5984736767

Committed 26 Aug 2023 12:20PM CUT coverage: 78.856% (+0.2%) from 78.694%

Build # 5984736767

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Pull #1084

github

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web-flow

Commit Message

Merge 8bdb5a43d into 8f978f86b

Pull Request Pull Request #1084: Enhance bdk chain structures

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/crates/electrum/src/electrum_ext.rs

use bdk_chain::{
    bitcoin::{OutPoint, ScriptBuf, Transaction, Txid},
    local_chain::{self, CheckPoint},
    tx_graph::{self, TxGraph},
    Anchor, BlockId, ConfirmationHeightAnchor, ConfirmationTimeAnchor,
};
use electrum_client::{Client, ElectrumApi, Error, HeaderNotification};
use std::{
    collections::{BTreeMap, BTreeSet, HashMap, HashSet},
    fmt::Debug,
    str::FromStr,
};

/// We assume that a block of this depth and deeper cannot be reorged.
const ASSUME_FINAL_DEPTH: u32 = 8;

/// Represents an update fetched from an Electrum server, but excludes full
/// transactions.
///
/// To provide a complete update to [`TxGraph`], you'll need to call [`Self::missing_full_txs`] to
/// determine the full transactions missing from [`TxGraph`]. Then call [`Self::finalize`] to fetch
/// the full transactions from Electrum and finalize the update.
#[derive(Debug, Clone)]
pub struct ElectrumUpdate<K, A> {
    /// Map of [`Txid`]s to associated [`Anchor`]s.
    pub graph_update: HashMap<Txid, BTreeSet<A>>,
    /// The latest chain tip, as seen by the Electrum server.
    pub new_tip: local_chain::CheckPoint,
    /// Last-used index update for [`KeychainTxOutIndex`](bdk_chain::keychain::KeychainTxOutIndex).
    pub keychain_update: BTreeMap<K, u32>,
}

impl<K, A: Anchor> ElectrumUpdate<K, A> {
    fn new(new_tip: local_chain::CheckPoint) -> Self {
        Self {
            new_tip,
            graph_update: HashMap::new(),
            keychain_update: BTreeMap::new(),
        }
    }

    /// Determine the full transactions that are missing from `graph`.
    ///
    /// Refer to [`ElectrumUpdate`].
    pub fn missing_full_txs<A2>(&self, graph: &TxGraph<A2>) -> Vec<Txid> {
        self.graph_update
            .keys()
            .filter(move |&&txid| graph.as_ref().get_tx(txid).is_none())
            .cloned()
            .collect()
    }

    /// Finalizes update with `missing` txids to fetch from `client`.
    ///
    /// Refer to [`ElectrumUpdate`].
    pub fn finalize(
        self,
        client: &Client,
        seen_at: Option<u64>,
        missing: Vec<Txid>,
    ) -> Result<(TxGraph<A>, BTreeMap<K, u32>, local_chain::CheckPoint), Error> {
        let new_txs = client.batch_transaction_get(&missing)?;
        let mut graph_update = TxGraph::<A>::new(new_txs);
        for (txid, anchors) in self.graph_update {
            if let Some(seen_at) = seen_at {
                let _ = graph_update.insert_seen_at(txid, seen_at);
            }
            for anchor in anchors {
                let _ = graph_update.insert_anchor(txid, anchor);
            }
        }
        Ok((graph_update, self.keychain_update, self.new_tip))
    }
}

impl<K> ElectrumUpdate<K, ConfirmationHeightAnchor> {
    /// Finalizes the [`ElectrumUpdate`] with `new_txs` and anchors of type
    /// [`ConfirmationTimeAnchor`].
    ///
    /// **Note:** The confirmation time might not be precisely correct if there has been a reorg.
    /// Electrum's API intends that we use the merkle proof API, we should change `bdk_electrum` to
    /// use it.
    pub fn finalize_as_confirmation_time(
        self,
        client: &Client,
        seen_at: Option<u64>,
        missing: Vec<Txid>,
    ) -> Result<
        (
            TxGraph<ConfirmationTimeAnchor>,
            BTreeMap<K, u32>,
            local_chain::CheckPoint,
        ),
        Error,
    > {
        let (graph, keychain_update, update_tip) = self.finalize(client, seen_at, missing)?;

        let relevant_heights = {
            let mut visited_heights = HashSet::new();
            graph
                .all_anchors()
                .iter()
                .map(|(a, _)| a.confirmation_height_upper_bound())
                .filter(move |&h| visited_heights.insert(h))
                .collect::<Vec<_>>()
        };

