and
///    (2) we receive a preimage from a forward link that allows us to spend an HTLC output on
///        this channel's (the backward link's) broadcasted commitment transaction
/// then we allow the `ChannelManager` to send a `ChannelMonitorUpdate` with this update ID,
/// with the update providing said payment preimage. No other update types are allowed after
/// force-close.
pub const CLOSED_CHANNEL_UPDATE_ID: u64 = core::u64::MAX;

impl Writeable for ChannelMonitorUpdate {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
                write_ver_prefix!(w, SERIALIZATION_VERSION, MIN_SERIALIZATION_VERSION);
                self.update_id.write(w)?;
                (self.updates.len() as u64).write(w)?;
                for update_step in self.updates.iter() {
                        update_step.write(w)?;
                }
                write_tlv_fields!(w, {});
                Ok(())
        }
}
impl Readable for ChannelMonitorUpdate {
        fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
                let _ver = read_ver_prefix!(r, SERIALIZATION_VERSION);
                let update_id: u64 = Readable::read(r)?;
                let len: u64 = Readable::read(r)?;
                let mut updates = Vec::with_capacity(cmp::min(len as usize, MAX_ALLOC_SIZE / ::core::mem::size_of::<ChannelMonitorUpdateStep>()));
                for _ in 0..len {
                        if let Some(upd) = MaybeReadable::read(r)? {
                                updates.push(upd);
                        }
                }
                read_tlv_fields!(r, {});
                Ok(Self { update_id, updates })
        }
}

/// An event to be processed by the ChannelManager.
#[derive(Clone, PartialEq)]
pub enum MonitorEvent {
        /// A monitor event containing an HTLCUpdate.
        HTLCEvent(HTLCUpdate),

        /// A monitor event that the Channel's commitment transaction was confirmed.
        CommitmentTxConfirmed(OutPoint),

        /// Indicates a [`ChannelMonitor`] update has completed. See
        /// [`ChannelMonitorUpdateErr::TemporaryFailure`] for more information on how this is used.
        ///
        /// [`ChannelMonitorUpdateErr::TemporaryFailure`]: super::ChannelMonitorUpdateErr::TemporaryFailure
        UpdateCompleted {
                /// The funding outpoint of the [`ChannelMonitor`] that was updated
                funding_txo: OutPoint,
                /// The Update ID from [`ChannelMonitorUpdate::update_id`] which was applied or
                /// [`ChannelMonitor::get_latest_update_id`].
                ///
                /// Note that this should only be set to a given update's ID if all previous updates for the
                /// same [`ChannelMonitor`] have been applied and persisted.
                monitor_update_id: u64,
        },

        /// Indicates a [`ChannelMonitor`] update has failed. See
        /// [`ChannelMonitorUpdateErr::PermanentFailure`] for more information on how this is used.
        ///
        /// [`ChannelMonitorUpdateErr::PermanentFailure`]: super::ChannelMonitorUpdateErr::PermanentFailure
        UpdateFailed(OutPoint),
}
impl_writeable_tlv_based_enum_upgradable!(MonitorEvent,
        // Note that UpdateCompleted and UpdateFailed are currently never serialized to disk as they are
        // generated only in ChainMonitor
        (0, UpdateCompleted) => {
                (0, funding_txo, required),
                (2, monitor_update_id, required),
        },
;
        (2, HTLCEvent),
        (4, CommitmentTxConfirmed),
        (6, UpdateFailed),
);

/// Simple structure sent back by `chain::Watch` when an HTLC from a forward channel is detected on
/// chain. Used to update the corresponding HTLC in the backward channel. Failing to pass the
/// preimage claim backward will lead to loss of funds.
#[derive(Clone, PartialEq)]
pub struct HTLCUpdate {
        pub(crate) payment_hash: PaymentHash,
        pub(crate) payment_preimage: Option<PaymentPreimage>,
        pub(crate) source: HTLCSource,
        pub(crate) htlc_value_satoshis: Option<u64>,
}
impl_writeable_tlv_based!(HTLCUpdate, {
        (0, payment_hash, required),
        (1, htlc_value_satoshis, option),
        (2, source, required),
        (4, payment_preimage, option),
});

/// If an HTLC expires within this many blocks, don't try to claim it in a shared transaction,
/// instead claiming it in its own individual transaction.
pub(crate) const CLTV_SHARED_CLAIM_BUFFER: u32 = 12;
/// If an HTLC expires within this many blocks, force-close the channel to broadcast the
/// HTLC-Success transaction.
/// In other words, this is an upper bound on how many blocks we think it can take us to get a
/// transaction confirmed (and we use it in a few more, equivalent, places).
pub(crate) const CLTV_CLAIM_BUFFER: u32 = 18;
/// Number of blocks by which point we expect our counterparty to have seen new blocks on the
/// network and done a full update_fail_htlc/commitment_signed dance (+ we've updated all our
/// copies of ChannelMonitors, including watchtowers). We could enforce the contract by failing
/// at CLTV expiration height but giving a grace period to our peer may be profitable for us if he
/// can provide an over-late preimage. Nevertheless, grace period has to be accounted in our
/// CLTV_EXPIRY_DELTA to be secure. Following this policy we may decrease the rate of channel failures
/// due to expiration but increase the cost of funds being locked longuer in case of failure.
/// This delay also cover a low-power peer being slow to process blocks and so being behind us on
/// accurate block height.
/// In case of onchain failure to be pass backward we may see the last block of ANTI_REORG_DELAY
/// with at worst this delay, so we are not only using this value as a mercy for them but also
/// us as a safeguard to delay with enough time.
pub(crate) const LATENCY_GRACE_PERIOD_BLOCKS: u32 = 3;
/// Number of blocks we wait on seeing a HTLC output being solved before we fail corresponding
/// inbound HTLCs. This prevents us from failing backwards and then getting a reorg resulting in us
/// losing money.
///
/// Note that this is a library-wide security assumption. If a reorg deeper than this number of
/// blocks occurs, counterparties may be able to steal funds or claims made by and balances exposed
/// by a  [`ChannelMonitor`] may be incorrect.
// We also use this delay to be sure we can remove our in-flight claim txn from bump candidates buffer.
// It may cause spurious generation of bumped claim txn but that's alright given the outpoint is already
// solved by a previous claim tx. What we want to avoid is reorg evicting our claim tx and us not
// keep bumping another claim tx to solve the outpoint.
pub const ANTI_REORG_DELAY: u32 = 6;
/// Number of blocks before confirmation at which we fail back an un-relayed HTLC or at which we
/// refuse to accept a new HTLC.
///
/// This is used for a few separate purposes:
/// 1) if we've received an MPP HTLC to us and it expires within this many blocks and we are
///    waiting on additional parts (or waiting on the preimage for any HTLC from the user), we will
///    fail this HTLC,
/// 2) if we receive an HTLC within this many blocks of its expiry (plus one to avoid a race
///    condition with the above), we will fail this HTLC without telling the user we received it,
///
/// (1) is all about protecting us - we need enough time to update the channel state before we hit
/// CLTV_CLAIM_BUFFER, at which point we'd go on chain to claim the HTLC with the preimage.
///
/// (2) is the same, but with an additional buffer to avoid accepting an HTLC which is immediately
/// in a race condition between the user connecting a block (which would fail it) and the user
/// providing us the preimage (which would claim it).
pub(crate) const HTLC_FAIL_BACK_BUFFER: u32 = CLTV_CLAIM_BUFFER + LATENCY_GRACE_PERIOD_BLOCKS;

// TODO(devrandom) replace this with HolderCommitmentTransaction
#[derive(Clone, PartialEq)]
struct HolderSignedTx {
        /// txid of the transaction in tx, just used to make comparison faster
        txid: Txid,
        revocation_key: PublicKey,
        a_htlc_key: PublicKey,
        b_htlc_key: PublicKey,
        delayed_payment_key: PublicKey,
        per_commitment_point: PublicKey,
        htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Signature>, Option<HTLCSource>)>,
        to_self_value_sat: u64,
        feerate_per_kw: u32,
}
impl_writeable_tlv_based!(HolderSignedTx, {
        (0, txid, required),
        // Note that this is filled in with data from OnchainTxHandler if it's missing.
        // For HolderSignedTx objects serialized with 0.0.100+, this should be filled in.
        (1, to_self_value_sat, (default_value, u64::max_value())),
        (2, revocation_key, required),
        (4, a_htlc_key, required),
        (6, b_htlc_key, required),
        (8, delayed_payment_key, required),
        (10, per_commitment_point, required),
        (12, feerate_per_kw, required),
        (14, htlc_outputs, vec_type)
});

/// We use this to track static counterparty commitment transaction data and to generate any
/// justice or 2nd-stage preimage/timeout transactions.
#[derive(PartialEq)]
struct CounterpartyCommitmentParameters {
        counterparty_delayed_payment_base_key: PublicKey,
        counterparty_htlc_base_key: PublicKey,
        on_counterparty_tx_csv: u16,
}

impl Writeable for CounterpartyCommitmentParameters {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
                w.write_all(&byte_utils::be64_to_array(0))?;
                write_tlv_fields!(w, {
                        (0, self.counterparty_delayed_payment_base_key, required),
                        (2, self.counterparty_htlc_base_key, required),
                        (4, self.on_counterparty_tx_csv, required),
                });
                Ok(())
        }
}
impl Readable for CounterpartyCommitmentParameters {
        fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
                let counterparty_commitment_transaction = {
                        // Versions prior to 0.0.100 had some per-HTLC state stored here, which is no longer
                        // used. Read it for compatibility.
                        let per_htlc_len: u64 = Readable::read(r)?;
                        for _  in 0..per_htlc_len {
                                let _txid: Txid = Readable::read(r)?;
                                let htlcs_count: u64 = Readable::read(r)?;
                                for _ in 0..htlcs_count {
                                        let _htlc: HTLCOutputInCommitment = Readable::read(r)?;
                                }
                        }

                        let mut counterparty_delayed_payment_base_key = OptionDeserWrapper(None);
                        let mut counterparty_htlc_base_key = OptionDeserWrapper(None);
                        let mut on_counterparty_tx_csv: u16 = 0;
                        read_tlv_fields!(r, {
                                (0, counterparty_delayed_payment_base_key, required),
                                (2, counterparty_htlc_base_key, required),
                                (4, on_counterparty_tx_csv, required),
                        });
                        CounterpartyCommitmentParameters {
                                counterparty_delayed_payment_base_key: counterparty_delayed_payment_base_key.0.unwrap(),
                                counterparty_htlc_base_key: counterparty_htlc_base_key.0.unwrap(),
                                on_counterparty_tx_csv,
                        }
                };
                Ok(counterparty_commitment_transaction)
        }
}

/// An entry for an [`OnchainEvent`], stating the block height when the event was observed and the
/// transaction causing it.
///
/// Used to determine when the on-chain event can be considered safe from a chain reorganization.
#[derive(PartialEq)]
struct OnchainEventEntry {
        txid: Txid,
        height: u32,
        event: OnchainEvent,
}

impl OnchainEventEntry {
        fn confirmation_threshold(&self) -> u32 {
                let mut conf_threshold = self.height + ANTI_REORG_DELAY - 1;
                match self.event {
                        OnchainEvent::MaturingOutput {
                                descriptor: SpendableOutputDescriptor::DelayedPaymentOutput(ref descriptor)
                        } => {
                                // A CSV'd transaction is confirmable in block (input height) + CSV delay, which means
                                // it's broadcastable when we see the previous block.
                                conf_threshold = cmp::max(conf_threshold, self.height + descriptor.to_self_delay as u32 - 1);
                        },
                        OnchainEvent::FundingSpendConfirmation { on_local_output_csv: Some(csv), .. } |
                        OnchainEvent::HTLCSpendConfirmation { on_to_local_output_csv: Some(csv), .. } => {
                                // A CSV'd transaction is confirmable in block (input height) + CSV delay, which means
                                // it's broadcastable when we see the previous block.
                                conf_threshold = cmp::max(conf_threshold, self.height + csv as u32 - 1);
                        },
                        _ => {},
                }
                conf_threshold
        }

        fn has_reached_confirmation_threshold(&self, best_block: &BestBlock) -> bool {
                best_block.height() >= self.confirmation_threshold()
        }
}

/// Upon discovering of some classes of onchain tx by ChannelMonitor, we may have to take actions on it
/// once they mature to enough confirmations (ANTI_REORG_DELAY)
#[derive(PartialEq)]
enum OnchainEvent {
        /// An outbound HTLC failing after a transaction is confirmed. Used
        ///  * when an outbound HTLC output is spent by us after the HTLC timed out
        ///  * an outbound HTLC which was not present in the commitment transaction which appeared
        ///    on-chain (either because it was not fully committed to or it was dust).
        /// Note that this is *not* used for preimage claims, as those are passed upstream immediately,
        /// appearing only as an `HTLCSpendConfirmation`, below.
        HTLCUpdate {
                source: HTLCSource,
                payment_hash: PaymentHash,
                htlc_value_satoshis: Option<u64>,
                /// None in the second case, above, ie when there is no relevant output in the commitment
                /// transaction which appeared on chain.
                commitment_tx_output_idx: Option<u32>,
        },
        MaturingOutput {
                descriptor: SpendableOutputDescriptor,
        },
        /// A spend of the funding output, either a commitment transaction or a cooperative closing
        /// transaction.
        FundingSpendConfirmation {
                /// The CSV delay for the output of the funding spend transaction (implying it is a local
                /// commitment transaction, and this is the delay on the to_self output).
                on_local_output_csv: Option<u16>,
        },
        /// A spend of a commitment transaction HTLC output, set in the cases where *no* `HTLCUpdate`
        /// is constructed. This is used when
        ///  * an outbound HTLC is claimed by our counterparty with a preimage, causing us to
        ///    immediately claim the HTLC on the inbound edge and track the resolution here,
        ///  * an inbound HTLC is claimed by our counterparty (with a timeout),
        ///  * an inbound HTLC is claimed by us (with a preimage).
        ///  * a revoked-state HTLC transaction was broadcasted, which was claimed by the revocation
        ///    signature.
        HTLCSpendConfirmation {
                commitment_tx_output_idx: u32,
                /// If the claim was made by either party with a preimage, this is filled in
                preimage: Option<PaymentPreimage>,
                /// If the claim was made by us on an inbound HTLC against a local commitment transaction,
                /// we set this to the output CSV value which we will have to wait until to spend the
                /// output (and generate a SpendableOutput event).
                on_to_local_output_csv: Option<u16>,
        },
}

impl Writeable for OnchainEventEntry {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
                write_tlv_fields!(writer, {
                        (0, self.txid, required),
                        (2, self.height, required),
                        (4, self.event, required),
                });
                Ok(())
        }
}

impl MaybeReadable for OnchainEventEntry {
        fn read<R: io::Read>(reader: &mut R) -> Result<Option<Self>, DecodeError> {
                let mut txid = Default::default();
                let mut height = 0;
                let mut event = None;
                read_tlv_fields!(reader, {
                        (0, txid, required),
                        (2, height, required),
                        (4, event, ignorable),
                });
                if let Some(ev) = event {
                        Ok(Some(Self { txid, height, event: ev }))
                } else {
                        Ok(None)
                }
        }
}

impl_writeable_tlv_based_enum_upgradable!(OnchainEvent,
        (0, HTLCUpdate) => {
                (0, source, required),
                (1, htlc_value_satoshis, option),
                (2, payment_hash, required),
                (3, commitment_tx_output_idx, option),
        },
        (1, MaturingOutput) => {
                (0, descriptor, required),
        },
        (3, FundingSpendConfirmation) => {
                (0, on_local_output_csv, option),
        },
        (5, HTLCSpendConfirmation) => {
                (0, commitment_tx_output_idx, required),
                (2, preimage, option),
                (4, on_to_local_output_csv, option),
        },

);

#[cfg_attr(any(test, fuzzing, feature = "_test_utils"), derive(PartialEq))]
#[derive(Clone)]
pub(crate) enum ChannelMonitorUpdateStep {
        LatestHolderCommitmentTXInfo {
                commitment_tx: HolderCommitmentTransaction,
                htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Signature>, Option<HTLCSource>)>,
        },
        LatestCounterpartyCommitmentTXInfo {
                commitment_txid: Txid,
                htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>,
                commitment_number: u64,
                their_per_commitment_point: PublicKey,
        },
        PaymentPreimage {
                payment_preimage: PaymentPreimage,
        },
        CommitmentSecret {
                idx: u64,
                secret: [u8; 32],
        },
        /// Used to indicate that the no future updates will occur, and likely that the latest holder
        /// commitment transaction(s) should be broadcast, as the channel has been force-closed.
        ChannelForceClosed {
                /// If set to false, we shouldn't broadcast the latest holder commitment transaction as we
                /// think we've fallen behind!
                should_broadcast: bool,
        },
        ShutdownScript {
                scriptpubkey: Script,
        },
}

impl ChannelMonitorUpdateStep {
        fn variant_name(&self) -> &'static str {
                match self {
                        ChannelMonitorUpdateStep::LatestHolderCommitmentTXInfo { .. } => "LatestHolderCommitmentTXInfo",
                        ChannelMonitorUpdateStep::LatestCounterpartyCommitmentTXInfo { .. } => "LatestCounterpartyCommitmentTXInfo",
                        ChannelMonitorUpdateStep::PaymentPreimage { .. } => "PaymentPreimage",
                        ChannelMonitorUpdateStep::CommitmentSecret { .. } => "CommitmentSecret",
                        ChannelMonitorUpdateStep::ChannelForceClosed { .. } => "ChannelForceClosed",
                        ChannelMonitorUpdateStep::ShutdownScript { .. } => "ShutdownScript",
                }
        }
}

impl_writeable_tlv_based_enum_upgradable!(ChannelMonitorUpdateStep,
        (0, LatestHolderCommitmentTXInfo) => {
                (0, commitment_tx, required),
                (2, htlc_outputs, vec_type),
        },
        (1, LatestCounterpartyCommitmentTXInfo) => {
                (0, commitment_txid, required),
                (2, commitment_number, required),
                (4, their_per_commitment_point, required),
                (6, htlc_outputs, vec_type),
        },
        (2, PaymentPreimage) => {
                (0, payment_preimage, required),
        },
        (3, CommitmentSecret) => {
                (0, idx, required),
                (2, secret, required),
        },
        (4, ChannelForceClosed) => {
                (0, should_broadcast, required),
        },
        (5, ShutdownScript) => {
                (0, scriptpubkey, required),
        },
);

/// Details about the balance(s) available for spending once the channel appears on chain.
///
/// See [`ChannelMonitor::get_claimable_balances`] for more details on when these will or will not
/// be provided.
#[derive(Clone, Debug, PartialEq, Eq)]
#[cfg_attr(test, derive(PartialOrd, Ord))]
pub enum Balance {
        /// The channel is not yet closed (or the commitment or closing transaction has not yet
        /// appeared in a block). The given balance is claimable (less on-chain fees) if the channel is
        /// force-closed now.
        ClaimableOnChannelClose {
                /// The amount available to claim, in satoshis, excluding the on-chain fees which will be
                /// required to do so.
                claimable_amount_satoshis: u64,
        },
        /// The channel has been closed, and the given balance is ours but awaiting confirmations until
        /// we consider it spendable.
        ClaimableAwaitingConfirmations {
                /// The amount available to claim, in satoshis, possibly excluding the on-chain fees which
                /// were spent in broadcasting the transaction.
                claimable_amount_satoshis: u64,
                /// The height at which an [`Event::SpendableOutputs`] event will be generated for this
                /// amount.
                confirmation_height: u32,
        },
        /// The channel has been closed, and the given balance should be ours but awaiting spending
        /// transaction confirmation. If the spending transaction does not confirm in time, it is
        /// possible our counterparty can take the funds by broadcasting an HTLC timeout on-chain.
        ///
        /// Once the spending transaction confirms, before it has reached enough confirmations to be
        /// considered safe from chain reorganizations, the balance will instead be provided via
        /// [`Balance::ClaimableAwaitingConfirmations`].
        ContentiousClaimable {
                /// The amount available to claim, in satoshis, excluding the on-chain fees which will be
                /// required to do so.
                claimable_amount_satoshis: u64,
                /// The height at which the counterparty may be able to claim the balance if we have not
                /// done so.
                timeout_height: u32,
        },
        /// HTLCs which we sent to our counterparty which are claimable after a timeout (less on-chain
        /// fees) if the counterparty does not know the preimage for the HTLCs. These are somewhat
        /// likely to be claimed by our counterparty before we do.
        MaybeClaimableHTLCAwaitingTimeout {
                /// The amount available to claim, in satoshis, excluding the on-chain fees which will be
                /// required to do so.
                claimable_amount_satoshis: u64,
                /// The height at which we will be able to claim the balance if our counterparty has not
                /// done so.
                claimable_height: u32,
        },
}

/// An HTLC which has been irrevocably resolved on-chain, and has reached ANTI_REORG_DELAY.
#[derive(PartialEq)]
struct IrrevocablyResolvedHTLC {
        commitment_tx_output_idx: u32,
        /// Only set if the HTLC claim was ours using a payment preimage
        payment_preimage: Option<PaymentPreimage>,
}

impl_writeable_tlv_based!(IrrevocablyResolvedHTLC, {
        (0, commitment_tx_output_idx, required),
        (2, payment_preimage, option),
});

/// A ChannelMonitor handles chain events (blocks connected and disconnected) and generates
/// on-chain transactions to ensure no loss of funds occurs.
///
/// You MUST ensure that no ChannelMonitors for a given channel anywhere contain out-of-date
/// information and are actively monitoring the chain.
///
/// Pending Events or updated HTLCs which have not yet been read out by
/// get_and_clear_pending_monitor_events or get_and_clear_pending_events are serialized to disk and
/// reloaded at deserialize-time. Thus, you must ensure that, when handling events, all events
/// gotten are fully handled before re-serializing the new state.
///
/// Note that the deserializer is only implemented for (BlockHash, ChannelMonitor), which
/// tells you the last block hash which was block_connect()ed. You MUST rescan any blocks along
/// the "reorg path" (ie disconnecting blocks until you find a common ancestor from both the
/// returned block hash and the the current chain and then reconnecting blocks to get to the
/// best chain) upon deserializing the object!
pub struct ChannelMonitor<Signer: Sign> {
        #[cfg(test)]
        pub(crate) inner: Mutex<ChannelMonitorImpl<Signer>>,
        #[cfg(not(test))]
        inner: Mutex<ChannelMonitorImpl<Signer>>,
}

pub(crate) struct ChannelMonitorImpl<Signer: Sign> {
        latest_update_id: u64,
        commitment_transaction_number_obscure_factor: u64,

        destination_script: Script,
        broadcasted_holder_revokable_script: Option<(Script, PublicKey, PublicKey)>,
        counterparty_payment_script: Script,
        shutdown_script: Option<Script>,

        channel_keys_id: [u8; 32],
        holder_revocation_basepoint: PublicKey,
        funding_info: (OutPoint, Script),
        current_counterparty_commitment_txid: Option<Txid>,
        prev_counterparty_commitment_txid: Option<Txid>,

        counterparty_commitment_params: CounterpartyCommitmentParameters,
        funding_redeemscript: Script,
        channel_value_satoshis: u64,
        // first is the idx of the first of the two per-commitment points
        their_cur_per_commitment_points: Option<(u64, PublicKey, Option<PublicKey>)>,

        on_holder_tx_csv: u16,

        commitment_secrets: CounterpartyCommitmentSecrets,
        /// The set of outpoints in each counterparty commitment transaction. We always need at least
        /// the payment hash from `HTLCOutputInCommitment` to claim even a revoked commitment
        /// transaction broadcast as we need to be able to construct the witness script in all cases.
        counterparty_claimable_outpoints: HashMap<Txid, Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>>,
        /// We cannot identify HTLC-Success or HTLC-Timeout transactions by themselves on the chain.
        /// Nor can we figure out their commitment numbers without the commitment transaction they are
        /// spending. Thus, in order to claim them via revocation key, we track all the counterparty
        /// commitment transactions which we find on-chain, mapping them to the commitment number which
        /// can be used to derive the revocation key and claim the transactions.
        counterparty_commitment_txn_on_chain: HashMap<Txid, u64>,
        /// Cache used to make pruning of payment_preimages faster.
        /// Maps payment_hash values to commitment numbers for counterparty transactions for non-revoked
        /// counterparty transactions (ie should remain pretty small).
        /// Serialized to disk but should generally not be sent to Watchtowers.
        counterparty_hash_commitment_number: HashMap<PaymentHash, u64>,

