Refactor EventsProvider to take an EventHandler

[rust-lightning] / lightning / src / util / events.rs

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

//! Events are returned from various bits in the library which indicate some action must be taken
//! by the client.
//!
//! Because we don't have a built-in runtime, it's up to the client to call events at a time in the
//! future, as well as generate and broadcast funding transactions handle payment preimages and a
//! few other things.

use ln::msgs;
use ln::{PaymentPreimage, PaymentHash, PaymentSecret};
use chain::keysinterface::SpendableOutputDescriptor;
use util::ser::{Writeable, Writer, MaybeReadable, Readable};

use bitcoin::blockdata::script::Script;

use bitcoin::secp256k1::key::PublicKey;

use core::time::Duration;
use std::ops::Deref;

/// An Event which you should probably take some action in response to.
///
/// Note that while Writeable and Readable are implemented for Event, you probably shouldn't use
/// them directly as they don't round-trip exactly (for example FundingGenerationReady is never
/// written as it makes no sense to respond to it after reconnecting to peers).
#[derive(Clone, Debug)]
pub enum Event {
        /// Used to indicate that the client should generate a funding transaction with the given
        /// parameters and then call ChannelManager::funding_transaction_generated.
        /// Generated in ChannelManager message handling.
        /// Note that *all inputs* in the funding transaction must spend SegWit outputs or your
        /// counterparty can steal your funds!
        FundingGenerationReady {
                /// The random channel_id we picked which you'll need to pass into
                /// ChannelManager::funding_transaction_generated.
                temporary_channel_id: [u8; 32],
                /// The value, in satoshis, that the output should have.
                channel_value_satoshis: u64,
                /// The script which should be used in the transaction output.
                output_script: Script,
                /// The value passed in to ChannelManager::create_channel
                user_channel_id: u64,
        },
        /// Indicates we've received money! Just gotta dig out that payment preimage and feed it to
        /// ChannelManager::claim_funds to get it....
        /// Note that if the preimage is not known or the amount paid is incorrect, you should call
        /// ChannelManager::fail_htlc_backwards to free up resources for this HTLC and avoid
        /// network congestion.
        /// The amount paid should be considered 'incorrect' when it is less than or more than twice
        /// the amount expected.
        /// If you fail to call either ChannelManager::claim_funds or
        /// ChannelManager::fail_htlc_backwards within the HTLC's timeout, the HTLC will be
        /// automatically failed.
        PaymentReceived {
                /// The hash for which the preimage should be handed to the ChannelManager.
                payment_hash: PaymentHash,
                /// The preimage to the payment_hash, if the payment hash (and secret) were fetched via
                /// [`ChannelManager::create_inbound_payment`]. If provided, this can be handed directly to
                /// [`ChannelManager::claim_funds`].
                ///
                /// [`ChannelManager::create_inbound_payment`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment
                /// [`ChannelManager::claim_funds`]: crate::ln::channelmanager::ChannelManager::claim_funds
                payment_preimage: Option<PaymentPreimage>,
                /// The "payment secret". This authenticates the sender to the recipient, preventing a
                /// number of deanonymization attacks during the routing process.
                /// It is provided here for your reference, however its accuracy is enforced directly by
                /// [`ChannelManager`] using the values you previously provided to
                /// [`ChannelManager::create_inbound_payment`] or
                /// [`ChannelManager::create_inbound_payment_for_hash`].
                ///
                /// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
                /// [`ChannelManager::create_inbound_payment`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment
                /// [`ChannelManager::create_inbound_payment_for_hash`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment_for_hash
                payment_secret: PaymentSecret,
                /// The value, in thousandths of a satoshi, that this payment is for. Note that you must
                /// compare this to the expected value before accepting the payment (as otherwise you are
                /// providing proof-of-payment for less than the value you expected!).
                amt: u64,
                /// This is the `user_payment_id` which was provided to
                /// [`ChannelManager::create_inbound_payment_for_hash`] or
                /// [`ChannelManager::create_inbound_payment`]. It has no meaning inside of LDK and is
                /// simply copied here. It may be used to correlate PaymentReceived events with invoice
                /// metadata stored elsewhere.
                ///
                /// [`ChannelManager::create_inbound_payment`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment
                /// [`ChannelManager::create_inbound_payment_for_hash`]: crate::ln::channelmanager::ChannelManager::create_inbound_payment_for_hash
                user_payment_id: u64,
        },
        /// Indicates an outbound payment we made succeeded (ie it made it all the way to its target
        /// and we got back the payment preimage for it).
        PaymentSent {
                /// The preimage to the hash given to ChannelManager::send_payment.
                /// Note that this serves as a payment receipt, if you wish to have such a thing, you must
                /// store it somehow!
                payment_preimage: PaymentPreimage,
        },
        /// Indicates an outbound payment we made failed. Probably some intermediary node dropped
        /// something. You may wish to retry with a different route.
        PaymentFailed {
                /// The hash which was given to ChannelManager::send_payment.
                payment_hash: PaymentHash,
                /// Indicates the payment was rejected for some reason by the recipient. This implies that
                /// the payment has failed, not just the route in question. If this is not set, you may
                /// retry the payment via a different route.
                rejected_by_dest: bool,
#[cfg(test)]
                error_code: Option<u16>,
#[cfg(test)]
                error_data: Option<Vec<u8>>,
        },
        /// Used to indicate that ChannelManager::process_pending_htlc_forwards should be called at a
        /// time in the future.
        PendingHTLCsForwardable {
                /// The minimum amount of time that should be waited prior to calling
                /// process_pending_htlc_forwards. To increase the effort required to correlate payments,
                /// you should wait a random amount of time in roughly the range (now + time_forwardable,
                /// now + 5*time_forwardable).
                time_forwardable: Duration,
        },
        /// Used to indicate that an output was generated on-chain which you should know how to spend.
        /// Such an output will *not* ever be spent by rust-lightning, and are not at risk of your
        /// counterparty spending them due to some kind of timeout. Thus, you need to store them
        /// somewhere and spend them when you create on-chain transactions.
        SpendableOutputs {
                /// The outputs which you should store as spendable by you.
                outputs: Vec<SpendableOutputDescriptor>,
        },
}

