Add transaction sync crate

This crate provides utilities for syncing LDK via the transaction-based
`Confirm` interface. The initial implementation facilitates
synchronization with an Esplora backend server.

Author: tnull

.github/workflows/build.yml

@@ -108,6 +108,18 @@ jobs:
           RUSTFLAGS="-C link-dead-code" cargo build --verbose --color always --features rpc-client
           RUSTFLAGS="-C link-dead-code" cargo build --verbose --color always --features rpc-client,rest-client
           RUSTFLAGS="-C link-dead-code" cargo build --verbose --color always --features rpc-client,rest-client,tokio
+      - name: Build Transaction Sync Clients on Rust ${{ matrix.toolchain }} with features
+        if: "!matrix.coverage"
+        run: |
+          cd lightning-transaction-sync
+          cargo build --verbose --color always --features esplora-blocking
+          cargo build --verbose --color always --features esplora-async
+      - name: Build Transaction Sync Clients on Rust ${{ matrix.toolchain }} with features and full code-linking for coverage generation
+        if: matrix.coverage
+        run: |
+          cd lightning-transaction-sync
+          RUSTFLAGS="-C link-dead-code" cargo build --verbose --color always --features esplora-blocking
+          RUSTFLAGS="-C link-dead-code" cargo build --verbose --color always --features esplora-async
       - name: Test backtrace-debug builds on Rust ${{ matrix.toolchain }}
         if: "matrix.build-no-std"
         run: |

Cargo.toml

@@ -3,6 +3,7 @@
 members = [
     "lightning",
     "lightning-block-sync",
+    "lightning-transaction-sync",
     "lightning-invoice",
     "lightning-net-tokio",
     "lightning-persister",

lightning-transaction-sync/Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "lightning-transaction-sync"
+version = "0.0.112"
+authors = ["Elias Rohrer"]
+license = "MIT OR Apache-2.0"
+repository = "http://github.com/lightningdevkit/rust-lightning"
+description = """
+Utilities to fetch transaction data from a chain source and feed them into LDK.
+"""
+edition = "2018"
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[features]
+default = ["esplora-blocking"]
+esplora-async = ["async-interface", "esplora-client/async", "tokio"]
+esplora-blocking = ["esplora-client/blocking"]
+async-interface = []
+
+[dependencies]
+lightning = { version = "0.0.112", path = "../lightning" }
+bitcoin = "0.29.0"
+bdk-macros = "0.6"
+tokio = { version = "1.0", default-features = false, features = [], optional = true }
+esplora-client = { git = "https://github.com/tnull/rust-esplora-client", branch = "2022-10-get-merkle-block", default-features = false, optional = true }

lightning-transaction-sync/src/error.rs

@@ -0,0 +1,30 @@
+use std::fmt;
+use esplora_client::Error as EsploraError;
+
+#[derive(Debug)]
+/// An error that possibly needs to be handled by the user.
+pub enum TxSyncError {
+	/// A transaction sync failed.
+	Failed,
+	/// An inconsisteny was encounterd during transaction sync.
+	Inconsistency,
+}
+
+impl fmt::Display for TxSyncError {
+	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+		match *self {
+			Self::Failed => write!(f, "Failed to conduct transaction sync."),
+			Self::Inconsistency => {
+				write!(f, "Encountered an inconsisteny during transaction sync.")
+			}
+		}
+	}
+}
+
+impl std::error::Error for TxSyncError {}
+
+impl From<EsploraError> for TxSyncError {
+	fn from(_e: EsploraError) -> Self {
+		Self::Failed
+	}
+}