Merge pull request #1025 from TheBlueMatt/2021-07-detect-htlcs-on-local-commitment

[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 latest ChannelMonitor must always be actively monitoring for chain updates (and no out-of-date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::{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,Signature};
use bitcoin::secp256k1::key::{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};
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, feature = "fuzztarget", 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 {
                        updates.push(Readable::read(r)?);
                }
                read_tlv_fields!(r, {});
                Ok(Self { update_id, updates })
        }
}

/// An error enum representing a failure to persist a channel monitor update.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum ChannelMonitorUpdateErr {
        /// Used to indicate a temporary failure (eg connection to a watchtower or remote backup of
        /// our state failed, but is expected to succeed at some point in the future).
        ///
        /// Such a failure will "freeze" a channel, preventing us from revoking old states or
        /// submitting new commitment transactions to the counterparty. Once the update(s) which failed
        /// have been successfully applied, ChannelManager::channel_monitor_updated can be used to
        /// restore the channel to an operational state.
        ///
        /// Note that a given ChannelManager will *never* re-generate a given ChannelMonitorUpdate. If
        /// you return a TemporaryFailure you must ensure that it is written to disk safely before
        /// writing out the latest ChannelManager state.
        ///
        /// Even when a channel has been "frozen" updates to the ChannelMonitor can continue to occur
        /// (eg if an inbound HTLC which we forwarded was claimed upstream resulting in us attempting
        /// to claim it on this channel) and those updates must be applied wherever they can be. At
        /// least one such updated ChannelMonitor must be persisted otherwise PermanentFailure should
        /// be returned to get things on-chain ASAP using only the in-memory copy. Obviously updates to
        /// the channel which would invalidate previous ChannelMonitors are not made when a channel has
        /// been "frozen".
        ///
        /// Note that even if updates made after TemporaryFailure succeed you must still call
        /// channel_monitor_updated to ensure you have the latest monitor and re-enable normal channel
        /// operation.
        ///
        /// Note that the update being processed here will not be replayed for you when you call
        /// ChannelManager::channel_monitor_updated, so you must store the update itself along
        /// with the persisted ChannelMonitor on your own local disk prior to returning a
        /// TemporaryFailure. You may, of course, employ a journaling approach, storing only the
        /// ChannelMonitorUpdate on disk without updating the monitor itself, replaying the journal at
        /// reload-time.
        ///
        /// For deployments where a copy of ChannelMonitors and other local state are backed up in a
        /// remote location (with local copies persisted immediately), it is anticipated that all
        /// updates will return TemporaryFailure until the remote copies could be updated.
        TemporaryFailure,
        /// Used to indicate no further channel monitor updates will be allowed (eg we've moved on to a
        /// different watchtower and cannot update with all watchtowers that were previously informed
        /// of this channel).
        ///
        /// At reception of this error, ChannelManager will force-close the channel and return at
        /// least a final ChannelMonitorUpdate::ChannelForceClosed which must be delivered to at
        /// least one ChannelMonitor copy. Revocation secret MUST NOT be released and offchain channel
        /// update must be rejected.
        ///
        /// This failure may also signal a failure to update the local persisted copy of one of
        /// the channel monitor instance.
        ///
        /// Note that even when you fail a holder commitment transaction update, you must store the
        /// update to ensure you can claim from it in case of a duplicate copy of this ChannelMonitor
        /// broadcasts it (e.g distributed channel-monitor deployment)
        ///
        /// In case of distributed watchtowers deployment, the new version must be written to disk, as
        /// state may have been stored but rejected due to a block forcing a commitment broadcast. This
        /// storage is used to claim outputs of rejected state confirmed onchain by another watchtower,
        /// lagging behind on block processing.
        PermanentFailure,
}

/// General Err type for ChannelMonitor actions. Generally, this implies that the data provided is
/// inconsistent with the ChannelMonitor being called. eg for ChannelMonitor::update_monitor this
/// means you tried to update a monitor for a different channel or the ChannelMonitorUpdate was
/// corrupted.
/// Contains a developer-readable error message.
#[derive(Clone, Debug)]
pub struct MonitorUpdateError(pub &'static str);

/// 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 broadcasted.
        CommitmentTxBroadcasted(OutPoint),
}

