Clarify documentation on deserialization reorg requirements

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

//! 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 ManyChannelMonitor for more.
//!
//! Note that ChannelMonitors are an important part of the lightning trust model and a copy of the
//! latest ChannelMonitor must always be actively monitoring for chain updates (and no out-of-date
//! ChannelMonitors should do so). Thus, if you're building rust-lightning into an HSM or other
//! security-domain-separated system design, you should consider having multiple paths for
//! ChannelMonitors to get out of the HSM and onto monitoring devices.

use bitcoin::blockdata::block::BlockHeader;
use bitcoin::blockdata::transaction::{TxOut,Transaction};
use bitcoin::blockdata::transaction::OutPoint as BitcoinOutPoint;
use bitcoin::blockdata::script::{Script, Builder};
use bitcoin::blockdata::opcodes;
use bitcoin::consensus::encode;
use bitcoin::util::hash::BitcoinHash;

use bitcoin_hashes::Hash;
use bitcoin_hashes::sha256::Hash as Sha256;
use bitcoin_hashes::hash160::Hash as Hash160;
use bitcoin_hashes::sha256d::Hash as Sha256dHash;

use secp256k1::{Secp256k1,Signature};
use secp256k1::key::{SecretKey,PublicKey};
use secp256k1;

use ln::msgs::DecodeError;
use ln::chan_utils;
use ln::chan_utils::{CounterpartyCommitmentSecrets, HTLCOutputInCommitment, LocalCommitmentTransaction, HTLCType};
use ln::channelmanager::{HTLCSource, PaymentPreimage, PaymentHash};
use ln::onchaintx::OnchainTxHandler;
use chain::chaininterface::{ChainListener, ChainWatchInterface, BroadcasterInterface, FeeEstimator};
use chain::transaction::OutPoint;
use chain::keysinterface::{SpendableOutputDescriptor, ChannelKeys};
use util::logger::Logger;
use util::ser::{ReadableArgs, Readable, MaybeReadable, Writer, Writeable, U48};
use util::{byte_utils, events};

use std::collections::{HashMap, hash_map};
use std::sync::{Arc,Mutex};
use std::{hash,cmp, mem};
use std::ops::Deref;

/// An update generated by the underlying Channel itself which contains some new information the
/// ChannelMonitor should be made aware of.
#[cfg_attr(test, derive(PartialEq))]
#[derive(Clone)]
#[must_use]
pub struct ChannelMonitorUpdate {
        pub(super) 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.
        ///
        /// 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.
        pub update_id: u64,
}

impl Writeable for ChannelMonitorUpdate {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                self.update_id.write(w)?;
                (self.updates.len() as u64).write(w)?;
                for update_step in self.updates.iter() {
                        update_step.write(w)?;
                }
                Ok(())
        }
}
impl Readable for ChannelMonitorUpdate {
        fn read<R: ::std::io::Read>(r: &mut R) -> Result<Self, DecodeError> {
                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 / ::std::mem::size_of::<ChannelMonitorUpdateStep>()));
                for _ in 0..len {
                        updates.push(Readable::read(r)?);
                }
                Ok(Self { update_id, updates })
        }
}

/// An error enum representing a failure to persist a channel monitor update.
#[derive(Clone)]
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 remote party. 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). This will force-close the channel in question (which will generate one
        /// final ChannelMonitorUpdate which must be delivered to at least one ChannelMonitor copy).
        ///
        /// Should also be used to indicate a failure to update the local persisted copy of the channel
        /// monitor.
        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 human-readable error message.
#[derive(Debug)]
pub struct MonitorUpdateError(pub &'static str);

/// Simple structure send back by ManyChannelMonitor in case of HTLC detected onchain from a
/// forward channel and from which info are needed to update HTLC in a backward channel.
#[derive(Clone, PartialEq)]
pub struct HTLCUpdate {
        pub(super) payment_hash: PaymentHash,
        pub(super) payment_preimage: Option<PaymentPreimage>,
        pub(super) source: HTLCSource
}
impl_writeable!(HTLCUpdate, 0, { payment_hash, payment_preimage, source });

/// Simple trait indicating ability to track a set of ChannelMonitors and multiplex events between
/// them. Generally should be implemented by keeping a local SimpleManyChannelMonitor and passing
/// events to it, while also taking any add/update_monitor events and passing them to some remote
/// server(s).
///
/// In general, you must always have at least one local copy in memory, which must never fail to
/// update (as it is responsible for broadcasting the latest state in case the channel is closed),
/// and then persist it to various on-disk locations. If, for some reason, the in-memory copy fails
/// to update (eg out-of-memory or some other condition), you must immediately shut down without
/// taking any further action such as writing the current state to disk. This should likely be
/// accomplished via panic!() or abort().
///
/// Note that any updates to a channel's monitor *must* be applied to each instance of the
/// channel's monitor everywhere (including remote watchtowers) *before* this function returns. If
/// an update occurs and a remote watchtower is left with old state, it may broadcast transactions
/// which we have revoked, allowing our counterparty to claim all funds in the channel!
///
/// User needs to notify implementors of ManyChannelMonitor when a new block is connected or
/// disconnected using their `block_connected` and `block_disconnected` methods. However, rather
/// than calling these methods directly, the user should register implementors as listeners to the
/// BlockNotifier and call the BlockNotifier's `block_(dis)connected` methods, which will notify
/// all registered listeners in one go.
pub trait ManyChannelMonitor<ChanSigner: ChannelKeys>: Send + Sync {
        /// Adds a monitor for the given `funding_txo`.
        ///
        /// Implementer must also ensure that the funding_txo txid *and* outpoint are registered with
        /// any relevant ChainWatchInterfaces such that the provided monitor receives block_connected
        /// callbacks with the funding transaction, or any spends of it.
        ///
        /// Further, the implementer must also ensure that each output returned in
        /// monitor.get_outputs_to_watch() is registered to ensure that the provided monitor learns about
        /// any spends of any of the outputs.
        ///
        /// Any spends of outputs which should have been registered which aren't passed to
        /// ChannelMonitors via block_connected may result in FUNDS LOSS.
        fn add_monitor(&self, funding_txo: OutPoint, monitor: ChannelMonitor<ChanSigner>) -> Result<(), ChannelMonitorUpdateErr>;

        /// Updates a monitor for the given `funding_txo`.
        ///
        /// Implementer must also ensure that the funding_txo txid *and* outpoint are registered with
        /// any relevant ChainWatchInterfaces such that the provided monitor receives block_connected
        /// callbacks with the funding transaction, or any spends of it.
        ///
        /// Further, the implementer must also ensure that each output returned in
        /// monitor.get_watch_outputs() is registered to ensure that the provided monitor learns about
        /// any spends of any of the outputs.
        ///
        /// Any spends of outputs which should have been registered which aren't passed to
        /// ChannelMonitors via block_connected may result in FUNDS LOSS.
        fn update_monitor(&self, funding_txo: OutPoint, monitor: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr>;

        /// Used by ChannelManager to get list of HTLC resolved onchain and which needed to be updated
        /// with success or failure.
        ///
        /// You should probably just call through to
        /// ChannelMonitor::get_and_clear_pending_htlcs_updated() for each ChannelMonitor and return
        /// the full list.
        fn get_and_clear_pending_htlcs_updated(&self) -> Vec<HTLCUpdate>;
}

/// A simple implementation of a ManyChannelMonitor and ChainListener. Can be used to create a
/// watchtower or watch our own channels.
///
/// Note that you must provide your own key by which to refer to channels.
///
/// If you're accepting remote monitors (ie are implementing a watchtower), you must verify that
/// users cannot overwrite a given channel by providing a duplicate key. ie you should probably
/// index by a PublicKey which is required to sign any updates.
///
/// If you're using this for local monitoring of your own channels, you probably want to use
/// `OutPoint` as the key, which will give you a ManyChannelMonitor implementation.
pub struct SimpleManyChannelMonitor<Key, ChanSigner: ChannelKeys, T: Deref, F: Deref>
        where T::Target: BroadcasterInterface,
        F::Target: FeeEstimator
{
        #[cfg(test)] // Used in ChannelManager tests to manipulate channels directly
        pub monitors: Mutex<HashMap<Key, ChannelMonitor<ChanSigner>>>,
        #[cfg(not(test))]
        monitors: Mutex<HashMap<Key, ChannelMonitor<ChanSigner>>>,
        chain_monitor: Arc<ChainWatchInterface>,
        broadcaster: T,
        logger: Arc<Logger>,
        fee_estimator: F
}

impl<'a, Key : Send + cmp::Eq + hash::Hash, ChanSigner: ChannelKeys, T: Deref + Sync + Send, F: Deref + Sync + Send>
        ChainListener for SimpleManyChannelMonitor<Key, ChanSigner, T, F>
        where T::Target: BroadcasterInterface,
              F::Target: FeeEstimator
{
        fn block_connected(&self, header: &BlockHeader, height: u32, txn_matched: &[&Transaction], _indexes_of_txn_matched: &[u32]) {
                let block_hash = header.bitcoin_hash();
                {
                        let mut monitors = self.monitors.lock().unwrap();
                        for monitor in monitors.values_mut() {
                                let txn_outputs = monitor.block_connected(txn_matched, height, &block_hash, &*self.broadcaster, &*self.fee_estimator);

                                for (ref txid, ref outputs) in txn_outputs {
                                        for (idx, output) in outputs.iter().enumerate() {
                                                self.chain_monitor.install_watch_outpoint((txid.clone(), idx as u32), &output.script_pubkey);
                                        }
                                }
                        }
                }
        }

        fn block_disconnected(&self, header: &BlockHeader, disconnected_height: u32) {
                let block_hash = header.bitcoin_hash();
                let mut monitors = self.monitors.lock().unwrap();
                for monitor in monitors.values_mut() {
                        monitor.block_disconnected(disconnected_height, &block_hash, &*self.broadcaster, &*self.fee_estimator);
                }
        }
}

impl<Key : Send + cmp::Eq + hash::Hash + 'static, ChanSigner: ChannelKeys, T: Deref, F: Deref> SimpleManyChannelMonitor<Key, ChanSigner, T, F>
        where T::Target: BroadcasterInterface,
              F::Target: FeeEstimator
{
        /// Creates a new object which can be used to monitor several channels given the chain
        /// interface with which to register to receive notifications.
        pub fn new(chain_monitor: Arc<ChainWatchInterface>, broadcaster: T, logger: Arc<Logger>, feeest: F) -> SimpleManyChannelMonitor<Key, ChanSigner, T, F> {
                let res = SimpleManyChannelMonitor {
                        monitors: Mutex::new(HashMap::new()),
                        chain_monitor,
                        broadcaster,
                        logger,
                        fee_estimator: feeest,
                };

                res
        }

        /// Adds or updates the monitor which monitors the channel referred to by the given key.
        pub fn add_monitor_by_key(&self, key: Key, monitor: ChannelMonitor<ChanSigner>) -> Result<(), MonitorUpdateError> {
                let mut monitors = self.monitors.lock().unwrap();
                let entry = match monitors.entry(key) {
                        hash_map::Entry::Occupied(_) => return Err(MonitorUpdateError("Channel monitor for given key is already present")),
                        hash_map::Entry::Vacant(e) => e,
                };
                log_trace!(self, "Got new Channel Monitor for channel {}", log_bytes!(monitor.funding_info.0.to_channel_id()[..]));
                self.chain_monitor.install_watch_tx(&monitor.funding_info.0.txid, &monitor.funding_info.1);
                self.chain_monitor.install_watch_outpoint((monitor.funding_info.0.txid, monitor.funding_info.0.index as u32), &monitor.funding_info.1);
                for (txid, outputs) in monitor.get_outputs_to_watch().iter() {
                        for (idx, script) in outputs.iter().enumerate() {
                                self.chain_monitor.install_watch_outpoint((*txid, idx as u32), script);
                        }
                }
                entry.insert(monitor);
                Ok(())
        }