impl Writeable for Event {
        fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
                match self {
                        &Event::FundingGenerationReady { .. } => {
                                0u8.write(writer)?;
                                // We never write out FundingGenerationReady events as, upon disconnection, peers
                                // drop any channels which have not yet exchanged funding_signed.
                        },
                        &Event::PaymentReceived { ref payment_hash, ref payment_preimage, ref payment_secret, ref amt, ref user_payment_id } => {
                                1u8.write(writer)?;
                                payment_hash.write(writer)?;
                                payment_preimage.write(writer)?;
                                payment_secret.write(writer)?;
                                amt.write(writer)?;
                                user_payment_id.write(writer)?;
                        },
                        &Event::PaymentSent { ref payment_preimage } => {
                                2u8.write(writer)?;
                                payment_preimage.write(writer)?;
                        },
                        &Event::PaymentFailed { ref payment_hash, ref rejected_by_dest,
                                #[cfg(test)]
                                ref error_code,
                                #[cfg(test)]
                                ref error_data,
                        } => {
                                3u8.write(writer)?;
                                payment_hash.write(writer)?;
                                rejected_by_dest.write(writer)?;
                                #[cfg(test)]
                                error_code.write(writer)?;
                                #[cfg(test)]
                                error_data.write(writer)?;
                        },
                        &Event::PendingHTLCsForwardable { time_forwardable: _ } => {
                                4u8.write(writer)?;
                                // We don't write the time_fordwardable out at all, as we presume when the user
                                // deserializes us at least that much time has elapsed.
                        },
                        &Event::SpendableOutputs { ref outputs } => {
                                5u8.write(writer)?;
                                (outputs.len() as u64).write(writer)?;
                                for output in outputs.iter() {
                                        output.write(writer)?;
                                }
                        },
                }
                Ok(())
        }
}
impl MaybeReadable for Event {
        fn read<R: ::std::io::Read>(reader: &mut R) -> Result<Option<Self>, msgs::DecodeError> {
                match Readable::read(reader)? {
                        0u8 => Ok(None),
                        1u8 => Ok(Some(Event::PaymentReceived {
                                        payment_hash: Readable::read(reader)?,
                                        payment_preimage: Readable::read(reader)?,
                                        payment_secret: Readable::read(reader)?,
                                        amt: Readable::read(reader)?,
                                        user_payment_id: Readable::read(reader)?,
                                })),
                        2u8 => Ok(Some(Event::PaymentSent {
                                        payment_preimage: Readable::read(reader)?,
                                })),
                        3u8 => Ok(Some(Event::PaymentFailed {
                                        payment_hash: Readable::read(reader)?,
                                        rejected_by_dest: Readable::read(reader)?,
                                        #[cfg(test)]
                                        error_code: Readable::read(reader)?,
                                        #[cfg(test)]
                                        error_data: Readable::read(reader)?,
                                })),
                        4u8 => Ok(Some(Event::PendingHTLCsForwardable {
                                        time_forwardable: Duration::from_secs(0)
                                })),
                        5u8 => {
                                let outputs_len: u64 = Readable::read(reader)?;
                                let mut outputs = Vec::new();
                                for _ in 0..outputs_len {
                                        outputs.push(Readable::read(reader)?);
                                }
                                Ok(Some(Event::SpendableOutputs { outputs }))
                        },
                        _ => Err(msgs::DecodeError::InvalidValue)
                }
        }
}