        // We store two holder commitment transactions to avoid any race conditions where we may update
        // some monitors (potentially on watchtowers) but then fail to update others, resulting in the
        // various monitors for one channel being out of sync, and us broadcasting a holder
        // transaction for which we have deleted claim information on some watchtowers.
        prev_holder_signed_commitment_tx: Option<HolderSignedTx>,
        current_holder_commitment_tx: HolderSignedTx,

        // Used just for ChannelManager to make sure it has the latest channel data during
        // deserialization
        current_counterparty_commitment_number: u64,
        // Used just for ChannelManager to make sure it has the latest channel data during
        // deserialization
        current_holder_commitment_number: u64,

        /// The set of payment hashes from inbound payments for which we know the preimage. Payment
        /// preimages that are not included in any unrevoked local commitment transaction or unrevoked
        /// remote commitment transactions are automatically removed when commitment transactions are
        /// revoked.
        payment_preimages: HashMap<PaymentHash, PaymentPreimage>,

        // Note that `MonitorEvent`s MUST NOT be generated during update processing, only generated
        // during chain data processing. This prevents a race in `ChainMonitor::update_channel` (and
        // presumably user implementations thereof as well) where we update the in-memory channel
        // object, then before the persistence finishes (as it's all under a read-lock), we return
        // pending events to the user or to the relevant `ChannelManager`. Then, on reload, we'll have
        // the pre-event state here, but have processed the event in the `ChannelManager`.
        // Note that because the `event_lock` in `ChainMonitor` is only taken in
        // block/transaction-connected events and *not* during block/transaction-disconnected events,
        // we further MUST NOT generate events during block/transaction-disconnection.
        pending_monitor_events: Vec<MonitorEvent>,

        pending_events: Vec<Event>,

        // Used to track on-chain events (i.e., transactions part of channels confirmed on chain) on
        // which to take actions once they reach enough confirmations. Each entry includes the
        // transaction's id and the height when the transaction was confirmed on chain.
        onchain_events_awaiting_threshold_conf: Vec<OnchainEventEntry>,

        // If we get serialized out and re-read, we need to make sure that the chain monitoring
        // interface knows about the TXOs that we want to be notified of spends of. We could probably
        // be smart and derive them from the above storage fields, but its much simpler and more
        // Obviously Correct (tm) if we just keep track of them explicitly.
        outputs_to_watch: HashMap<Txid, Vec<(u32, Script)>>,

        #[cfg(test)]
        pub onchain_tx_handler: OnchainTxHandler<Signer>,
        #[cfg(not(test))]
        onchain_tx_handler: OnchainTxHandler<Signer>,

        // This is set when the Channel[Manager] generated a ChannelMonitorUpdate which indicated the
        // channel has been force-closed. After this is set, no further holder commitment transaction
        // updates may occur, and we panic!() if one is provided.
        lockdown_from_offchain: bool,

        // Set once we've signed a holder commitment transaction and handed it over to our
        // OnchainTxHandler. After this is set, no future updates to our holder commitment transactions
        // may occur, and we fail any such monitor updates.
        //
        // In case of update rejection due to a locally already signed commitment transaction, we
        // nevertheless store update content to track in case of concurrent broadcast by another
        // remote monitor out-of-order with regards to the block view.
        holder_tx_signed: bool,

        // If a spend of the funding output is seen, we set this to true and reject any further
        // updates. This prevents any further changes in the offchain state no matter the order
        // of block connection between ChannelMonitors and the ChannelManager.
        funding_spend_seen: bool,

        funding_spend_confirmed: Option<Txid>,
        /// The set of HTLCs which have been either claimed or failed on chain and have reached
        /// the requisite confirmations on the claim/fail transaction (either ANTI_REORG_DELAY or the
        /// spending CSV for revocable outputs).
        htlcs_resolved_on_chain: Vec<IrrevocablyResolvedHTLC>,

        // We simply modify best_block in Channel's block_connected so that serialization is
        // consistent but hopefully the users' copy handles block_connected in a consistent way.
        // (we do *not*, however, update them in update_monitor to ensure any local user copies keep
        // their best_block from its state and not based on updated copies that didn't run through
        // the full block_connected).
        best_block: BestBlock,

        /// The node_id of our counterparty
        counterparty_node_id: Option<PublicKey>,

        secp_ctx: Secp256k1<secp256k1::All>, //TODO: dedup this a bit...
}

/// Transaction outputs to watch for on-chain spends.
pub type TransactionOutputs = (Txid, Vec<(u32, TxOut)>);

#[cfg(any(test, fuzzing, feature = "_test_utils"))]
/// Used only in testing and fuzzing to check serialization roundtrips don't change the underlying
/// object
impl<Signer: Sign> PartialEq for ChannelMonitor<Signer> {
        fn eq(&self, other: &Self) -> bool {
                let inner = self.inner.lock().unwrap();
                let other = other.inner.lock().unwrap();
                inner.eq(&other)
        }
}

#[cfg(any(test, fuzzing, feature = "_test_utils"))]
/// Used only in testing and fuzzing to check serialization roundtrips don't change the underlying
/// object
impl<Signer: Sign> PartialEq for ChannelMonitorImpl<Signer> {
        fn eq(&self, other: &Self) -> bool {
                if self.latest_update_id != other.latest_update_id ||
                        self.commitment_transaction_number_obscure_factor != other.commitment_transaction_number_obscure_factor ||
                        self.destination_script != other.destination_script ||
                        self.broadcasted_holder_revokable_script != other.broadcasted_holder_revokable_script ||
                        self.counterparty_payment_script != other.counterparty_payment_script ||
                        self.channel_keys_id != other.channel_keys_id ||
                        self.holder_revocation_basepoint != other.holder_revocation_basepoint ||
                        self.funding_info != other.funding_info ||
                        self.current_counterparty_commitment_txid != other.current_counterparty_commitment_txid ||
                        self.prev_counterparty_commitment_txid != other.prev_counterparty_commitment_txid ||
                        self.counterparty_commitment_params != other.counterparty_commitment_params ||
                        self.funding_redeemscript != other.funding_redeemscript ||
                        self.channel_value_satoshis != other.channel_value_satoshis ||
                        self.their_cur_per_commitment_points != other.their_cur_per_commitment_points ||
                        self.on_holder_tx_csv != other.on_holder_tx_csv ||
                        self.commitment_secrets != other.commitment_secrets ||
                        self.counterparty_claimable_outpoints != other.counterparty_claimable_outpoints ||
                        self.counterparty_commitment_txn_on_chain != other.counterparty_commitment_txn_on_chain ||
                        self.counterparty_hash_commitment_number != other.counterparty_hash_commitment_number ||
                        self.prev_holder_signed_commitment_tx != other.prev_holder_signed_commitment_tx ||
                        self.current_counterparty_commitment_number != other.current_counterparty_commitment_number ||
                        self.current_holder_commitment_number != other.current_holder_commitment_number ||
                        self.current_holder_commitment_tx != other.current_holder_commitment_tx ||
                        self.payment_preimages != other.payment_preimages ||
                        self.pending_monitor_events != other.pending_monitor_events ||
                        self.pending_events.len() != other.pending_events.len() || // We trust events to round-trip properly
                        self.onchain_events_awaiting_threshold_conf != other.onchain_events_awaiting_threshold_conf ||
                        self.outputs_to_watch != other.outputs_to_watch ||
                        self.lockdown_from_offchain != other.lockdown_from_offchain ||
                        self.holder_tx_signed != other.holder_tx_signed ||
                        self.funding_spend_seen != other.funding_spend_seen ||
                        self.funding_spend_confirmed != other.funding_spend_confirmed ||
                        self.htlcs_resolved_on_chain != other.htlcs_resolved_on_chain
                {
                        false
                } else {
                        true
                }
        }
}

impl<Signer: Sign> Writeable for ChannelMonitor<Signer> {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
                self.inner.lock().unwrap().write(writer)
        }
}

// These are also used for ChannelMonitorUpdate, above.
const SERIALIZATION_VERSION: u8 = 1;
const MIN_SERIALIZATION_VERSION: u8 = 1;

impl<Signer: Sign> Writeable for ChannelMonitorImpl<Signer> {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error> {
                write_ver_prefix!(writer, SERIALIZATION_VERSION, MIN_SERIALIZATION_VERSION);

                self.latest_update_id.write(writer)?;

                // Set in initial Channel-object creation, so should always be set by now:
                U48(self.commitment_transaction_number_obscure_factor).write(writer)?;

                self.destination_script.write(writer)?;
                if let Some(ref broadcasted_holder_revokable_script) = self.broadcasted_holder_revokable_script {
                        writer.write_all(&[0; 1])?;
                        broadcasted_holder_revokable_script.0.write(writer)?;
                        broadcasted_holder_revokable_script.1.write(writer)?;
                        broadcasted_holder_revokable_script.2.write(writer)?;
                } else {
                        writer.write_all(&[1; 1])?;
                }

                self.counterparty_payment_script.write(writer)?;
                match &self.shutdown_script {
                        Some(script) => script.write(writer)?,
                        None => Script::new().write(writer)?,
                }

                self.channel_keys_id.write(writer)?;
                self.holder_revocation_basepoint.write(writer)?;
                writer.write_all(&self.funding_info.0.txid[..])?;
                writer.write_all(&byte_utils::be16_to_array(self.funding_info.0.index))?;
                self.funding_info.1.write(writer)?;
                self.current_counterparty_commitment_txid.write(writer)?;
                self.prev_counterparty_commitment_txid.write(writer)?;

                self.counterparty_commitment_params.write(writer)?;
                self.funding_redeemscript.write(writer)?;
                self.channel_value_satoshis.write(writer)?;

                match self.their_cur_per_commitment_points {
                        Some((idx, pubkey, second_option)) => {
                                writer.write_all(&byte_utils::be48_to_array(idx))?;
                                writer.write_all(&pubkey.serialize())?;
                                match second_option {
                                        Some(second_pubkey) => {
                                                writer.write_all(&second_pubkey.serialize())?;
                                        },
                                        None => {
                                                writer.write_all(&[0; 33])?;
                                        },
                                }
                        },
                        None => {
                                writer.write_all(&byte_utils::be48_to_array(0))?;
                        },
                }

                writer.write_all(&byte_utils::be16_to_array(self.on_holder_tx_csv))?;

                self.commitment_secrets.write(writer)?;

                macro_rules! serialize_htlc_in_commitment {
                        ($htlc_output: expr) => {
                                writer.write_all(&[$htlc_output.offered as u8; 1])?;
                                writer.write_all(&byte_utils::be64_to_array($htlc_output.amount_msat))?;
                                writer.write_all(&byte_utils::be32_to_array($htlc_output.cltv_expiry))?;
                                writer.write_all(&$htlc_output.payment_hash.0[..])?;
                                $htlc_output.transaction_output_index.write(writer)?;
                        }
                }

                writer.write_all(&byte_utils::be64_to_array(self.counterparty_claimable_outpoints.len() as u64))?;
                for (ref txid, ref htlc_infos) in self.counterparty_claimable_outpoints.iter() {
                        writer.write_all(&txid[..])?;
                        writer.write_all(&byte_utils::be64_to_array(htlc_infos.len() as u64))?;
                        for &(ref htlc_output, ref htlc_source) in htlc_infos.iter() {
                                debug_assert!(htlc_source.is_none() || Some(**txid) == self.current_counterparty_commitment_txid
                                                || Some(**txid) == self.prev_counterparty_commitment_txid,
                                        "HTLC Sources for all revoked commitment transactions should be none!");
                                serialize_htlc_in_commitment!(htlc_output);
                                htlc_source.as_ref().map(|b| b.as_ref()).write(writer)?;
                        }
                }

                writer.write_all(&byte_utils::be64_to_array(self.counterparty_commitment_txn_on_chain.len() as u64))?;
                for (ref txid, commitment_number) in self.counterparty_commitment_txn_on_chain.iter() {
                        writer.write_all(&txid[..])?;
                        writer.write_all(&byte_utils::be48_to_array(*commitment_number))?;
                }

                writer.write_all(&byte_utils::be64_to_array(self.counterparty_hash_commitment_number.len() as u64))?;
                for (ref payment_hash, commitment_number) in self.counterparty_hash_commitment_number.iter() {
                        writer.write_all(&payment_hash.0[..])?;
                        writer.write_all(&byte_utils::be48_to_array(*commitment_number))?;
                }

                if let Some(ref prev_holder_tx) = self.prev_holder_signed_commitment_tx {
                        writer.write_all(&[1; 1])?;
                        prev_holder_tx.write(writer)?;
                } else {
                        writer.write_all(&[0; 1])?;
                }

                self.current_holder_commitment_tx.write(writer)?;

                writer.write_all(&byte_utils::be48_to_array(self.current_counterparty_commitment_number))?;
                writer.write_all(&byte_utils::be48_to_array(self.current_holder_commitment_number))?;

                writer.write_all(&byte_utils::be64_to_array(self.payment_preimages.len() as u64))?;
                for payment_preimage in self.payment_preimages.values() {
                        writer.write_all(&payment_preimage.0[..])?;
                }

                writer.write_all(&(self.pending_monitor_events.iter().filter(|ev| match ev {
                        MonitorEvent::HTLCEvent(_) => true,
                        MonitorEvent::CommitmentTxConfirmed(_) => true,
                        _ => false,
                }).count() as u64).to_be_bytes())?;
                for event in self.pending_monitor_events.iter() {
                        match event {
                                MonitorEvent::HTLCEvent(upd) => {
                                        0u8.write(writer)?;
                                        upd.write(writer)?;
                                },
                                MonitorEvent::CommitmentTxConfirmed(_) => 1u8.write(writer)?,
                                _ => {}, // Covered in the TLV writes below
                        }
                }

                writer.write_all(&byte_utils::be64_to_array(self.pending_events.len() as u64))?;
                for event in self.pending_events.iter() {
                        event.write(writer)?;
                }

                self.best_block.block_hash().write(writer)?;
                writer.write_all(&byte_utils::be32_to_array(self.best_block.height()))?;

                writer.write_all(&byte_utils::be64_to_array(self.onchain_events_awaiting_threshold_conf.len() as u64))?;
                for ref entry in self.onchain_events_awaiting_threshold_conf.iter() {
                        entry.write(writer)?;
                }

                (self.outputs_to_watch.len() as u64).write(writer)?;
                for (txid, idx_scripts) in self.outputs_to_watch.iter() {
                        txid.write(writer)?;
                        (idx_scripts.len() as u64).write(writer)?;
                        for (idx, script) in idx_scripts.iter() {
                                idx.write(writer)?;
                                script.write(writer)?;
                        }
                }
                self.onchain_tx_handler.write(writer)?;

                self.lockdown_from_offchain.write(writer)?;
                self.holder_tx_signed.write(writer)?;

                write_tlv_fields!(writer, {
                        (1, self.funding_spend_confirmed, option),
                        (3, self.htlcs_resolved_on_chain, vec_type),
                        (5, self.pending_monitor_events, vec_type),
                        (7, self.funding_spend_seen, required),
                        (9, self.counterparty_node_id, option),
                });

                Ok(())
        }
}

impl<Signer: Sign> ChannelMonitor<Signer> {
        pub(crate) fn new(secp_ctx: Secp256k1<secp256k1::All>, keys: Signer, shutdown_script: Option<Script>,
                          on_counterparty_tx_csv: u16, destination_script: &Script, funding_info: (OutPoint, Script),
                          channel_parameters: &ChannelTransactionParameters,
                          funding_redeemscript: Script, channel_value_satoshis: u64,
                          commitment_transaction_number_obscure_factor: u64,
                          initial_holder_commitment_tx: HolderCommitmentTransaction,
                          best_block: BestBlock, counterparty_node_id: PublicKey) -> ChannelMonitor<Signer> {

                assert!(commitment_transaction_number_obscure_factor <= (1 << 48));
                let payment_key_hash = WPubkeyHash::hash(&keys.pubkeys().payment_point.serialize());
                let counterparty_payment_script = Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0).push_slice(&payment_key_hash[..]).into_script();

                let counterparty_channel_parameters = channel_parameters.counterparty_parameters.as_ref().unwrap();
                let counterparty_delayed_payment_base_key = counterparty_channel_parameters.pubkeys.delayed_payment_basepoint;
                let counterparty_htlc_base_key = counterparty_channel_parameters.pubkeys.htlc_basepoint;
                let counterparty_commitment_params = CounterpartyCommitmentParameters { counterparty_delayed_payment_base_key, counterparty_htlc_base_key, on_counterparty_tx_csv };

                let channel_keys_id = keys.channel_keys_id();
                let holder_revocation_basepoint = keys.pubkeys().revocation_basepoint;

                // block for Rust 1.34 compat
                let (holder_commitment_tx, current_holder_commitment_number) = {
                        let trusted_tx = initial_holder_commitment_tx.trust();
                        let txid = trusted_tx.txid();

                        let tx_keys = trusted_tx.keys();
                        let holder_commitment_tx = HolderSignedTx {
                                txid,
                                revocation_key: tx_keys.revocation_key,
                                a_htlc_key: tx_keys.broadcaster_htlc_key,
                                b_htlc_key: tx_keys.countersignatory_htlc_key,
                                delayed_payment_key: tx_keys.broadcaster_delayed_payment_key,
                                per_commitment_point: tx_keys.per_commitment_point,
                                htlc_outputs: Vec::new(), // There are never any HTLCs in the initial commitment transactions
                                to_self_value_sat: initial_holder_commitment_tx.to_broadcaster_value_sat(),
                                feerate_per_kw: trusted_tx.feerate_per_kw(),
                        };
                        (holder_commitment_tx, trusted_tx.commitment_number())
                };

                let onchain_tx_handler =
                        OnchainTxHandler::new(destination_script.clone(), keys,
                        channel_parameters.clone(), initial_holder_commitment_tx, secp_ctx.clone());

                let mut outputs_to_watch = HashMap::new();
                outputs_to_watch.insert(funding_info.0.txid, vec![(funding_info.0.index as u32, funding_info.1.clone())]);

                ChannelMonitor {
                        inner: Mutex::new(ChannelMonitorImpl {
                                latest_update_id: 0,
                                commitment_transaction_number_obscure_factor,

                                destination_script: destination_script.clone(),
                                broadcasted_holder_revokable_script: None,
                                counterparty_payment_script,
                                shutdown_script,

                                channel_keys_id,
                                holder_revocation_basepoint,
                                funding_info,
                                current_counterparty_commitment_txid: None,
                                prev_counterparty_commitment_txid: None,

                                counterparty_commitment_params,
                                funding_redeemscript,
                                channel_value_satoshis,
                                their_cur_per_commitment_points: None,

                                on_holder_tx_csv: counterparty_channel_parameters.selected_contest_delay,

                                commitment_secrets: CounterpartyCommitmentSecrets::new(),
                                counterparty_claimable_outpoints: HashMap::new(),
                                counterparty_commitment_txn_on_chain: HashMap::new(),
                                counterparty_hash_commitment_number: HashMap::new(),

                                prev_holder_signed_commitment_tx: None,
                                current_holder_commitment_tx: holder_commitment_tx,
                                current_counterparty_commitment_number: 1 << 48,
                                current_holder_commitment_number,

                                payment_preimages: HashMap::new(),
                                pending_monitor_events: Vec::new(),
                                pending_events: Vec::new(),

                                onchain_events_awaiting_threshold_conf: Vec::new(),
                                outputs_to_watch,

                                onchain_tx_handler,

                                lockdown_from_offchain: false,
                                holder_tx_signed: false,
                                funding_spend_seen: false,
                                funding_spend_confirmed: None,
                                htlcs_resolved_on_chain: Vec::new(),

                                best_block,
                                counterparty_node_id: Some(counterparty_node_id),

                                secp_ctx,
                        }),
                }
        }

        #[cfg(test)]
        fn provide_secret(&self, idx: u64, secret: [u8; 32]) -> Result<(), &'static str> {
                self.inner.lock().unwrap().provide_secret(idx, secret)
        }

        /// Informs this monitor of the latest counterparty (ie non-broadcastable) commitment transaction.
        /// The monitor watches for it to be broadcasted and then uses the HTLC information (and
        /// possibly future revocation/preimage information) to claim outputs where possible.
        /// We cache also the mapping hash:commitment number to lighten pruning of old preimages by watchtowers.
        pub(crate) fn provide_latest_counterparty_commitment_tx<L: Deref>(
                &self,
                txid: Txid,
                htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>,
                commitment_number: u64,
                their_per_commitment_point: PublicKey,
                logger: &L,
        ) where L::Target: Logger {
                self.inner.lock().unwrap().provide_latest_counterparty_commitment_tx(
                        txid, htlc_outputs, commitment_number, their_per_commitment_point, logger)
        }

        #[cfg(test)]
        fn provide_latest_holder_commitment_tx(
                &self, holder_commitment_tx: HolderCommitmentTransaction,
                htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Signature>, Option<HTLCSource>)>,
        ) -> Result<(), ()> {
                self.inner.lock().unwrap().provide_latest_holder_commitment_tx(holder_commitment_tx, htlc_outputs).map_err(|_| ())
        }

        /// This is used to provide payment preimage(s) out-of-band during startup without updating the
        /// off-chain state with a new commitment transaction.
        pub(crate) fn provide_payment_preimage<B: Deref, F: Deref, L: Deref>(
                &self,
                payment_hash: &PaymentHash,
                payment_preimage: &PaymentPreimage,
                broadcaster: &B,
                fee_estimator: &LowerBoundedFeeEstimator<F>,
                logger: &L,
        ) where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                self.inner.lock().unwrap().provide_payment_preimage(
                        payment_hash, payment_preimage, broadcaster, fee_estimator, logger)
        }

        pub(crate) fn broadcast_latest_holder_commitment_txn<B: Deref, L: Deref>(
                &self,
                broadcaster: &B,
                logger: &L,
        ) where
                B::Target: BroadcasterInterface,
                L::Target: Logger,
        {
                self.inner.lock().unwrap().broadcast_latest_holder_commitment_txn(broadcaster, logger)
        }