        /// Updates the monitor which monitors the channel referred to by the given key.
        pub fn update_monitor_by_key(&self, key: Key, update: ChannelMonitorUpdate) -> Result<(), MonitorUpdateError> {
                let mut monitors = self.monitors.lock().unwrap();
                match monitors.get_mut(&key) {
                        Some(orig_monitor) => {
                                log_trace!(self, "Updating Channel Monitor for channel {}", log_funding_info!(orig_monitor));
                                orig_monitor.update_monitor(update, &self.broadcaster)
                        },
                        None => Err(MonitorUpdateError("No such monitor registered"))
                }
        }
}

impl<ChanSigner: ChannelKeys, T: Deref + Sync + Send, F: Deref + Sync + Send> ManyChannelMonitor<ChanSigner> for SimpleManyChannelMonitor<OutPoint, ChanSigner, T, F>
        where T::Target: BroadcasterInterface,
              F::Target: FeeEstimator
{
        fn add_monitor(&self, funding_txo: OutPoint, monitor: ChannelMonitor<ChanSigner>) -> Result<(), ChannelMonitorUpdateErr> {
                match self.add_monitor_by_key(funding_txo, monitor) {
                        Ok(_) => Ok(()),
                        Err(_) => Err(ChannelMonitorUpdateErr::PermanentFailure),
                }
        }

        fn update_monitor(&self, funding_txo: OutPoint, update: ChannelMonitorUpdate) -> Result<(), ChannelMonitorUpdateErr> {
                match self.update_monitor_by_key(funding_txo, update) {
                        Ok(_) => Ok(()),
                        Err(_) => Err(ChannelMonitorUpdateErr::PermanentFailure),
                }
        }

        fn get_and_clear_pending_htlcs_updated(&self) -> Vec<HTLCUpdate> {
                let mut pending_htlcs_updated = Vec::new();
                for chan in self.monitors.lock().unwrap().values_mut() {
                        pending_htlcs_updated.append(&mut chan.get_and_clear_pending_htlcs_updated());
                }
                pending_htlcs_updated
        }
}

impl<Key : Send + cmp::Eq + hash::Hash, ChanSigner: ChannelKeys, T: Deref, F: Deref> events::EventsProvider for SimpleManyChannelMonitor<Key, ChanSigner, T, F>
        where T::Target: BroadcasterInterface,
              F::Target: FeeEstimator
{
        fn get_and_clear_pending_events(&self) -> Vec<events::Event> {
                let mut pending_events = Vec::new();
                for chan in self.monitors.lock().unwrap().values_mut() {
                        pending_events.append(&mut chan.get_and_clear_pending_events());
                }
                pending_events
        }
}

/// 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 = 6;
/// 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 use also this delay to be sure we can remove our in-flight claim txn from bump candidates buffer.
/// It may cause spurrious generation of bumped claim txn but that's allright 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
/// keeping bumping another claim tx to solve the outpoint.
pub(crate) const ANTI_REORG_DELAY: u32 = 6;

#[derive(Clone, PartialEq)]
struct LocalSignedTx {
        /// txid of the transaction in tx, just used to make comparison faster
        txid: Sha256dHash,
        revocation_key: PublicKey,
        a_htlc_key: PublicKey,
        b_htlc_key: PublicKey,
        delayed_payment_key: PublicKey,
        per_commitment_point: PublicKey,
        feerate_per_kw: u64,
        htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Signature>, Option<HTLCSource>)>,
}

/// When ChannelMonitor discovers an onchain outpoint being a step of a channel and that it needs
/// to generate a tx to push channel state forward, we cache outpoint-solving tx material to build
/// a new bumped one in case of lenghty confirmation delay
#[derive(Clone, PartialEq)]
pub(crate) enum InputMaterial {
        Revoked {
                witness_script: Script,
                pubkey: Option<PublicKey>,
                key: SecretKey,
                is_htlc: bool,
                amount: u64,
        },
        RemoteHTLC {
                witness_script: Script,
                key: SecretKey,
                preimage: Option<PaymentPreimage>,
                amount: u64,
                locktime: u32,
        },
        LocalHTLC {
                preimage: Option<PaymentPreimage>,
                amount: u64,
        },
        Funding {
                channel_value: u64,
        }
}

impl Writeable for InputMaterial  {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                match self {
                        &InputMaterial::Revoked { ref witness_script, ref pubkey, ref key, ref is_htlc, ref amount} => {
                                writer.write_all(&[0; 1])?;
                                witness_script.write(writer)?;
                                pubkey.write(writer)?;
                                writer.write_all(&key[..])?;
                                is_htlc.write(writer)?;
                                writer.write_all(&byte_utils::be64_to_array(*amount))?;
                        },
                        &InputMaterial::RemoteHTLC { ref witness_script, ref key, ref preimage, ref amount, ref locktime } => {
                                writer.write_all(&[1; 1])?;
                                witness_script.write(writer)?;
                                key.write(writer)?;
                                preimage.write(writer)?;
                                writer.write_all(&byte_utils::be64_to_array(*amount))?;
                                writer.write_all(&byte_utils::be32_to_array(*locktime))?;
                        },
                        &InputMaterial::LocalHTLC { ref preimage, ref amount } => {
                                writer.write_all(&[2; 1])?;
                                preimage.write(writer)?;
                                writer.write_all(&byte_utils::be64_to_array(*amount))?;
                        },
                        &InputMaterial::Funding { ref channel_value } => {
                                writer.write_all(&[3; 1])?;
                                channel_value.write(writer)?;
                        }
                }
                Ok(())
        }
}

impl Readable for InputMaterial {
        fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
                let input_material = match <u8 as Readable>::read(reader)? {
                        0 => {
                                let witness_script = Readable::read(reader)?;
                                let pubkey = Readable::read(reader)?;
                                let key = Readable::read(reader)?;
                                let is_htlc = Readable::read(reader)?;
                                let amount = Readable::read(reader)?;
                                InputMaterial::Revoked {
                                        witness_script,
                                        pubkey,
                                        key,
                                        is_htlc,
                                        amount
                                }
                        },
                        1 => {
                                let witness_script = Readable::read(reader)?;
                                let key = Readable::read(reader)?;
                                let preimage = Readable::read(reader)?;
                                let amount = Readable::read(reader)?;
                                let locktime = Readable::read(reader)?;
                                InputMaterial::RemoteHTLC {
                                        witness_script,
                                        key,
                                        preimage,
                                        amount,
                                        locktime
                                }
                        },
                        2 => {
                                let preimage = Readable::read(reader)?;
                                let amount = Readable::read(reader)?;
                                InputMaterial::LocalHTLC {
                                        preimage,
                                        amount,
                                }
                        },
                        3 => {
                                let channel_value = Readable::read(reader)?;
                                InputMaterial::Funding {
                                        channel_value
                                }
                        }
                        _ => return Err(DecodeError::InvalidValue),
                };
                Ok(input_material)
        }
}

/// ClaimRequest is a descriptor structure to communicate between detection
/// and reaction module. They are generated by ChannelMonitor while parsing
/// onchain txn leaked from a channel and handed over to OnchainTxHandler which
/// is responsible for opportunistic aggregation, selecting and enforcing
/// bumping logic, building and signing transactions.
pub(crate) struct ClaimRequest {
        // Block height before which claiming is exclusive to one party,
        // after reaching it, claiming may be contentious.
        pub(crate) absolute_timelock: u32,
        // Timeout tx must have nLocktime set which means aggregating multiple
        // ones must take the higher nLocktime among them to satisfy all of them.
        // Sadly it has few pitfalls, a) it takes longuer to get fund back b) CLTV_DELTA
        // of a sooner-HTLC could be swallowed by the highest nLocktime of the HTLC set.
        // Do simplify we mark them as non-aggregable.
        pub(crate) aggregable: bool,
        // Basic bitcoin outpoint (txid, vout)
        pub(crate) outpoint: BitcoinOutPoint,
        // Following outpoint type, set of data needed to generate transaction digest
        // and satisfy witness program.
        pub(crate) witness_data: InputMaterial
}

/// 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(Clone, 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 {
                htlc_update: (HTLCSource, PaymentHash),
        },
        MaturingOutput {
                descriptor: SpendableOutputDescriptor,
        },
}

const SERIALIZATION_VERSION: u8 = 1;
const MIN_SERIALIZATION_VERSION: u8 = 1;

#[cfg_attr(test, derive(PartialEq))]
#[derive(Clone)]
pub(super) enum ChannelMonitorUpdateStep {
        LatestLocalCommitmentTXInfo {
                // TODO: We really need to not be generating a fully-signed transaction in Channel and
                // passing it here, we need to hold off so that the ChanSigner can enforce a
                // only-sign-local-state-for-broadcast once invariant:
                commitment_tx: LocalCommitmentTransaction,
                local_keys: chan_utils::TxCreationKeys,
                feerate_per_kw: u64,
                htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Signature>, Option<HTLCSource>)>,
        },
        LatestRemoteCommitmentTXInfo {
                unsigned_commitment_tx: Transaction, // TODO: We should actually only need the txid here
                htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>,
                commitment_number: u64,
                their_revocation_point: PublicKey,
        },
        PaymentPreimage {
                payment_preimage: PaymentPreimage,
        },
        CommitmentSecret {
                idx: u64,
                secret: [u8; 32],
        },
        /// Indicates our channel is likely a stale version, we're closing, but this update should
        /// allow us to spend what is ours if our counterparty broadcasts their latest state.
        RescueRemoteCommitmentTXInfo {
                their_current_per_commitment_point: PublicKey,
        },
        /// Used to indicate that the no future updates will occur, and likely that the latest local
        /// commitment transaction(s) should be broadcast, as the channel has been force-closed.
        ChannelForceClosed {
                /// If set to false, we shouldn't broadcast the latest local commitment transaction as we
                /// think we've fallen behind!
                should_broadcast: bool,
        },
}

impl Writeable for ChannelMonitorUpdateStep {
        fn write<W: Writer>(&self, w: &mut W) -> Result<(), ::std::io::Error> {
                match self {
                        &ChannelMonitorUpdateStep::LatestLocalCommitmentTXInfo { ref commitment_tx, ref local_keys, ref feerate_per_kw, ref htlc_outputs } => {
                                0u8.write(w)?;
                                commitment_tx.write(w)?;
                                local_keys.write(w)?;
                                feerate_per_kw.write(w)?;
                                (htlc_outputs.len() as u64).write(w)?;
                                for &(ref output, ref signature, ref source) in htlc_outputs.iter() {
                                        output.write(w)?;
                                        signature.write(w)?;
                                        source.write(w)?;
                                }
                        }
                        &ChannelMonitorUpdateStep::LatestRemoteCommitmentTXInfo { ref unsigned_commitment_tx, ref htlc_outputs, ref commitment_number, ref their_revocation_point } => {
                                1u8.write(w)?;
                                unsigned_commitment_tx.write(w)?;
                                commitment_number.write(w)?;
                                their_revocation_point.write(w)?;
                                (htlc_outputs.len() as u64).write(w)?;
                                for &(ref output, ref source) in htlc_outputs.iter() {
                                        output.write(w)?;
                                        source.as_ref().map(|b| b.as_ref()).write(w)?;
                                }
                        },
                        &ChannelMonitorUpdateStep::PaymentPreimage { ref payment_preimage } => {
                                2u8.write(w)?;
                                payment_preimage.write(w)?;
                        },
                        &ChannelMonitorUpdateStep::CommitmentSecret { ref idx, ref secret } => {
                                3u8.write(w)?;
                                idx.write(w)?;
                                secret.write(w)?;
                        },
                        &ChannelMonitorUpdateStep::RescueRemoteCommitmentTXInfo { ref their_current_per_commitment_point } => {
                                4u8.write(w)?;
                                their_current_per_commitment_point.write(w)?;
                        },
                        &ChannelMonitorUpdateStep::ChannelForceClosed { ref should_broadcast } => {
                                5u8.write(w)?;
                                should_broadcast.write(w)?;
                        },
                }
                Ok(())
        }
}
impl Readable for ChannelMonitorUpdateStep {
        fn read<R: ::std::io::Read>(r: &mut R) -> Result<Self, DecodeError> {
                match Readable::read(r)? {
                        0u8 => {
                                Ok(ChannelMonitorUpdateStep::LatestLocalCommitmentTXInfo {
                                        commitment_tx: Readable::read(r)?,
                                        local_keys: Readable::read(r)?,
                                        feerate_per_kw: Readable::read(r)?,
                                        htlc_outputs: {
                                                let len: u64 = Readable::read(r)?;
                                                let mut res = Vec::new();
                                                for _ in 0..len {
                                                        res.push((Readable::read(r)?, Readable::read(r)?, Readable::read(r)?));
                                                }
                                                res
                                        },
                                })
                        },
                        1u8 => {
                                Ok(ChannelMonitorUpdateStep::LatestRemoteCommitmentTXInfo {
                                        unsigned_commitment_tx: Readable::read(r)?,
                                        commitment_number: Readable::read(r)?,
                                        their_revocation_point: Readable::read(r)?,
                                        htlc_outputs: {
                                                let len: u64 = Readable::read(r)?;
                                                let mut res = Vec::new();
                                                for _ in 0..len {
                                                        res.push((Readable::read(r)?, <Option<HTLCSource> as Readable>::read(r)?.map(|o| Box::new(o))));
                                                }
                                                res
                                        },
                                })
                        },
                        2u8 => {
                                Ok(ChannelMonitorUpdateStep::PaymentPreimage {
                                        payment_preimage: Readable::read(r)?,
                                })
                        },
                        3u8 => {
                                Ok(ChannelMonitorUpdateStep::CommitmentSecret {
                                        idx: Readable::read(r)?,
                                        secret: Readable::read(r)?,
                                })
                        },
                        4u8 => {
                                Ok(ChannelMonitorUpdateStep::RescueRemoteCommitmentTXInfo {
                                        their_current_per_commitment_point: Readable::read(r)?,
                                })
                        },
                        5u8 => {
                                Ok(ChannelMonitorUpdateStep::ChannelForceClosed {
                                        should_broadcast: Readable::read(r)?
                                })
                        },
                        _ => Err(DecodeError::InvalidValue),
                }
        }
}

