Add HWI example in docs

Cargo.toml

@@ -32,7 +32,7 @@ async-trait = { version = "0.1", optional = true }
 rocksdb = { version = "0.14", default-features = false, features = ["snappy"], optional = true }
 cc = { version = ">=1.0.64", optional = true }
 socks = { version = "0.3", optional = true }
-hwi = { version = "0.2.2", optional = true }
+hwi = { version = "0.2.3", optional = true }
 
 bip39 = { version = "1.0.1", optional = true }
 bitcoinconsensus = { version = "0.19.0-3", optional = true }
@@ -126,6 +126,11 @@ name = "psbt_signer"
 path = "examples/psbt_signer.rs"
 required-features = ["electrum"]
 
+[[example]]
+name = "hardware_signer"
+path = "examples/hardware_signer.rs"
+required-features = ["electrum", "hardware-signer"]
+
 [workspace]
 members = ["macros"]
 [package.metadata.docs.rs]

examples/hardware_signer.rs

@@ -0,0 +1,103 @@
+use bdk::bitcoin::{Address, Network};
+use bdk::blockchain::{Blockchain, ElectrumBlockchain};
+use bdk::database::MemoryDatabase;
+use bdk::hwi::{types::HWIChain, HWIClient};
+use bdk::signer::SignerOrdering;
+use bdk::wallet::{hardwaresigner::HWISigner, AddressIndex};
+use bdk::{FeeRate, KeychainKind, SignOptions, SyncOptions, Wallet};
+use electrum_client::Client;
+use std::str::FromStr;
+use std::sync::Arc;
+
+// This example shows how to sync a wallet, create a transaction, sign it
+// and broadcast it using an external hardware wallet.
+// The hardware wallet must be connected to the computer and unlocked before
+// running the example. Also, the `hwi` python package should be installed
+// and available in the environment.
+//
+// To avoid loss of funds, consider using an hardware wallet simulator:
+// * Coldcard: https://github.com/Coldcard/firmware
+// * Ledger: https://github.com/LedgerHQ/speculos
+// * Trezor: https://docs.trezor.io/trezor-firmware/core/emulator/index.html
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    println!("Hold tight, I'm connecting to your hardware wallet...");
+
+    // Listing all the available hardware wallet devices...
+    let devices = HWIClient::enumerate()?;
+    let first_device = devices
+        .first()
+        .expect("No devices found. Either plug in a hardware wallet, or start a simulator.");
+    // ...and creating a client out of the first one
+    let client = HWIClient::get_client(first_device, true, HWIChain::Test)?;
+    println!("Look what I found, a {}!", first_device.model);
+
+    // Getting the HW's public descriptors
+    let descriptors = client.get_descriptors(None)?;
+    println!(
+        "The hardware wallet's descriptor is: {}",
+        descriptors.receive[0]
+    );
+
+    // Creating a custom signer from the device
+    let custom_signer = HWISigner::from_device(first_device, HWIChain::Test)?;
+    let mut wallet = Wallet::new(
+        &descriptors.receive[0],
+        Some(&descriptors.internal[0]),
+        Network::Testnet,
+        MemoryDatabase::default(),
+    )?;
+
+    // Adding the hardware signer to the BDK wallet
+    wallet.add_signer(
+        KeychainKind::External,
+        SignerOrdering(200),
+        Arc::new(custom_signer),
+    );
+
+    // create client for Blockstream's testnet electrum server
+    let blockchain =
+        ElectrumBlockchain::from(Client::new("ssl://electrum.blockstream.info:60002")?);
+
+    println!("Syncing the wallet...");
+    wallet.sync(&blockchain, SyncOptions::default())?;
+
+    // get deposit address
+    let deposit_address = wallet.get_address(AddressIndex::New)?;
+
+    let balance = wallet.get_balance()?;
+    println!("Wallet balances in SATs: {}", balance);
+
+    if balance.get_total() < 10000 {
+        println!(
+            "Send some sats from the u01.net testnet faucet to address '{addr}'.\nFaucet URL: https://bitcoinfaucet.uo1.net/?to={addr}",
+            addr = deposit_address.address
+        );
+        return Ok(());
+    }
+
+    let return_address = Address::from_str("tb1ql7w62elx9ucw4pj5lgw4l028hmuw80sndtntxt")?;
+    let (mut psbt, _details) = {
+        let mut builder = wallet.build_tx();
+        builder
+            .drain_wallet()
+            .drain_to(return_address.script_pubkey())
+            .enable_rbf()
+            .fee_rate(FeeRate::from_sat_per_vb(5.0));
+        builder.finish()?
+    };
+
+    // `sign` will call the hardware wallet asking for a signature
+    assert!(
+        wallet.sign(&mut psbt, SignOptions::default())?,
+        "The hardware wallet couldn't finalize the transaction :("
+    );
+
+    println!("Let's broadcast your tx...");
+    let raw_transaction = psbt.extract_tx();
+    let txid = raw_transaction.txid();
+
+    blockchain.broadcast(&raw_transaction)?;
+    println!("Transaction broadcasted! TXID: {txid}.\nExplorer URL: https://mempool.space/testnet/tx/{txid}", txid = txid);
+
+    Ok(())
+}

src/lib.rs

@@ -203,6 +203,8 @@ pub extern crate miniscript;
 extern crate serde;
 #[macro_use]
 extern crate serde_json;
+#[cfg(feature = "hardware-signer")]
+pub extern crate hwi;
 
 #[cfg(all(feature = "reqwest", feature = "ureq"))]
 compile_error!("Features reqwest and ureq are mutually exclusive and cannot be enabled together");

src/wallet/hardwaresigner.rs

@@ -11,7 +11,40 @@
 
 //! HWI Signer
 //!
-//! This module contains a simple implementation of a Custom signer for rust-hwi
+//! This module contains HWISigner, an implementation of a [TransactionSigner] to be
+//! used with hardware wallets.
+//! ```no_run
+//! # use bdk::bitcoin::Network;
+//! # use bdk::database::MemoryDatabase;
+//! # use bdk::signer::SignerOrdering;
+//! # use bdk::wallet::hardwaresigner::HWISigner;
+//! # use bdk::wallet::AddressIndex::New;
+//! # use bdk::{FeeRate, KeychainKind, SignOptions, SyncOptions, Wallet};
+//! # use hwi::{types::HWIChain, HWIClient};
+//! # use std::sync::Arc;
+//! #
+//! # fn main() -> Result<(), Box<dyn std::error::Error>> {
+//! let devices = HWIClient::enumerate()?;
+//! let first_device = devices.first().expect("No devices found!");
+//! let custom_signer = HWISigner::from_device(first_device, HWIChain::Test)?;
+//!
+//! # let mut wallet = Wallet::new(
+//! #     "",
+//! #     None,
+//! #     Network::Testnet,
+//! #     MemoryDatabase::default(),
+//! # )?;
+//! #
+//! // Adding the hardware signer to the BDK wallet
+//! wallet.add_signer(
+//!     KeychainKind::External,
+//!     SignerOrdering(200),
+//!     Arc::new(custom_signer),
+//! );
+//!
+//! # Ok(())
+//! # }
+//! ```
 
 use bitcoin::psbt::PartiallySignedTransaction;
 use bitcoin::secp256k1::{All, Secp256k1};