        /// Updates a ChannelMonitor on the basis of some new information provided by the Channel
        /// itself.
        ///
        /// panics if the given update is not the next update by update_id.
        pub fn update_monitor<B: Deref, F: Deref, L: Deref>(
                &self,
                updates: &ChannelMonitorUpdate,
                broadcaster: &B,
                fee_estimator: &F,
                logger: &L,
        ) -> Result<(), ()>
        where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                self.inner.lock().unwrap().update_monitor(updates, broadcaster, fee_estimator, logger)
        }

        /// Gets the update_id from the latest ChannelMonitorUpdate which was applied to this
        /// ChannelMonitor.
        pub fn get_latest_update_id(&self) -> u64 {
                self.inner.lock().unwrap().get_latest_update_id()
        }

        /// Gets the funding transaction outpoint of the channel this ChannelMonitor is monitoring for.
        pub fn get_funding_txo(&self) -> (OutPoint, Script) {
                self.inner.lock().unwrap().get_funding_txo().clone()
        }

        /// Gets a list of txids, with their output scripts (in the order they appear in the
        /// transaction), which we must learn about spends of via block_connected().
        pub fn get_outputs_to_watch(&self) -> Vec<(Txid, Vec<(u32, Script)>)> {
                self.inner.lock().unwrap().get_outputs_to_watch()
                        .iter().map(|(txid, outputs)| (*txid, outputs.clone())).collect()
        }

        /// Loads the funding txo and outputs to watch into the given `chain::Filter` by repeatedly
        /// calling `chain::Filter::register_output` and `chain::Filter::register_tx` until all outputs
        /// have been registered.
        pub fn load_outputs_to_watch<F: Deref>(&self, filter: &F) where F::Target: chain::Filter {
                let lock = self.inner.lock().unwrap();
                filter.register_tx(&lock.get_funding_txo().0.txid, &lock.get_funding_txo().1);
                for (txid, outputs) in lock.get_outputs_to_watch().iter() {
                        for (index, script_pubkey) in outputs.iter() {
                                assert!(*index <= u16::max_value() as u32);
                                filter.register_output(WatchedOutput {
                                        block_hash: None,
                                        outpoint: OutPoint { txid: *txid, index: *index as u16 },
                                        script_pubkey: script_pubkey.clone(),
                                });
                        }
                }
        }

        /// Get the list of HTLCs who's status has been updated on chain. This should be called by
        /// ChannelManager via [`chain::Watch::release_pending_monitor_events`].
        pub fn get_and_clear_pending_monitor_events(&self) -> Vec<MonitorEvent> {
                self.inner.lock().unwrap().get_and_clear_pending_monitor_events()
        }

        /// Gets the list of pending events which were generated by previous actions, clearing the list
        /// in the process.
        ///
        /// This is called by ChainMonitor::get_and_clear_pending_events() and is equivalent to
        /// EventsProvider::get_and_clear_pending_events() except that it requires &mut self as we do
        /// no internal locking in ChannelMonitors.
        pub fn get_and_clear_pending_events(&self) -> Vec<Event> {
                self.inner.lock().unwrap().get_and_clear_pending_events()
        }

        pub(crate) fn get_min_seen_secret(&self) -> u64 {
                self.inner.lock().unwrap().get_min_seen_secret()
        }

        pub(crate) fn get_cur_counterparty_commitment_number(&self) -> u64 {
                self.inner.lock().unwrap().get_cur_counterparty_commitment_number()
        }

        pub(crate) fn get_cur_holder_commitment_number(&self) -> u64 {
                self.inner.lock().unwrap().get_cur_holder_commitment_number()
        }

        pub(crate) fn get_counterparty_node_id(&self) -> Option<PublicKey> {
                self.inner.lock().unwrap().counterparty_node_id
        }

        /// Used by ChannelManager deserialization to broadcast the latest holder state if its copy of
        /// the Channel was out-of-date. You may use it to get a broadcastable holder toxic tx in case of
        /// fallen-behind, i.e when receiving a channel_reestablish with a proof that our counterparty side knows
        /// a higher revocation secret than the holder commitment number we are aware of. Broadcasting these
        /// transactions are UNSAFE, as they allow counterparty side to punish you. Nevertheless you may want to
        /// broadcast them if counterparty don't close channel with his higher commitment transaction after a
        /// substantial amount of time (a month or even a year) to get back funds. Best may be to contact
        /// out-of-band the other node operator to coordinate with him if option is available to you.
        /// In any-case, choice is up to the user.
        pub fn get_latest_holder_commitment_txn<L: Deref>(&self, logger: &L) -> Vec<Transaction>
        where L::Target: Logger {
                self.inner.lock().unwrap().get_latest_holder_commitment_txn(logger)
        }

        /// Unsafe test-only version of get_latest_holder_commitment_txn used by our test framework
        /// to bypass HolderCommitmentTransaction state update lockdown after signature and generate
        /// revoked commitment transaction.
        #[cfg(any(test, feature = "unsafe_revoked_tx_signing"))]
        pub fn unsafe_get_latest_holder_commitment_txn<L: Deref>(&self, logger: &L) -> Vec<Transaction>
        where L::Target: Logger {
                self.inner.lock().unwrap().unsafe_get_latest_holder_commitment_txn(logger)
        }

        /// Processes transactions in a newly connected block, which may result in any of the following:
        /// - update the monitor's state against resolved HTLCs
        /// - punish the counterparty in the case of seeing a revoked commitment transaction
        /// - force close the channel and claim/timeout incoming/outgoing HTLCs if near expiration
        /// - detect settled outputs for later spending
        /// - schedule and bump any in-flight claims
        ///
        /// Returns any new outputs to watch from `txdata`; after called, these are also included in
        /// [`get_outputs_to_watch`].
        ///
        /// [`get_outputs_to_watch`]: #method.get_outputs_to_watch
        pub fn block_connected<B: Deref, F: Deref, L: Deref>(
                &self,
                header: &BlockHeader,
                txdata: &TransactionData,
                height: u32,
                broadcaster: B,
                fee_estimator: F,
                logger: L,
        ) -> Vec<TransactionOutputs>
        where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                self.inner.lock().unwrap().block_connected(
                        header, txdata, height, broadcaster, fee_estimator, logger)
        }

        /// Determines if the disconnected block contained any transactions of interest and updates
        /// appropriately.
        pub fn block_disconnected<B: Deref, F: Deref, L: Deref>(
                &self,
                header: &BlockHeader,
                height: u32,
                broadcaster: B,
                fee_estimator: F,
                logger: L,
        ) where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                self.inner.lock().unwrap().block_disconnected(
                        header, height, broadcaster, fee_estimator, logger)
        }

        /// Processes transactions confirmed in a block with the given header and height, returning new
        /// outputs to watch. See [`block_connected`] for details.
        ///
        /// Used instead of [`block_connected`] by clients that are notified of transactions rather than
        /// blocks. See [`chain::Confirm`] for calling expectations.
        ///
        /// [`block_connected`]: Self::block_connected
        pub fn transactions_confirmed<B: Deref, F: Deref, L: Deref>(
                &self,
                header: &BlockHeader,
                txdata: &TransactionData,
                height: u32,
                broadcaster: B,
                fee_estimator: F,
                logger: L,
        ) -> Vec<TransactionOutputs>
        where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                let bounded_fee_estimator = LowerBoundedFeeEstimator::new(fee_estimator);
                self.inner.lock().unwrap().transactions_confirmed(
                        header, txdata, height, broadcaster, &bounded_fee_estimator, logger)
        }

        /// Processes a transaction that was reorganized out of the chain.
        ///
        /// Used instead of [`block_disconnected`] by clients that are notified of transactions rather
        /// than blocks. See [`chain::Confirm`] for calling expectations.
        ///
        /// [`block_disconnected`]: Self::block_disconnected
        pub fn transaction_unconfirmed<B: Deref, F: Deref, L: Deref>(
                &self,
                txid: &Txid,
                broadcaster: B,
                fee_estimator: F,
                logger: L,
        ) where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                let bounded_fee_estimator = LowerBoundedFeeEstimator::new(fee_estimator);
                self.inner.lock().unwrap().transaction_unconfirmed(
                        txid, broadcaster, &bounded_fee_estimator, logger);
        }

        /// Updates the monitor with the current best chain tip, returning new outputs to watch. See
        /// [`block_connected`] for details.
        ///
        /// Used instead of [`block_connected`] by clients that are notified of transactions rather than
        /// blocks. See [`chain::Confirm`] for calling expectations.
        ///
        /// [`block_connected`]: Self::block_connected
        pub fn best_block_updated<B: Deref, F: Deref, L: Deref>(
                &self,
                header: &BlockHeader,
                height: u32,
                broadcaster: B,
                fee_estimator: F,
                logger: L,
        ) -> Vec<TransactionOutputs>
        where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                let bounded_fee_estimator = LowerBoundedFeeEstimator::new(fee_estimator);
                self.inner.lock().unwrap().best_block_updated(
                        header, height, broadcaster, &bounded_fee_estimator, logger)
        }

        /// Returns the set of txids that should be monitored for re-organization out of the chain.
        pub fn get_relevant_txids(&self) -> Vec<Txid> {
                let inner = self.inner.lock().unwrap();
                let mut txids: Vec<Txid> = inner.onchain_events_awaiting_threshold_conf
                        .iter()
                        .map(|entry| entry.txid)
                        .chain(inner.onchain_tx_handler.get_relevant_txids().into_iter())
                        .collect();
                txids.sort_unstable();
                txids.dedup();
                txids
        }

        /// Gets the latest best block which was connected either via the [`chain::Listen`] or
        /// [`chain::Confirm`] interfaces.
        pub fn current_best_block(&self) -> BestBlock {
                self.inner.lock().unwrap().best_block.clone()
        }

        /// Gets the balances in this channel which are either claimable by us if we were to
        /// force-close the channel now or which are claimable on-chain (possibly awaiting
        /// confirmation).
        ///
        /// Any balances in the channel which are available on-chain (excluding on-chain fees) are
        /// included here until an [`Event::SpendableOutputs`] event has been generated for the
        /// balance, or until our counterparty has claimed the balance and accrued several
        /// confirmations on the claim transaction.
        ///
        /// Note that the balances available when you or your counterparty have broadcasted revoked
        /// state(s) may not be fully captured here.
        // TODO, fix that ^
        ///
        /// See [`Balance`] for additional details on the types of claimable balances which
        /// may be returned here and their meanings.
        pub fn get_claimable_balances(&self) -> Vec<Balance> {
                let mut res = Vec::new();
                let us = self.inner.lock().unwrap();

                let mut confirmed_txid = us.funding_spend_confirmed;
                let mut pending_commitment_tx_conf_thresh = None;
                let funding_spend_pending = us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
                        if let OnchainEvent::FundingSpendConfirmation { .. } = event.event {
                                Some((event.txid, event.confirmation_threshold()))
                        } else { None }
                });
                if let Some((txid, conf_thresh)) = funding_spend_pending {
                        debug_assert!(us.funding_spend_confirmed.is_none(),
                                "We have a pending funding spend awaiting anti-reorg confirmation, we can't have confirmed it already!");
                        confirmed_txid = Some(txid);
                        pending_commitment_tx_conf_thresh = Some(conf_thresh);
                }

                macro_rules! walk_htlcs {
                        ($holder_commitment: expr, $htlc_iter: expr) => {
                                for htlc in $htlc_iter {
                                        if let Some(htlc_commitment_tx_output_idx) = htlc.transaction_output_index {
                                                if let Some(conf_thresh) = us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
                                                        if let OnchainEvent::MaturingOutput { descriptor: SpendableOutputDescriptor::DelayedPaymentOutput(descriptor) } = &event.event {
                                                                if descriptor.outpoint.index as u32 == htlc_commitment_tx_output_idx { Some(event.confirmation_threshold()) } else { None }
                                                        } else { None }
                                                }) {
                                                        debug_assert!($holder_commitment);
                                                        res.push(Balance::ClaimableAwaitingConfirmations {
                                                                claimable_amount_satoshis: htlc.amount_msat / 1000,
                                                                confirmation_height: conf_thresh,
                                                        });
                                                } else if us.htlcs_resolved_on_chain.iter().any(|v| v.commitment_tx_output_idx == htlc_commitment_tx_output_idx) {
                                                        // Funding transaction spends should be fully confirmed by the time any
                                                        // HTLC transactions are resolved, unless we're talking about a holder
                                                        // commitment tx, whose resolution is delayed until the CSV timeout is
                                                        // reached, even though HTLCs may be resolved after only
                                                        // ANTI_REORG_DELAY confirmations.
                                                        debug_assert!($holder_commitment || us.funding_spend_confirmed.is_some());
                                                } else if htlc.offered == $holder_commitment {
                                                        // If the payment was outbound, check if there's an HTLCUpdate
                                                        // indicating we have spent this HTLC with a timeout, claiming it back
                                                        // and awaiting confirmations on it.
                                                        let htlc_update_pending = us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
                                                                if let OnchainEvent::HTLCUpdate { commitment_tx_output_idx: Some(commitment_tx_output_idx), .. } = event.event {
                                                                        if commitment_tx_output_idx == htlc_commitment_tx_output_idx {
                                                                                Some(event.confirmation_threshold()) } else { None }
                                                                } else { None }
                                                        });
                                                        if let Some(conf_thresh) = htlc_update_pending {
                                                                res.push(Balance::ClaimableAwaitingConfirmations {
                                                                        claimable_amount_satoshis: htlc.amount_msat / 1000,
                                                                        confirmation_height: conf_thresh,
                                                                });
                                                        } else {
                                                                res.push(Balance::MaybeClaimableHTLCAwaitingTimeout {
                                                                        claimable_amount_satoshis: htlc.amount_msat / 1000,
                                                                        claimable_height: htlc.cltv_expiry,
                                                                });
                                                        }
                                                } else if us.payment_preimages.get(&htlc.payment_hash).is_some() {
                                                        // Otherwise (the payment was inbound), only expose it as claimable if
                                                        // we know the preimage.
                                                        // Note that if there is a pending claim, but it did not use the
                                                        // preimage, we lost funds to our counterparty! We will then continue
                                                        // to show it as ContentiousClaimable until ANTI_REORG_DELAY.
                                                        let htlc_spend_pending = us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
                                                                if let OnchainEvent::HTLCSpendConfirmation { commitment_tx_output_idx, preimage, .. } = event.event {
                                                                        if commitment_tx_output_idx == htlc_commitment_tx_output_idx {
                                                                                Some((event.confirmation_threshold(), preimage.is_some()))
                                                                        } else { None }
                                                                } else { None }
                                                        });
                                                        if let Some((conf_thresh, true)) = htlc_spend_pending {
                                                                res.push(Balance::ClaimableAwaitingConfirmations {
                                                                        claimable_amount_satoshis: htlc.amount_msat / 1000,
                                                                        confirmation_height: conf_thresh,
                                                                });
                                                        } else {
                                                                res.push(Balance::ContentiousClaimable {
                                                                        claimable_amount_satoshis: htlc.amount_msat / 1000,
                                                                        timeout_height: htlc.cltv_expiry,
                                                                });
                                                        }
                                                }
                                        }
                                }
                        }
                }

                if let Some(txid) = confirmed_txid {
                        let mut found_commitment_tx = false;
                        if Some(txid) == us.current_counterparty_commitment_txid || Some(txid) == us.prev_counterparty_commitment_txid {
                                walk_htlcs!(false, us.counterparty_claimable_outpoints.get(&txid).unwrap().iter().map(|(a, _)| a));
                                if let Some(conf_thresh) = pending_commitment_tx_conf_thresh {
                                        if let Some(value) = us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
                                                if let OnchainEvent::MaturingOutput {
                                                        descriptor: SpendableOutputDescriptor::StaticPaymentOutput(descriptor)
                                                } = &event.event {
                                                        Some(descriptor.output.value)
                                                } else { None }
                                        }) {
                                                res.push(Balance::ClaimableAwaitingConfirmations {
                                                        claimable_amount_satoshis: value,
                                                        confirmation_height: conf_thresh,
                                                });
                                        } else {
                                                // If a counterparty commitment transaction is awaiting confirmation, we
                                                // should either have a StaticPaymentOutput MaturingOutput event awaiting
                                                // confirmation with the same height or have never met our dust amount.
                                        }
                                }
                                found_commitment_tx = true;
                        } else if txid == us.current_holder_commitment_tx.txid {
                                walk_htlcs!(true, us.current_holder_commitment_tx.htlc_outputs.iter().map(|(a, _, _)| a));
                                if let Some(conf_thresh) = pending_commitment_tx_conf_thresh {
                                        res.push(Balance::ClaimableAwaitingConfirmations {
                                                claimable_amount_satoshis: us.current_holder_commitment_tx.to_self_value_sat,
                                                confirmation_height: conf_thresh,
                                        });
                                }
                                found_commitment_tx = true;
                        } else if let Some(prev_commitment) = &us.prev_holder_signed_commitment_tx {
                                if txid == prev_commitment.txid {
                                        walk_htlcs!(true, prev_commitment.htlc_outputs.iter().map(|(a, _, _)| a));
                                        if let Some(conf_thresh) = pending_commitment_tx_conf_thresh {
                                                res.push(Balance::ClaimableAwaitingConfirmations {
                                                        claimable_amount_satoshis: prev_commitment.to_self_value_sat,
                                                        confirmation_height: conf_thresh,
                                                });
                                        }
                                        found_commitment_tx = true;
                                }
                        }
                        if !found_commitment_tx {
                                if let Some(conf_thresh) = pending_commitment_tx_conf_thresh {
                                        // We blindly assume this is a cooperative close transaction here, and that
                                        // neither us nor our counterparty misbehaved. At worst we've under-estimated
                                        // the amount we can claim as we'll punish a misbehaving counterparty.
                                        res.push(Balance::ClaimableAwaitingConfirmations {
                                                claimable_amount_satoshis: us.current_holder_commitment_tx.to_self_value_sat,
                                                confirmation_height: conf_thresh,
                                        });
                                }
                        }
                        // TODO: Add logic to provide claimable balances for counterparty broadcasting revoked
                        // outputs.
                } else {
                        let mut claimable_inbound_htlc_value_sat = 0;
                        for (htlc, _, _) in us.current_holder_commitment_tx.htlc_outputs.iter() {
                                if htlc.transaction_output_index.is_none() { continue; }
                                if htlc.offered {
                                        res.push(Balance::MaybeClaimableHTLCAwaitingTimeout {
                                                claimable_amount_satoshis: htlc.amount_msat / 1000,
                                                claimable_height: htlc.cltv_expiry,
                                        });
                                } else if us.payment_preimages.get(&htlc.payment_hash).is_some() {
                                        claimable_inbound_htlc_value_sat += htlc.amount_msat / 1000;
                                }
                        }
                        res.push(Balance::ClaimableOnChannelClose {
                                claimable_amount_satoshis: us.current_holder_commitment_tx.to_self_value_sat + claimable_inbound_htlc_value_sat,
                        });
                }

                res
        }

        /// Gets the set of outbound HTLCs which are pending resolution in this channel.
        /// This is used to reconstruct pending outbound payments on restart in the ChannelManager.
        pub(crate) fn get_pending_outbound_htlcs(&self) -> HashMap<HTLCSource, HTLCOutputInCommitment> {
                let mut res = HashMap::new();
                let us = self.inner.lock().unwrap();

                macro_rules! walk_htlcs {
                        ($holder_commitment: expr, $htlc_iter: expr) => {
                                for (htlc, source) in $htlc_iter {
                                        if us.htlcs_resolved_on_chain.iter().any(|v| Some(v.commitment_tx_output_idx) == htlc.transaction_output_index) {
                                                // We should assert that funding_spend_confirmed is_some() here, but we
                                                // have some unit tests which violate HTLC transaction CSVs entirely and
                                                // would fail.
                                                // TODO: Once tests all connect transactions at consensus-valid times, we
                                                // should assert here like we do in `get_claimable_balances`.
                                        } else if htlc.offered == $holder_commitment {
                                                // If the payment was outbound, check if there's an HTLCUpdate
                                                // indicating we have spent this HTLC with a timeout, claiming it back
                                                // and awaiting confirmations on it.
                                                let htlc_update_confd = us.onchain_events_awaiting_threshold_conf.iter().any(|event| {
                                                        if let OnchainEvent::HTLCUpdate { commitment_tx_output_idx: Some(commitment_tx_output_idx), .. } = event.event {
                                                                // If the HTLC was timed out, we wait for ANTI_REORG_DELAY blocks
                                                                // before considering it "no longer pending" - this matches when we
                                                                // provide the ChannelManager an HTLC failure event.
                                                                Some(commitment_tx_output_idx) == htlc.transaction_output_index &&
                                                                        us.best_block.height() >= event.height + ANTI_REORG_DELAY - 1
                                                        } else if let OnchainEvent::HTLCSpendConfirmation { commitment_tx_output_idx, .. } = event.event {
                                                                // If the HTLC was fulfilled with a preimage, we consider the HTLC
                                                                // immediately non-pending, matching when we provide ChannelManager
                                                                // the preimage.
                                                                Some(commitment_tx_output_idx) == htlc.transaction_output_index
                                                        } else { false }
                                                });
                                                if !htlc_update_confd {
                                                        res.insert(source.clone(), htlc.clone());
                                                }
                                        }
                                }
                        }
                }

                // We're only concerned with the confirmation count of HTLC transactions, and don't
                // actually care how many confirmations a commitment transaction may or may not have. Thus,
                // we look for either a FundingSpendConfirmation event or a funding_spend_confirmed.
                let confirmed_txid = us.funding_spend_confirmed.or_else(|| {
                        us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
                                if let OnchainEvent::FundingSpendConfirmation { .. } = event.event {
                                        Some(event.txid)
                                } else { None }
                        })
                });
                if let Some(txid) = confirmed_txid {
                        if Some(txid) == us.current_counterparty_commitment_txid || Some(txid) == us.prev_counterparty_commitment_txid {
                                walk_htlcs!(false, us.counterparty_claimable_outpoints.get(&txid).unwrap().iter().filter_map(|(a, b)| {
                                        if let &Some(ref source) = b {
                                                Some((a, &**source))
                                        } else { None }
                                }));
                        } else if txid == us.current_holder_commitment_tx.txid {
                                walk_htlcs!(true, us.current_holder_commitment_tx.htlc_outputs.iter().filter_map(|(a, _, c)| {
                                        if let Some(source) = c { Some((a, source)) } else { None }
                                }));
                        } else if let Some(prev_commitment) = &us.prev_holder_signed_commitment_tx {
                                if txid == prev_commitment.txid {
                                        walk_htlcs!(true, prev_commitment.htlc_outputs.iter().filter_map(|(a, _, c)| {
                                                if let Some(source) = c { Some((a, source)) } else { None }
                                        }));
                                }
                        }
                } else {
                        // If we have not seen a commitment transaction on-chain (ie the channel is not yet
                        // closed), just examine the available counterparty commitment transactions. See docs
                        // on `fail_unbroadcast_htlcs`, below, for justification.
                        macro_rules! walk_counterparty_commitment {
                                ($txid: expr) => {
                                        if let Some(ref latest_outpoints) = us.counterparty_claimable_outpoints.get($txid) {
                                                for &(ref htlc, ref source_option) in latest_outpoints.iter() {
                                                        if let &Some(ref source) = source_option {
                                                                res.insert((**source).clone(), htlc.clone());
                                                        }
                                                }
                                        }
                                }
                        }
                        if let Some(ref txid) = us.current_counterparty_commitment_txid {
                                walk_counterparty_commitment!(txid);
                        }
                        if let Some(ref txid) = us.prev_counterparty_commitment_txid {
                                walk_counterparty_commitment!(txid);
                        }
                }

                res
        }

        pub(crate) fn get_stored_preimages(&self) -> HashMap<PaymentHash, PaymentPreimage> {
                self.inner.lock().unwrap().payment_preimages.clone()
        }
}