/// 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) onchain_value_satoshis: Option<u64>,
}
impl_writeable_tlv_based!(HTLCUpdate, {
        (0, payment_hash, required),
        (1, onchain_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.
// 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,
/// 3) if we are waiting on a connection or a channel state update to send an HTLC to a peer, and
///    that HTLC expires within this many blocks, we will simply fail the HTLC instead.
///
/// (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).
///
/// (3) is about our counterparty - we don't want to relay an HTLC to a counterparty when they may
/// end up force-closing the channel on us to 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,
        feerate_per_kw: u32,
        htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Signature>, Option<HTLCSource>)>,
}
impl_writeable_tlv_based!(HolderSignedTx, {
        (0, txid, required),
        (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 counterparty commitment transactions and htlcs outputs and
/// use it to generate any justice or 2nd-stage preimage/timeout transactions.
#[derive(PartialEq)]
struct CounterpartyCommitmentTransaction {
        counterparty_delayed_payment_base_key: PublicKey,
        counterparty_htlc_base_key: PublicKey,
        on_counterparty_tx_csv: u16,
        per_htlc: HashMap<Txid, Vec<HTLCOutputInCommitment>>
}

impl Writeable for CounterpartyCommitmentTransaction {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), io::Error> {
                w.write_all(&byte_utils::be64_to_array(self.per_htlc.len() as u64))?;
                for (ref txid, ref htlcs) in self.per_htlc.iter() {
                        w.write_all(&txid[..])?;
                        w.write_all(&byte_utils::be64_to_array(htlcs.len() as u64))?;
                        for &ref htlc in htlcs.iter() {
                                htlc.write(w)?;
                        }
                }
                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 CounterpartyCommitmentTransaction {
        fn read<R: io::Read>(r: &mut R) -> Result<Self, DecodeError> {
                let counterparty_commitment_transaction = {
                        let per_htlc_len: u64 = Readable::read(r)?;
                        let mut per_htlc = HashMap::with_capacity(cmp::min(per_htlc_len as usize, MAX_ALLOC_SIZE / 64));
                        for _  in 0..per_htlc_len {
                                let txid: Txid = Readable::read(r)?;
                                let htlcs_count: u64 = Readable::read(r)?;
                                let mut htlcs = Vec::with_capacity(cmp::min(htlcs_count as usize, MAX_ALLOC_SIZE / 32));
                                for _ in 0..htlcs_count {
                                        let htlc = Readable::read(r)?;
                                        htlcs.push(htlc);
                                }
                                if let Some(_) = per_htlc.insert(txid, htlcs) {
                                        return Err(DecodeError::InvalidValue);
                                }
                        }
                        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),
                        });
                        CounterpartyCommitmentTransaction {
                                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,
                                per_htlc,
                        }
                };
                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;
                if let OnchainEvent::MaturingOutput {
                        descriptor: SpendableOutputDescriptor::DelayedPaymentOutput(ref descriptor)
                } = self.event {
                        // 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);
                }
                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 {
        /// HTLC output getting solved by a timeout, at maturation we pass upstream payment source information to solve
        /// inbound HTLC in backward channel. Note, in case of preimage, we pass info to upstream without delay as we can
        /// only win from it, so it's never an OnchainEvent
        HTLCUpdate {
                source: HTLCSource,
                payment_hash: PaymentHash,
                onchain_value_satoshis: Option<u64>,
        },
        MaturingOutput {
                descriptor: SpendableOutputDescriptor,
        },
}

impl_writeable_tlv_based!(OnchainEventEntry, {
        (0, txid, required),
        (2, height, required),
        (4, event, required),
});

impl_writeable_tlv_based_enum!(OnchainEvent,
        (0, HTLCUpdate) => {
                (0, source, required),
                (1, onchain_value_satoshis, option),
                (2, payment_hash, required),
        },
        (1, MaturingOutput) => {
                (0, descriptor, required),
        },
;);

#[cfg_attr(any(test, feature = "fuzztarget", 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_revocation_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_writeable_tlv_based_enum!(ChannelMonitorUpdateStep,
        (0, LatestHolderCommitmentTXInfo) => {
                (0, commitment_tx, required),
                (2, htlc_outputs, vec_type),
        },
        (1, LatestCounterpartyCommitmentTXInfo) => {
                (0, commitment_txid, required),
                (2, commitment_number, required),
                (4, their_revocation_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),
        },
;);

