Merge #744: Add psbt_signer.rs example

fa998de Add psbt_signer.rs example (Steve Myers)

Pull request description:

  ### Description

  Adding a simple example of how to create a PSBT with a watch only wallet and then sign it with a signing wallet.

  ### Notes to the reviewers

  This example was inspired by a question from a user.

  ### Changelog notice

  none.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### New Features:

  * [ ] I've added tests for the new feature
  * [ ] I've added docs for the new feature

  #### Bugfixes:

  * [ ] This pull request breaks the existing API
  * [ ] I've added tests to reproduce the issue which are now passing
  * [ ] I'm linking the issue being fixed by this PR

ACKs for top commit:
  danielabrozzoni:
    ACK fa998de
  afilini:
    ACK fa998de

Tree-SHA512: 2e178ee59ce94eb1e9b5616a499e106e1d2843589036bdb6cff2c987e280588ad9989b026cdbf01290cc60f02eccbc410a3e1d1cd45eb4b8ff04353ae31b23ea

Author: afilini

Cargo.toml

@@ -119,6 +119,11 @@ name = "rpcwallet"
 path = "examples/rpcwallet.rs"
 required-features = ["keys-bip39", "key-value-db", "rpc", "electrsd/bitcoind_22_0"]
 
+[[example]]
+name = "psbt_signer"
+path = "examples/psbt_signer.rs"
+required-features = ["electrum"]
+
 [workspace]
 members = ["macros"]
 [package.metadata.docs.rs]

examples/psbt_signer.rs

@@ -0,0 +1,102 @@
+// Copyright (c) 2020-2022 Bitcoin Dev Kit Developers
+//
+// 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.
+
+use bdk::blockchain::{Blockchain, ElectrumBlockchain};
+use bdk::database::MemoryDatabase;
+use bdk::wallet::AddressIndex;
+use bdk::SyncOptions;
+use bdk::{FeeRate, SignOptions, Wallet};
+use bitcoin::{Address, Network};
+use electrum_client::Client;
+use std::error::Error;
+use std::str::FromStr;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    // test keys created with `bdk-cli key generate` and `bdk-cli key derive` commands
+    let signing_external_descriptor = "wpkh([e9824965/84'/1'/0']tprv8fvem7qWxY3SGCQczQpRpqTKg455wf1zgixn6MZ4ze8gRfHjov5gXBQTadNfDgqs9ERbZZ3Bi1PNYrCCusFLucT39K525MWLpeURjHwUsfX/0/*)";
+    let signing_internal_descriptor = "wpkh([e9824965/84'/1'/0']tprv8fvem7qWxY3SGCQczQpRpqTKg455wf1zgixn6MZ4ze8gRfHjov5gXBQTadNfDgqs9ERbZZ3Bi1PNYrCCusFLucT39K525MWLpeURjHwUsfX/1/*)";
+
+    let watch_only_external_descriptor = "wpkh([e9824965/84'/1'/0']tpubDCcguXsm6uj79fSQt4V2EF7SF5b26zCuG2ZZNsbNQuw5G9YWSJuGhg2KknQBywRq4VGTu41zYTCh3QeVFyBdbsymgRX9Mrts94SW7obEdqs/0/*)";
+    let watch_only_internal_descriptor = "wpkh([e9824965/84'/1'/0']tpubDCcguXsm6uj79fSQt4V2EF7SF5b26zCuG2ZZNsbNQuw5G9YWSJuGhg2KknQBywRq4VGTu41zYTCh3QeVFyBdbsymgRX9Mrts94SW7obEdqs/1/*)";
+
+    // create client for Blockstream's testnet electrum server
+    let blockchain =
+        ElectrumBlockchain::from(Client::new("ssl://electrum.blockstream.info:60002")?);
+
+    // create watch only wallet
+    let watch_only_wallet: Wallet<MemoryDatabase> = Wallet::new(
+        watch_only_external_descriptor,
+        Some(watch_only_internal_descriptor),
+        Network::Testnet,
+        MemoryDatabase::default(),
+    )?;
+
+    // create signing wallet
+    let signing_wallet: Wallet<MemoryDatabase> = Wallet::new(
+        signing_external_descriptor,
+        Some(signing_internal_descriptor),
+        Network::Testnet,
+        MemoryDatabase::default(),
+    )?;
+
+    println!("Syncing watch only wallet.");
+    watch_only_wallet.sync(&blockchain, SyncOptions::default())?;
+
+    // get deposit address
+    let deposit_address = watch_only_wallet.get_address(AddressIndex::New)?;
+
+    let balance = watch_only_wallet.get_balance()?;
+    println!("Watch only wallet balances in SATs: {}", balance);
+
+    if balance.get_total() < 10000 {
+        println!(
+            "Send at least 10000 SATs (0.0001 BTC) from the u01.net testnet faucet to address '{addr}'.\nFaucet URL: https://bitcoinfaucet.uo1.net/?to={addr}",
+            addr = deposit_address.address
+        );
+    } else if balance.get_spendable() < 10000 {
+        println!(
+            "Wait for at least 10000 SATs of your wallet transactions to be confirmed...\nBe patient, this could take 10 mins or longer depending on how testnet is behaving."
+        );
+        for tx_details in watch_only_wallet
+            .list_transactions(false)?
+            .iter()
+            .filter(|txd| txd.received > 0 && txd.confirmation_time.is_none())
+        {
+            println!(
+                "See unconfirmed tx for {} SATs: https://mempool.space/testnet/tx/{}",
+                tx_details.received, tx_details.txid
+            );
+        }
+    } else {
+        println!("Creating a PSBT sending 9800 SATs plus fee to the u01.net testnet faucet return address 'tb1ql7w62elx9ucw4pj5lgw4l028hmuw80sndtntxt'.");
+        let return_address = Address::from_str("tb1ql7w62elx9ucw4pj5lgw4l028hmuw80sndtntxt")?;
+        let mut builder = watch_only_wallet.build_tx();
+        builder
+            .add_recipient(return_address.script_pubkey(), 9_800)
+            .enable_rbf()
+            .fee_rate(FeeRate::from_sat_per_vb(1.0));
+
+        let (mut psbt, details) = builder.finish()?;
+        println!("Transaction details: {:#?}", details);
+        println!("Unsigned PSBT: {}", psbt);
+
+        // Sign and finalize the PSBT with the signing wallet
+        let finalized = signing_wallet.sign(&mut psbt, SignOptions::default())?;
+        assert!(finalized, "The PSBT was not finalized!");
+        println!("The PSBT has been signed and finalized.");
+
+        // Broadcast the transaction
+        let raw_transaction = psbt.extract_tx();
+        let txid = raw_transaction.txid();
+
+        blockchain.broadcast(&raw_transaction)?;
+        println!("Transaction broadcast! TXID: {txid}.\nExplorer URL: https://mempool.space/testnet/tx/{txid}", txid = txid);
+    }
+
+    Ok(())
+}