/// 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_htlcs_updated 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.
pub struct ChannelMonitor<ChanSigner: ChannelKeys> {
        latest_update_id: u64,
        commitment_transaction_number_obscure_factor: u64,

        destination_script: Script,
        broadcasted_local_revokable_script: Option<(Script, SecretKey, Script)>,
        broadcasted_remote_payment_script: Option<(Script, SecretKey)>,
        shutdown_script: Script,

        keys: ChanSigner,
        funding_info: (OutPoint, Script),
        current_remote_commitment_txid: Option<Sha256dHash>,
        prev_remote_commitment_txid: Option<Sha256dHash>,

        their_htlc_base_key: PublicKey,
        their_delayed_payment_base_key: PublicKey,
        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>)>,

        our_to_self_delay: u16,
        their_to_self_delay: u16,

        commitment_secrets: CounterpartyCommitmentSecrets,
        remote_claimable_outpoints: HashMap<Sha256dHash, 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 remote
        /// 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.
        remote_commitment_txn_on_chain: HashMap<Sha256dHash, (u64, Vec<Script>)>,
        /// Cache used to make pruning of payment_preimages faster.
        /// Maps payment_hash values to commitment numbers for remote transactions for non-revoked
        /// remote transactions (ie should remain pretty small).
        /// Serialized to disk but should generally not be sent to Watchtowers.
        remote_hash_commitment_number: HashMap<PaymentHash, u64>,

        // We store two local 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 local
        // transaction for which we have deleted claim information on some watchtowers.
        prev_local_signed_commitment_tx: Option<LocalSignedTx>,
        current_local_signed_commitment_tx: Option<LocalSignedTx>,

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

        payment_preimages: HashMap<PaymentHash, PaymentPreimage>,

        pending_htlcs_updated: Vec<HTLCUpdate>,
        pending_events: Vec<events::Event>,

        // Used to track onchain events, i.e transactions parts of channels confirmed on chain, on which
        // we have to take actions once they reach enough confs. Key is a block height timer, i.e we enforce
        // actions when we receive a block with given height. Actions depend on OnchainEvent type.
        onchain_events_waiting_threshold_conf: HashMap<u32, Vec<OnchainEvent>>,

        // 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<Sha256dHash, Vec<Script>>,

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

        // Used to detect programming bug due to unsafe monitor update sequence { ChannelForceClosed, LatestLocalCommitmentTXInfo }
        lockdown_from_offchain: bool,

        // We simply modify last_block_hash 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 last_block_hash from its state and not based on updated copies that didn't run through
        // the full block_connected).
        pub(crate) last_block_hash: Sha256dHash,
        secp_ctx: Secp256k1<secp256k1::All>, //TODO: dedup this a bit...
        logger: Arc<Logger>,
}

#[cfg(any(test, feature = "fuzztarget"))]
/// Used only in testing and fuzztarget to check serialization roundtrips don't change the
/// underlying object
impl<ChanSigner: ChannelKeys> PartialEq for ChannelMonitor<ChanSigner> {
        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_local_revokable_script != other.broadcasted_local_revokable_script ||
                        self.broadcasted_remote_payment_script != other.broadcasted_remote_payment_script ||
                        self.keys.pubkeys() != other.keys.pubkeys() ||
                        self.funding_info != other.funding_info ||
                        self.current_remote_commitment_txid != other.current_remote_commitment_txid ||
                        self.prev_remote_commitment_txid != other.prev_remote_commitment_txid ||
                        self.their_htlc_base_key != other.their_htlc_base_key ||
                        self.their_delayed_payment_base_key != other.their_delayed_payment_base_key ||
                        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.our_to_self_delay != other.our_to_self_delay ||
                        self.their_to_self_delay != other.their_to_self_delay ||
                        self.commitment_secrets != other.commitment_secrets ||
                        self.remote_claimable_outpoints != other.remote_claimable_outpoints ||
                        self.remote_commitment_txn_on_chain != other.remote_commitment_txn_on_chain ||
                        self.remote_hash_commitment_number != other.remote_hash_commitment_number ||
                        self.prev_local_signed_commitment_tx != other.prev_local_signed_commitment_tx ||
                        self.current_remote_commitment_number != other.current_remote_commitment_number ||
                        self.current_local_commitment_number != other.current_local_commitment_number ||
                        self.current_local_signed_commitment_tx != other.current_local_signed_commitment_tx ||
                        self.payment_preimages != other.payment_preimages ||
                        self.pending_htlcs_updated != other.pending_htlcs_updated ||
                        self.pending_events.len() != other.pending_events.len() || // We trust events to round-trip properly
                        self.onchain_events_waiting_threshold_conf != other.onchain_events_waiting_threshold_conf ||
                        self.outputs_to_watch != other.outputs_to_watch
                {
                        false
                } else {
                        true
                }
        }
}

impl<ChanSigner: ChannelKeys + Writeable> ChannelMonitor<ChanSigner> {
        /// Writes this monitor into the given writer, suitable for writing to disk.
        ///
        /// Note that the deserializer is only implemented for (Sha256dHash, 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 fn write_for_disk<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                //TODO: We still write out all the serialization here manually instead of using the fancy
                //serialization framework we have, we should migrate things over to it.
                writer.write_all(&[SERIALIZATION_VERSION; 1])?;
                writer.write_all(&[MIN_SERIALIZATION_VERSION; 1])?;

                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_local_revokable_script) = self.broadcasted_local_revokable_script {
                        writer.write_all(&[0; 1])?;
                        broadcasted_local_revokable_script.0.write(writer)?;
                        broadcasted_local_revokable_script.1.write(writer)?;
                        broadcasted_local_revokable_script.2.write(writer)?;
                } else {
                        writer.write_all(&[1; 1])?;
                }

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

                self.keys.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_remote_commitment_txid.write(writer)?;
                self.prev_remote_commitment_txid.write(writer)?;

                writer.write_all(&self.their_htlc_base_key.serialize())?;
                writer.write_all(&self.their_delayed_payment_base_key.serialize())?;
                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.our_to_self_delay))?;
                writer.write_all(&byte_utils::be16_to_array(self.their_to_self_delay))?;

                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.remote_claimable_outpoints.len() as u64))?;
                for (ref txid, ref htlc_infos) in self.remote_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.remote_commitment_txn_on_chain.len() as u64))?;
                for (ref txid, &(commitment_number, ref txouts)) in self.remote_commitment_txn_on_chain.iter() {
                        writer.write_all(&txid[..])?;
                        writer.write_all(&byte_utils::be48_to_array(commitment_number))?;
                        (txouts.len() as u64).write(writer)?;
                        for script in txouts.iter() {
                                script.write(writer)?;
                        }
                }

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

                macro_rules! serialize_local_tx {
                        ($local_tx: expr) => {
                                $local_tx.txid.write(writer)?;
                                writer.write_all(&$local_tx.revocation_key.serialize())?;
                                writer.write_all(&$local_tx.a_htlc_key.serialize())?;
                                writer.write_all(&$local_tx.b_htlc_key.serialize())?;
                                writer.write_all(&$local_tx.delayed_payment_key.serialize())?;
                                writer.write_all(&$local_tx.per_commitment_point.serialize())?;

                                writer.write_all(&byte_utils::be64_to_array($local_tx.feerate_per_kw))?;
                                writer.write_all(&byte_utils::be64_to_array($local_tx.htlc_outputs.len() as u64))?;
                                for &(ref htlc_output, ref sig, ref htlc_source) in $local_tx.htlc_outputs.iter() {
                                        serialize_htlc_in_commitment!(htlc_output);
                                        if let &Some(ref their_sig) = sig {
                                                1u8.write(writer)?;
                                                writer.write_all(&their_sig.serialize_compact())?;
                                        } else {
                                                0u8.write(writer)?;
                                        }
                                        htlc_source.write(writer)?;
                                }
                        }
                }

                if let Some(ref prev_local_tx) = self.prev_local_signed_commitment_tx {
                        writer.write_all(&[1; 1])?;
                        serialize_local_tx!(prev_local_tx);
                } else {
                        writer.write_all(&[0; 1])?;
                }

                if let Some(ref cur_local_tx) = self.current_local_signed_commitment_tx {
                        writer.write_all(&[1; 1])?;
                        serialize_local_tx!(cur_local_tx);
                } else {
                        writer.write_all(&[0; 1])?;
                }

                writer.write_all(&byte_utils::be48_to_array(self.current_remote_commitment_number))?;
                writer.write_all(&byte_utils::be48_to_array(self.current_local_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_htlcs_updated.len() as u64))?;
                for data in self.pending_htlcs_updated.iter() {
                        data.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.last_block_hash.write(writer)?;

                writer.write_all(&byte_utils::be64_to_array(self.onchain_events_waiting_threshold_conf.len() as u64))?;
                for (ref target, ref events) in self.onchain_events_waiting_threshold_conf.iter() {
                        writer.write_all(&byte_utils::be32_to_array(**target))?;
                        writer.write_all(&byte_utils::be64_to_array(events.len() as u64))?;
                        for ev in events.iter() {
                                match *ev {
                                        OnchainEvent::HTLCUpdate { ref htlc_update } => {
                                                0u8.write(writer)?;
                                                htlc_update.0.write(writer)?;
                                                htlc_update.1.write(writer)?;
                                        },
                                        OnchainEvent::MaturingOutput { ref descriptor } => {
                                                1u8.write(writer)?;
                                                descriptor.write(writer)?;
                                        },
                                }
                        }
                }

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

                self.lockdown_from_offchain.write(writer)?;

                Ok(())
        }
}

impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
        pub(super) fn new(keys: ChanSigner, shutdown_pubkey: &PublicKey,
                        our_to_self_delay: u16, destination_script: &Script, funding_info: (OutPoint, Script),
                        their_htlc_base_key: &PublicKey, their_delayed_payment_base_key: &PublicKey,
                        their_to_self_delay: u16, funding_redeemscript: Script, channel_value_satoshis: u64,
                        commitment_transaction_number_obscure_factor: u64,
                        logger: Arc<Logger>) -> ChannelMonitor<ChanSigner> {

                assert!(commitment_transaction_number_obscure_factor <= (1 << 48));
                let our_channel_close_key_hash = Hash160::hash(&shutdown_pubkey.serialize());
                let shutdown_script = Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0).push_slice(&our_channel_close_key_hash[..]).into_script();

                ChannelMonitor {
                        latest_update_id: 0,
                        commitment_transaction_number_obscure_factor,

                        destination_script: destination_script.clone(),
                        broadcasted_local_revokable_script: None,
                        broadcasted_remote_payment_script: None,
                        shutdown_script,

                        keys: keys.clone(),
                        funding_info,
                        current_remote_commitment_txid: None,
                        prev_remote_commitment_txid: None,

                        their_htlc_base_key: their_htlc_base_key.clone(),
                        their_delayed_payment_base_key: their_delayed_payment_base_key.clone(),
                        funding_redeemscript: funding_redeemscript.clone(),
                        channel_value_satoshis: channel_value_satoshis,
                        their_cur_revocation_points: None,

                        our_to_self_delay,
                        their_to_self_delay,

                        commitment_secrets: CounterpartyCommitmentSecrets::new(),
                        remote_claimable_outpoints: HashMap::new(),
                        remote_commitment_txn_on_chain: HashMap::new(),
                        remote_hash_commitment_number: HashMap::new(),