        let height_to_time = relevant_heights
            .clone()
            .into_iter()
            .zip(
                client
                    .batch_block_header(relevant_heights)?
                    .into_iter()
                    .map(|bh| bh.time as u64),
            )
            .collect::<HashMap<u32, u64>>();

        let graph_changeset = {
            let old_changeset = TxGraph::default().apply_update(graph.clone());
            tx_graph::ChangeSet {
                txs: old_changeset.txs,
                txouts: old_changeset.txouts,
                last_seen: old_changeset.last_seen,
                anchors: old_changeset
                    .anchors
                    .into_iter()
                    .map(|(height_anchor, txid)| {
                        let confirmation_height = height_anchor.confirmation_height;
                        let confirmation_time = height_to_time[&confirmation_height];
                        let time_anchor = ConfirmationTimeAnchor {
                            anchor_block: height_anchor.anchor_block,
                            confirmation_height,
                            confirmation_time,
                        };
                        (time_anchor, txid)
                    })
                    .collect(),
            }
        };

        let mut update = TxGraph::default();
        update.apply_changeset(graph_changeset);

        Ok((update, keychain_update, update_tip))
    }
}

/// Trait to extend [`Client`] functionality.
pub trait ElectrumExt<A> {
    /// Scan the blockchain (via electrum) for the data specified and returns a [`ElectrumUpdate`].
    ///
    /// - `prev_tip`: the most recent blockchain tip present locally
    /// - `keychain_spks`: keychains that we want to scan transactions for
    /// - `txids`: transactions for which we want updated [`Anchor`]s
    /// - `outpoints`: transactions associated with these outpoints (residing, spending) that we
    ///     want to included in the update
    ///
    /// The scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
    /// transactions. `batch_size` specifies the max number of script pubkeys to request for in a
    /// single batch request.
    fn scan<K: Ord + Clone>(
        &self,
        prev_tip: Option<CheckPoint>,
        keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, ScriptBuf)>>,
        txids: impl IntoIterator<Item = Txid>,
        outpoints: impl IntoIterator<Item = OutPoint>,
        stop_gap: usize,
        batch_size: usize,
    ) -> Result<ElectrumUpdate<K, A>, Error>;

    /// Convenience method to call [`scan`] without requiring a keychain.
    ///
    /// [`scan`]: ElectrumExt::scan
    fn scan_without_keychain(
        &self,
        prev_tip: Option<CheckPoint>,
        misc_spks: impl IntoIterator<Item = ScriptBuf>,
        txids: impl IntoIterator<Item = Txid>,
        outpoints: impl IntoIterator<Item = OutPoint>,
        batch_size: usize,
    ) -> Result<ElectrumUpdate<(), A>, Error> {
        let spk_iter = misc_spks
            .into_iter()
            .enumerate()
            .map(|(i, spk)| (i as u32, spk));

        self.scan(
            prev_tip,
            [((), spk_iter)].into(),
            txids,
            outpoints,
            usize::MAX,
            batch_size,
        )
    }
}

impl ElectrumExt<ConfirmationHeightAnchor> for Client {
    fn scan<K: Ord + Clone>(
        &self,
        prev_tip: Option<CheckPoint>,
        keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, ScriptBuf)>>,
        txids: impl IntoIterator<Item = Txid>,
        outpoints: impl IntoIterator<Item = OutPoint>,
        stop_gap: usize,
        batch_size: usize,
    ) -> Result<ElectrumUpdate<K, ConfirmationHeightAnchor>, Error> {
        let mut request_spks = keychain_spks
            .into_iter()
            .map(|(k, s)| (k, s.into_iter()))
            .collect::<BTreeMap<K, _>>();
        let mut scanned_spks = BTreeMap::<(K, u32), (ScriptBuf, bool)>::new();

        let txids = txids.into_iter().collect::<Vec<_>>();
        let outpoints = outpoints.into_iter().collect::<Vec<_>>();

        let update = loop {
            let (tip, _) = construct_update_tip(self, prev_tip.clone())?;
            let mut update = ElectrumUpdate::<K, ConfirmationHeightAnchor>::new(tip.clone());
            let cps = update
                .new_tip
                .iter()
                .take(10)
                .map(|cp| (cp.height(), cp))
                .collect::<BTreeMap<u32, CheckPoint>>();

