Implement chain::Access trait

Author: tnull

src/access.rs

@@ -1,19 +1,19 @@
 use crate::logger::{
 	log_error, log_given_level, log_internal, log_trace, FilesystemLogger, Logger,
 };
-use crate::{Config, Error};
+use crate::{scid_utils, Config, Error};
 
 use lightning::chain::chaininterface::{BroadcasterInterface, ConfirmationTarget, FeeEstimator};
 use lightning::chain::WatchedOutput;
-use lightning::chain::{Confirm, Filter};
+use lightning::chain::{Access, AccessError, Confirm, Filter};
 
 use bdk::blockchain::{Blockchain, EsploraBlockchain};
 use bdk::database::BatchDatabase;
 use bdk::esplora_client;
 use bdk::wallet::AddressIndex;
 use bdk::{SignOptions, SyncOptions};
 
-use bitcoin::{Script, Transaction, Txid};
+use bitcoin::{BlockHash, Script, Transaction, TxOut, Txid};
 
 use std::collections::HashSet;
 use std::sync::{Arc, Mutex, RwLock};
@@ -33,15 +33,15 @@ where
 	D: BatchDatabase,
 {
 	blockchain: EsploraBlockchain,
-	_client: Arc<esplora_client::AsyncClient>,
+	client: Arc<esplora_client::AsyncClient>,
 	wallet: Mutex<bdk::Wallet<D>>,
 	queued_transactions: Mutex<Vec<Txid>>,
 	watched_transactions: Mutex<Vec<Txid>>,
 	queued_outputs: Mutex<Vec<WatchedOutput>>,
 	watched_outputs: Mutex<Vec<WatchedOutput>>,
 	last_sync_height: tokio::sync::Mutex<Option<u32>>,
 	tokio_runtime: RwLock<Option<Arc<tokio::runtime::Runtime>>>,
-	_config: Arc<Config>,
+	config: Arc<Config>,
 	logger: Arc<FilesystemLogger>,
 }
 
@@ -68,15 +68,15 @@ where
 		let client = Arc::new(client_builder.build_async().unwrap());
 		Self {
 			blockchain,
-			_client: client,
+			client,
 			wallet,
 			queued_transactions,
 			watched_transactions,
 			queued_outputs,
 			watched_outputs,
 			last_sync_height,
 			tokio_runtime,
-			_config: config,
+			config,
 			logger,
 		}
 	}
@@ -361,6 +361,61 @@ where
 	}
 }
 
+impl<D> Access for ChainAccess<D>
+where
+	D: BatchDatabase,
+{
+	fn get_utxo(
+		&self, genesis_hash: &BlockHash, short_channel_id: u64,
+	) -> Result<TxOut, AccessError> {
+		if genesis_hash
+			!= &bitcoin::blockdata::constants::genesis_block(self.config.network)
+				.header
+				.block_hash()
+		{
+			return Err(AccessError::UnknownChain);
+		}
+
+		let locked_runtime = self.tokio_runtime.read().unwrap();
+		if locked_runtime.as_ref().is_none() {
+			return Err(AccessError::UnknownTx);
+		}
+
+		let block_height = scid_utils::block_from_scid(&short_channel_id);
+		let tx_index = scid_utils::tx_index_from_scid(&short_channel_id);
+		let vout = scid_utils::vout_from_scid(&short_channel_id);
+
+		let client_tokio = Arc::clone(&self.client);
+		locked_runtime.as_ref().unwrap().block_on(async move {
+			// TODO: migrate to https://github.com/bitcoindevkit/rust-esplora-client/pull/13 with
+			// next release.
+			let block_hash = client_tokio
+				.get_header(block_height.into())
+				.await
+				.map_err(|_| AccessError::UnknownTx)?
+				.block_hash();
+
+			let txid = client_tokio
+				.get_txid_at_block_index(&block_hash, tx_index as usize)
+				.await
+				.map_err(|_| AccessError::UnknownTx)?
+				.ok_or(AccessError::UnknownTx)?;
+
+			let tx = client_tokio
+				.get_tx(&txid)
+				.await
+				.map_err(|_| AccessError::UnknownTx)?
+				.ok_or(AccessError::UnknownTx)?;
+
+			if let Some(tx_out) = tx.output.get(vout as usize) {
+				return Ok(tx_out.clone());
+			} else {
+				Err(AccessError::UnknownTx)
+			}
+		})
+	}
+}
+
 fn num_blocks_from_conf_target(confirmation_target: ConfirmationTarget) -> usize {
 	match confirmation_target {
 		ConfirmationTarget::Background => 12,

src/lib.rs

@@ -31,6 +31,7 @@ mod hex_utils;
 mod io_utils;
 mod logger;
 mod peer_store;
+mod scid_utils;
 
 use access::ChainAccess;
 pub use error::Error;

src/scid_utils.rs

@@ -0,0 +1,33 @@
+// Copied from `rust-lightning`
+//
+// 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.
+
+/// Maximum transaction index that can be used in a `short_channel_id`.
+/// This value is based on the 3-bytes available for tx index.
+pub const MAX_SCID_TX_INDEX: u64 = 0x00ffffff;
+
+/// Maximum vout index that can be used in a `short_channel_id`. This
+/// value is based on the 2-bytes available for the vout index.
+pub const MAX_SCID_VOUT_INDEX: u64 = 0xffff;
+
+/// Extracts the block height (most significant 3-bytes) from the `short_channel_id`
+pub fn block_from_scid(short_channel_id: &u64) -> u32 {
+	return (short_channel_id >> 40) as u32;
+}
+
+/// Extracts the tx index (bytes [2..4]) from the `short_channel_id`
+pub fn tx_index_from_scid(short_channel_id: &u64) -> u32 {
+	return ((short_channel_id >> 16) & MAX_SCID_TX_INDEX) as u32;
+}
+
+/// Extracts the vout (bytes [0..2]) from the `short_channel_id`
+pub fn vout_from_scid(short_channel_id: &u64) -> u16 {
+	return ((short_channel_id) & MAX_SCID_VOUT_INDEX) as u16;
+}