                        prev_local_signed_commitment_tx: None,
                        current_local_signed_commitment_tx: None,
                        current_remote_commitment_number: 1 << 48,
                        current_local_commitment_number: 0xffff_ffff_ffff,

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

                        onchain_events_waiting_threshold_conf: HashMap::new(),
                        outputs_to_watch: HashMap::new(),

                        onchain_tx_handler: OnchainTxHandler::new(destination_script.clone(), keys, funding_redeemscript, their_to_self_delay, logger.clone()),

                        lockdown_from_offchain: false,

                        last_block_hash: Default::default(),
                        secp_ctx: Secp256k1::new(),
                        logger,
                }
        }

        /// Inserts a revocation secret into this channel monitor. Prunes old preimages if neither
        /// needed by local commitment transactions HTCLs nor by remote ones. Unless we haven't already seen remote
        /// commitment transaction's secret, they are de facto pruned (we can use revocation key).
        pub(super) 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 remote commitment tx so we don't generate failure/fulfill
                // events for now-revoked/fulfilled HTLCs.
                if let Some(txid) = self.prev_remote_commitment_txid.take() {
                        for &mut (_, ref mut source) in self.remote_claimable_outpoints.get_mut(&txid).unwrap() {
                                *source = None;
                        }
                }

                if !self.payment_preimages.is_empty() {
                        let local_signed_commitment_tx = self.current_local_signed_commitment_tx.as_ref().expect("Channel needs at least an initial commitment tx !");
                        let prev_local_signed_commitment_tx = self.prev_local_signed_commitment_tx.as_ref();
                        let min_idx = self.get_min_seen_secret();
                        let remote_hash_commitment_number = &mut self.remote_hash_commitment_number;

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

                Ok(())
        }

        /// Informs this monitor of the latest remote (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(super) fn provide_latest_remote_commitment_tx_info(&mut self, unsigned_commitment_tx: &Transaction, htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Box<HTLCSource>>)>, commitment_number: u64, their_revocation_point: PublicKey) {
                // 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.remote_hash_commitment_number.insert(htlc.payment_hash, commitment_number);
                }

                let new_txid = unsigned_commitment_tx.txid();
                log_trace!(self, "Tracking new remote commitment transaction with txid {} at commitment number {} with {} HTLC outputs", new_txid, commitment_number, htlc_outputs.len());
                log_trace!(self, "New potential remote commitment transaction: {}", encode::serialize_hex(unsigned_commitment_tx));
                self.prev_remote_commitment_txid = self.current_remote_commitment_txid.take();
                self.current_remote_commitment_txid = Some(new_txid);
                self.remote_claimable_outpoints.insert(new_txid, htlc_outputs);
                self.current_remote_commitment_number = commitment_number;
                //TODO: Merge this into the other per-remote-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));
                        }
                }
        }

        pub(super) fn provide_rescue_remote_commitment_tx_info(&mut self, their_revocation_point: PublicKey) {
                if let Ok(payment_key) = chan_utils::derive_public_key(&self.secp_ctx, &their_revocation_point, &self.keys.pubkeys().payment_basepoint) {
                        let to_remote_script =  Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0)
                                .push_slice(&Hash160::hash(&payment_key.serialize())[..])
                                .into_script();
                        if let Ok(to_remote_key) = chan_utils::derive_private_key(&self.secp_ctx, &their_revocation_point, &self.keys.payment_base_key()) {
                                self.broadcasted_remote_payment_script = Some((to_remote_script, to_remote_key));
                        }
                }
        }

        /// Informs this monitor of the latest local (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 local commitment transaction is updated.
        /// Panics if set_their_to_self_delay has never been called.
        pub(super) fn provide_latest_local_commitment_tx_info(&mut self, mut commitment_tx: LocalCommitmentTransaction, local_keys: chan_utils::TxCreationKeys, feerate_per_kw: u64, htlc_outputs: Vec<(HTLCOutputInCommitment, Option<Signature>, Option<HTLCSource>)>) -> Result<(), MonitorUpdateError> {
                let txid = commitment_tx.txid();
                let sequence = commitment_tx.without_valid_witness().input[0].sequence as u64;
                let locktime = commitment_tx.without_valid_witness().lock_time as u64;
                let mut htlcs = Vec::with_capacity(htlc_outputs.len());
                for htlc in htlc_outputs.clone() {
                        if let Some(_) = htlc.0.transaction_output_index {
                                htlcs.push((htlc.0, htlc.1, None));
                        }
                }
                commitment_tx.set_htlc_cache(local_keys.clone(), feerate_per_kw, htlcs);
                // Returning a monitor error before updating tracking points means in case of using
                // a concurrent watchtower implementation for same channel, if this one doesn't
                // reject update as we do, you MAY have the latest local valid commitment tx onchain
                // for which you want to spend outputs. We're NOT robust again this scenario right
                // now but we should consider it later.
                if let Err(_) = self.onchain_tx_handler.provide_latest_local_tx(commitment_tx) {
                        return Err(MonitorUpdateError("Local commitment signed has already been signed, no further update of LOCAL commitment transaction is allowed"));
                }
                self.current_local_commitment_number = 0xffff_ffff_ffff - ((((sequence & 0xffffff) << 3*8) | (locktime as u64 & 0xffffff)) ^ self.commitment_transaction_number_obscure_factor);
                self.prev_local_signed_commitment_tx = self.current_local_signed_commitment_tx.take();
                self.current_local_signed_commitment_tx = Some(LocalSignedTx {
                        txid,
                        revocation_key: local_keys.revocation_key,
                        a_htlc_key: local_keys.a_htlc_key,
                        b_htlc_key: local_keys.b_htlc_key,
                        delayed_payment_key: local_keys.a_delayed_payment_key,
                        per_commitment_point: local_keys.per_commitment_point,
                        feerate_per_kw,
                        htlc_outputs: htlc_outputs,
                });
                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.
        pub(super) fn provide_payment_preimage(&mut self, payment_hash: &PaymentHash, payment_preimage: &PaymentPreimage) {
                self.payment_preimages.insert(payment_hash.clone(), payment_preimage.clone());
        }

        pub(super) fn broadcast_latest_local_commitment_txn<B: Deref>(&mut self, broadcaster: &B)
                where B::Target: BroadcasterInterface,
        {
                for tx in self.get_latest_local_commitment_txn().iter() {
                        broadcaster.broadcast_transaction(tx);
                }
        }

        /// Used in Channel to cheat wrt the update_ids since it plays games, will be removed soon!
        pub(super) fn update_monitor_ooo(&mut self, mut updates: ChannelMonitorUpdate) -> Result<(), MonitorUpdateError> {
                for update in updates.updates.drain(..) {
                        match update {
                                ChannelMonitorUpdateStep::LatestLocalCommitmentTXInfo { commitment_tx, local_keys, feerate_per_kw, htlc_outputs } => {
                                        if self.lockdown_from_offchain { panic!(); }
                                        self.provide_latest_local_commitment_tx_info(commitment_tx, local_keys, feerate_per_kw, htlc_outputs)?
                                },
                                ChannelMonitorUpdateStep::LatestRemoteCommitmentTXInfo { unsigned_commitment_tx, htlc_outputs, commitment_number, their_revocation_point } =>
                                        self.provide_latest_remote_commitment_tx_info(&unsigned_commitment_tx, htlc_outputs, commitment_number, their_revocation_point),
                                ChannelMonitorUpdateStep::PaymentPreimage { payment_preimage } =>
                                        self.provide_payment_preimage(&PaymentHash(Sha256::hash(&payment_preimage.0[..]).into_inner()), &payment_preimage),
                                ChannelMonitorUpdateStep::CommitmentSecret { idx, secret } =>
                                        self.provide_secret(idx, secret)?,
                                ChannelMonitorUpdateStep::RescueRemoteCommitmentTXInfo { their_current_per_commitment_point } =>
                                        self.provide_rescue_remote_commitment_tx_info(their_current_per_commitment_point),
                                ChannelMonitorUpdateStep::ChannelForceClosed { .. } => {},
                        }
                }
                self.latest_update_id = updates.update_id;
                Ok(())
        }

        /// 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>(&mut self, mut updates: ChannelMonitorUpdate, broadcaster: &B) -> Result<(), MonitorUpdateError>
                where B::Target: BroadcasterInterface,
        {
                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.drain(..) {
                        match update {
                                ChannelMonitorUpdateStep::LatestLocalCommitmentTXInfo { commitment_tx, local_keys, feerate_per_kw, htlc_outputs } => {
                                        if self.lockdown_from_offchain { panic!(); }
                                        self.provide_latest_local_commitment_tx_info(commitment_tx, local_keys, feerate_per_kw, htlc_outputs)?
                                },
                                ChannelMonitorUpdateStep::LatestRemoteCommitmentTXInfo { unsigned_commitment_tx, htlc_outputs, commitment_number, their_revocation_point } =>
                                        self.provide_latest_remote_commitment_tx_info(&unsigned_commitment_tx, htlc_outputs, commitment_number, their_revocation_point),
                                ChannelMonitorUpdateStep::PaymentPreimage { payment_preimage } =>
                                        self.provide_payment_preimage(&PaymentHash(Sha256::hash(&payment_preimage.0[..]).into_inner()), &payment_preimage),
                                ChannelMonitorUpdateStep::CommitmentSecret { idx, secret } =>
                                        self.provide_secret(idx, secret)?,
                                ChannelMonitorUpdateStep::RescueRemoteCommitmentTXInfo { their_current_per_commitment_point } =>
                                        self.provide_rescue_remote_commitment_tx_info(their_current_per_commitment_point),
                                ChannelMonitorUpdateStep::ChannelForceClosed { should_broadcast } => {
                                        self.lockdown_from_offchain = true;
                                        if should_broadcast {
                                                self.broadcast_latest_local_commitment_txn(broadcaster);
                                        } else {
                                                log_error!(self, "You have a toxic local commitment transaction avaible in channel monitor, read comment in ChannelMonitor::get_latest_local_commitment_txn to be informed of manual action to take");
                                        }
                                }
                        }
                }
                self.latest_update_id = updates.update_id;
                Ok(())
        }

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

        /// Gets the funding transaction outpoint of the channel this ChannelMonitor is monitoring for.
        pub fn get_funding_txo(&self) -> OutPoint {
                self.funding_info.0
        }

        /// 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) -> &HashMap<Sha256dHash, Vec<Script>> {
                &self.outputs_to_watch
        }

        /// Gets the sets of all outpoints which this ChannelMonitor expects to hear about spends of.
        /// Generally useful when deserializing as during normal operation the return values of
        /// block_connected are sufficient to ensure all relevant outpoints are being monitored (note
        /// that the get_funding_txo outpoint and transaction must also be monitored for!).
        pub fn get_monitored_outpoints(&self) -> Vec<(Sha256dHash, u32, &Script)> {
                let mut res = Vec::with_capacity(self.remote_commitment_txn_on_chain.len() * 2);
                for (ref txid, &(_, ref outputs)) in self.remote_commitment_txn_on_chain.iter() {
                        for (idx, output) in outputs.iter().enumerate() {
                                res.push(((*txid).clone(), idx as u32, output));
                        }
                }
                res
        }

        /// Get the list of HTLCs who's status has been updated on chain. This should be called by
        /// ChannelManager via ManyChannelMonitor::get_and_clear_pending_htlcs_updated().
        pub fn get_and_clear_pending_htlcs_updated(&mut self) -> Vec<HTLCUpdate> {
                let mut ret = Vec::new();
                mem::swap(&mut ret, &mut self.pending_htlcs_updated);
                ret
        }

        /// Gets the list of pending events which were generated by previous actions, clearing the list
        /// in the process.
        ///
        /// This is called by ManyChannelMonitor::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(&mut self) -> Vec<events::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
        pub(super) fn get_secret(&self, idx: u64) -> Option<[u8; 32]> {
                self.commitment_secrets.get_secret(idx)
        }

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

        pub(super) fn get_cur_remote_commitment_number(&self) -> u64 {
                self.current_remote_commitment_number
        }

        pub(super) fn get_cur_local_commitment_number(&self) -> u64 {
                self.current_local_commitment_number
        }