/// 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_tx_cache: CounterpartyCommitmentTransaction,
        funding_redeemscript: Script,
        channel_value_satoshis: u64,
        // first is the idx of the first of the two revocation points
        their_cur_revocation_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,

        payment_preimages: HashMap<PaymentHash, PaymentPreimage>,

        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,

        // 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,

        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, feature = "fuzztarget", feature = "_test_utils"))]
/// Used only in testing and fuzztarget 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, feature = "fuzztarget", feature = "_test_utils"))]
/// Used only in testing and fuzztarget 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_tx_cache != other.counterparty_tx_cache ||
                        self.funding_redeemscript != other.funding_redeemscript ||
                        self.channel_value_satoshis != other.channel_value_satoshis ||
                        self.their_cur_revocation_points != other.their_cur_revocation_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
                {
                        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_tx_cache.write(writer)?;
                self.funding_redeemscript.write(writer)?;
                self.channel_value_satoshis.write(writer)?;

                match self.their_cur_revocation_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() {
                                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(&byte_utils::be64_to_array(self.pending_monitor_events.len() as u64))?;
                for event in self.pending_monitor_events.iter() {
                        match event {
                                MonitorEvent::HTLCEvent(upd) => {
                                        0u8.write(writer)?;
                                        upd.write(writer)?;
                                },
                                MonitorEvent::CommitmentTxBroadcasted(_) => 1u8.write(writer)?
                        }
                }

                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, {});

                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) -> 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_tx_cache = CounterpartyCommitmentTransaction { counterparty_delayed_payment_base_key, counterparty_htlc_base_key, on_counterparty_tx_csv, per_htlc: HashMap::new() };

                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,
                                feerate_per_kw: trusted_tx.feerate_per_kw(),
                                htlc_outputs: Vec::new(), // There are never any HTLCs in the initial commitment transactions
                        };
                        (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_tx_cache,
                                funding_redeemscript,
                                channel_value_satoshis,
                                their_cur_revocation_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,

                                best_block,

                                secp_ctx,
                        }),
                }
        }

        #[cfg(test)]
        fn provide_secret(&self, idx: u64, secret: [u8; 32]) -> Result<(), MonitorUpdateError> {
                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_revocation_point: PublicKey,
                logger: &L,
        ) where L::Target: Logger {
                self.inner.lock().unwrap().provide_latest_counterparty_commitment_tx(
                        txid, htlc_outputs, commitment_number, their_revocation_point, logger)
        }

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

        #[cfg(test)]
        pub(crate) fn provide_payment_preimage<B: Deref, F: Deref, L: Deref>(
                &self,
                payment_hash: &PaymentHash,
                payment_preimage: &PaymentPreimage,
                broadcaster: &B,
                fee_estimator: &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<(), MonitorUpdateError>
        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()
        }

        /// 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,
        {
                self.inner.lock().unwrap().transactions_confirmed(
                        header, txdata, height, broadcaster, 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,
        {
                self.inner.lock().unwrap().transaction_unconfirmed(
                        txid, broadcaster, 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,
        {
                self.inner.lock().unwrap().best_block_updated(
                        header, height, broadcaster, 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()
        }
}

/// 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_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 {
                                                                        matched_htlc = true;
                                                                        break;
                                                                }
                                                        }
                                                        if matched_htlc { continue; }
                                                        $self.onchain_events_awaiting_threshold_conf.retain(|ref entry| {
                                                                if entry.height != $commitment_tx_conf_height { return true; }
                                                                match entry.event {
                                                                        OnchainEvent::HTLCUpdate { source: ref update_source, .. } => {
                                                                                *update_source != **source
                                                                        },
                                                                        _ => true,
                                                                }
                                                        });
                                                        let entry = OnchainEventEntry {
                                                                txid: *$txid,
                                                                height: $commitment_tx_conf_height,
                                                                event: OnchainEvent::HTLCUpdate {
                                                                        source: (**source).clone(),
                                                                        payment_hash: htlc.payment_hash.clone(),
                                                                        onchain_value_satoshis: Some(htlc.amount_msat / 1000),
                                                                },
                                                        };
                                                        log_trace!($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, 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");
                }
        } }
}