/// Compares a broadcasted commitment transaction's HTLCs with those in the latest state,
/// failing any HTLCs which didn't make it into the broadcasted commitment transaction back
/// after ANTI_REORG_DELAY blocks.
///
/// We always compare against the set of HTLCs in counterparty commitment transactions, as those
/// are the commitment transactions which are generated by us. The off-chain state machine in
/// `Channel` will automatically resolve any HTLCs which were never included in a commitment
/// transaction when it detects channel closure, but it is up to us to ensure any HTLCs which were
/// included in a remote commitment transaction are failed back if they are not present in the
/// broadcasted commitment transaction.
///
/// Specifically, the removal process for HTLCs in `Channel` is always based on the counterparty
/// sending a `revoke_and_ack`, which causes us to clear `prev_counterparty_commitment_txid`. Thus,
/// as long as we examine both the current counterparty commitment transaction and, if it hasn't
/// been revoked yet, the previous one, we we will never "forget" to resolve an HTLC.
macro_rules! fail_unbroadcast_htlcs {
        ($self: expr, $commitment_tx_type: expr, $commitment_txid_confirmed: expr,
         $commitment_tx_conf_height: expr, $confirmed_htlcs_list: expr, $logger: expr) => { {
                macro_rules! check_htlc_fails {
                        ($txid: expr, $commitment_tx: expr) => {
                                if let Some(ref latest_outpoints) = $self.counterparty_claimable_outpoints.get($txid) {
                                        for &(ref htlc, ref source_option) in latest_outpoints.iter() {
                                                if let &Some(ref source) = source_option {
                                                        // Check if the HTLC is present in the commitment transaction that was
                                                        // broadcast, but not if it was below the dust limit, which we should
                                                        // fail backwards immediately as there is no way for us to learn the
                                                        // payment_preimage.
                                                        // Note that if the dust limit were allowed to change between
                                                        // commitment transactions we'd want to be check whether *any*
                                                        // broadcastable commitment transaction has the HTLC in it, but it
                                                        // cannot currently change after channel initialization, so we don't
                                                        // need to here.
                                                        let confirmed_htlcs_iter: &mut Iterator<Item = (&HTLCOutputInCommitment, Option<&HTLCSource>)> = &mut $confirmed_htlcs_list;

                                                        let mut matched_htlc = false;
                                                        for (ref broadcast_htlc, ref broadcast_source) in confirmed_htlcs_iter {
                                                                if broadcast_htlc.transaction_output_index.is_some() &&
                                                                        (Some(&**source) == *broadcast_source ||
                                                                         (broadcast_source.is_none() &&
                                                                          broadcast_htlc.payment_hash == htlc.payment_hash &&
                                                                          broadcast_htlc.amount_msat == htlc.amount_msat)) {
                                                                        matched_htlc = true;
                                                                        break;
                                                                }
                                                        }
                                                        if matched_htlc { continue; }
                                                        $self.onchain_events_awaiting_threshold_conf.retain(|ref entry| {
                                                                if entry.height != $commitment_tx_conf_height { return true; }
                                                                match entry.event {
                                                                        OnchainEvent::HTLCUpdate { source: ref update_source, .. } => {
                                                                                *update_source != **source
                                                                        },
                                                                        _ => true,
                                                                }
                                                        });
                                                        let entry = OnchainEventEntry {
                                                                txid: $commitment_txid_confirmed,
                                                                height: $commitment_tx_conf_height,
                                                                event: OnchainEvent::HTLCUpdate {
                                                                        source: (**source).clone(),
                                                                        payment_hash: htlc.payment_hash.clone(),
                                                                        htlc_value_satoshis: Some(htlc.amount_msat / 1000),
                                                                        commitment_tx_output_idx: None,
                                                                },
                                                        };
                                                        log_trace!($logger, "Failing HTLC with payment_hash {} from {} counterparty commitment tx due to broadcast of {} commitment transaction {}, waiting for confirmation (at height {})",
                                                                log_bytes!(htlc.payment_hash.0), $commitment_tx, $commitment_tx_type,
                                                                $commitment_txid_confirmed, entry.confirmation_threshold());
                                                        $self.onchain_events_awaiting_threshold_conf.push(entry);
                                                }
                                        }
                                }
                        }
                }
                if let Some(ref txid) = $self.current_counterparty_commitment_txid {
                        check_htlc_fails!(txid, "current");
                }
                if let Some(ref txid) = $self.prev_counterparty_commitment_txid {
                        check_htlc_fails!(txid, "previous");
                }
        } }
}

// In the `test_invalid_funding_tx` test, we need a bogus script which matches the HTLC-Accepted
// witness length match (ie is 136 bytes long). We generate one here which we also use in some
// in-line tests later.

#[cfg(test)]
pub fn deliberately_bogus_accepted_htlc_witness_program() -> Vec<u8> {
        let mut ret = [opcodes::all::OP_NOP.into_u8(); 136];
        ret[131] = opcodes::all::OP_DROP.into_u8();
        ret[132] = opcodes::all::OP_DROP.into_u8();
        ret[133] = opcodes::all::OP_DROP.into_u8();
        ret[134] = opcodes::all::OP_DROP.into_u8();
        ret[135] = opcodes::OP_TRUE.into_u8();
        Vec::from(&ret[..])
}

#[cfg(test)]
pub fn deliberately_bogus_accepted_htlc_witness() -> Vec<Vec<u8>> {
        vec![Vec::new(), Vec::new(), Vec::new(), Vec::new(), deliberately_bogus_accepted_htlc_witness_program().into()].into()
}

impl<Signer: Sign> ChannelMonitorImpl<Signer> {
        /// Inserts a revocation secret into this channel monitor. Prunes old preimages if neither
        /// needed by holder commitment transactions HTCLs nor by counterparty ones. Unless we haven't already seen
        /// counterparty commitment transaction's secret, they are de facto pruned (we can use revocation key).
        fn provide_secret(&mut self, idx: u64, secret: [u8; 32]) -> Result<(), &'static str> {
                if let Err(()) = self.commitment_secrets.provide_secret(idx, secret) {
                        return Err("Previous secret did not match new one");
                }

                // Prune HTLCs from the previous counterparty commitment tx so we don't generate failure/fulfill
                // events for now-revoked/fulfilled HTLCs.
                if let Some(txid) = self.prev_counterparty_commitment_txid.take() {
                        for &mut (_, ref mut source) in self.counterparty_claimable_outpoints.get_mut(&txid).unwrap() {
                                *source = None;
                        }
                }

                if !self.payment_preimages.is_empty() {
                        let cur_holder_signed_commitment_tx = &self.current_holder_commitment_tx;
                        let prev_holder_signed_commitment_tx = self.prev_holder_signed_commitment_tx.as_ref();
                        let min_idx = self.get_min_seen_secret();
                        let counterparty_hash_commitment_number = &mut self.counterparty_hash_commitment_number;

                        self.payment_preimages.retain(|&k, _| {
                                for &(ref htlc, _, _) in cur_holder_signed_commitment_tx.htlc_outputs.iter() {
                                        if k == htlc.payment_hash {
                                                return true
                                        }
                                }
                                if let Some(prev_holder_commitment_tx) = prev_holder_signed_commitment_tx {
                                        for &(ref htlc, _, _) in prev_holder_commitment_tx.htlc_outputs.iter() {
                                                if k == htlc.payment_hash {
                                                        return true
                                                }
                                        }
                                }
                                let contains = if let Some(cn) = counterparty_hash_commitment_number.get(&k) {
                                        if *cn < min_idx {
                                                return true
                                        }
                                        true
                                } else { false };
                                if contains {
                                        counterparty_hash_commitment_number.remove(&k);
                                }
                                false
                        });
                }

                Ok(())
        }

        pub(crate) fn provide_latest_counterparty_commitment_tx<L: Deref>(&mut self, txid: Txid, htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>, commitment_number: u64, their_per_commitment_point: PublicKey, logger: &L) where L::Target: Logger {
                // TODO: Encrypt the htlc_outputs data with the single-hash of the commitment transaction
                // so that a remote monitor doesn't learn anything unless there is a malicious close.
                // (only maybe, sadly we cant do the same for local info, as we need to be aware of
                // timeouts)
                for &(ref htlc, _) in &htlc_outputs {
                        self.counterparty_hash_commitment_number.insert(htlc.payment_hash, commitment_number);
                }

                log_trace!(logger, "Tracking new counterparty commitment transaction with txid {} at commitment number {} with {} HTLC outputs", txid, commitment_number, htlc_outputs.len());
                self.prev_counterparty_commitment_txid = self.current_counterparty_commitment_txid.take();
                self.current_counterparty_commitment_txid = Some(txid);
                self.counterparty_claimable_outpoints.insert(txid, htlc_outputs.clone());
                self.current_counterparty_commitment_number = commitment_number;
                //TODO: Merge this into the other per-counterparty-transaction output storage stuff
                match self.their_cur_per_commitment_points {
                        Some(old_points) => {
                                if old_points.0 == commitment_number + 1 {
                                        self.their_cur_per_commitment_points = Some((old_points.0, old_points.1, Some(their_per_commitment_point)));
                                } else if old_points.0 == commitment_number + 2 {
                                        if let Some(old_second_point) = old_points.2 {
                                                self.their_cur_per_commitment_points = Some((old_points.0 - 1, old_second_point, Some(their_per_commitment_point)));
                                        } else {
                                                self.their_cur_per_commitment_points = Some((commitment_number, their_per_commitment_point, None));
                                        }
                                } else {
                                        self.their_cur_per_commitment_points = Some((commitment_number, their_per_commitment_point, None));
                                }
                        },
                        None => {
                                self.their_cur_per_commitment_points = Some((commitment_number, their_per_commitment_point, None));
                        }
                }
                let mut htlcs = Vec::with_capacity(htlc_outputs.len());
                for htlc in htlc_outputs {
                        if htlc.0.transaction_output_index.is_some() {
                                htlcs.push(htlc.0);
                        }
                }
        }

        /// Informs this monitor of the latest holder (ie broadcastable) commitment transaction. The
        /// monitor watches for timeouts and may broadcast it if we approach such a timeout. Thus, it
        /// is important that any clones of this channel monitor (including remote clones) by kept
        /// up-to-date as our holder commitment transaction is updated.
        /// Panics if set_on_holder_tx_csv has never been called.
        fn provide_latest_holder_commitment_tx(&mut self, holder_commitment_tx: HolderCommitmentTransaction, htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Signature>, Option<HTLCSource>)>) -> Result<(), &'static str> {
                // block for Rust 1.34 compat
                let mut new_holder_commitment_tx = {
                        let trusted_tx = holder_commitment_tx.trust();
                        let txid = trusted_tx.txid();
                        let tx_keys = trusted_tx.keys();
                        self.current_holder_commitment_number = trusted_tx.commitment_number();
                        HolderSignedTx {
                                txid,
                                revocation_key: tx_keys.revocation_key,
                                a_htlc_key: tx_keys.broadcaster_htlc_key,
                                b_htlc_key: tx_keys.countersignatory_htlc_key,
                                delayed_payment_key: tx_keys.broadcaster_delayed_payment_key,
                                per_commitment_point: tx_keys.per_commitment_point,
                                htlc_outputs,
                                to_self_value_sat: holder_commitment_tx.to_broadcaster_value_sat(),
                                feerate_per_kw: trusted_tx.feerate_per_kw(),
                        }
                };
                self.onchain_tx_handler.provide_latest_holder_tx(holder_commitment_tx);
                mem::swap(&mut new_holder_commitment_tx, &mut self.current_holder_commitment_tx);
                self.prev_holder_signed_commitment_tx = Some(new_holder_commitment_tx);
                if self.holder_tx_signed {
                        return Err("Latest holder commitment signed has already been signed, update is rejected");
                }
                Ok(())
        }

        /// Provides a payment_hash->payment_preimage mapping. Will be automatically pruned when all
        /// commitment_tx_infos which contain the payment hash have been revoked.
        fn provide_payment_preimage<B: Deref, F: Deref, L: Deref>(
                &mut self, payment_hash: &PaymentHash, payment_preimage: &PaymentPreimage, broadcaster: &B,
                fee_estimator: &LowerBoundedFeeEstimator<F>, logger: &L)
        where B::Target: BroadcasterInterface,
                    F::Target: FeeEstimator,
                    L::Target: Logger,
        {
                self.payment_preimages.insert(payment_hash.clone(), payment_preimage.clone());

                // If the channel is force closed, try to claim the output from this preimage.
                // First check if a counterparty commitment transaction has been broadcasted:
                macro_rules! claim_htlcs {
                        ($commitment_number: expr, $txid: expr) => {
                                let htlc_claim_reqs = self.get_counterparty_htlc_output_claim_reqs($commitment_number, $txid, None);
                                self.onchain_tx_handler.update_claims_view(&Vec::new(), htlc_claim_reqs, self.best_block.height(), self.best_block.height(), broadcaster, fee_estimator, logger);
                        }
                }
                if let Some(txid) = self.current_counterparty_commitment_txid {
                        if let Some(commitment_number) = self.counterparty_commitment_txn_on_chain.get(&txid) {
                                claim_htlcs!(*commitment_number, txid);
                                return;
                        }
                }
                if let Some(txid) = self.prev_counterparty_commitment_txid {
                        if let Some(commitment_number) = self.counterparty_commitment_txn_on_chain.get(&txid) {
                                claim_htlcs!(*commitment_number, txid);
                                return;
                        }
                }

                // Then if a holder commitment transaction has been seen on-chain, broadcast transactions
                // claiming the HTLC output from each of the holder commitment transactions.
                // Note that we can't just use `self.holder_tx_signed`, because that only covers the case where
                // *we* sign a holder commitment transaction, not when e.g. a watchtower broadcasts one of our
                // holder commitment transactions.
                if self.broadcasted_holder_revokable_script.is_some() {
                        // Assume that the broadcasted commitment transaction confirmed in the current best
                        // block. Even if not, its a reasonable metric for the bump criteria on the HTLC
                        // transactions.
                        let (claim_reqs, _) = self.get_broadcasted_holder_claims(&self.current_holder_commitment_tx, self.best_block.height());
                        self.onchain_tx_handler.update_claims_view(&Vec::new(), claim_reqs, self.best_block.height(), self.best_block.height(), broadcaster, fee_estimator, logger);
                        if let Some(ref tx) = self.prev_holder_signed_commitment_tx {
                                let (claim_reqs, _) = self.get_broadcasted_holder_claims(&tx, self.best_block.height());
                                self.onchain_tx_handler.update_claims_view(&Vec::new(), claim_reqs, self.best_block.height(), self.best_block.height(), broadcaster, fee_estimator, logger);
                        }
                }
        }

        pub(crate) fn broadcast_latest_holder_commitment_txn<B: Deref, L: Deref>(&mut self, broadcaster: &B, logger: &L)
                where B::Target: BroadcasterInterface,
                                        L::Target: Logger,
        {
                for tx in self.get_latest_holder_commitment_txn(logger).iter() {
                        log_info!(logger, "Broadcasting local {}", log_tx!(tx));
                        broadcaster.broadcast_transaction(tx);
                }
                self.pending_monitor_events.push(MonitorEvent::CommitmentTxConfirmed(self.funding_info.0));
        }

        pub fn update_monitor<B: Deref, F: Deref, L: Deref>(&mut self, updates: &ChannelMonitorUpdate, broadcaster: &B, fee_estimator: &F, logger: &L) -> Result<(), ()>
        where B::Target: BroadcasterInterface,
                    F::Target: FeeEstimator,
                    L::Target: Logger,
        {
                log_info!(logger, "Applying update to monitor {}, bringing update_id from {} to {} with {} changes.",
                        log_funding_info!(self), self.latest_update_id, updates.update_id, updates.updates.len());
                // ChannelMonitor updates may be applied after force close if we receive a
                // preimage for a broadcasted commitment transaction HTLC output that we'd
                // like to claim on-chain. If this is the case, we no longer have guaranteed
                // access to the monitor's update ID, so we use a sentinel value instead.
                if updates.update_id == CLOSED_CHANNEL_UPDATE_ID {
                        assert_eq!(updates.updates.len(), 1);
                        match updates.updates[0] {
                                ChannelMonitorUpdateStep::PaymentPreimage { .. } => {},
                                _ => {
                                        log_error!(logger, "Attempted to apply post-force-close ChannelMonitorUpdate of type {}", updates.updates[0].variant_name());
                                        panic!("Attempted to apply post-force-close ChannelMonitorUpdate that wasn't providing a payment preimage");
                                },
                        }
                } else if self.latest_update_id + 1 != updates.update_id {
                        panic!("Attempted to apply ChannelMonitorUpdates out of order, check the update_id before passing an update to update_monitor!");
                }
                let mut ret = Ok(());
                for update in updates.updates.iter() {
                        match update {
                                ChannelMonitorUpdateStep::LatestHolderCommitmentTXInfo { commitment_tx, htlc_outputs } => {
                                        log_trace!(logger, "Updating ChannelMonitor with latest holder commitment transaction info");
                                        if self.lockdown_from_offchain { panic!(); }
                                        if let Err(e) = self.provide_latest_holder_commitment_tx(commitment_tx.clone(), htlc_outputs.clone()) {
                                                log_error!(logger, "Providing latest holder commitment transaction failed/was refused:");
                                                log_error!(logger, "    {}", e);
                                                ret = Err(());
                                        }
                                }
                                ChannelMonitorUpdateStep::LatestCounterpartyCommitmentTXInfo { commitment_txid, htlc_outputs, commitment_number, their_per_commitment_point } => {
                                        log_trace!(logger, "Updating ChannelMonitor with latest counterparty commitment transaction info");
                                        self.provide_latest_counterparty_commitment_tx(*commitment_txid, htlc_outputs.clone(), *commitment_number, *their_per_commitment_point, logger)
                                },
                                ChannelMonitorUpdateStep::PaymentPreimage { payment_preimage } => {
                                        log_trace!(logger, "Updating ChannelMonitor with payment preimage");
                                        let bounded_fee_estimator = LowerBoundedFeeEstimator::new(fee_estimator);
                                        self.provide_payment_preimage(&PaymentHash(Sha256::hash(&payment_preimage.0[..]).into_inner()), &payment_preimage, broadcaster, &bounded_fee_estimator, logger)
                                },
                                ChannelMonitorUpdateStep::CommitmentSecret { idx, secret } => {
                                        log_trace!(logger, "Updating ChannelMonitor with commitment secret");
                                        if let Err(e) = self.provide_secret(*idx, *secret) {
                                                log_error!(logger, "Providing latest counterparty commitment secret failed/was refused:");
                                                log_error!(logger, "    {}", e);
                                                ret = Err(());
                                        }
                                },
                                ChannelMonitorUpdateStep::ChannelForceClosed { should_broadcast } => {
                                        log_trace!(logger, "Updating ChannelMonitor: channel force closed, should broadcast: {}", should_broadcast);
                                        self.lockdown_from_offchain = true;
                                        if *should_broadcast {
                                                self.broadcast_latest_holder_commitment_txn(broadcaster, logger);
                                        } else if !self.holder_tx_signed {
                                                log_error!(logger, "You have a toxic holder commitment transaction avaible in channel monitor, read comment in ChannelMonitor::get_latest_holder_commitment_txn to be informed of manual action to take");
                                        } else {
                                                // If we generated a MonitorEvent::CommitmentTxConfirmed, the ChannelManager
                                                // will still give us a ChannelForceClosed event with !should_broadcast, but we
                                                // shouldn't print the scary warning above.
                                                log_info!(logger, "Channel off-chain state closed after we broadcasted our latest commitment transaction.");
                                        }
                                },
                                ChannelMonitorUpdateStep::ShutdownScript { scriptpubkey } => {
                                        log_trace!(logger, "Updating ChannelMonitor with shutdown script");
                                        if let Some(shutdown_script) = self.shutdown_script.replace(scriptpubkey.clone()) {
                                                panic!("Attempted to replace shutdown script {} with {}", shutdown_script, scriptpubkey);
                                        }
                                },
                        }
                }
                self.latest_update_id = updates.update_id;

                if ret.is_ok() && self.funding_spend_seen {
                        log_error!(logger, "Refusing Channel Monitor Update as counterparty attempted to update commitment after funding was spent");
                        Err(())
                } else { ret }
        }

        pub fn get_latest_update_id(&self) -> u64 {
                self.latest_update_id
        }

        pub fn get_funding_txo(&self) -> &(OutPoint, Script) {
                &self.funding_info
        }

        pub fn get_outputs_to_watch(&self) -> &HashMap<Txid, Vec<(u32, Script)>> {
                // If we've detected a counterparty commitment tx on chain, we must include it in the set
                // of outputs to watch for spends of, otherwise we're likely to lose user funds. Because
                // its trivial to do, double-check that here.
                for (txid, _) in self.counterparty_commitment_txn_on_chain.iter() {
                        self.outputs_to_watch.get(txid).expect("Counterparty commitment txn which have been broadcast should have outputs registered");
                }
                &self.outputs_to_watch
        }

        pub fn get_and_clear_pending_monitor_events(&mut self) -> Vec<MonitorEvent> {
                let mut ret = Vec::new();
                mem::swap(&mut ret, &mut self.pending_monitor_events);
                ret
        }

        pub fn get_and_clear_pending_events(&mut self) -> Vec<Event> {
                let mut ret = Vec::new();
                mem::swap(&mut ret, &mut self.pending_events);
                ret
        }

        /// Can only fail if idx is < get_min_seen_secret
        fn get_secret(&self, idx: u64) -> Option<[u8; 32]> {
                self.commitment_secrets.get_secret(idx)
        }

        pub(crate) fn get_min_seen_secret(&self) -> u64 {
                self.commitment_secrets.get_min_seen_secret()
        }

        pub(crate) fn get_cur_counterparty_commitment_number(&self) -> u64 {
                self.current_counterparty_commitment_number
        }

        pub(crate) fn get_cur_holder_commitment_number(&self) -> u64 {
                self.current_holder_commitment_number
        }