        /// Attempts to claim a remote commitment transaction's outputs using the revocation key and
        /// data in remote_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 remote commitment tx
        fn check_spend_remote_transaction(&mut self, tx: &Transaction, height: u32) -> (Vec<ClaimRequest>, (Sha256dHash, Vec<TxOut>)) {
                // 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.remote_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.keys.pubkeys().revocation_basepoint));
                        let revocation_key = ignore_error!(chan_utils::derive_private_revocation_key(&self.secp_ctx, &per_commitment_key, &self.keys.revocation_base_key()));
                        let b_htlc_key = ignore_error!(chan_utils::derive_public_key(&self.secp_ctx, &per_commitment_point, &self.keys.pubkeys().htlc_basepoint));
                        let local_payment_key = ignore_error!(chan_utils::derive_private_key(&self.secp_ctx, &per_commitment_point, &self.keys.payment_base_key()));
                        let delayed_key = ignore_error!(chan_utils::derive_public_key(&self.secp_ctx, &PublicKey::from_secret_key(&self.secp_ctx, &per_commitment_key), &self.their_delayed_payment_base_key));
                        let a_htlc_key = ignore_error!(chan_utils::derive_public_key(&self.secp_ctx, &PublicKey::from_secret_key(&self.secp_ctx, &per_commitment_key), &self.their_htlc_base_key));

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

                        self.broadcasted_remote_payment_script = {
                                // Note that the Network here is ignored as we immediately drop the address for the
                                // script_pubkey version
                                let payment_hash160 = Hash160::hash(&PublicKey::from_secret_key(&self.secp_ctx, &local_payment_key).serialize());
                                Some((Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0).push_slice(&payment_hash160[..]).into_script(), local_payment_key))
                        };

                        // First, process non-htlc outputs (to_local & to_remote)
                        for (idx, outp) in tx.output.iter().enumerate() {
                                if outp.script_pubkey == revokeable_p2wsh {
                                        let witness_data = InputMaterial::Revoked { witness_script: revokeable_redeemscript.clone(), pubkey: Some(revocation_pubkey), key: revocation_key, is_htlc: false, amount: outp.value };
                                        claimable_outpoints.push(ClaimRequest { absolute_timelock: height + self.our_to_self_delay as u32, aggregable: true, outpoint: BitcoinOutPoint { txid: commitment_txid, vout: idx as u32 }, witness_data});
                                }
                        }

                        // 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 {
                                                let expected_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&htlc, &a_htlc_key, &b_htlc_key, &revocation_pubkey);
                                                if transaction_output_index as usize >= tx.output.len() ||
                                                                tx.output[transaction_output_index as usize].value != htlc.amount_msat / 1000 ||
                                                                tx.output[transaction_output_index as usize].script_pubkey != expected_script.to_v0_p2wsh() {
                                                        return (claimable_outpoints, (commitment_txid, watch_outputs)); // Corrupted per_commitment_data, fuck this user
                                                }
                                                let witness_data = InputMaterial::Revoked { witness_script: expected_script, pubkey: Some(revocation_pubkey), key: revocation_key, is_htlc: true, amount: tx.output[transaction_output_index as usize].value };
                                                claimable_outpoints.push(ClaimRequest { absolute_timelock: htlc.cltv_expiry, aggregable: true, outpoint: BitcoinOutPoint { txid: commitment_txid, vout: transaction_output_index }, witness_data });
                                        }
                                }
                        }

                        // 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 remote commitment transaction!
                                log_trace!(self, "Got broadcast of revoked remote commitment transaction, going to generate general spend tx with {} inputs", claimable_outpoints.len());
                                watch_outputs.append(&mut tx.output.clone());
                                self.remote_commitment_txn_on_chain.insert(commitment_txid, (commitment_number, tx.output.iter().map(|output| { output.script_pubkey.clone() }).collect()));

                                macro_rules! check_htlc_fails {
                                        ($txid: expr, $commitment_tx: expr) => {
                                                if let Some(ref outpoints) = self.remote_claimable_outpoints.get($txid) {
                                                        for &(ref htlc, ref source_option) in outpoints.iter() {
                                                                if let &Some(ref source) = source_option {
                                                                        log_info!(self, "Failing HTLC with payment_hash {} from {} remote commitment tx due to broadcast of revoked remote commitment transaction, waiting for confirmation (at height {})", log_bytes!(htlc.payment_hash.0), $commitment_tx, height + ANTI_REORG_DELAY - 1);
                                                                        match self.onchain_events_waiting_threshold_conf.entry(height + ANTI_REORG_DELAY - 1) {
                                                                                hash_map::Entry::Occupied(mut entry) => {
                                                                                        let e = entry.get_mut();
                                                                                        e.retain(|ref event| {
                                                                                                match **event {
                                                                                                        OnchainEvent::HTLCUpdate { ref htlc_update } => {
                                                                                                                return htlc_update.0 != **source
                                                                                                        },
                                                                                                        _ => true
                                                                                                }
                                                                                        });
                                                                                        e.push(OnchainEvent::HTLCUpdate { htlc_update: ((**source).clone(), htlc.payment_hash.clone())});
                                                                                }
                                                                                hash_map::Entry::Vacant(entry) => {
                                                                                        entry.insert(vec![OnchainEvent::HTLCUpdate { htlc_update: ((**source).clone(), htlc.payment_hash.clone())}]);
                                                                                }
                                                                        }
                                                                }
                                                        }
                                                }
                                        }
                                }
                                if let Some(ref txid) = self.current_remote_commitment_txid {
                                        check_htlc_fails!(txid, "current");
                                }
                                if let Some(ref txid) = self.prev_remote_commitment_txid {
                                        check_htlc_fails!(txid, "remote");
                                }
                                // No need to check local commitment txn, symmetric HTLCSource must be present as per-htlc data on remote commitment tx
                        }
                } 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 remote_commitment_txn_on_chain entry
                        // not being generated by the above conditional. Thus, to be safe, we go ahead and
                        // insert it here.
                        watch_outputs.append(&mut tx.output.clone());
                        self.remote_commitment_txn_on_chain.insert(commitment_txid, (commitment_number, tx.output.iter().map(|output| { output.script_pubkey.clone() }).collect()));

                        log_trace!(self, "Got broadcast of non-revoked remote commitment transaction {}", commitment_txid);

                        macro_rules! check_htlc_fails {
                                ($txid: expr, $commitment_tx: expr, $id: tt) => {
                                        if let Some(ref latest_outpoints) = self.remote_claimable_outpoints.get($txid) {
                                                $id: 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.
                                                                for &(ref broadcast_htlc, ref broadcast_source) in per_commitment_data.iter() {
                                                                        if broadcast_htlc.transaction_output_index.is_some() && Some(source) == broadcast_source.as_ref() {
                                                                                continue $id;
                                                                        }
                                                                }
                                                                log_trace!(self, "Failing HTLC with payment_hash {} from {} remote commitment tx due to broadcast of remote commitment transaction", log_bytes!(htlc.payment_hash.0), $commitment_tx);
                                                                match self.onchain_events_waiting_threshold_conf.entry(height + ANTI_REORG_DELAY - 1) {
                                                                        hash_map::Entry::Occupied(mut entry) => {
                                                                                let e = entry.get_mut();
                                                                                e.retain(|ref event| {
                                                                                        match **event {
                                                                                                OnchainEvent::HTLCUpdate { ref htlc_update } => {
                                                                                                        return htlc_update.0 != **source
                                                                                                },
                                                                                                _ => true
                                                                                        }
                                                                                });
                                                                                e.push(OnchainEvent::HTLCUpdate { htlc_update: ((**source).clone(), htlc.payment_hash.clone())});
                                                                        }
                                                                        hash_map::Entry::Vacant(entry) => {
                                                                                entry.insert(vec![OnchainEvent::HTLCUpdate { htlc_update: ((**source).clone(), htlc.payment_hash.clone())}]);
                                                                        }
                                                                }
                                                        }
                                                }
                                        }
                                }
                        }
                        if let Some(ref txid) = self.current_remote_commitment_txid {
                                check_htlc_fails!(txid, "current", 'current_loop);
                        }
                        if let Some(ref txid) = self.prev_remote_commitment_txid {
                                check_htlc_fails!(txid, "previous", 'prev_loop);
                        }

                        if let Some(revocation_points) = self.their_cur_revocation_points {
                                let revocation_point_option =
                                        if revocation_points.0 == commitment_number { Some(&revocation_points.1) }
                                        else if let Some(point) = revocation_points.2.as_ref() {
                                                if revocation_points.0 == commitment_number + 1 { Some(point) } else { None }
                                        } else { None };
                                if let Some(revocation_point) = revocation_point_option {
                                        let revocation_pubkey = ignore_error!(chan_utils::derive_public_revocation_key(&self.secp_ctx, revocation_point, &self.keys.pubkeys().revocation_basepoint));
                                        let b_htlc_key = ignore_error!(chan_utils::derive_public_key(&self.secp_ctx, revocation_point, &self.keys.pubkeys().htlc_basepoint));
                                        let htlc_privkey = ignore_error!(chan_utils::derive_private_key(&self.secp_ctx, revocation_point, &self.keys.htlc_base_key()));
                                        let a_htlc_key = ignore_error!(chan_utils::derive_public_key(&self.secp_ctx, revocation_point, &self.their_htlc_base_key));
                                        let local_payment_key = ignore_error!(chan_utils::derive_private_key(&self.secp_ctx, revocation_point, &self.keys.payment_base_key()));

                                        self.broadcasted_remote_payment_script = {
                                                // Note that the Network here is ignored as we immediately drop the address for the
                                                // script_pubkey version
                                                let payment_hash160 = Hash160::hash(&PublicKey::from_secret_key(&self.secp_ctx, &local_payment_key).serialize());
                                                Some((Builder::new().push_opcode(opcodes::all::OP_PUSHBYTES_0).push_slice(&payment_hash160[..]).into_script(), local_payment_key))
                                        };

                                        // Then, try to find htlc outputs
                                        for (_, &(ref htlc, _)) in per_commitment_data.iter().enumerate() {
                                                if let Some(transaction_output_index) = htlc.transaction_output_index {
                                                        let expected_script = chan_utils::get_htlc_redeemscript_with_explicit_keys(&htlc, &a_htlc_key, &b_htlc_key, &revocation_pubkey);
                                                        if transaction_output_index as usize >= tx.output.len() ||
                                                                        tx.output[transaction_output_index as usize].value != htlc.amount_msat / 1000 ||
                                                                        tx.output[transaction_output_index as usize].script_pubkey != expected_script.to_v0_p2wsh() {
                                                                return (claimable_outpoints, (commitment_txid, watch_outputs)); // 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 };
                                                        let aggregable = if !htlc.offered { false } else { true };
                                                        if preimage.is_some() || !htlc.offered {
                                                                let witness_data = InputMaterial::RemoteHTLC { witness_script: expected_script, key: htlc_privkey, preimage, amount: htlc.amount_msat / 1000, locktime: htlc.cltv_expiry };
                                                                claimable_outpoints.push(ClaimRequest { absolute_timelock: htlc.cltv_expiry, aggregable, outpoint: BitcoinOutPoint { txid: commitment_txid, vout: transaction_output_index }, witness_data });
                                                        }
                                                }
                                        }
                                }
                        }
                }
                (claimable_outpoints, (commitment_txid, watch_outputs))
        }

