builder.rs

//! Construct a [`LightClient`] by using a reference to a [`Wallet`].
//!
//! ## Details
//!
//! The node has a number of configurations. Notably, the height of in the blockchain to start a
//! wallet recovery and the nodes on the peer-to-peer network are both configurable.
//!
//! ```no_run
//! # const RECEIVE: &str = "tr([7d94197e/86'/1'/0']tpubDCyQVJj8KzjiQsFjmb3KwECVXPvMwvAxxZGCP9XmWSopmjW3bCV3wD7TgxrUhiGSueDS1MU5X1Vb1YjYcp8jitXc5fXfdC1z68hDDEyKRNr/0/*)";
//! # const CHANGE: &str = "tr([7d94197e/86'/1'/0']tpubDCyQVJj8KzjiQsFjmb3KwECVXPvMwvAxxZGCP9XmWSopmjW3bCV3wD7TgxrUhiGSueDS1MU5X1Vb1YjYcp8jitXc5fXfdC1z68hDDEyKRNr/1/*)";
//! use std::net::{IpAddr, Ipv4Addr};
//! use std::path::PathBuf;
//! use std::time::Duration;
//! use bdk_wallet::Wallet;
//! use bdk_kyoto::bip157::{Network, TrustedPeer};
//! use bdk_kyoto::builder::{Builder, BuilderExt};
//! use bdk_kyoto::{LightClient, ScanType};
//!
//! #[tokio::main]
//! async fn main() -> anyhow::Result<()> {
//!     // Add specific peers to connect to.
//!     let peer = IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1));
//!     let trusted = TrustedPeer::from_ip(peer);
//!
//!     let db_path = ".".parse::<PathBuf>()?;
//!
//!     let mut wallet = Wallet::create(RECEIVE, CHANGE)
//!         .network(Network::Signet)
//!         .create_wallet_no_persist()?;
//!
//!     let scan_type = ScanType::Sync;
//!
//!     let LightClient {
//!         requester,
//!         info_subscriber,
//!         warning_subscriber,
//!         update_subscriber,
//!         node
//!     } = Builder::new(Network::Signet)
//!         // A node may handle multiple connections
//!         .required_peers(2)
//!         // Choose where to store node data
//!         .data_dir(db_path)
//!         // How long peers have to respond messages
//!         .response_timeout(Duration::from_secs(2))
//!         // Added trusted peers to initialize the sync
//!         .add_peer(trusted)
//!         .build_with_wallet(&wallet, scan_type)?;
//!     Ok(())
//! }
//! ```

use std::fmt::Display;

use bdk_wallet::bitcoin::Network;
use bdk_wallet::chain::keychain_txout::KeychainTxOutIndex;
use bdk_wallet::{
    chain::{CheckPoint, IndexedTxGraph},
    KeychainKind,
};
pub use bip157::Builder;
use bip157::{chain::ChainState, HeaderCheckpoint};

use crate::{LightClient, ScanType, UpdateSubscriber};

const IMPOSSIBLE_REORG_DEPTH: usize = 7;

/// Build a compact block filter client and node for a specified wallet
pub trait BuilderExt {
    /// Attempt to build the node with scripts from a [`Wallet`] and following a [`ScanType`].
    fn build_with_wallet(
        self,
        txout_index: KeychainTxOutIndex<KeychainKind>,
        chain_tip: CheckPoint,
        network: Network,
        scan_type: ScanType,
    ) -> Result<LightClient, BuilderError>;
}

impl BuilderExt for Builder {
    fn build_with_wallet(
        mut self,
        txout_index: KeychainTxOutIndex<KeychainKind>,
        chain_tip: CheckPoint,
        network: Network,
        scan_type: ScanType,
    ) -> Result<LightClient, BuilderError> {
        if self.network().ne(&network) {
            return Err(BuilderError::NetworkMismatch);
        }
        match scan_type {
            ScanType::Sync => {
                let current_cp = chain_tip.clone();
                let sync_start = walk_back_max_reorg(current_cp);
                self = self.chain_state(ChainState::Checkpoint(sync_start));
            }
            ScanType::Recovery {
                used_script_index: _,
                checkpoint,
            } => self = self.chain_state(ChainState::Checkpoint(checkpoint)),
        }
        let (node, client) = self.build();
        let bip157::Client {
            requester,
            info_rx,
            warn_rx,
            event_rx,
        } = client;
        let indexed_graph = IndexedTxGraph::new(txout_index);
        let update_subscriber = UpdateSubscriber::new(
            requester.clone(),
            scan_type,
            event_rx,
            chain_tip,
            indexed_graph,
        );
        Ok(LightClient {
            requester,
            info_subscriber: info_rx,
            warning_subscriber: warn_rx,
            update_subscriber,
            node,
        })
    }
}

/// Walk back 7 blocks in case the last sync was an orphan block.
fn walk_back_max_reorg(checkpoint: CheckPoint) -> HeaderCheckpoint {
    let mut ret_cp = HeaderCheckpoint::new(checkpoint.height(), checkpoint.hash());
    let cp_iter = checkpoint.iter();
    for (index, next) in cp_iter.enumerate() {
        if index > IMPOSSIBLE_REORG_DEPTH {
            return ret_cp;
        }
        ret_cp = HeaderCheckpoint::new(next.height(), next.hash());
    }
    ret_cp
}

/// Errors the builder may throw.
#[derive(Debug)]
pub enum BuilderError {
    /// The wallet network and node network do not match.
    NetworkMismatch,
}

impl Display for BuilderError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            BuilderError::NetworkMismatch => {
                write!(f, "wallet network and node network do not match")
            }
        }
    }
}

impl std::error::Error for BuilderError {}