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<(), MonitorUpdateError> {
                if let Err(()) = self.commitment_secrets.provide_secret(idx, secret) {
                        return Err(MonitorUpdateError("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_revocation_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_revocation_points {
                        Some(old_points) => {
                                if old_points.0 == commitment_number + 1 {
                                        self.their_cur_revocation_points = Some((old_points.0, old_points.1, Some(their_revocation_point)));
                                } else if old_points.0 == commitment_number + 2 {
                                        if let Some(old_second_point) = old_points.2 {
                                                self.their_cur_revocation_points = Some((old_points.0 - 1, old_second_point, Some(their_revocation_point)));
                                        } else {
                                                self.their_cur_revocation_points = Some((commitment_number, their_revocation_point, None));
                                        }
                                } else {
                                        self.their_cur_revocation_points = Some((commitment_number, their_revocation_point, None));
                                }
                        },
                        None => {
                                self.their_cur_revocation_points = Some((commitment_number, their_revocation_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);
                        }
                }
                self.counterparty_tx_cache.per_htlc.insert(txid, htlcs);
        }

        /// 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<(), MonitorUpdateError> {
                // 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,
                                feerate_per_kw: trusted_tx.feerate_per_kw(),
                                htlc_outputs,
                        }
                };
                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(MonitorUpdateError("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: &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::CommitmentTxBroadcasted(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<(), MonitorUpdateError>
        where B::Target: BroadcasterInterface,
                    F::Target: FeeEstimator,
                    L::Target: Logger,
        {
                // 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 {
                        match updates.updates[0] {
                                ChannelMonitorUpdateStep::PaymentPreimage { .. } => {},
                                _ => panic!("Attempted to apply post-force-close ChannelMonitorUpdate that wasn't providing a payment preimage"),
                        }
                        assert_eq!(updates.updates.len(), 1);
                } 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!");
                }
                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!(); }
                                        self.provide_latest_holder_commitment_tx(commitment_tx.clone(), htlc_outputs.clone())?
                                }
                                ChannelMonitorUpdateStep::LatestCounterpartyCommitmentTXInfo { commitment_txid, htlc_outputs, commitment_number, their_revocation_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_revocation_point, logger)
                                },
                                ChannelMonitorUpdateStep::PaymentPreimage { payment_preimage } => {
                                        log_trace!(logger, "Updating ChannelMonitor with payment preimage");
                                        self.provide_payment_preimage(&PaymentHash(Sha256::hash(&payment_preimage.0[..]).into_inner()), &payment_preimage, broadcaster, fee_estimator, logger)
                                },
                                ChannelMonitorUpdateStep::CommitmentSecret { idx, secret } => {
                                        log_trace!(logger, "Updating ChannelMonitor with commitment secret");
                                        self.provide_secret(*idx, *secret)?
                                },
                                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::CommitmentTxBroadcasted, 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;
                Ok(())
        }

        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_tx_cache.counterparty_delayed_payment_base_key));

                        let revokeable_redeemscript = chan_utils::get_revokeable_redeemscript(&revocation_pubkey, self.counterparty_tx_cache.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_tx_cache.counterparty_delayed_payment_base_key, self.counterparty_tx_cache.counterparty_htlc_base_key, per_commitment_key, outp.value, self.counterparty_tx_cache.on_counterparty_tx_csv);
                                        let justice_package = PackageTemplate::build_package(commitment_txid, idx as u32, PackageSolvingData::RevokedOutput(revk_outp), height + self.counterparty_tx_cache.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_tx_cache.counterparty_delayed_payment_base_key, self.counterparty_tx_cache.counterparty_htlc_base_key, per_commitment_key, htlc.amount_msat / 1000, htlc.clone());
                                                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);