/// An event generated by ChannelManager which indicates a message should be sent to a peer (or
/// broadcast to most peers).
/// These events are handled by PeerManager::process_events if you are using a PeerManager.
#[derive(Clone, Debug)]
pub enum MessageSendEvent {
        /// Used to indicate that we've accepted a channel open and should send the accept_channel
        /// message provided to the given peer.
        SendAcceptChannel {
                /// The node_id of the node which should receive this message
                node_id: PublicKey,
                /// The message which should be sent.
                msg: msgs::AcceptChannel,
        },
        /// Used to indicate that we've initiated a channel open and should send the open_channel
        /// message provided to the given peer.
        SendOpenChannel {
                /// The node_id of the node which should receive this message
                node_id: PublicKey,
                /// The message which should be sent.
                msg: msgs::OpenChannel,
        },
        /// Used to indicate that a funding_created message should be sent to the peer with the given node_id.
        SendFundingCreated {
                /// The node_id of the node which should receive this message
                node_id: PublicKey,
                /// The message which should be sent.
                msg: msgs::FundingCreated,
        },
        /// Used to indicate that a funding_signed message should be sent to the peer with the given node_id.
        SendFundingSigned {
                /// The node_id of the node which should receive this message
                node_id: PublicKey,
                /// The message which should be sent.
                msg: msgs::FundingSigned,
        },
        /// Used to indicate that a funding_locked message should be sent to the peer with the given node_id.
        SendFundingLocked {
                /// The node_id of the node which should receive these message(s)
                node_id: PublicKey,
                /// The funding_locked message which should be sent.
                msg: msgs::FundingLocked,
        },
        /// Used to indicate that an announcement_signatures message should be sent to the peer with the given node_id.
        SendAnnouncementSignatures {
                /// The node_id of the node which should receive these message(s)
                node_id: PublicKey,
                /// The announcement_signatures message which should be sent.
                msg: msgs::AnnouncementSignatures,
        },
        /// Used to indicate that a series of HTLC update messages, as well as a commitment_signed
        /// message should be sent to the peer with the given node_id.
        UpdateHTLCs {
                /// The node_id of the node which should receive these message(s)
                node_id: PublicKey,
                /// The update messages which should be sent. ALL messages in the struct should be sent!
                updates: msgs::CommitmentUpdate,
        },
        /// Used to indicate that a revoke_and_ack message should be sent to the peer with the given node_id.
        SendRevokeAndACK {
                /// The node_id of the node which should receive this message
                node_id: PublicKey,
                /// The message which should be sent.
                msg: msgs::RevokeAndACK,
        },
        /// Used to indicate that a closing_signed message should be sent to the peer with the given node_id.
        SendClosingSigned {
                /// The node_id of the node which should receive this message
                node_id: PublicKey,
                /// The message which should be sent.
                msg: msgs::ClosingSigned,
        },
        /// Used to indicate that a shutdown message should be sent to the peer with the given node_id.
        SendShutdown {
                /// The node_id of the node which should receive this message
                node_id: PublicKey,
                /// The message which should be sent.
                msg: msgs::Shutdown,
        },
        /// Used to indicate that a channel_reestablish message should be sent to the peer with the given node_id.
        SendChannelReestablish {
                /// The node_id of the node which should receive this message
                node_id: PublicKey,
                /// The message which should be sent.
                msg: msgs::ChannelReestablish,
        },
        /// Used to indicate that a channel_announcement and channel_update should be broadcast to all
        /// peers (except the peer with node_id either msg.contents.node_id_1 or msg.contents.node_id_2).
        ///
        /// Note that after doing so, you very likely (unless you did so very recently) want to call
        /// ChannelManager::broadcast_node_announcement to trigger a BroadcastNodeAnnouncement event.
        /// This ensures that any nodes which see our channel_announcement also have a relevant
        /// node_announcement, including relevant feature flags which may be important for routing
        /// through or to us.
        BroadcastChannelAnnouncement {
                /// The channel_announcement which should be sent.
                msg: msgs::ChannelAnnouncement,
                /// The followup channel_update which should be sent.
                update_msg: msgs::ChannelUpdate,
        },
        /// Used to indicate that a node_announcement should be broadcast to all peers.
        BroadcastNodeAnnouncement {
                /// The node_announcement which should be sent.
                msg: msgs::NodeAnnouncement,
        },
        /// Used to indicate that a channel_update should be broadcast to all peers.
        BroadcastChannelUpdate {
                /// The channel_update which should be sent.
                msg: msgs::ChannelUpdate,
        },
        /// Broadcast an error downstream to be handled
        HandleError {
                /// The node_id of the node which should receive this message
                node_id: PublicKey,
                /// The action which should be taken.
                action: msgs::ErrorAction
        },
        /// When a payment fails we may receive updates back from the hop where it failed. In such
        /// cases this event is generated so that we can inform the network graph of this information.
        PaymentFailureNetworkUpdate {
                /// The channel/node update which should be sent to NetGraphMsgHandler
                update: msgs::HTLCFailChannelUpdate,
        },
        /// Query a peer for channels with funding transaction UTXOs in a block range.
        SendChannelRangeQuery {
                /// The node_id of this message recipient
                node_id: PublicKey,
                /// The query_channel_range which should be sent.
                msg: msgs::QueryChannelRange,
        },
        /// Request routing gossip messages from a peer for a list of channels identified by
        /// their short_channel_ids.
        SendShortIdsQuery {
                /// The node_id of this message recipient
                node_id: PublicKey,
                /// The query_short_channel_ids which should be sent.
                msg: msgs::QueryShortChannelIds,
        },
        /// Sends a reply to a channel range query. This may be one of several SendReplyChannelRange events
        /// emitted during processing of the query.
        SendReplyChannelRange {
                /// The node_id of this message recipient
                node_id: PublicKey,
                /// The reply_channel_range which should be sent.
                msg: msgs::ReplyChannelRange,
        }
}