        /// Attempts to claim a counterparty commitment transaction's outputs using the revocation key and
        /// data in counterparty_claimable_outpoints. Will directly claim any HTLC outputs which expire at a
        /// height > height + CLTV_SHARED_CLAIM_BUFFER. In any case, will install monitoring for
        /// HTLC-Success/HTLC-Timeout transactions.
        /// Return updates for HTLC pending in the channel and failed automatically by the broadcast of
        /// revoked counterparty commitment tx
        fn check_spend_counterparty_transaction<L: Deref>(&mut self, tx: &Transaction, height: u32, logger: &L) -> (Vec<PackageTemplate>, TransactionOutputs) where L::Target: Logger {
                // Most secp and related errors trying to create keys means we have no hope of constructing
                // a spend transaction...so we return no transactions to broadcast
                let mut claimable_outpoints = Vec::new();
                let mut watch_outputs = Vec::new();

                let commitment_txid = tx.txid(); //TODO: This is gonna be a performance bottleneck for watchtowers!
                let per_commitment_option = self.counterparty_claimable_outpoints.get(&commitment_txid);

                macro_rules! ignore_error {
                        ( $thing : expr ) => {
                                match $thing {
                                        Ok(a) => a,
                                        Err(_) => return (claimable_outpoints, (commitment_txid, watch_outputs))
                                }
                        };
                }

                let commitment_number = 0xffffffffffff - ((((tx.input[0].sequence as u64 & 0xffffff) << 3*8) | (tx.lock_time as u64 & 0xffffff)) ^ self.commitment_transaction_number_obscure_factor);
                if commitment_number >= self.get_min_seen_secret() {
                        let secret = self.get_secret(commitment_number).unwrap();
                        let per_commitment_key = ignore_error!(SecretKey::from_slice(&secret));
                        let per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &per_commitment_key);
                        let revocation_pubkey = ignore_error!(chan_utils::derive_public_revocation_key(&self.secp_ctx, &per_commitment_point, &self.holder_revocation_basepoint));
                        let delayed_key = ignore_error!(chan_utils::derive_public_key(&self.secp_ctx, &PublicKey::from_secret_key(&self.secp_ctx, &per_commitment_key), &self.counterparty_commitment_params.counterparty_delayed_payment_base_key));

                        let revokeable_redeemscript = chan_utils::get_revokeable_redeemscript(&revocation_pubkey, self.counterparty_commitment_params.on_counterparty_tx_csv, &delayed_key);
                        let revokeable_p2wsh = revokeable_redeemscript.to_v0_p2wsh();

                        // First, process non-htlc outputs (to_holder & to_counterparty)
                        for (idx, outp) in tx.output.iter().enumerate() {
                                if outp.script_pubkey == revokeable_p2wsh {
                                        let revk_outp = RevokedOutput::build(per_commitment_point, self.counterparty_commitment_params.counterparty_delayed_payment_base_key, self.counterparty_commitment_params.counterparty_htlc_base_key, per_commitment_key, outp.value, self.counterparty_commitment_params.on_counterparty_tx_csv);
                                        let justice_package = PackageTemplate::build_package(commitment_txid, idx as u32, PackageSolvingData::RevokedOutput(revk_outp), height + self.counterparty_commitment_params.on_counterparty_tx_csv as u32, true, height);
                                        claimable_outpoints.push(justice_package);
                                }
                        }

                        // Then, try to find revoked htlc outputs
                        if let Some(ref per_commitment_data) = per_commitment_option {
                                for (_, &(ref htlc, _)) in per_commitment_data.iter().enumerate() {
                                        if let Some(transaction_output_index) = htlc.transaction_output_index {
                                                if transaction_output_index as usize >= tx.output.len() ||
                                                                tx.output[transaction_output_index as usize].value != htlc.amount_msat / 1000 {
                                                        return (claimable_outpoints, (commitment_txid, watch_outputs)); // Corrupted per_commitment_data, fuck this user
                                                }
                                                let revk_htlc_outp = RevokedHTLCOutput::build(per_commitment_point, self.counterparty_commitment_params.counterparty_delayed_payment_base_key, self.counterparty_commitment_params.counterparty_htlc_base_key, per_commitment_key, htlc.amount_msat / 1000, htlc.clone(), self.onchain_tx_handler.channel_transaction_parameters.opt_anchors.is_some());
                                                let justice_package = PackageTemplate::build_package(commitment_txid, transaction_output_index, PackageSolvingData::RevokedHTLCOutput(revk_htlc_outp), htlc.cltv_expiry, true, height);
                                                claimable_outpoints.push(justice_package);
                                        }
                                }
                        }

                        // Last, track onchain revoked commitment transaction and fail backward outgoing HTLCs as payment path is broken
                        if !claimable_outpoints.is_empty() || per_commitment_option.is_some() { // ie we're confident this is actually ours
                                // We're definitely a counterparty commitment transaction!
                                log_error!(logger, "Got broadcast of revoked counterparty commitment transaction, going to generate general spend tx with {} inputs", claimable_outpoints.len());
                                for (idx, outp) in tx.output.iter().enumerate() {
                                        watch_outputs.push((idx as u32, outp.clone()));
                                }
                                self.counterparty_commitment_txn_on_chain.insert(commitment_txid, commitment_number);

                                if let Some(per_commitment_data) = per_commitment_option {
                                        fail_unbroadcast_htlcs!(self, "revoked_counterparty", commitment_txid, height,
                                                per_commitment_data.iter().map(|(htlc, htlc_source)|
                                                        (htlc, htlc_source.as_ref().map(|htlc_source| htlc_source.as_ref()))
                                                ), logger);
                                } else {
                                        debug_assert!(false, "We should have per-commitment option for any recognized old commitment txn");
                                        fail_unbroadcast_htlcs!(self, "revoked counterparty", commitment_txid, height,
                                                [].iter().map(|reference| *reference), logger);
                                }
                        }
                } else if let Some(per_commitment_data) = per_commitment_option {
                        // While this isn't useful yet, there is a potential race where if a counterparty
                        // revokes a state at the same time as the commitment transaction for that state is
                        // confirmed, and the watchtower receives the block before the user, the user could
                        // upload a new ChannelMonitor with the revocation secret but the watchtower has
                        // already processed the block, resulting in the counterparty_commitment_txn_on_chain entry
                        // not being generated by the above conditional. Thus, to be safe, we go ahead and
                        // insert it here.
                        for (idx, outp) in tx.output.iter().enumerate() {
                                watch_outputs.push((idx as u32, outp.clone()));
                        }
                        self.counterparty_commitment_txn_on_chain.insert(commitment_txid, commitment_number);

                        log_info!(logger, "Got broadcast of non-revoked counterparty commitment transaction {}", commitment_txid);
                        fail_unbroadcast_htlcs!(self, "counterparty", commitment_txid, height,
                                per_commitment_data.iter().map(|(htlc, htlc_source)|
                                        (htlc, htlc_source.as_ref().map(|htlc_source| htlc_source.as_ref()))
                                ), logger);

                        let htlc_claim_reqs = self.get_counterparty_htlc_output_claim_reqs(commitment_number, commitment_txid, Some(tx));
                        for req in htlc_claim_reqs {
                                claimable_outpoints.push(req);
                        }

                }
                (claimable_outpoints, (commitment_txid, watch_outputs))
        }

        fn get_counterparty_htlc_output_claim_reqs(&self, commitment_number: u64, commitment_txid: Txid, tx: Option<&Transaction>) -> Vec<PackageTemplate> {
                let mut claimable_outpoints = Vec::new();
                if let Some(htlc_outputs) = self.counterparty_claimable_outpoints.get(&commitment_txid) {
                        if let Some(per_commitment_points) = self.their_cur_per_commitment_points {
                                let per_commitment_point_option =
                                        // If the counterparty commitment tx is the latest valid state, use their latest
                                        // per-commitment point
                                        if per_commitment_points.0 == commitment_number { Some(&per_commitment_points.1) }
                                        else if let Some(point) = per_commitment_points.2.as_ref() {
                                                // If counterparty commitment tx is the state previous to the latest valid state, use
                                                // their previous per-commitment point (non-atomicity of revocation means it's valid for
                                                // them to temporarily have two valid commitment txns from our viewpoint)
                                                if per_commitment_points.0 == commitment_number + 1 { Some(point) } else { None }
                                        } else { None };
                                if let Some(per_commitment_point) = per_commitment_point_option {
                                        for (_, &(ref htlc, _)) in htlc_outputs.iter().enumerate() {
                                                if let Some(transaction_output_index) = htlc.transaction_output_index {
                                                        if let Some(transaction) = tx {
                                                                if transaction_output_index as usize >= transaction.output.len() ||
                                                                        transaction.output[transaction_output_index as usize].value != htlc.amount_msat / 1000 {
                                                                                return claimable_outpoints; // Corrupted per_commitment_data, fuck this user
                                                                        }
                                                        }
                                                        let preimage = if htlc.offered { if let Some(p) = self.payment_preimages.get(&htlc.payment_hash) { Some(*p) } else { None } } else { None };
                                                        if preimage.is_some() || !htlc.offered {
                                                                let counterparty_htlc_outp = if htlc.offered {
                                                                        PackageSolvingData::CounterpartyOfferedHTLCOutput(
                                                                                CounterpartyOfferedHTLCOutput::build(*per_commitment_point,
                                                                                        self.counterparty_commitment_params.counterparty_delayed_payment_base_key,
                                                                                        self.counterparty_commitment_params.counterparty_htlc_base_key,
                                                                                        preimage.unwrap(), htlc.clone()))
                                                                } else {
                                                                        PackageSolvingData::CounterpartyReceivedHTLCOutput(
                                                                                CounterpartyReceivedHTLCOutput::build(*per_commitment_point,
                                                                                        self.counterparty_commitment_params.counterparty_delayed_payment_base_key,
                                                                                        self.counterparty_commitment_params.counterparty_htlc_base_key,
                                                                                        htlc.clone()))
                                                                };
                                                                let aggregation = if !htlc.offered { false } else { true };
                                                                let counterparty_package = PackageTemplate::build_package(commitment_txid, transaction_output_index, counterparty_htlc_outp, htlc.cltv_expiry,aggregation, 0);
                                                                claimable_outpoints.push(counterparty_package);
                                                        }
                                                }
                                        }
                                }
                        }
                }
                claimable_outpoints
        }

        /// Attempts to claim a counterparty HTLC-Success/HTLC-Timeout's outputs using the revocation key
        fn check_spend_counterparty_htlc<L: Deref>(&mut self, tx: &Transaction, commitment_number: u64, height: u32, logger: &L) -> (Vec<PackageTemplate>, Option<TransactionOutputs>) where L::Target: Logger {
                let htlc_txid = tx.txid();
                if tx.input.len() != 1 || tx.output.len() != 1 || tx.input[0].witness.len() != 5 {
                        return (Vec::new(), None)
                }

                macro_rules! ignore_error {
                        ( $thing : expr ) => {
                                match $thing {
                                        Ok(a) => a,
                                        Err(_) => return (Vec::new(), None)
                                }
                        };
                }

                let secret = if let Some(secret) = self.get_secret(commitment_number) { secret } else { return (Vec::new(), None); };
                let per_commitment_key = ignore_error!(SecretKey::from_slice(&secret));
                let per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &per_commitment_key);

                log_error!(logger, "Got broadcast of revoked counterparty HTLC transaction, spending {}:{}", htlc_txid, 0);
                let revk_outp = RevokedOutput::build(per_commitment_point, self.counterparty_commitment_params.counterparty_delayed_payment_base_key, self.counterparty_commitment_params.counterparty_htlc_base_key, per_commitment_key, tx.output[0].value, self.counterparty_commitment_params.on_counterparty_tx_csv);
                let justice_package = PackageTemplate::build_package(htlc_txid, 0, PackageSolvingData::RevokedOutput(revk_outp), height + self.counterparty_commitment_params.on_counterparty_tx_csv as u32, true, height);
                let claimable_outpoints = vec!(justice_package);
                let outputs = vec![(0, tx.output[0].clone())];
                (claimable_outpoints, Some((htlc_txid, outputs)))
        }

        // Returns (1) `PackageTemplate`s that can be given to the OnChainTxHandler, so that the handler can
        // broadcast transactions claiming holder HTLC commitment outputs and (2) a holder revokable
        // script so we can detect whether a holder transaction has been seen on-chain.
        fn get_broadcasted_holder_claims(&self, holder_tx: &HolderSignedTx, conf_height: u32) -> (Vec<PackageTemplate>, Option<(Script, PublicKey, PublicKey)>) {
                let mut claim_requests = Vec::with_capacity(holder_tx.htlc_outputs.len());

                let redeemscript = chan_utils::get_revokeable_redeemscript(&holder_tx.revocation_key, self.on_holder_tx_csv, &holder_tx.delayed_payment_key);
                let broadcasted_holder_revokable_script = Some((redeemscript.to_v0_p2wsh(), holder_tx.per_commitment_point.clone(), holder_tx.revocation_key.clone()));

                for &(ref htlc, _, _) in holder_tx.htlc_outputs.iter() {
                        if let Some(transaction_output_index) = htlc.transaction_output_index {
                                let htlc_output = if htlc.offered {
                                                HolderHTLCOutput::build_offered(htlc.amount_msat, htlc.cltv_expiry)
                                        } else {
                                                let payment_preimage = if let Some(preimage) = self.payment_preimages.get(&htlc.payment_hash) {
                                                        preimage.clone()
                                                } else {
                                                        // We can't build an HTLC-Success transaction without the preimage
                                                        continue;
                                                };
                                                HolderHTLCOutput::build_accepted(payment_preimage, htlc.amount_msat)
                                        };
                                let htlc_package = PackageTemplate::build_package(holder_tx.txid, transaction_output_index, PackageSolvingData::HolderHTLCOutput(htlc_output), htlc.cltv_expiry, false, conf_height);
                                claim_requests.push(htlc_package);
                        }
                }

                (claim_requests, broadcasted_holder_revokable_script)
        }

        // Returns holder HTLC outputs to watch and react to in case of spending.
        fn get_broadcasted_holder_watch_outputs(&self, holder_tx: &HolderSignedTx, commitment_tx: &Transaction) -> Vec<(u32, TxOut)> {
                let mut watch_outputs = Vec::with_capacity(holder_tx.htlc_outputs.len());
                for &(ref htlc, _, _) in holder_tx.htlc_outputs.iter() {
                        if let Some(transaction_output_index) = htlc.transaction_output_index {
                                watch_outputs.push((transaction_output_index, commitment_tx.output[transaction_output_index as usize].clone()));
                        }
                }
                watch_outputs
        }

        /// Attempts to claim any claimable HTLCs in a commitment transaction which was not (yet)
        /// revoked using data in holder_claimable_outpoints.
        /// Should not be used if check_spend_revoked_transaction succeeds.
        /// Returns None unless the transaction is definitely one of our commitment transactions.
        fn check_spend_holder_transaction<L: Deref>(&mut self, tx: &Transaction, height: u32, logger: &L) -> Option<(Vec<PackageTemplate>, TransactionOutputs)> where L::Target: Logger {
                let commitment_txid = tx.txid();
                let mut claim_requests = Vec::new();
                let mut watch_outputs = Vec::new();

                macro_rules! append_onchain_update {
                        ($updates: expr, $to_watch: expr) => {
                                claim_requests = $updates.0;
                                self.broadcasted_holder_revokable_script = $updates.1;
                                watch_outputs.append(&mut $to_watch);
                        }
                }

                // HTLCs set may differ between last and previous holder commitment txn, in case of one them hitting chain, ensure we cancel all HTLCs backward
                let mut is_holder_tx = false;

                if self.current_holder_commitment_tx.txid == commitment_txid {
                        is_holder_tx = true;
                        log_info!(logger, "Got broadcast of latest holder commitment tx {}, searching for available HTLCs to claim", commitment_txid);
                        let res = self.get_broadcasted_holder_claims(&self.current_holder_commitment_tx, height);
                        let mut to_watch = self.get_broadcasted_holder_watch_outputs(&self.current_holder_commitment_tx, tx);
                        append_onchain_update!(res, to_watch);
                        fail_unbroadcast_htlcs!(self, "latest holder", commitment_txid, height,
                                self.current_holder_commitment_tx.htlc_outputs.iter()
                                .map(|(htlc, _, htlc_source)| (htlc, htlc_source.as_ref())), logger);
                } else if let &Some(ref holder_tx) = &self.prev_holder_signed_commitment_tx {
                        if holder_tx.txid == commitment_txid {
                                is_holder_tx = true;
                                log_info!(logger, "Got broadcast of previous holder commitment tx {}, searching for available HTLCs to claim", commitment_txid);
                                let res = self.get_broadcasted_holder_claims(holder_tx, height);
                                let mut to_watch = self.get_broadcasted_holder_watch_outputs(holder_tx, tx);
                                append_onchain_update!(res, to_watch);
                                fail_unbroadcast_htlcs!(self, "previous holder", commitment_txid, height,
                                        holder_tx.htlc_outputs.iter().map(|(htlc, _, htlc_source)| (htlc, htlc_source.as_ref())),
                                        logger);
                        }
                }

                if is_holder_tx {
                        Some((claim_requests, (commitment_txid, watch_outputs)))
                } else {
                        None
                }
        }

        pub fn get_latest_holder_commitment_txn<L: Deref>(&mut self, logger: &L) -> Vec<Transaction> where L::Target: Logger {
                log_debug!(logger, "Getting signed latest holder commitment transaction!");
                self.holder_tx_signed = true;
                let commitment_tx = self.onchain_tx_handler.get_fully_signed_holder_tx(&self.funding_redeemscript);
                let txid = commitment_tx.txid();
                let mut holder_transactions = vec![commitment_tx];
                for htlc in self.current_holder_commitment_tx.htlc_outputs.iter() {
                        if let Some(vout) = htlc.0.transaction_output_index {
                                let preimage = if !htlc.0.offered {
                                        if let Some(preimage) = self.payment_preimages.get(&htlc.0.payment_hash) { Some(preimage.clone()) } else {
                                                // We can't build an HTLC-Success transaction without the preimage
                                                continue;
                                        }
                                } else if htlc.0.cltv_expiry > self.best_block.height() + 1 {
                                        // Don't broadcast HTLC-Timeout transactions immediately as they don't meet the
                                        // current locktime requirements on-chain. We will broadcast them in
                                        // `block_confirmed` when `should_broadcast_holder_commitment_txn` returns true.
                                        // Note that we add + 1 as transactions are broadcastable when they can be
                                        // confirmed in the next block.
                                        continue;
                                } else { None };
                                if let Some(htlc_tx) = self.onchain_tx_handler.get_fully_signed_htlc_tx(
                                        &::bitcoin::OutPoint { txid, vout }, &preimage) {
                                        holder_transactions.push(htlc_tx);
                                }
                        }
                }
                // We throw away the generated waiting_first_conf data as we aren't (yet) confirmed and we don't actually know what the caller wants to do.
                // The data will be re-generated and tracked in check_spend_holder_transaction if we get a confirmation.
                holder_transactions
        }

        #[cfg(any(test,feature = "unsafe_revoked_tx_signing"))]
        /// Note that this includes possibly-locktimed-in-the-future transactions!
        fn unsafe_get_latest_holder_commitment_txn<L: Deref>(&mut self, logger: &L) -> Vec<Transaction> where L::Target: Logger {
                log_debug!(logger, "Getting signed copy of latest holder commitment transaction!");
                let commitment_tx = self.onchain_tx_handler.get_fully_signed_copy_holder_tx(&self.funding_redeemscript);
                let txid = commitment_tx.txid();
                let mut holder_transactions = vec![commitment_tx];
                for htlc in self.current_holder_commitment_tx.htlc_outputs.iter() {
                        if let Some(vout) = htlc.0.transaction_output_index {
                                let preimage = if !htlc.0.offered {
                                        if let Some(preimage) = self.payment_preimages.get(&htlc.0.payment_hash) { Some(preimage.clone()) } else {
                                                // We can't build an HTLC-Success transaction without the preimage
                                                continue;
                                        }
                                } else { None };
                                if let Some(htlc_tx) = self.onchain_tx_handler.unsafe_get_fully_signed_htlc_tx(
                                        &::bitcoin::OutPoint { txid, vout }, &preimage) {
                                        holder_transactions.push(htlc_tx);
                                }
                        }
                }
                holder_transactions
        }

        pub fn block_connected<B: Deref, F: Deref, L: Deref>(&mut self, header: &BlockHeader, txdata: &TransactionData, height: u32, broadcaster: B, fee_estimator: F, logger: L) -> Vec<TransactionOutputs>
                where B::Target: BroadcasterInterface,
                      F::Target: FeeEstimator,
                                        L::Target: Logger,
        {
                let block_hash = header.block_hash();
                self.best_block = BestBlock::new(block_hash, height);

                let bounded_fee_estimator = LowerBoundedFeeEstimator::new(fee_estimator);
                self.transactions_confirmed(header, txdata, height, broadcaster, &bounded_fee_estimator, logger)
        }

        fn best_block_updated<B: Deref, F: Deref, L: Deref>(
                &mut self,
                header: &BlockHeader,
                height: u32,
                broadcaster: B,
                fee_estimator: &LowerBoundedFeeEstimator<F>,
                logger: L,
        ) -> Vec<TransactionOutputs>
        where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                let block_hash = header.block_hash();

                if height > self.best_block.height() {
                        self.best_block = BestBlock::new(block_hash, height);
                        self.block_confirmed(height, vec![], vec![], vec![], &broadcaster, &fee_estimator, &logger)
                } else if block_hash != self.best_block.block_hash() {
                        self.best_block = BestBlock::new(block_hash, height);
                        self.onchain_events_awaiting_threshold_conf.retain(|ref entry| entry.height <= height);
                        self.onchain_tx_handler.block_disconnected(height + 1, broadcaster, fee_estimator, logger);
                        Vec::new()
                } else { Vec::new() }
        }

        fn transactions_confirmed<B: Deref, F: Deref, L: Deref>(
                &mut self,
                header: &BlockHeader,
                txdata: &TransactionData,
                height: u32,
                broadcaster: B,
                fee_estimator: &LowerBoundedFeeEstimator<F>,
                logger: L,
        ) -> Vec<TransactionOutputs>
        where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                let txn_matched = self.filter_block(txdata);
                for tx in &txn_matched {
                        let mut output_val = 0;
                        for out in tx.output.iter() {
                                if out.value > 21_000_000_0000_0000 { panic!("Value-overflowing transaction provided to block connected"); }
                                output_val += out.value;
                                if output_val > 21_000_000_0000_0000 { panic!("Value-overflowing transaction provided to block connected"); }
                        }
                }

                let block_hash = header.block_hash();

                let mut watch_outputs = Vec::new();
                let mut claimable_outpoints = Vec::new();
                for tx in &txn_matched {
                        if tx.input.len() == 1 {
                                // Assuming our keys were not leaked (in which case we're screwed no matter what),
                                // commitment transactions and HTLC transactions will all only ever have one input,
                                // which is an easy way to filter out any potential non-matching txn for lazy
                                // filters.
                                let prevout = &tx.input[0].previous_output;
                                if prevout.txid == self.funding_info.0.txid && prevout.vout == self.funding_info.0.index as u32 {
                                        let mut balance_spendable_csv = None;
                                        log_info!(logger, "Channel {} closed by funding output spend in txid {}.",
                                                log_bytes!(self.funding_info.0.to_channel_id()), tx.txid());
                                        self.funding_spend_seen = true;
                                        if (tx.input[0].sequence >> 8*3) as u8 == 0x80 && (tx.lock_time >> 8*3) as u8 == 0x20 {
                                                let (mut new_outpoints, new_outputs) = self.check_spend_counterparty_transaction(&tx, height, &logger);
                                                if !new_outputs.1.is_empty() {
                                                        watch_outputs.push(new_outputs);
                                                }
                                                claimable_outpoints.append(&mut new_outpoints);
                                                if new_outpoints.is_empty() {
                                                        if let Some((mut new_outpoints, new_outputs)) = self.check_spend_holder_transaction(&tx, height, &logger) {
                                                                if !new_outputs.1.is_empty() {
                                                                        watch_outputs.push(new_outputs);
                                                                }
                                                                claimable_outpoints.append(&mut new_outpoints);
                                                                balance_spendable_csv = Some(self.on_holder_tx_csv);
                                                        }
                                                }
                                        }
                                        let txid = tx.txid();
                                        self.onchain_events_awaiting_threshold_conf.push(OnchainEventEntry {
                                                txid,
                                                height: height,
                                                event: OnchainEvent::FundingSpendConfirmation {
                                                        on_local_output_csv: balance_spendable_csv,
                                                },
                                        });
                                } else {
                                        if let Some(&commitment_number) = self.counterparty_commitment_txn_on_chain.get(&prevout.txid) {
                                                let (mut new_outpoints, new_outputs_option) = self.check_spend_counterparty_htlc(&tx, commitment_number, height, &logger);
                                                claimable_outpoints.append(&mut new_outpoints);
                                                if let Some(new_outputs) = new_outputs_option {
                                                        watch_outputs.push(new_outputs);
                                                }
                                        }
                                }
                        }
                        // While all commitment/HTLC-Success/HTLC-Timeout transactions have one input, HTLCs
                        // can also be resolved in a few other ways which can have more than one output. Thus,
                        // we call is_resolving_htlc_output here outside of the tx.input.len() == 1 check.
                        self.is_resolving_htlc_output(&tx, height, &logger);