                                fail_unbroadcast_htlcs!(self, "revoked counterparty", height, [].iter().map(|a| *a), 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", height, per_commitment_data.iter().map(|(a, b)| (a, b.as_ref().map(|b| b.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(revocation_points) = self.their_cur_revocation_points {
                                let revocation_point_option =
                                        // If the counterparty commitment tx is the latest valid state, use their latest
                                        // per-commitment point
                                        if revocation_points.0 == commitment_number { Some(&revocation_points.1) }
                                        else if let Some(point) = revocation_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 revocation_points.0 == commitment_number + 1 { Some(point) } else { None }
                                        } else { None };
                                if let Some(revocation_point) = revocation_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(*revocation_point, self.counterparty_tx_cache.counterparty_delayed_payment_base_key, self.counterparty_tx_cache.counterparty_htlc_base_key, preimage.unwrap(), htlc.clone())) } else { PackageSolvingData::CounterpartyReceivedHTLCOutput(CounterpartyReceivedHTLCOutput::build(*revocation_point, self.counterparty_tx_cache.counterparty_delayed_payment_base_key, self.counterparty_tx_cache.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_tx_cache.counterparty_delayed_payment_base_key, self.counterparty_tx_cache.counterparty_htlc_base_key, per_commitment_key, tx.output[0].value, self.counterparty_tx_cache.on_counterparty_tx_csv);
                let justice_package = PackageTemplate::build_package(htlc_txid, 0, PackageSolvingData::RevokedOutput(revk_outp), height + self.counterparty_tx_cache.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.
        fn check_spend_holder_transaction<L: Deref>(&mut self, tx: &Transaction, height: u32, logger: &L) -> (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", height, self.current_holder_commitment_tx.htlc_outputs.iter().map(|(a, _, c)| (a, c.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", height, holder_tx.htlc_outputs.iter().map(|(a, _, c)| (a, c.as_ref())), logger);
                        }
                }

                if is_holder_tx {
                }

                (claim_requests, (commitment_txid, watch_outputs))
        }

        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();
                log_trace!(logger, "New best block {} at height {}", block_hash, height);
                self.best_block = BestBlock::new(block_hash, height);

                self.transactions_confirmed(header, txdata, height, broadcaster, fee_estimator, logger)
        }

        fn best_block_updated<B: Deref, F: Deref, L: Deref>(
                &mut 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 block_hash = header.block_hash();
                log_trace!(logger, "New best block {} at height {}", block_hash, height);

                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: 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();
                log_trace!(logger, "Block {} at height {} connected with {} txn matched", block_hash, height, txn_matched.len());

                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 {
                                        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);
                                                }
                                                if new_outpoints.is_empty() {
                                                        let (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);
                                                }
                                                claimable_outpoints.append(&mut new_outpoints);
                                        }
                                } 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: &F,
                logger: &L,
        ) -> Vec<TransactionOutputs>
        where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                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::CommitmentTxBroadcasted(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),
                                OnchainEvent::MaturingOutput { .. } => 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, onchain_value_satoshis } => {
                                        // 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 has got enough confirmations to be passed upstream", log_bytes!(payment_hash.0));
                                        self.pending_monitor_events.push(MonitorEvent::HTLCEvent(HTLCUpdate {
                                                payment_hash,
                                                payment_preimage: None,
                                                source: source.clone(),
                                                onchain_value_satoshis,
                                        }));
                                },
                                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]
                                        });
                                }
                        }
                }

                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);

                self.onchain_tx_handler.block_disconnected(height, broadcaster, 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: F,
                logger: L,
        ) where
                B::Target: BroadcasterInterface,
                F::Target: FeeEstimator,
                L::Target: Logger,
        {
                self.onchain_events_awaiting_threshold_conf.retain(|ref entry| entry.txid != *txid);
                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() {
                                                                assert_eq!(&bitcoin::Address::p2wsh(&Script::from(input.witness.last().unwrap().clone()), 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 revocation_sig_claim = (input.witness.len() == 3 && HTLCType::scriptlen_to_htlctype(input.witness[2].len()) == Some(HTLCType::OfferedHTLC) && input.witness[1].len() == 33)
                                || (input.witness.len() == 3 && HTLCType::scriptlen_to_htlctype(input.witness[2].len()) == Some(HTLCType::AcceptedHTLC) && input.witness[1].len() == 33);
                        let accepted_preimage_claim = input.witness.len() == 5 && HTLCType::scriptlen_to_htlctype(input.witness[4].len()) == Some(HTLCType::AcceptedHTLC);
                        let offered_preimage_claim = input.witness.len() == 3 && HTLCType::scriptlen_to_htlctype(input.witness[2].len()) == Some(HTLCType::OfferedHTLC);