/// A trait indicating an object may generate message send events
pub trait MessageSendEventsProvider {
        /// Gets the list of pending events which were generated by previous actions, clearing the list
        /// in the process.
        fn get_and_clear_pending_msg_events(&self) -> Vec<MessageSendEvent>;
}

/// A trait indicating an object may generate events.
///
/// Events are processed by passing an [`EventHandler`] to [`process_pending_events`].
///
/// # Requirements
///
/// See [`process_pending_events`] for requirements around event processing.
///
/// When using this trait, [`process_pending_events`] will call [`handle_event`] for each pending
/// event since the last invocation. The handler must either act upon the event immediately
/// or preserve it for later handling.
///
/// Note, handlers may call back into the provider and thus deadlocking must be avoided. Be sure to
/// consult the provider's documentation on the implication of processing events and how a handler
/// may safely use the provider (e.g., see [`ChannelManager::process_pending_events`] and
/// [`ChainMonitor::process_pending_events`]).
///
/// [`process_pending_events`]: Self::process_pending_events
/// [`handle_event`]: EventHandler::handle_event
/// [`ChannelManager::process_pending_events`]: crate::ln::channelmanager::ChannelManager#method.process_pending_events
/// [`ChainMonitor::process_pending_events`]: crate::chain::chainmonitor::ChainMonitor#method.process_pending_events
pub trait EventsProvider {
        /// Processes any events generated since the last call using the given event handler.
        ///
        /// Subsequent calls must only process new events. However, handlers must be capable of handling
        /// duplicate events across process restarts. This may occur if the provider was recovered from
        /// an old state (i.e., it hadn't been successfully persisted after processing pending events).
        fn process_pending_events<H: Deref>(&self, handler: H) where H::Target: EventHandler;
}

/// A trait implemented for objects handling events from [`EventsProvider`].
pub trait EventHandler {
        /// Handles the given [`Event`].
        ///
        /// See [`EventsProvider`] for details that must be considered when implementing this method.
        fn handle_event(&self, event: Event);
}

impl<F> EventHandler for F where F: Fn(Event) {
        fn handle_event(&self, event: Event) {
                self(event)
        }
}