                        self.is_paying_spendable_output(&tx, height, &logger);
                }

                if height > self.best_block.height() {
                        self.best_block = BestBlock::new(block_hash, height);
                }

                self.block_confirmed(height, txn_matched, watch_outputs, claimable_outpoints, &broadcaster, &fee_estimator, &logger)
        }

        /// Update state for new block(s)/transaction(s) confirmed. Note that the caller must update
        /// `self.best_block` before calling if a new best blockchain tip is available. More
        /// concretely, `self.best_block` must never be at a lower height than `conf_height`, avoiding
        /// complexity especially in `OnchainTx::update_claims_view`.
        ///
        /// `conf_height` should be set to the height at which any new transaction(s)/block(s) were
        /// confirmed at, even if it is not the current best height.
        fn block_confirmed<B: Deref, F: Deref, L: Deref>(
                &mut self,
                conf_height: u32,
                txn_matched: Vec<&Transaction>,
                mut watch_outputs: Vec<TransactionOutputs>,
                mut claimable_outpoints: Vec<PackageTemplate>,
                broadcaster: &B,
                fee_estimator: &LowerBoundedFeeEstimator<F>,
                logger: &L,
        ) -> Vec<TransactionOutputs>
        where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                log_trace!(logger, "Processing {} matched transactions for block at height {}.", txn_matched.len(), conf_height);
                debug_assert!(self.best_block.height() >= conf_height);

                let should_broadcast = self.should_broadcast_holder_commitment_txn(logger);
                if should_broadcast {
                        let funding_outp = HolderFundingOutput::build(self.funding_redeemscript.clone());
                        let commitment_package = PackageTemplate::build_package(self.funding_info.0.txid.clone(), self.funding_info.0.index as u32, PackageSolvingData::HolderFundingOutput(funding_outp), self.best_block.height(), false, self.best_block.height());
                        claimable_outpoints.push(commitment_package);
                        self.pending_monitor_events.push(MonitorEvent::CommitmentTxConfirmed(self.funding_info.0));
                        let commitment_tx = self.onchain_tx_handler.get_fully_signed_holder_tx(&self.funding_redeemscript);
                        self.holder_tx_signed = true;
                        // Because we're broadcasting a commitment transaction, we should construct the package
                        // assuming it gets confirmed in the next block. Sadly, we have code which considers
                        // "not yet confirmed" things as discardable, so we cannot do that here.
                        let (mut new_outpoints, _) = self.get_broadcasted_holder_claims(&self.current_holder_commitment_tx, self.best_block.height());
                        let new_outputs = self.get_broadcasted_holder_watch_outputs(&self.current_holder_commitment_tx, &commitment_tx);
                        if !new_outputs.is_empty() {
                                watch_outputs.push((self.current_holder_commitment_tx.txid.clone(), new_outputs));
                        }
                        claimable_outpoints.append(&mut new_outpoints);
                }

                // Find which on-chain events have reached their confirmation threshold.
                let onchain_events_awaiting_threshold_conf =
                        self.onchain_events_awaiting_threshold_conf.drain(..).collect::<Vec<_>>();
                let mut onchain_events_reaching_threshold_conf = Vec::new();
                for entry in onchain_events_awaiting_threshold_conf {
                        if entry.has_reached_confirmation_threshold(&self.best_block) {
                                onchain_events_reaching_threshold_conf.push(entry);
                        } else {
                                self.onchain_events_awaiting_threshold_conf.push(entry);
                        }
                }

                // Used to check for duplicate HTLC resolutions.
                #[cfg(debug_assertions)]
                let unmatured_htlcs: Vec<_> = self.onchain_events_awaiting_threshold_conf
                        .iter()
                        .filter_map(|entry| match &entry.event {
                                OnchainEvent::HTLCUpdate { source, .. } => Some(source),
                                _ => None,
                        })
                        .collect();
                #[cfg(debug_assertions)]
                let mut matured_htlcs = Vec::new();

                // Produce actionable events from on-chain events having reached their threshold.
                for entry in onchain_events_reaching_threshold_conf.drain(..) {
                        match entry.event {
                                OnchainEvent::HTLCUpdate { ref source, payment_hash, htlc_value_satoshis, commitment_tx_output_idx } => {
                                        // Check for duplicate HTLC resolutions.
                                        #[cfg(debug_assertions)]
                                        {
                                                debug_assert!(
                                                        unmatured_htlcs.iter().find(|&htlc| htlc == &source).is_none(),
                                                        "An unmature HTLC transaction conflicts with a maturing one; failed to \
                                                         call either transaction_unconfirmed for the conflicting transaction \
                                                         or block_disconnected for a block containing it.");
                                                debug_assert!(
                                                        matured_htlcs.iter().find(|&htlc| htlc == source).is_none(),
                                                        "A matured HTLC transaction conflicts with a maturing one; failed to \
                                                         call either transaction_unconfirmed for the conflicting transaction \
                                                         or block_disconnected for a block containing it.");
                                                matured_htlcs.push(source.clone());
                                        }

                                        log_debug!(logger, "HTLC {} failure update in {} has got enough confirmations to be passed upstream",
                                                log_bytes!(payment_hash.0), entry.txid);
                                        self.pending_monitor_events.push(MonitorEvent::HTLCEvent(HTLCUpdate {
                                                payment_hash,
                                                payment_preimage: None,
                                                source: source.clone(),
                                                htlc_value_satoshis,
                                        }));
                                        if let Some(idx) = commitment_tx_output_idx {
                                                self.htlcs_resolved_on_chain.push(IrrevocablyResolvedHTLC { commitment_tx_output_idx: idx, payment_preimage: None });
                                        }
                                },
                                OnchainEvent::MaturingOutput { descriptor } => {
                                        log_debug!(logger, "Descriptor {} has got enough confirmations to be passed upstream", log_spendable!(descriptor));
                                        self.pending_events.push(Event::SpendableOutputs {
                                                outputs: vec![descriptor]
                                        });
                                },
                                OnchainEvent::HTLCSpendConfirmation { commitment_tx_output_idx, preimage, .. } => {
                                        self.htlcs_resolved_on_chain.push(IrrevocablyResolvedHTLC { commitment_tx_output_idx, payment_preimage: preimage });
                                },
                                OnchainEvent::FundingSpendConfirmation { .. } => {
                                        self.funding_spend_confirmed = Some(entry.txid);
                                },
                        }
                }

                self.onchain_tx_handler.update_claims_view(&txn_matched, claimable_outpoints, conf_height, self.best_block.height(), broadcaster, fee_estimator, logger);

                // Determine new outputs to watch by comparing against previously known outputs to watch,
                // updating the latter in the process.
                watch_outputs.retain(|&(ref txid, ref txouts)| {
                        let idx_and_scripts = txouts.iter().map(|o| (o.0, o.1.script_pubkey.clone())).collect();
                        self.outputs_to_watch.insert(txid.clone(), idx_and_scripts).is_none()
                });
                #[cfg(test)]
                {
                        // If we see a transaction for which we registered outputs previously,
                        // make sure the registered scriptpubkey at the expected index match
                        // the actual transaction output one. We failed this case before #653.
                        for tx in &txn_matched {
                                if let Some(outputs) = self.get_outputs_to_watch().get(&tx.txid()) {
                                        for idx_and_script in outputs.iter() {
                                                assert!((idx_and_script.0 as usize) < tx.output.len());
                                                assert_eq!(tx.output[idx_and_script.0 as usize].script_pubkey, idx_and_script.1);
                                        }
                                }
                        }
                }
                watch_outputs
        }

        pub fn block_disconnected<B: Deref, F: Deref, L: Deref>(&mut self, header: &BlockHeader, height: u32, broadcaster: B, fee_estimator: F, logger: L)
                where B::Target: BroadcasterInterface,
                      F::Target: FeeEstimator,
                      L::Target: Logger,
        {
                log_trace!(logger, "Block {} at height {} disconnected", header.block_hash(), height);

                //We may discard:
                //- htlc update there as failure-trigger tx (revoked commitment tx, non-revoked commitment tx, HTLC-timeout tx) has been disconnected
                //- maturing spendable output has transaction paying us has been disconnected
                self.onchain_events_awaiting_threshold_conf.retain(|ref entry| entry.height < height);

                let bounded_fee_estimator = LowerBoundedFeeEstimator::new(fee_estimator);
                self.onchain_tx_handler.block_disconnected(height, broadcaster, &bounded_fee_estimator, logger);

                self.best_block = BestBlock::new(header.prev_blockhash, height - 1);
        }

        fn transaction_unconfirmed<B: Deref, F: Deref, L: Deref>(
                &mut self,
                txid: &Txid,
                broadcaster: B,
                fee_estimator: &LowerBoundedFeeEstimator<F>,
                logger: L,
        ) where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                self.onchain_events_awaiting_threshold_conf.retain(|ref entry| if entry.txid == *txid {
                        log_info!(logger, "Removing onchain event with txid {}", txid);
                        false
                } else { true });
                self.onchain_tx_handler.transaction_unconfirmed(txid, broadcaster, fee_estimator, logger);
        }

        /// Filters a block's `txdata` for transactions spending watched outputs or for any child
        /// transactions thereof.
        fn filter_block<'a>(&self, txdata: &TransactionData<'a>) -> Vec<&'a Transaction> {
                let mut matched_txn = HashSet::new();
                txdata.iter().filter(|&&(_, tx)| {
                        let mut matches = self.spends_watched_output(tx);
                        for input in tx.input.iter() {
                                if matches { break; }
                                if matched_txn.contains(&input.previous_output.txid) {
                                        matches = true;
                                }
                        }
                        if matches {
                                matched_txn.insert(tx.txid());
                        }
                        matches
                }).map(|(_, tx)| *tx).collect()
        }

        /// Checks if a given transaction spends any watched outputs.
        fn spends_watched_output(&self, tx: &Transaction) -> bool {
                for input in tx.input.iter() {
                        if let Some(outputs) = self.get_outputs_to_watch().get(&input.previous_output.txid) {
                                for (idx, _script_pubkey) in outputs.iter() {
                                        if *idx == input.previous_output.vout {
                                                #[cfg(test)]
                                                {
                                                        // If the expected script is a known type, check that the witness
                                                        // appears to be spending the correct type (ie that the match would
                                                        // actually succeed in BIP 158/159-style filters).
                                                        if _script_pubkey.is_v0_p2wsh() {
                                                                if input.witness.last().unwrap().to_vec() == deliberately_bogus_accepted_htlc_witness_program() {
                                                                        // In at least one test we use a deliberately bogus witness
                                                                        // script which hit an old panic. Thus, we check for that here
                                                                        // and avoid the assert if its the expected bogus script.
                                                                        return true;
                                                                }

                                                                assert_eq!(&bitcoin::Address::p2wsh(&Script::from(input.witness.last().unwrap().to_vec()), bitcoin::Network::Bitcoin).script_pubkey(), _script_pubkey);
                                                        } else if _script_pubkey.is_v0_p2wpkh() {
                                                                assert_eq!(&bitcoin::Address::p2wpkh(&bitcoin::PublicKey::from_slice(&input.witness.last().unwrap()).unwrap(), bitcoin::Network::Bitcoin).unwrap().script_pubkey(), _script_pubkey);
                                                        } else { panic!(); }
                                                }
                                                return true;
                                        }
                                }
                        }
                }

                false
        }

        fn should_broadcast_holder_commitment_txn<L: Deref>(&self, logger: &L) -> bool where L::Target: Logger {
                // We need to consider all HTLCs which are:
                //  * in any unrevoked counterparty commitment transaction, as they could broadcast said
                //    transactions and we'd end up in a race, or
                //  * are in our latest holder commitment transaction, as this is the thing we will
                //    broadcast if we go on-chain.
                // Note that we consider HTLCs which were below dust threshold here - while they don't
                // strictly imply that we need to fail the channel, we need to go ahead and fail them back
                // to the source, and if we don't fail the channel we will have to ensure that the next
                // updates that peer sends us are update_fails, failing the channel if not. It's probably
                // easier to just fail the channel as this case should be rare enough anyway.
                let height = self.best_block.height();
                macro_rules! scan_commitment {
                        ($htlcs: expr, $holder_tx: expr) => {
                                for ref htlc in $htlcs {
                                        // For inbound HTLCs which we know the preimage for, we have to ensure we hit the
                                        // chain with enough room to claim the HTLC without our counterparty being able to
                                        // time out the HTLC first.
                                        // For outbound HTLCs which our counterparty hasn't failed/claimed, our primary
                                        // concern is being able to claim the corresponding inbound HTLC (on another
                                        // channel) before it expires. In fact, we don't even really care if our
                                        // counterparty here claims such an outbound HTLC after it expired as long as we
                                        // can still claim the corresponding HTLC. Thus, to avoid needlessly hitting the
                                        // chain when our counterparty is waiting for expiration to off-chain fail an HTLC
                                        // we give ourselves a few blocks of headroom after expiration before going
                                        // on-chain for an expired HTLC.
                                        // Note that, to avoid a potential attack whereby a node delays claiming an HTLC
                                        // from us until we've reached the point where we go on-chain with the
                                        // corresponding inbound HTLC, we must ensure that outbound HTLCs go on chain at
                                        // least CLTV_CLAIM_BUFFER blocks prior to the inbound HTLC.
                                        //  aka outbound_cltv + LATENCY_GRACE_PERIOD_BLOCKS == height - CLTV_CLAIM_BUFFER
                                        //      inbound_cltv == height + CLTV_CLAIM_BUFFER
                                        //      outbound_cltv + LATENCY_GRACE_PERIOD_BLOCKS + CLTV_CLAIM_BUFFER <= inbound_cltv - CLTV_CLAIM_BUFFER
                                        //      LATENCY_GRACE_PERIOD_BLOCKS + 2*CLTV_CLAIM_BUFFER <= inbound_cltv - outbound_cltv
                                        //      CLTV_EXPIRY_DELTA <= inbound_cltv - outbound_cltv (by check in ChannelManager::decode_update_add_htlc_onion)
                                        //      LATENCY_GRACE_PERIOD_BLOCKS + 2*CLTV_CLAIM_BUFFER <= CLTV_EXPIRY_DELTA
                                        //  The final, above, condition is checked for statically in channelmanager
                                        //  with CHECK_CLTV_EXPIRY_SANITY_2.
                                        let htlc_outbound = $holder_tx == htlc.offered;
                                        if ( htlc_outbound && htlc.cltv_expiry + LATENCY_GRACE_PERIOD_BLOCKS <= height) ||
                                           (!htlc_outbound && htlc.cltv_expiry <= height + CLTV_CLAIM_BUFFER && self.payment_preimages.contains_key(&htlc.payment_hash)) {
                                                log_info!(logger, "Force-closing channel due to {} HTLC timeout, HTLC expiry is {}", if htlc_outbound { "outbound" } else { "inbound "}, htlc.cltv_expiry);
                                                return true;
                                        }
                                }
                        }
                }

                scan_commitment!(self.current_holder_commitment_tx.htlc_outputs.iter().map(|&(ref a, _, _)| a), true);

                if let Some(ref txid) = self.current_counterparty_commitment_txid {
                        if let Some(ref htlc_outputs) = self.counterparty_claimable_outpoints.get(txid) {
                                scan_commitment!(htlc_outputs.iter().map(|&(ref a, _)| a), false);
                        }
                }
                if let Some(ref txid) = self.prev_counterparty_commitment_txid {
                        if let Some(ref htlc_outputs) = self.counterparty_claimable_outpoints.get(txid) {
                                scan_commitment!(htlc_outputs.iter().map(|&(ref a, _)| a), false);
                        }
                }

                false
        }

        /// Check if any transaction broadcasted is resolving HTLC output by a success or timeout on a holder
        /// or counterparty commitment tx, if so send back the source, preimage if found and payment_hash of resolved HTLC
        fn is_resolving_htlc_output<L: Deref>(&mut self, tx: &Transaction, height: u32, logger: &L) where L::Target: Logger {
                'outer_loop: for input in &tx.input {
                        let mut payment_data = None;
                        let witness_items = input.witness.len();
                        let htlctype = input.witness.last().map(|w| w.len()).and_then(HTLCType::scriptlen_to_htlctype);
                        let prev_last_witness_len = input.witness.second_to_last().map(|w| w.len()).unwrap_or(0);
                        let revocation_sig_claim = (witness_items == 3 && htlctype == Some(HTLCType::OfferedHTLC) && prev_last_witness_len == 33)
                                || (witness_items == 3 && htlctype == Some(HTLCType::AcceptedHTLC) && prev_last_witness_len == 33);
                        let accepted_preimage_claim = witness_items == 5 && htlctype == Some(HTLCType::AcceptedHTLC)
                                && input.witness.second_to_last().unwrap().len() == 32;
                        #[cfg(not(fuzzing))]
                        let accepted_timeout_claim = witness_items == 3 && htlctype == Some(HTLCType::AcceptedHTLC) && !revocation_sig_claim;
                        let offered_preimage_claim = witness_items == 3 && htlctype == Some(HTLCType::OfferedHTLC) &&
                                !revocation_sig_claim && input.witness.second_to_last().unwrap().len() == 32;

                        #[cfg(not(fuzzing))]
                        let offered_timeout_claim = witness_items == 5 && htlctype == Some(HTLCType::OfferedHTLC);

                        let mut payment_preimage = PaymentPreimage([0; 32]);
                        if accepted_preimage_claim {
                                payment_preimage.0.copy_from_slice(input.witness.second_to_last().unwrap());
                        } else if offered_preimage_claim {
                                payment_preimage.0.copy_from_slice(input.witness.second_to_last().unwrap());
                        }

                        macro_rules! log_claim {
                                ($tx_info: expr, $holder_tx: expr, $htlc: expr, $source_avail: expr) => {
                                        let outbound_htlc = $holder_tx == $htlc.offered;
                                        // HTLCs must either be claimed by a matching script type or through the
                                        // revocation path:
                                        #[cfg(not(fuzzing))] // Note that the fuzzer is not bound by pesky things like "signatures"
                                        debug_assert!(!$htlc.offered || offered_preimage_claim || offered_timeout_claim || revocation_sig_claim);
                                        #[cfg(not(fuzzing))] // Note that the fuzzer is not bound by pesky things like "signatures"
                                        debug_assert!($htlc.offered || accepted_preimage_claim || accepted_timeout_claim || revocation_sig_claim);
                                        // Further, only exactly one of the possible spend paths should have been
                                        // matched by any HTLC spend:
                                        #[cfg(not(fuzzing))] // Note that the fuzzer is not bound by pesky things like "signatures"
                                        debug_assert_eq!(accepted_preimage_claim as u8 + accepted_timeout_claim as u8 +
                                                         offered_preimage_claim as u8 + offered_timeout_claim as u8 +
                                                         revocation_sig_claim as u8, 1);
                                        if ($holder_tx && revocation_sig_claim) ||
                                                        (outbound_htlc && !$source_avail && (accepted_preimage_claim || offered_preimage_claim)) {
                                                log_error!(logger, "Input spending {} ({}:{}) in {} resolves {} HTLC with payment hash {} with {}!",
                                                        $tx_info, input.previous_output.txid, input.previous_output.vout, tx.txid(),
                                                        if outbound_htlc { "outbound" } else { "inbound" }, log_bytes!($htlc.payment_hash.0),
                                                        if revocation_sig_claim { "revocation sig" } else { "preimage claim after we'd passed the HTLC resolution back" });
                                        } else {
                                                log_info!(logger, "Input spending {} ({}:{}) in {} resolves {} HTLC with payment hash {} with {}",
                                                        $tx_info, input.previous_output.txid, input.previous_output.vout, tx.txid(),
                                                        if outbound_htlc { "outbound" } else { "inbound" }, log_bytes!($htlc.payment_hash.0),
                                                        if revocation_sig_claim { "revocation sig" } else if accepted_preimage_claim || offered_preimage_claim { "preimage" } else { "timeout" });
                                        }
                                }
                        }

                        macro_rules! check_htlc_valid_counterparty {
                                ($counterparty_txid: expr, $htlc_output: expr) => {
                                        if let Some(txid) = $counterparty_txid {
                                                for &(ref pending_htlc, ref pending_source) in self.counterparty_claimable_outpoints.get(&txid).unwrap() {
                                                        if pending_htlc.payment_hash == $htlc_output.payment_hash && pending_htlc.amount_msat == $htlc_output.amount_msat {
                                                                if let &Some(ref source) = pending_source {
                                                                        log_claim!("revoked counterparty commitment tx", false, pending_htlc, true);
                                                                        payment_data = Some(((**source).clone(), $htlc_output.payment_hash, $htlc_output.amount_msat));
                                                                        break;
                                                                }
                                                        }
                                                }
                                        }
                                }
                        }