                        macro_rules! log_claim {
                                ($tx_info: expr, $holder_tx: expr, $htlc: expr, $source_avail: expr) => {
                                        // We found the output in question, but aren't failing it backwards
                                        // as we have no corresponding source and no valid counterparty commitment txid
                                        // to try a weak source binding with same-hash, same-value still-valid offered HTLC.
                                        // This implies either it is an inbound HTLC or an outbound HTLC on a revoked transaction.
                                        let outbound_htlc = $holder_tx == $htlc.offered;
                                        if ($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);
                                                                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 {
                                let mut payment_preimage = PaymentPreimage([0; 32]);
                                if accepted_preimage_claim {
                                        if !self.pending_monitor_events.iter().any(
                                                |update| if let &MonitorEvent::HTLCEvent(ref upd) = update { upd.source == source } else { false }) {
                                                payment_preimage.0.copy_from_slice(&input.witness[3]);
                                                self.pending_monitor_events.push(MonitorEvent::HTLCEvent(HTLCUpdate {
                                                        source,
                                                        payment_preimage: Some(payment_preimage),
                                                        payment_hash,
                                                        onchain_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 }) {
                                                payment_preimage.0.copy_from_slice(&input.witness[1]);
                                                self.pending_monitor_events.push(MonitorEvent::HTLCEvent(HTLCUpdate {
                                                        source,
                                                        payment_preimage: Some(payment_preimage),
                                                        payment_hash,
                                                        onchain_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,
                                                        onchain_value_satoshis: Some(amount_msat / 1000),
                                                },
                                        };
                                        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);
                }
        }
}

/// `Persist` defines behavior for persisting channel monitors: this could mean
/// writing once to disk, and/or uploading to one or more backup services.
///
/// Note that for every new monitor, you **must** persist the new `ChannelMonitor`
/// to disk/backups. And, on every update, you **must** persist either the
/// `ChannelMonitorUpdate` or the updated monitor itself. Otherwise, there is risk
/// of situations such as revoking a transaction, then crashing before this
/// revocation can be persisted, then unintentionally broadcasting a revoked
/// transaction and losing money. This is a risk because previous channel states
/// are toxic, so it's important that whatever channel state is persisted is
/// kept up-to-date.
pub trait Persist<ChannelSigner: Sign> {
        /// Persist a new channel's data. The data can be stored any way you want, but
        /// the identifier provided by Rust-Lightning is the channel's outpoint (and
        /// it is up to you to maintain a correct mapping between the outpoint and the
        /// stored channel data). Note that you **must** persist every new monitor to
        /// disk. See the `Persist` trait documentation for more details.
        ///
        /// See [`ChannelMonitor::write`] for writing out a `ChannelMonitor`,
        /// and [`ChannelMonitorUpdateErr`] for requirements when returning errors.
        fn persist_new_channel(&self, id: OutPoint, data: &ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr>;

        /// Update one channel's data. The provided `ChannelMonitor` has already
        /// applied the given update.
        ///
        /// Note that on every update, you **must** persist either the
        /// `ChannelMonitorUpdate` or the updated monitor itself to disk/backups. See
        /// the `Persist` trait documentation for more details.
        ///
        /// If an implementer chooses to persist the updates only, they need to make
        /// sure that all the updates are applied to the `ChannelMonitors` *before*
        /// the set of channel monitors is given to the `ChannelManager`
        /// deserialization routine. See [`ChannelMonitor::update_monitor`] for
        /// applying a monitor update to a monitor. If full `ChannelMonitors` are
        /// persisted, then there is no need to persist individual updates.
        ///
        /// Note that there could be a performance tradeoff between persisting complete
        /// channel monitors on every update vs. persisting only updates and applying
        /// them in batches. The size of each monitor grows `O(number of state updates)`
        /// whereas updates are small and `O(1)`.
        ///
        /// See [`ChannelMonitor::write`] for writing out a `ChannelMonitor`,
        /// [`ChannelMonitorUpdate::write`] for writing out an update, and
        /// [`ChannelMonitorUpdateErr`] for requirements when returning errors.
        fn update_persisted_channel(&self, id: OutPoint, update: &ChannelMonitorUpdate, data: &ChannelMonitor<ChannelSigner>) -> Result<(), ChannelMonitorUpdateErr>;
}