        /// Attempts to claim a remote HTLC-Success/HTLC-Timeout's outputs using the revocation key
        fn check_spend_remote_htlc(&mut self, tx: &Transaction, commitment_number: u64, height: u32) -> (Vec<ClaimRequest>, Option<(Sha256dHash, Vec<TxOut>)>) {
                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);
                let revocation_pubkey = ignore_error!(chan_utils::derive_public_revocation_key(&self.secp_ctx, &per_commitment_point, &self.keys.pubkeys().revocation_basepoint));
                let revocation_key = ignore_error!(chan_utils::derive_private_revocation_key(&self.secp_ctx, &per_commitment_key, &self.keys.revocation_base_key()));
                let delayed_key = ignore_error!(chan_utils::derive_public_key(&self.secp_ctx, &per_commitment_point, &self.their_delayed_payment_base_key));
                let redeemscript = chan_utils::get_revokeable_redeemscript(&revocation_pubkey, self.our_to_self_delay, &delayed_key);

                log_trace!(self, "Remote HTLC broadcast {}:{}", htlc_txid, 0);
                let witness_data = InputMaterial::Revoked { witness_script: redeemscript, pubkey: Some(revocation_pubkey), key: revocation_key, is_htlc: false, amount: tx.output[0].value };
                let claimable_outpoints = vec!(ClaimRequest { absolute_timelock: height + self.our_to_self_delay as u32, aggregable: true, outpoint: BitcoinOutPoint { txid: htlc_txid, vout: 0}, witness_data });
                (claimable_outpoints, Some((htlc_txid, tx.output.clone())))
        }

        fn broadcast_by_local_state(&self, commitment_tx: &Transaction, local_tx: &LocalSignedTx) -> (Vec<ClaimRequest>, Vec<TxOut>, Option<(Script, SecretKey, Script)>) {
                let mut claim_requests = Vec::with_capacity(local_tx.htlc_outputs.len());
                let mut watch_outputs = Vec::with_capacity(local_tx.htlc_outputs.len());

                let redeemscript = chan_utils::get_revokeable_redeemscript(&local_tx.revocation_key, self.their_to_self_delay, &local_tx.delayed_payment_key);
                let broadcasted_local_revokable_script = if let Ok(local_delayedkey) = chan_utils::derive_private_key(&self.secp_ctx, &local_tx.per_commitment_point, self.keys.delayed_payment_base_key()) {
                        Some((redeemscript.to_v0_p2wsh(), local_delayedkey, redeemscript))
                } else { None };

                for &(ref htlc, _, _) in local_tx.htlc_outputs.iter() {
                        if let Some(transaction_output_index) = htlc.transaction_output_index {
                                let preimage = if let Some(preimage) = self.payment_preimages.get(&htlc.payment_hash) { Some(*preimage) } else { None };
                                claim_requests.push(ClaimRequest { absolute_timelock: ::std::u32::MAX, aggregable: false, outpoint: BitcoinOutPoint { txid: local_tx.txid, vout: transaction_output_index as u32 }, witness_data: InputMaterial::LocalHTLC { preimage, amount: htlc.amount_msat / 1000 }});
                                watch_outputs.push(commitment_tx.output[transaction_output_index as usize].clone());
                        }
                }

                (claim_requests, watch_outputs, broadcasted_local_revokable_script)
        }

        /// Attempts to claim any claimable HTLCs in a commitment transaction which was not (yet)
        /// revoked using data in local_claimable_outpoints.
        /// Should not be used if check_spend_revoked_transaction succeeds.
        fn check_spend_local_transaction(&mut self, tx: &Transaction, height: u32) -> (Vec<ClaimRequest>, (Sha256dHash, Vec<TxOut>)) {
                let commitment_txid = tx.txid();
                let mut claim_requests = Vec::new();
                let mut watch_outputs = Vec::new();

                macro_rules! wait_threshold_conf {
                        ($height: expr, $source: expr, $commitment_tx: expr, $payment_hash: expr) => {
                                log_trace!(self, "Failing HTLC with payment_hash {} from {} local commitment tx due to broadcast of transaction, waiting confirmation (at height{})", log_bytes!($payment_hash.0), $commitment_tx, height + ANTI_REORG_DELAY - 1);
                                match self.onchain_events_waiting_threshold_conf.entry($height + ANTI_REORG_DELAY - 1) {
                                        hash_map::Entry::Occupied(mut entry) => {
                                                let e = entry.get_mut();
                                                e.retain(|ref event| {
                                                        match **event {
                                                                OnchainEvent::HTLCUpdate { ref htlc_update } => {
                                                                        return htlc_update.0 != $source
                                                                },
                                                                _ => true
                                                        }
                                                });
                                                e.push(OnchainEvent::HTLCUpdate { htlc_update: ($source, $payment_hash)});
                                        }
                                        hash_map::Entry::Vacant(entry) => {
                                                entry.insert(vec![OnchainEvent::HTLCUpdate { htlc_update: ($source, $payment_hash)}]);
                                        }
                                }
                        }
                }

                macro_rules! append_onchain_update {
                        ($updates: expr) => {
                                claim_requests = $updates.0;
                                watch_outputs.append(&mut $updates.1);
                                self.broadcasted_local_revokable_script = $updates.2;
                        }
                }

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

                if let &Some(ref local_tx) = &self.current_local_signed_commitment_tx {
                        if local_tx.txid == commitment_txid {
                                is_local_tx = true;
                                log_trace!(self, "Got latest local commitment tx broadcast, searching for available HTLCs to claim");
                                let mut res = self.broadcast_by_local_state(tx, local_tx);
                                append_onchain_update!(res);
                        }
                }
                if let &Some(ref local_tx) = &self.prev_local_signed_commitment_tx {
                        if local_tx.txid == commitment_txid {
                                is_local_tx = true;
                                log_trace!(self, "Got previous local commitment tx broadcast, searching for available HTLCs to claim");
                                let mut res = self.broadcast_by_local_state(tx, local_tx);
                                append_onchain_update!(res);
                        }
                }

                macro_rules! fail_dust_htlcs_after_threshold_conf {
                        ($local_tx: expr) => {
                                for &(ref htlc, _, ref source) in &$local_tx.htlc_outputs {
                                        if htlc.transaction_output_index.is_none() {
                                                if let &Some(ref source) = source {
                                                        wait_threshold_conf!(height, source.clone(), "lastest", htlc.payment_hash.clone());
                                                }
                                        }
                                }
                        }
                }

                if is_local_tx {
                        if let &Some(ref local_tx) = &self.current_local_signed_commitment_tx {
                                fail_dust_htlcs_after_threshold_conf!(local_tx);
                        }
                        if let &Some(ref local_tx) = &self.prev_local_signed_commitment_tx {
                                fail_dust_htlcs_after_threshold_conf!(local_tx);
                        }
                }

                (claim_requests, (commitment_txid, watch_outputs))
        }

        /// Used by ChannelManager deserialization to broadcast the latest local state if its copy of
        /// the Channel was out-of-date. You may use it to get a broadcastable local toxic tx in case of
        /// fallen-behind, i.e when receiving a channel_reestablish with a proof that our remote side knows
        /// a higher revocation secret than the local commitment number we are aware of. Broadcasting these
        /// transactions are UNSAFE, as they allow remote side to punish you. Nevertheless you may want to
        /// broadcast them if remote 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_local_commitment_txn(&mut self) -> Vec<Transaction> {
                log_trace!(self, "Getting signed latest local commitment transaction!");
                if let Some(commitment_tx) = self.onchain_tx_handler.get_fully_signed_local_tx(self.channel_value_satoshis) {
                        let txid = commitment_tx.txid();
                        let mut res = vec![commitment_tx];
                        if let &Some(ref local_tx) = &self.current_local_signed_commitment_tx {
                                for htlc in local_tx.htlc_outputs.iter() {
                                        if let Some(htlc_index) = htlc.0.transaction_output_index {
                                                let preimage = if let Some(preimage) = self.payment_preimages.get(&htlc.0.payment_hash) { Some(*preimage) } else { None };
                                                if let Some(htlc_tx) = self.onchain_tx_handler.get_fully_signed_htlc_tx(txid, htlc_index, preimage) {
                                                        res.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_local_transaction if we get a confirmation.
                        }
                        return res
                }
                Vec::new()
        }

        /// Unsafe test-only version of get_latest_local_commitment_txn used by our test framework
        /// to bypass LocalCommitmentTransaction state update lockdown after signature and generate
        /// revoked commitment transaction.
        #[cfg(test)]
        pub fn unsafe_get_latest_local_commitment_txn(&mut self) -> Vec<Transaction> {
                log_trace!(self, "Getting signed copy of latest local commitment transaction!");
                if let Some(commitment_tx) = self.onchain_tx_handler.get_fully_signed_copy_local_tx(self.channel_value_satoshis) {
                        let txid = commitment_tx.txid();
                        let mut res = vec![commitment_tx];
                        if let &Some(ref local_tx) = &self.current_local_signed_commitment_tx {
                                for htlc in local_tx.htlc_outputs.iter() {
                                        if let Some(htlc_index) = htlc.0.transaction_output_index {
                                                let preimage = if let Some(preimage) = self.payment_preimages.get(&htlc.0.payment_hash) { Some(*preimage) } else { None };
                                                if let Some(htlc_tx) = self.onchain_tx_handler.get_fully_signed_htlc_tx(txid, htlc_index, preimage) {
                                                        res.push(htlc_tx);
                                                }
                                        }
                                }
                        }
                        return res
                }
                Vec::new()
        }

        /// Called by SimpleManyChannelMonitor::block_connected, which implements
        /// ChainListener::block_connected.
        /// Eventually this should be pub and, roughly, implement ChainListener, however this requires
        /// &mut self, as well as returns new spendable outputs and outpoints to watch for spending of
        /// on-chain.
        fn block_connected<B: Deref, F: Deref>(&mut self, txn_matched: &[&Transaction], height: u32, block_hash: &Sha256dHash, broadcaster: B, fee_estimator: F)-> Vec<(Sha256dHash, Vec<TxOut>)>
                where B::Target: BroadcasterInterface,
                      F::Target: FeeEstimator
        {
                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"); }
                        }
                }

                log_trace!(self, "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_remote_transaction(&tx, height);
                                                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_local_transaction(&tx, height);
                                                        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.remote_commitment_txn_on_chain.get(&prevout.txid) {
                                                let (mut new_outpoints, new_outputs_option) = self.check_spend_remote_htlc(&tx, commitment_number, height);
                                                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);

                        self.is_paying_spendable_output(&tx, height);
                }
                let should_broadcast = if let Some(_) = self.current_local_signed_commitment_tx {
                        self.would_broadcast_at_height(height)
                } else { false };
                if should_broadcast {
                        claimable_outpoints.push(ClaimRequest { absolute_timelock: height, aggregable: false, outpoint: BitcoinOutPoint { txid: self.funding_info.0.txid.clone(), vout: self.funding_info.0.index as u32 }, witness_data: InputMaterial::Funding { channel_value: self.channel_value_satoshis }});
                }
                if let Some(ref cur_local_tx) = self.current_local_signed_commitment_tx {
                        if should_broadcast {
                                if let Some(commitment_tx) = self.onchain_tx_handler.get_fully_signed_local_tx(self.channel_value_satoshis) {
                                        let (mut new_outpoints, new_outputs, _) = self.broadcast_by_local_state(&commitment_tx, cur_local_tx);
                                        if !new_outputs.is_empty() {
                                                watch_outputs.push((cur_local_tx.txid.clone(), new_outputs));
                                        }
                                        claimable_outpoints.append(&mut new_outpoints);
                                }
                        }
                }
                if let Some(events) = self.onchain_events_waiting_threshold_conf.remove(&height) {
                        for ev in events {
                                match ev {
                                        OnchainEvent::HTLCUpdate { htlc_update } => {
                                                log_trace!(self, "HTLC {} failure update has got enough confirmations to be passed upstream", log_bytes!((htlc_update.1).0));
                                                self.pending_htlcs_updated.push(HTLCUpdate {
                                                        payment_hash: htlc_update.1,
                                                        payment_preimage: None,
                                                        source: htlc_update.0,
                                                });
                                        },
                                        OnchainEvent::MaturingOutput { descriptor } => {
                                                log_trace!(self, "Descriptor {} has got enough confirmations to be passed upstream", log_spendable!(descriptor));
                                                self.pending_events.push(events::Event::SpendableOutputs {
                                                        outputs: vec![descriptor]
                                                });
                                        }
                                }
                        }
                }
                self.onchain_tx_handler.block_connected(txn_matched, claimable_outpoints, height, &*broadcaster, &*fee_estimator);

                self.last_block_hash = block_hash.clone();
                for &(ref txid, ref output_scripts) in watch_outputs.iter() {
                        self.outputs_to_watch.insert(txid.clone(), output_scripts.iter().map(|o| o.script_pubkey.clone()).collect());
                }

                watch_outputs
        }

        fn block_disconnected<B: Deref, F: Deref>(&mut self, height: u32, block_hash: &Sha256dHash, broadcaster: B, fee_estimator: F)
                where B::Target: BroadcasterInterface,
                      F::Target: FeeEstimator
        {
                log_trace!(self, "Block {} at height {} disconnected", block_hash, height);
                if let Some(_) = self.onchain_events_waiting_threshold_conf.remove(&(height + ANTI_REORG_DELAY - 1)) {
                        //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_tx_handler.block_disconnected(height, broadcaster, fee_estimator);

                self.last_block_hash = block_hash.clone();
        }

        pub(super) fn would_broadcast_at_height(&self, height: u32) -> bool {
                // We need to consider all HTLCs which are:
                //  * in any unrevoked remote commitment transaction, as they could broadcast said
                //    transactions and we'd end up in a race, or
                //  * are in our latest local 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.
                macro_rules! scan_commitment {
                        ($htlcs: expr, $local_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 = $local_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!(self, "Force-closing channel due to {} HTLC timeout, HTLC expiry is {}", if htlc_outbound { "outbound" } else { "inbound "}, htlc.cltv_expiry);
                                                return true;
                                        }
                                }
                        }
                }

                if let Some(ref cur_local_tx) = self.current_local_signed_commitment_tx {
                        scan_commitment!(cur_local_tx.htlc_outputs.iter().map(|&(ref a, _, _)| a), true);
                }

                if let Some(ref txid) = self.current_remote_commitment_txid {
                        if let Some(ref htlc_outputs) = self.remote_claimable_outpoints.get(txid) {
                                scan_commitment!(htlc_outputs.iter().map(|&(ref a, _)| a), false);
                        }
                }
                if let Some(ref txid) = self.prev_remote_commitment_txid {
                        if let Some(ref htlc_outputs) = self.remote_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 local
        /// or remote commitment tx, if so send back the source, preimage if found and payment_hash of resolved HTLC
        fn is_resolving_htlc_output(&mut self, tx: &Transaction, height: u32) {
                '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, $local_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 remote 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 = $local_tx == $htlc.offered;
                                        if ($local_tx && revocation_sig_claim) ||
                                                        (outbound_htlc && !$source_avail && (accepted_preimage_claim || offered_preimage_claim)) {
                                                log_error!(self, "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!(self, "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_remote {
                                ($remote_txid: expr, $htlc_output: expr) => {
                                        if let Some(txid) = $remote_txid {
                                                for &(ref pending_htlc, ref pending_source) in self.remote_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 remote commitment tx", false, pending_htlc, true);
                                                                        payment_data = Some(((**source).clone(), $htlc_output.payment_hash));
                                                                        break;
                                                                }
                                                        }
                                                }
                                        }
                                }
                        }