                        macro_rules! scan_commitment {
                                ($htlcs: expr, $tx_info: expr, $holder_tx: expr) => {
                                        for (ref htlc_output, source_option) in $htlcs {
                                                if Some(input.previous_output.vout) == htlc_output.transaction_output_index {
                                                        if let Some(ref source) = source_option {
                                                                log_claim!($tx_info, $holder_tx, htlc_output, true);
                                                                // We have a resolution of an HTLC either from one of our latest
                                                                // holder commitment transactions or an unrevoked counterparty commitment
                                                                // transaction. This implies we either learned a preimage, the HTLC
                                                                // has timed out, or we screwed up. In any case, we should now
                                                                // resolve the source HTLC with the original sender.
                                                                payment_data = Some(((*source).clone(), htlc_output.payment_hash, htlc_output.amount_msat));
                                                        } else if !$holder_tx {
                                                                check_htlc_valid_counterparty!(self.current_counterparty_commitment_txid, htlc_output);
                                                                if payment_data.is_none() {
                                                                        check_htlc_valid_counterparty!(self.prev_counterparty_commitment_txid, htlc_output);
                                                                }
                                                        }
                                                        if payment_data.is_none() {
                                                                log_claim!($tx_info, $holder_tx, htlc_output, false);
                                                                let outbound_htlc = $holder_tx == htlc_output.offered;
                                                                if !outbound_htlc || revocation_sig_claim {
                                                                        self.onchain_events_awaiting_threshold_conf.push(OnchainEventEntry {
                                                                                txid: tx.txid(), height,
                                                                                event: OnchainEvent::HTLCSpendConfirmation {
                                                                                        commitment_tx_output_idx: input.previous_output.vout,
                                                                                        preimage: if accepted_preimage_claim || offered_preimage_claim {
                                                                                                Some(payment_preimage) } else { None },
                                                                                        // If this is a payment to us (!outbound_htlc, above),
                                                                                        // wait for the CSV delay before dropping the HTLC from
                                                                                        // claimable balance if the claim was an HTLC-Success
                                                                                        // transaction.
                                                                                        on_to_local_output_csv: if accepted_preimage_claim {
                                                                                                Some(self.on_holder_tx_csv) } else { None },
                                                                                },
                                                                        });
                                                                } else {
                                                                        // Outbound claims should always have payment_data, unless
                                                                        // we've already failed the HTLC as the commitment transaction
                                                                        // which was broadcasted was revoked. In that case, we should
                                                                        // spend the HTLC output here immediately, and expose that fact
                                                                        // as a Balance, something which we do not yet do.
                                                                        // TODO: Track the above as claimable!
                                                                }
                                                                continue 'outer_loop;
                                                        }
                                                }
                                        }
                                }
                        }

                        if input.previous_output.txid == self.current_holder_commitment_tx.txid {
                                scan_commitment!(self.current_holder_commitment_tx.htlc_outputs.iter().map(|&(ref a, _, ref b)| (a, b.as_ref())),
                                        "our latest holder commitment tx", true);
                        }
                        if let Some(ref prev_holder_signed_commitment_tx) = self.prev_holder_signed_commitment_tx {
                                if input.previous_output.txid == prev_holder_signed_commitment_tx.txid {
                                        scan_commitment!(prev_holder_signed_commitment_tx.htlc_outputs.iter().map(|&(ref a, _, ref b)| (a, b.as_ref())),
                                                "our previous holder commitment tx", true);
                                }
                        }
                        if let Some(ref htlc_outputs) = self.counterparty_claimable_outpoints.get(&input.previous_output.txid) {
                                scan_commitment!(htlc_outputs.iter().map(|&(ref a, ref b)| (a, (b.as_ref().clone()).map(|boxed| &**boxed))),
                                        "counterparty commitment tx", false);
                        }

                        // Check that scan_commitment, above, decided there is some source worth relaying an
                        // HTLC resolution backwards to and figure out whether we learned a preimage from it.
                        if let Some((source, payment_hash, amount_msat)) = payment_data {
                                if accepted_preimage_claim {
                                        if !self.pending_monitor_events.iter().any(
                                                |update| if let &MonitorEvent::HTLCEvent(ref upd) = update { upd.source == source } else { false }) {
                                                self.onchain_events_awaiting_threshold_conf.push(OnchainEventEntry {
                                                        txid: tx.txid(),
                                                        height,
                                                        event: OnchainEvent::HTLCSpendConfirmation {
                                                                commitment_tx_output_idx: input.previous_output.vout,
                                                                preimage: Some(payment_preimage),
                                                                on_to_local_output_csv: None,
                                                        },
                                                });
                                                self.pending_monitor_events.push(MonitorEvent::HTLCEvent(HTLCUpdate {
                                                        source,
                                                        payment_preimage: Some(payment_preimage),
                                                        payment_hash,
                                                        htlc_value_satoshis: Some(amount_msat / 1000),
                                                }));
                                        }
                                } else if offered_preimage_claim {
                                        if !self.pending_monitor_events.iter().any(
                                                |update| if let &MonitorEvent::HTLCEvent(ref upd) = update {
                                                        upd.source == source
                                                } else { false }) {
                                                self.onchain_events_awaiting_threshold_conf.push(OnchainEventEntry {
                                                        txid: tx.txid(),
                                                        height,
                                                        event: OnchainEvent::HTLCSpendConfirmation {
                                                                commitment_tx_output_idx: input.previous_output.vout,
                                                                preimage: Some(payment_preimage),
                                                                on_to_local_output_csv: None,
                                                        },
                                                });
                                                self.pending_monitor_events.push(MonitorEvent::HTLCEvent(HTLCUpdate {
                                                        source,
                                                        payment_preimage: Some(payment_preimage),
                                                        payment_hash,
                                                        htlc_value_satoshis: Some(amount_msat / 1000),
                                                }));
                                        }
                                } else {
                                        self.onchain_events_awaiting_threshold_conf.retain(|ref entry| {
                                                if entry.height != height { return true; }
                                                match entry.event {
                                                        OnchainEvent::HTLCUpdate { source: ref htlc_source, .. } => {
                                                                *htlc_source != source
                                                        },
                                                        _ => true,
                                                }
                                        });
                                        let entry = OnchainEventEntry {
                                                txid: tx.txid(),
                                                height,
                                                event: OnchainEvent::HTLCUpdate {
                                                        source, payment_hash,
                                                        htlc_value_satoshis: Some(amount_msat / 1000),
                                                        commitment_tx_output_idx: Some(input.previous_output.vout),
                                                },
                                        };
                                        log_info!(logger, "Failing HTLC with payment_hash {} timeout by a spend tx, waiting for confirmation (at height {})", log_bytes!(payment_hash.0), entry.confirmation_threshold());
                                        self.onchain_events_awaiting_threshold_conf.push(entry);
                                }
                        }
                }
        }

        /// Check if any transaction broadcasted is paying fund back to some address we can assume to own
        fn is_paying_spendable_output<L: Deref>(&mut self, tx: &Transaction, height: u32, logger: &L) where L::Target: Logger {
                let mut spendable_output = None;
                for (i, outp) in tx.output.iter().enumerate() { // There is max one spendable output for any channel tx, including ones generated by us
                        if i > ::core::u16::MAX as usize {
                                // While it is possible that an output exists on chain which is greater than the
                                // 2^16th output in a given transaction, this is only possible if the output is not
                                // in a lightning transaction and was instead placed there by some third party who
                                // wishes to give us money for no reason.
                                // Namely, any lightning transactions which we pre-sign will never have anywhere
                                // near 2^16 outputs both because such transactions must have ~2^16 outputs who's
                                // scripts are not longer than one byte in length and because they are inherently
                                // non-standard due to their size.
                                // Thus, it is completely safe to ignore such outputs, and while it may result in
                                // us ignoring non-lightning fund to us, that is only possible if someone fills
                                // nearly a full block with garbage just to hit this case.
                                continue;
                        }
                        if outp.script_pubkey == self.destination_script {
                                spendable_output =  Some(SpendableOutputDescriptor::StaticOutput {
                                        outpoint: OutPoint { txid: tx.txid(), index: i as u16 },
                                        output: outp.clone(),
                                });
                                break;
                        }
                        if let Some(ref broadcasted_holder_revokable_script) = self.broadcasted_holder_revokable_script {
                                if broadcasted_holder_revokable_script.0 == outp.script_pubkey {
                                        spendable_output =  Some(SpendableOutputDescriptor::DelayedPaymentOutput(DelayedPaymentOutputDescriptor {
                                                outpoint: OutPoint { txid: tx.txid(), index: i as u16 },
                                                per_commitment_point: broadcasted_holder_revokable_script.1,
                                                to_self_delay: self.on_holder_tx_csv,
                                                output: outp.clone(),
                                                revocation_pubkey: broadcasted_holder_revokable_script.2.clone(),
                                                channel_keys_id: self.channel_keys_id,
                                                channel_value_satoshis: self.channel_value_satoshis,
                                        }));
                                        break;
                                }
                        }
                        if self.counterparty_payment_script == outp.script_pubkey {
                                spendable_output = Some(SpendableOutputDescriptor::StaticPaymentOutput(StaticPaymentOutputDescriptor {
                                        outpoint: OutPoint { txid: tx.txid(), index: i as u16 },
                                        output: outp.clone(),
                                        channel_keys_id: self.channel_keys_id,
                                        channel_value_satoshis: self.channel_value_satoshis,
                                }));
                                break;
                        }
                        if self.shutdown_script.as_ref() == Some(&outp.script_pubkey) {
                                spendable_output = Some(SpendableOutputDescriptor::StaticOutput {
                                        outpoint: OutPoint { txid: tx.txid(), index: i as u16 },
                                        output: outp.clone(),
                                });
                                break;
                        }
                }
                if let Some(spendable_output) = spendable_output {
                        let entry = OnchainEventEntry {
                                txid: tx.txid(),
                                height: height,
                                event: OnchainEvent::MaturingOutput { descriptor: spendable_output.clone() },
                        };
                        log_info!(logger, "Received spendable output {}, spendable at height {}", log_spendable!(spendable_output), entry.confirmation_threshold());
                        self.onchain_events_awaiting_threshold_conf.push(entry);
                }
        }
}

impl<Signer: Sign, T: Deref, F: Deref, L: Deref> chain::Listen for (ChannelMonitor<Signer>, T, F, L)
where
        T::Target: BroadcasterInterface,
        F::Target: FeeEstimator,
        L::Target: Logger,
{
        fn filtered_block_connected(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
                self.0.block_connected(header, txdata, height, &*self.1, &*self.2, &*self.3);
        }

        fn block_disconnected(&self, header: &BlockHeader, height: u32) {
                self.0.block_disconnected(header, height, &*self.1, &*self.2, &*self.3);
        }
}

impl<Signer: Sign, T: Deref, F: Deref, L: Deref> chain::Confirm for (ChannelMonitor<Signer>, T, F, L)
where
        T::Target: BroadcasterInterface,
        F::Target: FeeEstimator,
        L::Target: Logger,
{
        fn transactions_confirmed(&self, header: &BlockHeader, txdata: &TransactionData, height: u32) {
                self.0.transactions_confirmed(header, txdata, height, &*self.1, &*self.2, &*self.3);
        }

        fn transaction_unconfirmed(&self, txid: &Txid) {
                self.0.transaction_unconfirmed(txid, &*self.1, &*self.2, &*self.3);
        }

        fn best_block_updated(&self, header: &BlockHeader, height: u32) {
                self.0.best_block_updated(header, height, &*self.1, &*self.2, &*self.3);
        }

        fn get_relevant_txids(&self) -> Vec<Txid> {
                self.0.get_relevant_txids()
        }
}

const MAX_ALLOC_SIZE: usize = 64*1024;

impl<'a, Signer: Sign, K: KeysInterface<Signer = Signer>> ReadableArgs<&'a K>
                for (BlockHash, ChannelMonitor<Signer>) {
        fn read<R: io::Read>(reader: &mut R, keys_manager: &'a K) -> Result<Self, DecodeError> {
                macro_rules! unwrap_obj {
                        ($key: expr) => {
                                match $key {
                                        Ok(res) => res,
                                        Err(_) => return Err(DecodeError::InvalidValue),
                                }
                        }
                }

                let _ver = read_ver_prefix!(reader, SERIALIZATION_VERSION);

                let latest_update_id: u64 = Readable::read(reader)?;
                let commitment_transaction_number_obscure_factor = <U48 as Readable>::read(reader)?.0;

                let destination_script = Readable::read(reader)?;
                let broadcasted_holder_revokable_script = match <u8 as Readable>::read(reader)? {
                        0 => {
                                let revokable_address = Readable::read(reader)?;
                                let per_commitment_point = Readable::read(reader)?;
                                let revokable_script = Readable::read(reader)?;
                                Some((revokable_address, per_commitment_point, revokable_script))
                        },
                        1 => { None },
                        _ => return Err(DecodeError::InvalidValue),
                };
                let counterparty_payment_script = Readable::read(reader)?;
                let shutdown_script = {
                        let script = <Script as Readable>::read(reader)?;
                        if script.is_empty() { None } else { Some(script) }
                };

                let channel_keys_id = Readable::read(reader)?;
                let holder_revocation_basepoint = Readable::read(reader)?;
                // Technically this can fail and serialize fail a round-trip, but only for serialization of
                // barely-init'd ChannelMonitors that we can't do anything with.
                let outpoint = OutPoint {
                        txid: Readable::read(reader)?,
                        index: Readable::read(reader)?,
                };
                let funding_info = (outpoint, Readable::read(reader)?);
                let current_counterparty_commitment_txid = Readable::read(reader)?;
                let prev_counterparty_commitment_txid = Readable::read(reader)?;

                let counterparty_commitment_params = Readable::read(reader)?;
                let funding_redeemscript = Readable::read(reader)?;
                let channel_value_satoshis = Readable::read(reader)?;

                let their_cur_per_commitment_points = {
                        let first_idx = <U48 as Readable>::read(reader)?.0;
                        if first_idx == 0 {
                                None
                        } else {
                                let first_point = Readable::read(reader)?;
                                let second_point_slice: [u8; 33] = Readable::read(reader)?;
                                if second_point_slice[0..32] == [0; 32] && second_point_slice[32] == 0 {
                                        Some((first_idx, first_point, None))
                                } else {
                                        Some((first_idx, first_point, Some(unwrap_obj!(PublicKey::from_slice(&second_point_slice)))))
                                }
                        }
                };

                let on_holder_tx_csv: u16 = Readable::read(reader)?;

                let commitment_secrets = Readable::read(reader)?;

                macro_rules! read_htlc_in_commitment {
                        () => {
                                {
                                        let offered: bool = Readable::read(reader)?;
                                        let amount_msat: u64 = Readable::read(reader)?;
                                        let cltv_expiry: u32 = Readable::read(reader)?;
                                        let payment_hash: PaymentHash = Readable::read(reader)?;
                                        let transaction_output_index: Option<u32> = Readable::read(reader)?;

                                        HTLCOutputInCommitment {
                                                offered, amount_msat, cltv_expiry, payment_hash, transaction_output_index
                                        }
                                }
                        }
                }

                let counterparty_claimable_outpoints_len: u64 = Readable::read(reader)?;
                let mut counterparty_claimable_outpoints = HashMap::with_capacity(cmp::min(counterparty_claimable_outpoints_len as usize, MAX_ALLOC_SIZE / 64));
                for _ in 0..counterparty_claimable_outpoints_len {
                        let txid: Txid = Readable::read(reader)?;
                        let htlcs_count: u64 = Readable::read(reader)?;
                        let mut htlcs = Vec::with_capacity(cmp::min(htlcs_count as usize, MAX_ALLOC_SIZE / 32));
                        for _ in 0..htlcs_count {
                                htlcs.push((read_htlc_in_commitment!(), <Option<HTLCSource> as Readable>::read(reader)?.map(|o: HTLCSource| Box::new(o))));
                        }
                        if let Some(_) = counterparty_claimable_outpoints.insert(txid, htlcs) {
                                return Err(DecodeError::InvalidValue);
                        }
                }

                let counterparty_commitment_txn_on_chain_len: u64 = Readable::read(reader)?;
                let mut counterparty_commitment_txn_on_chain = HashMap::with_capacity(cmp::min(counterparty_commitment_txn_on_chain_len as usize, MAX_ALLOC_SIZE / 32));
                for _ in 0..counterparty_commitment_txn_on_chain_len {
                        let txid: Txid = Readable::read(reader)?;
                        let commitment_number = <U48 as Readable>::read(reader)?.0;
                        if let Some(_) = counterparty_commitment_txn_on_chain.insert(txid, commitment_number) {
                                return Err(DecodeError::InvalidValue);
                        }
                }

                let counterparty_hash_commitment_number_len: u64 = Readable::read(reader)?;
                let mut counterparty_hash_commitment_number = HashMap::with_capacity(cmp::min(counterparty_hash_commitment_number_len as usize, MAX_ALLOC_SIZE / 32));
                for _ in 0..counterparty_hash_commitment_number_len {
                        let payment_hash: PaymentHash = Readable::read(reader)?;
                        let commitment_number = <U48 as Readable>::read(reader)?.0;
                        if let Some(_) = counterparty_hash_commitment_number.insert(payment_hash, commitment_number) {
                                return Err(DecodeError::InvalidValue);
                        }
                }

                let mut prev_holder_signed_commitment_tx: Option<HolderSignedTx> =
                        match <u8 as Readable>::read(reader)? {
                                0 => None,
                                1 => {
                                        Some(Readable::read(reader)?)
                                },
                                _ => return Err(DecodeError::InvalidValue),
                        };
                let mut current_holder_commitment_tx: HolderSignedTx = Readable::read(reader)?;

                let current_counterparty_commitment_number = <U48 as Readable>::read(reader)?.0;
                let current_holder_commitment_number = <U48 as Readable>::read(reader)?.0;

                let payment_preimages_len: u64 = Readable::read(reader)?;
                let mut payment_preimages = HashMap::with_capacity(cmp::min(payment_preimages_len as usize, MAX_ALLOC_SIZE / 32));
                for _ in 0..payment_preimages_len {
                        let preimage: PaymentPreimage = Readable::read(reader)?;
                        let hash = PaymentHash(Sha256::hash(&preimage.0[..]).into_inner());
                        if let Some(_) = payment_preimages.insert(hash, preimage) {
                                return Err(DecodeError::InvalidValue);
                        }
                }

                let pending_monitor_events_len: u64 = Readable::read(reader)?;
                let mut pending_monitor_events = Some(
                        Vec::with_capacity(cmp::min(pending_monitor_events_len as usize, MAX_ALLOC_SIZE / (32 + 8*3))));
                for _ in 0..pending_monitor_events_len {
                        let ev = match <u8 as Readable>::read(reader)? {
                                0 => MonitorEvent::HTLCEvent(Readable::read(reader)?),
                                1 => MonitorEvent::CommitmentTxConfirmed(funding_info.0),
                                _ => return Err(DecodeError::InvalidValue)
                        };
                        pending_monitor_events.as_mut().unwrap().push(ev);
                }

                let pending_events_len: u64 = Readable::read(reader)?;
                let mut pending_events = Vec::with_capacity(cmp::min(pending_events_len as usize, MAX_ALLOC_SIZE / mem::size_of::<Event>()));
                for _ in 0..pending_events_len {
                        if let Some(event) = MaybeReadable::read(reader)? {
                                pending_events.push(event);
                        }
                }

                let best_block = BestBlock::new(Readable::read(reader)?, Readable::read(reader)?);

                let waiting_threshold_conf_len: u64 = Readable::read(reader)?;
                let mut onchain_events_awaiting_threshold_conf = Vec::with_capacity(cmp::min(waiting_threshold_conf_len as usize, MAX_ALLOC_SIZE / 128));
                for _ in 0..waiting_threshold_conf_len {
                        if let Some(val) = MaybeReadable::read(reader)? {
                                onchain_events_awaiting_threshold_conf.push(val);
                        }
                }

                let outputs_to_watch_len: u64 = Readable::read(reader)?;
                let mut outputs_to_watch = HashMap::with_capacity(cmp::min(outputs_to_watch_len as usize, MAX_ALLOC_SIZE / (mem::size_of::<Txid>() + mem::size_of::<u32>() + mem::size_of::<Vec<Script>>())));
                for _ in 0..outputs_to_watch_len {
                        let txid = Readable::read(reader)?;
                        let outputs_len: u64 = Readable::read(reader)?;
                        let mut outputs = Vec::with_capacity(cmp::min(outputs_len as usize, MAX_ALLOC_SIZE / (mem::size_of::<u32>() + mem::size_of::<Script>())));
                        for _ in 0..outputs_len {
                                outputs.push((Readable::read(reader)?, Readable::read(reader)?));
                        }
                        if let Some(_) = outputs_to_watch.insert(txid, outputs) {
                                return Err(DecodeError::InvalidValue);
                        }
                }
                let onchain_tx_handler: OnchainTxHandler<Signer> = ReadableArgs::read(reader, keys_manager)?;

                let lockdown_from_offchain = Readable::read(reader)?;
                let holder_tx_signed = Readable::read(reader)?;

                if let Some(prev_commitment_tx) = prev_holder_signed_commitment_tx.as_mut() {
                        let prev_holder_value = onchain_tx_handler.get_prev_holder_commitment_to_self_value();
                        if prev_holder_value.is_none() { return Err(DecodeError::InvalidValue); }
                        if prev_commitment_tx.to_self_value_sat == u64::max_value() {
                                prev_commitment_tx.to_self_value_sat = prev_holder_value.unwrap();
                        } else if prev_commitment_tx.to_self_value_sat != prev_holder_value.unwrap() {
                                return Err(DecodeError::InvalidValue);
                        }
                }

                let cur_holder_value = onchain_tx_handler.get_cur_holder_commitment_to_self_value();
                if current_holder_commitment_tx.to_self_value_sat == u64::max_value() {
                        current_holder_commitment_tx.to_self_value_sat = cur_holder_value;
                } else if current_holder_commitment_tx.to_self_value_sat != cur_holder_value {
                        return Err(DecodeError::InvalidValue);
                }

                let mut funding_spend_confirmed = None;
                let mut htlcs_resolved_on_chain = Some(Vec::new());
                let mut funding_spend_seen = Some(false);
                let mut counterparty_node_id = None;
                read_tlv_fields!(reader, {
                        (1, funding_spend_confirmed, option),
                        (3, htlcs_resolved_on_chain, vec_type),
                        (5, pending_monitor_events, vec_type),
                        (7, funding_spend_seen, option),
                        (9, counterparty_node_id, option),
                });

                let mut secp_ctx = Secp256k1::new();
                secp_ctx.seeded_randomize(&keys_manager.get_secure_random_bytes());

                Ok((best_block.block_hash(), ChannelMonitor {
                        inner: Mutex::new(ChannelMonitorImpl {
                                latest_update_id,
                                commitment_transaction_number_obscure_factor,

                                destination_script,
                                broadcasted_holder_revokable_script,
                                counterparty_payment_script,
                                shutdown_script,

                                channel_keys_id,
                                holder_revocation_basepoint,
                                funding_info,
                                current_counterparty_commitment_txid,
                                prev_counterparty_commitment_txid,

                                counterparty_commitment_params,
                                funding_redeemscript,
                                channel_value_satoshis,
                                their_cur_per_commitment_points,

                                on_holder_tx_csv,

                                commitment_secrets,
                                counterparty_claimable_outpoints,
                                counterparty_commitment_txn_on_chain,
                                counterparty_hash_commitment_number,

                                prev_holder_signed_commitment_tx,
                                current_holder_commitment_tx,
                                current_counterparty_commitment_number,
                                current_holder_commitment_number,

                                payment_preimages,
                                pending_monitor_events: pending_monitor_events.unwrap(),
                                pending_events,

                                onchain_events_awaiting_threshold_conf,
                                outputs_to_watch,

                                onchain_tx_handler,

                                lockdown_from_offchain,
                                holder_tx_signed,
                                funding_spend_seen: funding_spend_seen.unwrap(),
                                funding_spend_confirmed,
                                htlcs_resolved_on_chain: htlcs_resolved_on_chain.unwrap(),