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 block_connected(&self, block: &Block, height: u32) {
                let txdata: Vec<_> = block.txdata.iter().enumerate().collect();
                self.0.block_connected(&block.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_tx_cache = Readable::read(reader)?;
                let funding_redeemscript = Readable::read(reader)?;
                let channel_value_satoshis = Readable::read(reader)?;

                let their_cur_revocation_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 prev_holder_signed_commitment_tx = match <u8 as Readable>::read(reader)? {
                        0 => None,
                        1 => {
                                Some(Readable::read(reader)?)
                        },
                        _ => return Err(DecodeError::InvalidValue),
                };
                let current_holder_commitment_tx = 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 = 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::CommitmentTxBroadcasted(funding_info.0),
                                _ => return Err(DecodeError::InvalidValue)
                        };
                        pending_monitor_events.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 {
                        onchain_events_awaiting_threshold_conf.push(Readable::read(reader)?);
                }

                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 = ReadableArgs::read(reader, keys_manager)?;

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

                read_tlv_fields!(reader, {});

                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_tx_cache,
                                funding_redeemscript,
                                channel_value_satoshis,
                                their_cur_revocation_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_events,

                                onchain_events_awaiting_threshold_conf,
                                outputs_to_watch,

                                onchain_tx_handler,

                                lockdown_from_offchain,
                                holder_tx_signed,

                                best_block,

                                secp_ctx,
                        }),
                }))
        }
}

#[cfg(test)]
mod tests {
        use bitcoin::blockdata::script::{Script, Builder};
        use bitcoin::blockdata::opcodes;
        use bitcoin::blockdata::transaction::{Transaction, TxIn, TxOut, SigHashType};
        use bitcoin::blockdata::transaction::OutPoint as BitcoinOutPoint;
        use bitcoin::util::bip143;
        use bitcoin::hashes::Hash;
        use bitcoin::hashes::sha256::Hash as Sha256;
        use bitcoin::hashes::hex::FromHex;
        use bitcoin::hash_types::Txid;
        use bitcoin::network::constants::Network;
        use hex;
        use chain::BestBlock;
        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 ln::{PaymentPreimage, PaymentHash};
        use ln::chan_utils;
        use ln::chan_utils::{HTLCOutputInCommitment, ChannelPublicKeys, ChannelTransactionParameters, HolderCommitmentTransaction, CounterpartyChannelTransactionParameters};
        use ln::script::ShutdownScript;
        use util::test_utils::{TestLogger, TestBroadcaster, TestFeeEstimator};
        use bitcoin::secp256k1::key::{SecretKey,PublicKey};
        use bitcoin::secp256k1::Secp256k1;
        use sync::{Arc, Mutex};
        use chain::keysinterface::InMemorySigner;
        use prelude::*;

        #[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 = Arc::new(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(),
                        [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),
                };
                // 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);

                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() {
                        monitor.provide_payment_preimage(hash, preimage, &broadcaster, &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);
                let mut sum_actual_sigs = 0;