                        macro_rules! scan_commitment {
                                ($htlcs: expr, $tx_info: expr, $local_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, $local_tx, htlc_output, true);
                                                                // We have a resolution of an HTLC either from one of our latest
                                                                // local commitment transactions or an unrevoked remote commitment
                                                                // transaction. This implies we either learned a preimage, the HTLC
                                                                // has timed out, or we screwed up. In any case, we should now
                                                                // resolve the source HTLC with the original sender.
                                                                payment_data = Some(((*source).clone(), htlc_output.payment_hash));
                                                        } else if !$local_tx {
                                                                        check_htlc_valid_remote!(self.current_remote_commitment_txid, htlc_output);
                                                                if payment_data.is_none() {
                                                                        check_htlc_valid_remote!(self.prev_remote_commitment_txid, htlc_output);
                                                                }
                                                        }
                                                        if payment_data.is_none() {
                                                                log_claim!($tx_info, $local_tx, htlc_output, false);
                                                                continue 'outer_loop;
                                                        }
                                                }
                                        }
                                }
                        }

                        if let Some(ref current_local_signed_commitment_tx) = self.current_local_signed_commitment_tx {
                                if input.previous_output.txid == current_local_signed_commitment_tx.txid {
                                        scan_commitment!(current_local_signed_commitment_tx.htlc_outputs.iter().map(|&(ref a, _, ref b)| (a, b.as_ref())),
                                                "our latest local commitment tx", true);
                                }
                        }
                        if let Some(ref prev_local_signed_commitment_tx) = self.prev_local_signed_commitment_tx {
                                if input.previous_output.txid == prev_local_signed_commitment_tx.txid {
                                        scan_commitment!(prev_local_signed_commitment_tx.htlc_outputs.iter().map(|&(ref a, _, ref b)| (a, b.as_ref())),
                                                "our previous local commitment tx", true);
                                }
                        }
                        if let Some(ref htlc_outputs) = self.remote_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))),
                                        "remote 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)) = payment_data {
                                let mut payment_preimage = PaymentPreimage([0; 32]);
                                if accepted_preimage_claim {
                                        if !self.pending_htlcs_updated.iter().any(|update| update.source == source) {
                                                payment_preimage.0.copy_from_slice(&input.witness[3]);
                                                self.pending_htlcs_updated.push(HTLCUpdate {
                                                        source,
                                                        payment_preimage: Some(payment_preimage),
                                                        payment_hash
                                                });
                                        }
                                } else if offered_preimage_claim {
                                        if !self.pending_htlcs_updated.iter().any(|update| update.source == source) {
                                                payment_preimage.0.copy_from_slice(&input.witness[1]);
                                                self.pending_htlcs_updated.push(HTLCUpdate {
                                                        source,
                                                        payment_preimage: Some(payment_preimage),
                                                        payment_hash
                                                });
                                        }
                                } else {
                                        log_info!(self, "Failing HTLC with payment_hash {} timeout by a spend tx, waiting for confirmation (at height{})", log_bytes!(payment_hash.0), height + ANTI_REORG_DELAY - 1);
                                        match self.onchain_events_waiting_threshold_conf.entry(height + ANTI_REORG_DELAY - 1) {
                                                hash_map::Entry::Occupied(mut entry) => {
                                                        let e = entry.get_mut();
                                                        e.retain(|ref event| {
                                                                match **event {
                                                                        OnchainEvent::HTLCUpdate { ref htlc_update } => {
                                                                                return htlc_update.0 != source
                                                                        },
                                                                        _ => true
                                                                }
                                                        });
                                                        e.push(OnchainEvent::HTLCUpdate { htlc_update: (source, payment_hash)});
                                                }
                                                hash_map::Entry::Vacant(entry) => {
                                                        entry.insert(vec![OnchainEvent::HTLCUpdate { htlc_update: (source, payment_hash)}]);
                                                }
                                        }
                                }
                        }
                }
        }

        /// Check if any transaction broadcasted is paying fund back to some address we can assume to own
        fn is_paying_spendable_output(&mut self, tx: &Transaction, height: u32) {
                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 outp.script_pubkey == self.destination_script {
                                spendable_output =  Some(SpendableOutputDescriptor::StaticOutput {
                                        outpoint: BitcoinOutPoint { txid: tx.txid(), vout: i as u32 },
                                        output: outp.clone(),
                                });
                                break;
                        } else if let Some(ref broadcasted_local_revokable_script) = self.broadcasted_local_revokable_script {
                                if broadcasted_local_revokable_script.0 == outp.script_pubkey {
                                        spendable_output =  Some(SpendableOutputDescriptor::DynamicOutputP2WSH {
                                                outpoint: BitcoinOutPoint { txid: tx.txid(), vout: i as u32 },
                                                key: broadcasted_local_revokable_script.1,
                                                witness_script: broadcasted_local_revokable_script.2.clone(),
                                                to_self_delay: self.their_to_self_delay,
                                                output: outp.clone(),
                                        });
                                        break;
                                }
                        } else if let Some(ref broadcasted_remote_payment_script) = self.broadcasted_remote_payment_script {
                                if broadcasted_remote_payment_script.0 == outp.script_pubkey {
                                        spendable_output = Some(SpendableOutputDescriptor::DynamicOutputP2WPKH {
                                                outpoint: BitcoinOutPoint { txid: tx.txid(), vout: i as u32 },
                                                key: broadcasted_remote_payment_script.1,
                                                output: outp.clone(),
                                        });
                                        break;
                                }
                        } else if outp.script_pubkey == self.shutdown_script {
                                spendable_output = Some(SpendableOutputDescriptor::StaticOutput {
                                        outpoint: BitcoinOutPoint { txid: tx.txid(), vout: i as u32 },
                                        output: outp.clone(),
                                });
                        }
                }
                if let Some(spendable_output) = spendable_output {
                        log_trace!(self, "Maturing {} until {}", log_spendable!(spendable_output), height + ANTI_REORG_DELAY - 1);
                        match self.onchain_events_waiting_threshold_conf.entry(height + ANTI_REORG_DELAY - 1) {
                                hash_map::Entry::Occupied(mut entry) => {
                                        let e = entry.get_mut();
                                        e.push(OnchainEvent::MaturingOutput { descriptor: spendable_output });
                                }
                                hash_map::Entry::Vacant(entry) => {
                                        entry.insert(vec![OnchainEvent::MaturingOutput { descriptor: spendable_output }]);
                                }
                        }
                }
        }
}

const MAX_ALLOC_SIZE: usize = 64*1024;

impl<ChanSigner: ChannelKeys + Readable> ReadableArgs<Arc<Logger>> for (Sha256dHash, ChannelMonitor<ChanSigner>) {
        fn read<R: ::std::io::Read>(reader: &mut R, logger: Arc<Logger>) -> Result<Self, DecodeError> {
                macro_rules! unwrap_obj {
                        ($key: expr) => {
                                match $key {
                                        Ok(res) => res,
                                        Err(_) => return Err(DecodeError::InvalidValue),
                                }
                        }
                }

                let _ver: u8 = Readable::read(reader)?;
                let min_ver: u8 = Readable::read(reader)?;
                if min_ver > SERIALIZATION_VERSION {
                        return Err(DecodeError::UnknownVersion);
                }

                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_local_revokable_script = match <u8 as Readable>::read(reader)? {
                        0 => {
                                let revokable_address = Readable::read(reader)?;
                                let local_delayedkey = Readable::read(reader)?;
                                let revokable_script = Readable::read(reader)?;
                                Some((revokable_address, local_delayedkey, revokable_script))
                        },
                        1 => { None },
                        _ => return Err(DecodeError::InvalidValue),
                };
                let broadcasted_remote_payment_script = match <u8 as Readable>::read(reader)? {
                        0 => {
                                let payment_address = Readable::read(reader)?;
                                let payment_key = Readable::read(reader)?;
                                Some((payment_address, payment_key))
                        },
                        1 => { None },
                        _ => return Err(DecodeError::InvalidValue),
                };
                let shutdown_script = Readable::read(reader)?;

                let keys = 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_remote_commitment_txid = Readable::read(reader)?;
                let prev_remote_commitment_txid = Readable::read(reader)?;

                let their_htlc_base_key = Readable::read(reader)?;
                let their_delayed_payment_base_key = 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 our_to_self_delay: u16 = Readable::read(reader)?;
                let their_to_self_delay: 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 remote_claimable_outpoints_len: u64 = Readable::read(reader)?;
                let mut remote_claimable_outpoints = HashMap::with_capacity(cmp::min(remote_claimable_outpoints_len as usize, MAX_ALLOC_SIZE / 64));
                for _ in 0..remote_claimable_outpoints_len {
                        let txid: Sha256dHash = 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(_) = remote_claimable_outpoints.insert(txid, htlcs) {
                                return Err(DecodeError::InvalidValue);
                        }
                }

                let remote_commitment_txn_on_chain_len: u64 = Readable::read(reader)?;
                let mut remote_commitment_txn_on_chain = HashMap::with_capacity(cmp::min(remote_commitment_txn_on_chain_len as usize, MAX_ALLOC_SIZE / 32));
                for _ in 0..remote_commitment_txn_on_chain_len {
                        let txid: Sha256dHash = Readable::read(reader)?;
                        let commitment_number = <U48 as Readable>::read(reader)?.0;
                        let outputs_count = <u64 as Readable>::read(reader)?;
                        let mut outputs = Vec::with_capacity(cmp::min(outputs_count as usize, MAX_ALLOC_SIZE / 8));
                        for _ in 0..outputs_count {
                                outputs.push(Readable::read(reader)?);
                        }
                        if let Some(_) = remote_commitment_txn_on_chain.insert(txid, (commitment_number, outputs)) {
                                return Err(DecodeError::InvalidValue);
                        }
                }

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

                macro_rules! read_local_tx {
                        () => {
                                {
                                        let txid = Readable::read(reader)?;
                                        let revocation_key = Readable::read(reader)?;
                                        let a_htlc_key = Readable::read(reader)?;
                                        let b_htlc_key = Readable::read(reader)?;
                                        let delayed_payment_key = Readable::read(reader)?;
                                        let per_commitment_point = Readable::read(reader)?;
                                        let feerate_per_kw: u64 = Readable::read(reader)?;

                                        let htlcs_len: u64 = Readable::read(reader)?;
                                        let mut htlcs = Vec::with_capacity(cmp::min(htlcs_len as usize, MAX_ALLOC_SIZE / 128));
                                        for _ in 0..htlcs_len {
                                                let htlc = read_htlc_in_commitment!();
                                                let sigs = match <u8 as Readable>::read(reader)? {
                                                        0 => None,
                                                        1 => Some(Readable::read(reader)?),
                                                        _ => return Err(DecodeError::InvalidValue),
                                                };
                                                htlcs.push((htlc, sigs, Readable::read(reader)?));
                                        }