                                best_block,
                                counterparty_node_id,

                                secp_ctx,
                        }),
                }))
        }
}

#[cfg(test)]
mod tests {
        use bitcoin::blockdata::block::BlockHeader;
        use bitcoin::blockdata::script::{Script, Builder};
        use bitcoin::blockdata::opcodes;
        use bitcoin::blockdata::transaction::{Transaction, TxIn, TxOut, EcdsaSighashType};
        use bitcoin::blockdata::transaction::OutPoint as BitcoinOutPoint;
        use bitcoin::util::sighash;
        use bitcoin::hashes::Hash;
        use bitcoin::hashes::sha256::Hash as Sha256;
        use bitcoin::hashes::hex::FromHex;
        use bitcoin::hash_types::{BlockHash, Txid};
        use bitcoin::network::constants::Network;
        use bitcoin::secp256k1::{SecretKey,PublicKey};
        use bitcoin::secp256k1::Secp256k1;

        use hex;

        use crate::chain::chaininterface::LowerBoundedFeeEstimator;

        use super::ChannelMonitorUpdateStep;
        use ::{check_added_monitors, check_closed_broadcast, check_closed_event, check_spends, get_local_commitment_txn, get_monitor, get_route_and_payment_hash, unwrap_send_err};
        use chain::{BestBlock, Confirm};
        use chain::channelmonitor::ChannelMonitor;
        use chain::package::{weight_offered_htlc, weight_received_htlc, weight_revoked_offered_htlc, weight_revoked_received_htlc, WEIGHT_REVOKED_OUTPUT};
        use chain::transaction::OutPoint;
        use chain::keysinterface::InMemorySigner;
        use ln::{PaymentPreimage, PaymentHash};
        use ln::chan_utils;
        use ln::chan_utils::{HTLCOutputInCommitment, ChannelPublicKeys, ChannelTransactionParameters, HolderCommitmentTransaction, CounterpartyChannelTransactionParameters};
        use ln::channelmanager::PaymentSendFailure;
        use ln::features::InitFeatures;
        use ln::functional_test_utils::*;
        use ln::script::ShutdownScript;
        use util::errors::APIError;
        use util::events::{ClosureReason, MessageSendEventsProvider};
        use util::test_utils::{TestLogger, TestBroadcaster, TestFeeEstimator};
        use util::ser::{ReadableArgs, Writeable};
        use sync::{Arc, Mutex};
        use io;
        use bitcoin::Witness;
        use prelude::*;

        fn do_test_funding_spend_refuses_updates(use_local_txn: bool) {
                // Previously, monitor updates were allowed freely even after a funding-spend transaction
                // confirmed. This would allow a race condition where we could receive a payment (including
                // the counterparty revoking their broadcasted state!) and accept it without recourse as
                // long as the ChannelMonitor receives the block first, the full commitment update dance
                // occurs after the block is connected, and before the ChannelManager receives the block.
                // Obviously this is an incredibly contrived race given the counterparty would be risking
                // their full channel balance for it, but its worth fixing nonetheless as it makes the
                // potential ChannelMonitor states simpler to reason about.
                //
                // This test checks said behavior, as well as ensuring a ChannelMonitorUpdate with multiple
                // updates is handled correctly in such conditions.
                let chanmon_cfgs = create_chanmon_cfgs(3);
                let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
                let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, None, None]);
                let nodes = create_network(3, &node_cfgs, &node_chanmgrs);
                let channel = create_announced_chan_between_nodes(
                        &nodes, 0, 1, InitFeatures::known(), InitFeatures::known());
                create_announced_chan_between_nodes(
                        &nodes, 1, 2, InitFeatures::known(), InitFeatures::known());

                // Rebalance somewhat
                send_payment(&nodes[0], &[&nodes[1]], 10_000_000);

                // First route two payments for testing at the end
                let payment_preimage_1 = route_payment(&nodes[0], &[&nodes[1], &nodes[2]], 1_000_000).0;
                let payment_preimage_2 = route_payment(&nodes[0], &[&nodes[1], &nodes[2]], 1_000_000).0;

                let local_txn = get_local_commitment_txn!(nodes[1], channel.2);
                assert_eq!(local_txn.len(), 1);
                let remote_txn = get_local_commitment_txn!(nodes[0], channel.2);
                assert_eq!(remote_txn.len(), 3); // Commitment and two HTLC-Timeouts
                check_spends!(remote_txn[1], remote_txn[0]);
                check_spends!(remote_txn[2], remote_txn[0]);
                let broadcast_tx = if use_local_txn { &local_txn[0] } else { &remote_txn[0] };

                // Connect a commitment transaction, but only to the ChainMonitor/ChannelMonitor. The
                // channel is now closed, but the ChannelManager doesn't know that yet.
                let new_header = BlockHeader {
                        version: 2, time: 0, bits: 0, nonce: 0,
                        prev_blockhash: nodes[0].best_block_info().0,
                        merkle_root: Default::default() };
                let conf_height = nodes[0].best_block_info().1 + 1;
                nodes[1].chain_monitor.chain_monitor.transactions_confirmed(&new_header,
                        &[(0, broadcast_tx)], conf_height);

                let (_, pre_update_monitor) = <(BlockHash, ChannelMonitor<InMemorySigner>)>::read(
                                                &mut io::Cursor::new(&get_monitor!(nodes[1], channel.2).encode()),
                                                &nodes[1].keys_manager.backing).unwrap();

                // If the ChannelManager tries to update the channel, however, the ChainMonitor will pass
                // the update through to the ChannelMonitor which will refuse it (as the channel is closed).
                let (route, payment_hash, _, payment_secret) = get_route_and_payment_hash!(nodes[1], nodes[0], 100_000);
                unwrap_send_err!(nodes[1].node.send_payment(&route, payment_hash, &Some(payment_secret)),
                        true, APIError::ChannelUnavailable { ref err },
                        assert!(err.contains("ChannelMonitor storage failure")));
                check_added_monitors!(nodes[1], 2); // After the failure we generate a close-channel monitor update
                check_closed_broadcast!(nodes[1], true);
                check_closed_event!(nodes[1], 1, ClosureReason::ProcessingError { err: "ChannelMonitor storage failure".to_string() });

                // Build a new ChannelMonitorUpdate which contains both the failing commitment tx update
                // and provides the claim preimages for the two pending HTLCs. The first update generates
                // an error, but the point of this test is to ensure the later updates are still applied.
                let monitor_updates = nodes[1].chain_monitor.monitor_updates.lock().unwrap();
                let mut replay_update = monitor_updates.get(&channel.2).unwrap().iter().rev().skip(1).next().unwrap().clone();
                assert_eq!(replay_update.updates.len(), 1);
                if let ChannelMonitorUpdateStep::LatestCounterpartyCommitmentTXInfo { .. } = replay_update.updates[0] {
                } else { panic!(); }
                replay_update.updates.push(ChannelMonitorUpdateStep::PaymentPreimage { payment_preimage: payment_preimage_1 });
                replay_update.updates.push(ChannelMonitorUpdateStep::PaymentPreimage { payment_preimage: payment_preimage_2 });

                let broadcaster = TestBroadcaster::new(Arc::clone(&nodes[1].blocks));
                assert!(
                        pre_update_monitor.update_monitor(&replay_update, &&broadcaster, &&chanmon_cfgs[1].fee_estimator, &nodes[1].logger)
                        .is_err());
                // Even though we error'd on the first update, we should still have generated an HTLC claim
                // transaction
                let txn_broadcasted = broadcaster.txn_broadcasted.lock().unwrap().split_off(0);
                assert!(txn_broadcasted.len() >= 2);
                let htlc_txn = txn_broadcasted.iter().filter(|tx| {
                        assert_eq!(tx.input.len(), 1);
                        tx.input[0].previous_output.txid == broadcast_tx.txid()
                }).collect::<Vec<_>>();
                assert_eq!(htlc_txn.len(), 2);
                check_spends!(htlc_txn[0], broadcast_tx);
                check_spends!(htlc_txn[1], broadcast_tx);
        }
        #[test]
        fn test_funding_spend_refuses_updates() {
                do_test_funding_spend_refuses_updates(true);
                do_test_funding_spend_refuses_updates(false);
        }

        #[test]
        fn test_prune_preimages() {
                let secp_ctx = Secp256k1::new();
                let logger = Arc::new(TestLogger::new());
                let broadcaster = Arc::new(TestBroadcaster{txn_broadcasted: Mutex::new(Vec::new()), blocks: Arc::new(Mutex::new(Vec::new()))});
                let fee_estimator = TestFeeEstimator { sat_per_kw: Mutex::new(253) };

                let dummy_key = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let dummy_tx = Transaction { version: 0, lock_time: 0, input: Vec::new(), output: Vec::new() };

                let mut preimages = Vec::new();
                {
                        for i in 0..20 {
                                let preimage = PaymentPreimage([i; 32]);
                                let hash = PaymentHash(Sha256::hash(&preimage.0[..]).into_inner());
                                preimages.push((preimage, hash));
                        }
                }

                macro_rules! preimages_slice_to_htlc_outputs {
                        ($preimages_slice: expr) => {
                                {
                                        let mut res = Vec::new();
                                        for (idx, preimage) in $preimages_slice.iter().enumerate() {
                                                res.push((HTLCOutputInCommitment {
                                                        offered: true,
                                                        amount_msat: 0,
                                                        cltv_expiry: 0,
                                                        payment_hash: preimage.1.clone(),
                                                        transaction_output_index: Some(idx as u32),
                                                }, None));
                                        }
                                        res
                                }
                        }
                }
                macro_rules! preimages_to_holder_htlcs {
                        ($preimages_slice: expr) => {
                                {
                                        let mut inp = preimages_slice_to_htlc_outputs!($preimages_slice);
                                        let res: Vec<_> = inp.drain(..).map(|e| { (e.0, None, e.1) }).collect();
                                        res
                                }
                        }
                }

                macro_rules! test_preimages_exist {
                        ($preimages_slice: expr, $monitor: expr) => {
                                for preimage in $preimages_slice {
                                        assert!($monitor.inner.lock().unwrap().payment_preimages.contains_key(&preimage.1));
                                }
                        }
                }

                let keys = InMemorySigner::new(
                        &secp_ctx,
                        SecretKey::from_slice(&[41; 32]).unwrap(),
                        SecretKey::from_slice(&[41; 32]).unwrap(),
                        SecretKey::from_slice(&[41; 32]).unwrap(),
                        SecretKey::from_slice(&[41; 32]).unwrap(),
                        SecretKey::from_slice(&[41; 32]).unwrap(),
                        SecretKey::from_slice(&[41; 32]).unwrap(),
                        [41; 32],
                        0,
                        [0; 32]
                );

                let counterparty_pubkeys = ChannelPublicKeys {
                        funding_pubkey: PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[44; 32]).unwrap()),
                        revocation_basepoint: PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[45; 32]).unwrap()),
                        payment_point: PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[46; 32]).unwrap()),
                        delayed_payment_basepoint: PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[47; 32]).unwrap()),
                        htlc_basepoint: PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[48; 32]).unwrap())
                };
                let funding_outpoint = OutPoint { txid: Default::default(), index: u16::max_value() };
                let channel_parameters = ChannelTransactionParameters {
                        holder_pubkeys: keys.holder_channel_pubkeys.clone(),
                        holder_selected_contest_delay: 66,
                        is_outbound_from_holder: true,
                        counterparty_parameters: Some(CounterpartyChannelTransactionParameters {
                                pubkeys: counterparty_pubkeys,
                                selected_contest_delay: 67,
                        }),
                        funding_outpoint: Some(funding_outpoint),
                        opt_anchors: None,
                };
                // Prune with one old state and a holder commitment tx holding a few overlaps with the
                // old state.
                let shutdown_pubkey = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let best_block = BestBlock::from_genesis(Network::Testnet);
                let monitor = ChannelMonitor::new(Secp256k1::new(), keys,
                                                  Some(ShutdownScript::new_p2wpkh_from_pubkey(shutdown_pubkey).into_inner()), 0, &Script::new(),
                                                  (OutPoint { txid: Txid::from_slice(&[43; 32]).unwrap(), index: 0 }, Script::new()),
                                                  &channel_parameters,
                                                  Script::new(), 46, 0,
                                                  HolderCommitmentTransaction::dummy(), best_block, dummy_key);

                monitor.provide_latest_holder_commitment_tx(HolderCommitmentTransaction::dummy(), preimages_to_holder_htlcs!(preimages[0..10])).unwrap();
                let dummy_txid = dummy_tx.txid();
                monitor.provide_latest_counterparty_commitment_tx(dummy_txid, preimages_slice_to_htlc_outputs!(preimages[5..15]), 281474976710655, dummy_key, &logger);
                monitor.provide_latest_counterparty_commitment_tx(dummy_txid, preimages_slice_to_htlc_outputs!(preimages[15..20]), 281474976710654, dummy_key, &logger);
                monitor.provide_latest_counterparty_commitment_tx(dummy_txid, preimages_slice_to_htlc_outputs!(preimages[17..20]), 281474976710653, dummy_key, &logger);
                monitor.provide_latest_counterparty_commitment_tx(dummy_txid, preimages_slice_to_htlc_outputs!(preimages[18..20]), 281474976710652, dummy_key, &logger);
                for &(ref preimage, ref hash) in preimages.iter() {
                        let bounded_fee_estimator = LowerBoundedFeeEstimator::new(&fee_estimator);
                        monitor.provide_payment_preimage(hash, preimage, &broadcaster, &bounded_fee_estimator, &logger);
                }

                // Now provide a secret, pruning preimages 10-15
                let mut secret = [0; 32];
                secret[0..32].clone_from_slice(&hex::decode("7cc854b54e3e0dcdb010d7a3fee464a9687be6e8db3be6854c475621e007a5dc").unwrap());
                monitor.provide_secret(281474976710655, secret.clone()).unwrap();
                assert_eq!(monitor.inner.lock().unwrap().payment_preimages.len(), 15);
                test_preimages_exist!(&preimages[0..10], monitor);
                test_preimages_exist!(&preimages[15..20], monitor);

                // Now provide a further secret, pruning preimages 15-17
                secret[0..32].clone_from_slice(&hex::decode("c7518c8ae4660ed02894df8976fa1a3659c1a8b4b5bec0c4b872abeba4cb8964").unwrap());
                monitor.provide_secret(281474976710654, secret.clone()).unwrap();
                assert_eq!(monitor.inner.lock().unwrap().payment_preimages.len(), 13);
                test_preimages_exist!(&preimages[0..10], monitor);
                test_preimages_exist!(&preimages[17..20], monitor);

                // Now update holder commitment tx info, pruning only element 18 as we still care about the
                // previous commitment tx's preimages too
                monitor.provide_latest_holder_commitment_tx(HolderCommitmentTransaction::dummy(), preimages_to_holder_htlcs!(preimages[0..5])).unwrap();
                secret[0..32].clone_from_slice(&hex::decode("2273e227a5b7449b6e70f1fb4652864038b1cbf9cd7c043a7d6456b7fc275ad8").unwrap());
                monitor.provide_secret(281474976710653, secret.clone()).unwrap();
                assert_eq!(monitor.inner.lock().unwrap().payment_preimages.len(), 12);
                test_preimages_exist!(&preimages[0..10], monitor);
                test_preimages_exist!(&preimages[18..20], monitor);

                // But if we do it again, we'll prune 5-10
                monitor.provide_latest_holder_commitment_tx(HolderCommitmentTransaction::dummy(), preimages_to_holder_htlcs!(preimages[0..3])).unwrap();
                secret[0..32].clone_from_slice(&hex::decode("27cddaa5624534cb6cb9d7da077cf2b22ab21e9b506fd4998a51d54502e99116").unwrap());
                monitor.provide_secret(281474976710652, secret.clone()).unwrap();
                assert_eq!(monitor.inner.lock().unwrap().payment_preimages.len(), 5);
                test_preimages_exist!(&preimages[0..5], monitor);
        }

        #[test]
        fn test_claim_txn_weight_computation() {
                // We test Claim txn weight, knowing that we want expected weigth and
                // not actual case to avoid sigs and time-lock delays hell variances.

                let secp_ctx = Secp256k1::new();
                let privkey = SecretKey::from_slice(&hex::decode("0101010101010101010101010101010101010101010101010101010101010101").unwrap()[..]).unwrap();
                let pubkey = PublicKey::from_secret_key(&secp_ctx, &privkey);

                macro_rules! sign_input {
                        ($sighash_parts: expr, $idx: expr, $amount: expr, $weight: expr, $sum_actual_sigs: expr, $opt_anchors: expr) => {
                                let htlc = HTLCOutputInCommitment {
                                        offered: if *$weight == weight_revoked_offered_htlc($opt_anchors) || *$weight == weight_offered_htlc($opt_anchors) { true } else { false },
                                        amount_msat: 0,
                                        cltv_expiry: 2 << 16,
                                        payment_hash: PaymentHash([1; 32]),
                                        transaction_output_index: Some($idx as u32),
                                };
                                let redeem_script = if *$weight == WEIGHT_REVOKED_OUTPUT { chan_utils::get_revokeable_redeemscript(&pubkey, 256, &pubkey) } else { chan_utils::get_htlc_redeemscript_with_explicit_keys(&htlc, $opt_anchors, &pubkey, &pubkey, &pubkey) };
                                let sighash = hash_to_message!(&$sighash_parts.segwit_signature_hash($idx, &redeem_script, $amount, EcdsaSighashType::All).unwrap()[..]);
                                let sig = secp_ctx.sign_ecdsa(&sighash, &privkey);
                                let mut ser_sig = sig.serialize_der().to_vec();
                                ser_sig.push(EcdsaSighashType::All as u8);
                                $sum_actual_sigs += ser_sig.len();
                                let witness = $sighash_parts.witness_mut($idx).unwrap();
                                witness.push(ser_sig);
                                if *$weight == WEIGHT_REVOKED_OUTPUT {
                                        witness.push(vec!(1));
                                } else if *$weight == weight_revoked_offered_htlc($opt_anchors) || *$weight == weight_revoked_received_htlc($opt_anchors) {
                                        witness.push(pubkey.clone().serialize().to_vec());
                                } else if *$weight == weight_received_htlc($opt_anchors) {
                                        witness.push(vec![0]);
                                } else {
                                        witness.push(PaymentPreimage([1; 32]).0.to_vec());
                                }
                                witness.push(redeem_script.into_bytes());
                                let witness = witness.to_vec();
                                println!("witness[0] {}", witness[0].len());
                                println!("witness[1] {}", witness[1].len());
                                println!("witness[2] {}", witness[2].len());
                        }
                }

                let script_pubkey = Builder::new().push_opcode(opcodes::all::OP_RETURN).into_script();
                let txid = Txid::from_hex("56944c5d3f98413ef45cf54545538103cc9f298e0575820ad3591376e2e0f65d").unwrap();

                // Justice tx with 1 to_holder, 2 revoked offered HTLCs, 1 revoked received HTLCs
                for &opt_anchors in [false, true].iter() {
                        let mut claim_tx = Transaction { version: 0, lock_time: 0, input: Vec::new(), output: Vec::new() };
                        let mut sum_actual_sigs = 0;
                        for i in 0..4 {
                                claim_tx.input.push(TxIn {
                                        previous_output: BitcoinOutPoint {
                                                txid,
                                                vout: i,
                                        },
                                        script_sig: Script::new(),
                                        sequence: 0xfffffffd,
                                        witness: Witness::new(),
                                });
                        }
                        claim_tx.output.push(TxOut {
                                script_pubkey: script_pubkey.clone(),
                                value: 0,
                        });
                        let base_weight = claim_tx.weight();
                        let inputs_weight = vec![WEIGHT_REVOKED_OUTPUT, weight_revoked_offered_htlc(opt_anchors), weight_revoked_offered_htlc(opt_anchors), weight_revoked_received_htlc(opt_anchors)];
                        let mut inputs_total_weight = 2; // count segwit flags
                        {
                                let mut sighash_parts = sighash::SighashCache::new(&mut claim_tx);
                                for (idx, inp) in inputs_weight.iter().enumerate() {
                                        sign_input!(sighash_parts, idx, 0, inp, sum_actual_sigs, opt_anchors);
                                        inputs_total_weight += inp;
                                }
                        }
                        assert_eq!(base_weight + inputs_total_weight as usize,  claim_tx.weight() + /* max_length_sig */ (73 * inputs_weight.len() - sum_actual_sigs));
                }

                // Claim tx with 1 offered HTLCs, 3 received HTLCs
                for &opt_anchors in [false, true].iter() {
                        let mut claim_tx = Transaction { version: 0, lock_time: 0, input: Vec::new(), output: Vec::new() };
                        let mut sum_actual_sigs = 0;
                        for i in 0..4 {
                                claim_tx.input.push(TxIn {
                                        previous_output: BitcoinOutPoint {
                                                txid,
                                                vout: i,
                                        },
                                        script_sig: Script::new(),
                                        sequence: 0xfffffffd,
                                        witness: Witness::new(),
                                });
                        }
                        claim_tx.output.push(TxOut {
                                script_pubkey: script_pubkey.clone(),
                                value: 0,
                        });
                        let base_weight = claim_tx.weight();
                        let inputs_weight = vec![weight_offered_htlc(opt_anchors), weight_received_htlc(opt_anchors), weight_received_htlc(opt_anchors), weight_received_htlc(opt_anchors)];
                        let mut inputs_total_weight = 2; // count segwit flags
                        {
                                let mut sighash_parts = sighash::SighashCache::new(&mut claim_tx);
                                for (idx, inp) in inputs_weight.iter().enumerate() {
                                        sign_input!(sighash_parts, idx, 0, inp, sum_actual_sigs, opt_anchors);
                                        inputs_total_weight += inp;
                                }
                        }
                        assert_eq!(base_weight + inputs_total_weight as usize,  claim_tx.weight() + /* max_length_sig */ (73 * inputs_weight.len() - sum_actual_sigs));
                }

                // Justice tx with 1 revoked HTLC-Success tx output
                for &opt_anchors in [false, true].iter() {
                        let mut claim_tx = Transaction { version: 0, lock_time: 0, input: Vec::new(), output: Vec::new() };
                        let mut sum_actual_sigs = 0;
                        claim_tx.input.push(TxIn {
                                previous_output: BitcoinOutPoint {
                                        txid,
                                        vout: 0,
                                },
                                script_sig: Script::new(),
                                sequence: 0xfffffffd,
                                witness: Witness::new(),
                        });
                        claim_tx.output.push(TxOut {
                                script_pubkey: script_pubkey.clone(),
                                value: 0,
                        });
                        let base_weight = claim_tx.weight();
                        let inputs_weight = vec![WEIGHT_REVOKED_OUTPUT];
                        let mut inputs_total_weight = 2; // count segwit flags
                        {
                                let mut sighash_parts = sighash::SighashCache::new(&mut claim_tx);
                                for (idx, inp) in inputs_weight.iter().enumerate() {
                                        sign_input!(sighash_parts, idx, 0, inp, sum_actual_sigs, opt_anchors);
                                        inputs_total_weight += inp;
                                }
                        }
                        assert_eq!(base_weight + inputs_total_weight as usize, claim_tx.weight() + /* max_length_isg */ (73 * inputs_weight.len() - sum_actual_sigs));
                }
        }

        // Further testing is done in the ChannelManager integration tests.
}