                macro_rules! sign_input {
                        ($sighash_parts: expr, $idx: expr, $amount: expr, $weight: expr, $sum_actual_sigs: expr) => {
                                let htlc = HTLCOutputInCommitment {
                                        offered: if *$weight == WEIGHT_REVOKED_OFFERED_HTLC || *$weight == WEIGHT_OFFERED_HTLC { true } else { false },
                                        amount_msat: 0,
                                        cltv_expiry: 2 << 16,
                                        payment_hash: PaymentHash([1; 32]),
                                        transaction_output_index: Some($idx as u32),
                                };
                                let redeem_script = if *$weight == WEIGHT_REVOKED_OUTPUT { chan_utils::get_revokeable_redeemscript(&pubkey, 256, &pubkey) } else { chan_utils::get_htlc_redeemscript_with_explicit_keys(&htlc, &pubkey, &pubkey, &pubkey) };
                                let sighash = hash_to_message!(&$sighash_parts.signature_hash($idx, &redeem_script, $amount, SigHashType::All)[..]);
                                let sig = secp_ctx.sign(&sighash, &privkey);
                                $sighash_parts.access_witness($idx).push(sig.serialize_der().to_vec());
                                $sighash_parts.access_witness($idx)[0].push(SigHashType::All as u8);
                                sum_actual_sigs += $sighash_parts.access_witness($idx)[0].len();
                                if *$weight == WEIGHT_REVOKED_OUTPUT {
                                        $sighash_parts.access_witness($idx).push(vec!(1));
                                } else if *$weight == WEIGHT_REVOKED_OFFERED_HTLC || *$weight == WEIGHT_REVOKED_RECEIVED_HTLC {
                                        $sighash_parts.access_witness($idx).push(pubkey.clone().serialize().to_vec());
                                } else if *$weight == WEIGHT_RECEIVED_HTLC {
                                        $sighash_parts.access_witness($idx).push(vec![0]);
                                } else {
                                        $sighash_parts.access_witness($idx).push(PaymentPreimage([1; 32]).0.to_vec());
                                }
                                $sighash_parts.access_witness($idx).push(redeem_script.into_bytes());
                                println!("witness[0] {}", $sighash_parts.access_witness($idx)[0].len());
                                println!("witness[1] {}", $sighash_parts.access_witness($idx)[1].len());
                                println!("witness[2] {}", $sighash_parts.access_witness($idx)[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
                let mut claim_tx = Transaction { version: 0, lock_time: 0, input: Vec::new(), output: Vec::new() };
                for i in 0..4 {
                        claim_tx.input.push(TxIn {
                                previous_output: BitcoinOutPoint {
                                        txid,
                                        vout: i,
                                },
                                script_sig: Script::new(),
                                sequence: 0xfffffffd,
                                witness: Vec::new(),
                        });
                }
                claim_tx.output.push(TxOut {
                        script_pubkey: script_pubkey.clone(),
                        value: 0,
                });
                let base_weight = claim_tx.get_weight();
                let inputs_weight = vec![WEIGHT_REVOKED_OUTPUT, WEIGHT_REVOKED_OFFERED_HTLC, WEIGHT_REVOKED_OFFERED_HTLC, WEIGHT_REVOKED_RECEIVED_HTLC];
                let mut inputs_total_weight = 2; // count segwit flags
                {
                        let mut sighash_parts = bip143::SigHashCache::new(&mut claim_tx);
                        for (idx, inp) in inputs_weight.iter().enumerate() {
                                sign_input!(sighash_parts, idx, 0, inp, sum_actual_sigs);
                                inputs_total_weight += inp;
                        }
                }
                assert_eq!(base_weight + inputs_total_weight as usize,  claim_tx.get_weight() + /* max_length_sig */ (73 * inputs_weight.len() - sum_actual_sigs));

                // Claim tx with 1 offered HTLCs, 3 received HTLCs
                claim_tx.input.clear();
                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: Vec::new(),
                        });
                }
                let base_weight = claim_tx.get_weight();
                let inputs_weight = vec![WEIGHT_OFFERED_HTLC, WEIGHT_RECEIVED_HTLC, WEIGHT_RECEIVED_HTLC, WEIGHT_RECEIVED_HTLC];
                let mut inputs_total_weight = 2; // count segwit flags
                {
                        let mut sighash_parts = bip143::SigHashCache::new(&mut claim_tx);
                        for (idx, inp) in inputs_weight.iter().enumerate() {
                                sign_input!(sighash_parts, idx, 0, inp, sum_actual_sigs);
                                inputs_total_weight += inp;
                        }
                }
                assert_eq!(base_weight + inputs_total_weight as usize,  claim_tx.get_weight() + /* max_length_sig */ (73 * inputs_weight.len() - sum_actual_sigs));

                // Justice tx with 1 revoked HTLC-Success tx output
                claim_tx.input.clear();
                sum_actual_sigs = 0;
                claim_tx.input.push(TxIn {
                        previous_output: BitcoinOutPoint {
                                txid,
                                vout: 0,
                        },
                        script_sig: Script::new(),
                        sequence: 0xfffffffd,
                        witness: Vec::new(),
                });
                let base_weight = claim_tx.get_weight();
                let inputs_weight = vec![WEIGHT_REVOKED_OUTPUT];
                let mut inputs_total_weight = 2; // count segwit flags
                {
                        let mut sighash_parts = bip143::SigHashCache::new(&mut claim_tx);
                        for (idx, inp) in inputs_weight.iter().enumerate() {
                                sign_input!(sighash_parts, idx, 0, inp, sum_actual_sigs);
                                inputs_total_weight += inp;
                        }
                }
                assert_eq!(base_weight + inputs_total_weight as usize, claim_tx.get_weight() + /* max_length_isg */ (73 * inputs_weight.len() - sum_actual_sigs));
        }

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