                                        LocalSignedTx {
                                                txid,
                                                revocation_key, a_htlc_key, b_htlc_key, delayed_payment_key, per_commitment_point, feerate_per_kw,
                                                htlc_outputs: htlcs
                                        }
                                }
                        }
                }

                let prev_local_signed_commitment_tx = match <u8 as Readable>::read(reader)? {
                        0 => None,
                        1 => {
                                Some(read_local_tx!())
                        },
                        _ => return Err(DecodeError::InvalidValue),
                };

                let current_local_signed_commitment_tx = match <u8 as Readable>::read(reader)? {
                        0 => None,
                        1 => {
                                Some(read_local_tx!())
                        },
                        _ => return Err(DecodeError::InvalidValue),
                };

                let current_remote_commitment_number = <U48 as Readable>::read(reader)?.0;
                let current_local_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_htlcs_updated_len: u64 = Readable::read(reader)?;
                let mut pending_htlcs_updated = Vec::with_capacity(cmp::min(pending_htlcs_updated_len as usize, MAX_ALLOC_SIZE / (32 + 8*3)));
                for _ in 0..pending_htlcs_updated_len {
                        pending_htlcs_updated.push(Readable::read(reader)?);
                }

                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::<events::Event>()));
                for _ in 0..pending_events_len {
                        if let Some(event) = MaybeReadable::read(reader)? {
                                pending_events.push(event);
                        }
                }

                let last_block_hash: Sha256dHash = Readable::read(reader)?;

                let waiting_threshold_conf_len: u64 = Readable::read(reader)?;
                let mut onchain_events_waiting_threshold_conf = HashMap::with_capacity(cmp::min(waiting_threshold_conf_len as usize, MAX_ALLOC_SIZE / 128));
                for _ in 0..waiting_threshold_conf_len {
                        let height_target = Readable::read(reader)?;
                        let events_len: u64 = Readable::read(reader)?;
                        let mut events = Vec::with_capacity(cmp::min(events_len as usize, MAX_ALLOC_SIZE / 128));
                        for _ in 0..events_len {
                                let ev = match <u8 as Readable>::read(reader)? {
                                        0 => {
                                                let htlc_source = Readable::read(reader)?;
                                                let hash = Readable::read(reader)?;
                                                OnchainEvent::HTLCUpdate {
                                                        htlc_update: (htlc_source, hash)
                                                }
                                        },
                                        1 => {
                                                let descriptor = Readable::read(reader)?;
                                                OnchainEvent::MaturingOutput {
                                                        descriptor
                                                }
                                        },
                                        _ => return Err(DecodeError::InvalidValue),
                                };
                                events.push(ev);
                        }
                        onchain_events_waiting_threshold_conf.insert(height_target, events);
                }

                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::<Sha256dHash>() + 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::<Script>()));
                        for _ in 0..outputs_len {
                                outputs.push(Readable::read(reader)?);
                        }
                        if let Some(_) = outputs_to_watch.insert(txid, outputs) {
                                return Err(DecodeError::InvalidValue);
                        }
                }
                let onchain_tx_handler = ReadableArgs::read(reader, logger.clone())?;

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

                Ok((last_block_hash.clone(), ChannelMonitor {
                        latest_update_id,
                        commitment_transaction_number_obscure_factor,

                        destination_script,
                        broadcasted_local_revokable_script,
                        broadcasted_remote_payment_script,
                        shutdown_script,

                        keys,
                        funding_info,
                        current_remote_commitment_txid,
                        prev_remote_commitment_txid,

                        their_htlc_base_key,
                        their_delayed_payment_base_key,
                        funding_redeemscript,
                        channel_value_satoshis,
                        their_cur_revocation_points,

                        our_to_self_delay,
                        their_to_self_delay,

                        commitment_secrets,
                        remote_claimable_outpoints,
                        remote_commitment_txn_on_chain,
                        remote_hash_commitment_number,

                        prev_local_signed_commitment_tx,
                        current_local_signed_commitment_tx,
                        current_remote_commitment_number,
                        current_local_commitment_number,

                        payment_preimages,
                        pending_htlcs_updated,
                        pending_events,

                        onchain_events_waiting_threshold_conf,
                        outputs_to_watch,

                        onchain_tx_handler,

                        lockdown_from_offchain,

                        last_block_hash,
                        secp_ctx: Secp256k1::new(),
                        logger,
                }))
        }
}

#[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::sha256d::Hash as Sha256dHash;
        use bitcoin_hashes::hex::FromHex;
        use hex;
        use chain::transaction::OutPoint;
        use ln::channelmanager::{PaymentPreimage, PaymentHash};
        use ln::channelmonitor::ChannelMonitor;
        use ln::onchaintx::{OnchainTxHandler, InputDescriptors};
        use ln::chan_utils;
        use ln::chan_utils::{HTLCOutputInCommitment, TxCreationKeys, LocalCommitmentTransaction};
        use util::test_utils::TestLogger;
        use secp256k1::key::{SecretKey,PublicKey};
        use secp256k1::Secp256k1;
        use rand::{thread_rng,Rng};
        use std::sync::Arc;
        use chain::keysinterface::InMemoryChannelKeys;

        #[test]
        fn test_prune_preimages() {
                let secp_ctx = Secp256k1::new();
                let logger = Arc::new(TestLogger::new());

                let dummy_key = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                macro_rules! dummy_keys {
                        () => {
                                {
                                        TxCreationKeys {
                                                per_commitment_point: dummy_key.clone(),
                                                revocation_key: dummy_key.clone(),
                                                a_htlc_key: dummy_key.clone(),
                                                b_htlc_key: dummy_key.clone(),
                                                a_delayed_payment_key: dummy_key.clone(),
                                                b_payment_key: dummy_key.clone(),
                                        }
                                }
                        }
                }
                let dummy_tx = Transaction { version: 0, lock_time: 0, input: Vec::new(), output: Vec::new() };

                let mut preimages = Vec::new();
                {
                        let mut rng  = thread_rng();
                        for _ in 0..20 {
                                let mut preimage = PaymentPreimage([0; 32]);
                                rng.fill_bytes(&mut preimage.0[..]);
                                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 $preimages_slice.iter().enumerate() {
                                                res.push((HTLCOutputInCommitment {
                                                        offered: true,
                                                        amount_msat: 0,
                                                        cltv_expiry: 0,
                                                        payment_hash: preimage.1.clone(),
                                                        transaction_output_index: Some(idx as u32),
                                                }, None));
                                        }
                                        res
                                }
                        }
                }
                macro_rules! preimages_to_local_htlcs {
                        ($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.payment_preimages.contains_key(&preimage.1));
                                }
                        }
                }

                let keys = InMemoryChannelKeys::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,
                );

                // Prune with one old state and a local commitment tx holding a few overlaps with the
                // old state.
                let mut monitor = ChannelMonitor::new(keys,
                        &PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap()), 0, &Script::new(),
                        (OutPoint { txid: Sha256dHash::from_slice(&[43; 32]).unwrap(), index: 0 }, Script::new()),
                        &PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[44; 32]).unwrap()),
                        &PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[45; 32]).unwrap()),
                        10, Script::new(), 46, 0, logger.clone());

                monitor.provide_latest_local_commitment_tx_info(LocalCommitmentTransaction::dummy(), dummy_keys!(), 0, preimages_to_local_htlcs!(preimages[0..10])).unwrap();
                monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[5..15]), 281474976710655, dummy_key);
                monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[15..20]), 281474976710654, dummy_key);
                monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[17..20]), 281474976710653, dummy_key);
                monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[18..20]), 281474976710652, dummy_key);
                for &(ref preimage, ref hash) in preimages.iter() {
                        monitor.provide_payment_preimage(hash, preimage);
                }

                // 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.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.payment_preimages.len(), 13);
                test_preimages_exist!(&preimages[0..10], monitor);
                test_preimages_exist!(&preimages[17..20], monitor);

                // Now update local commitment tx info, pruning only element 18 as we still care about the
                // previous commitment tx's preimages too
                monitor.provide_latest_local_commitment_tx_info(LocalCommitmentTransaction::dummy(), dummy_keys!(), 0, preimages_to_local_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.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_local_commitment_tx_info(LocalCommitmentTransaction::dummy(), dummy_keys!(), 0, preimages_to_local_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.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, $input: expr, $idx: expr, $amount: expr, $input_type: expr, $sum_actual_sigs: expr) => {
                                let htlc = HTLCOutputInCommitment {
                                        offered: if *$input_type == InputDescriptors::RevokedOfferedHTLC || *$input_type == InputDescriptors::OfferedHTLC { true } else { false },
                                        amount_msat: 0,
                                        cltv_expiry: 2 << 16,
                                        payment_hash: PaymentHash([1; 32]),
                                        transaction_output_index: Some($idx),
                                };
                                let redeem_script = if *$input_type == InputDescriptors::RevokedOutput { chan_utils::get_revokeable_redeemscript(&pubkey, 256, &pubkey) } else { chan_utils::get_htlc_redeemscript_with_explicit_keys(&htlc, &pubkey, &pubkey, &pubkey) };
                                let sighash = hash_to_message!(&$sighash_parts.sighash_all(&$input, &redeem_script, $amount)[..]);
                                let sig = secp_ctx.sign(&sighash, &privkey);
                                $input.witness.push(sig.serialize_der().to_vec());
                                $input.witness[0].push(SigHashType::All as u8);
                                sum_actual_sigs += $input.witness[0].len();
                                if *$input_type == InputDescriptors::RevokedOutput {
                                        $input.witness.push(vec!(1));
                                } else if *$input_type == InputDescriptors::RevokedOfferedHTLC || *$input_type == InputDescriptors::RevokedReceivedHTLC {
                                        $input.witness.push(pubkey.clone().serialize().to_vec());
                                } else if *$input_type == InputDescriptors::ReceivedHTLC {
                                        $input.witness.push(vec![0]);
                                } else {
                                        $input.witness.push(PaymentPreimage([1; 32]).0.to_vec());
                                }
                                $input.witness.push(redeem_script.into_bytes());
                                println!("witness[0] {}", $input.witness[0].len());
                                println!("witness[1] {}", $input.witness[1].len());
                                println!("witness[2] {}", $input.witness[2].len());
                        }
                }

                let script_pubkey = Builder::new().push_opcode(opcodes::all::OP_RETURN).into_script();
                let txid = Sha256dHash::from_hex("56944c5d3f98413ef45cf54545538103cc9f298e0575820ad3591376e2e0f65d").unwrap();

                // Justice tx with 1 to_local, 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 sighash_parts = bip143::SighashComponents::new(&claim_tx);
                let inputs_des = vec![InputDescriptors::RevokedOutput, InputDescriptors::RevokedOfferedHTLC, InputDescriptors::RevokedOfferedHTLC, InputDescriptors::RevokedReceivedHTLC];
                for (idx, inp) in claim_tx.input.iter_mut().zip(inputs_des.iter()).enumerate() {
                        sign_input!(sighash_parts, inp.0, idx as u32, 0, inp.1, sum_actual_sigs);
                }
                assert_eq!(base_weight + OnchainTxHandler::<InMemoryChannelKeys>::get_witnesses_weight(&inputs_des[..]),  claim_tx.get_weight() + /* max_length_sig */ (73 * inputs_des.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 sighash_parts = bip143::SighashComponents::new(&claim_tx);
                let inputs_des = vec![InputDescriptors::OfferedHTLC, InputDescriptors::ReceivedHTLC, InputDescriptors::ReceivedHTLC, InputDescriptors::ReceivedHTLC];
                for (idx, inp) in claim_tx.input.iter_mut().zip(inputs_des.iter()).enumerate() {
                        sign_input!(sighash_parts, inp.0, idx as u32, 0, inp.1, sum_actual_sigs);
                }
                assert_eq!(base_weight + OnchainTxHandler::<InMemoryChannelKeys>::get_witnesses_weight(&inputs_des[..]),  claim_tx.get_weight() + /* max_length_sig */ (73 * inputs_des.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 sighash_parts = bip143::SighashComponents::new(&claim_tx);
                let inputs_des = vec![InputDescriptors::RevokedOutput];
                for (idx, inp) in claim_tx.input.iter_mut().zip(inputs_des.iter()).enumerate() {
                        sign_input!(sighash_parts, inp.0, idx as u32, 0, inp.1, sum_actual_sigs);
                }
                assert_eq!(base_weight + OnchainTxHandler::<InMemoryChannelKeys>::get_witnesses_weight(&inputs_des[..]), claim_tx.get_weight() + /* max_length_isg */ (73 * inputs_des.len() - sum_actual_sigs));
        }

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