            if !request_spks.is_empty() {
                if !scanned_spks.is_empty() {
                    scanned_spks.append(&mut populate_with_spks(
                        self,
                        &cps,
                        &mut update,
                        &mut scanned_spks
                            .iter()
                            .map(|(i, (spk, _))| (i.clone(), spk.clone())),
                        stop_gap,
                        batch_size,
                    )?);
                }
                for (keychain, keychain_spks) in &mut request_spks {
                    scanned_spks.extend(
                        populate_with_spks(
                            self,
                            &cps,
                            &mut update,
                            keychain_spks,
                            stop_gap,
                            batch_size,
                        )?
                        .into_iter()
                        .map(|(spk_i, spk)| ((keychain.clone(), spk_i), spk)),
                    );
                }
            }

            populate_with_txids(self, &cps, &mut update, &mut txids.iter().cloned())?;

            let _txs =
                populate_with_outpoints(self, &cps, &mut update, &mut outpoints.iter().cloned())?;

            // check for reorgs during scan process
            let server_blockhash = self.block_header(tip.height() as usize)?.block_hash();
            if tip.hash() != server_blockhash {
                continue; // reorg
            }

            update.keychain_update = request_spks
                .into_keys()
                .filter_map(|k| {
                    scanned_spks
                        .range((k.clone(), u32::MIN)..=(k.clone(), u32::MAX))
                        .rev()
                        .find(|(_, (_, active))| *active)
                        .map(|((_, i), _)| (k, *i))
                })
                .collect::<BTreeMap<_, _>>();
            break update;
        };

        Ok(update)
    }
}

/// Return a [`CheckPoint`] of the latest tip, that connects with `prev_tip`.
fn construct_update_tip(
    client: &Client,
    prev_tip: Option<CheckPoint>,
) -> Result<(CheckPoint, Option<u32>), Error> {
    let HeaderNotification { height, .. } = client.block_headers_subscribe()?;
    let new_tip_height = height as u32;

    // If electrum returns a tip height that is lower than our previous tip, then checkpoints do
    // not need updating. We just return the previous tip and use that as the point of agreement.
    if let Some(prev_tip) = prev_tip.as_ref() {
        if new_tip_height < prev_tip.height() {
            return Ok((prev_tip.clone(), Some(prev_tip.height())));
        }
    }

    // Atomically fetch the latest `ASSUME_FINAL_DEPTH` count of blocks from Electrum. We use this
    // to construct our checkpoint update.
    let mut new_blocks = {
        let start_height = new_tip_height.saturating_sub(ASSUME_FINAL_DEPTH);
        let hashes = client
            .block_headers(start_height as _, ASSUME_FINAL_DEPTH as _)?
            .headers
            .into_iter()
            .map(|h| h.block_hash());
        (start_height..).zip(hashes).collect::<BTreeMap<u32, _>>()
    };

    // Find the "point of agreement" (if any).
    let agreement_cp = {
        let mut agreement_cp = Option::<CheckPoint>::None;
        for cp in prev_tip.iter().flat_map(CheckPoint::iter) {
            let cp_block = cp.block_id();
            let hash = match new_blocks.get(&cp_block.height) {
                Some(&hash) => hash,
                None => {
                    assert!(
                        new_tip_height >= cp_block.height,
                        "already checked that electrum's tip cannot be smaller"
                    );
                    let hash = client.block_header(cp_block.height as _)?.block_hash();
                    new_blocks.insert(cp_block.height, hash);
                    hash
                }
            };
            if hash == cp_block.hash {
                agreement_cp = Some(cp);
                break;
            }
        }
        agreement_cp
    };

    let agreement_height = agreement_cp.as_ref().map(CheckPoint::height);

    let new_tip = new_blocks
        .into_iter()
        // Prune `new_blocks` to only include blocks that are actually new.
        .filter(|(height, _)| Some(*height) > agreement_height)
        .map(|(height, hash)| BlockId { height, hash })
        .fold(agreement_cp, |prev_cp, block| {
            Some(match prev_cp {
                Some(cp) => cp.push(block).expect("must extend checkpoint"),
                None => CheckPoint::new(block),
            })
        })
        .expect("must have at least one checkpoint");

    Ok((new_tip, agreement_height))
}

/// A [tx status] comprises of a concatenation of `tx_hash:height:`s. We transform a single one of
/// these concatenations into a [`ConfirmationHeightAnchor`] if possible.
///
/// We use the lowest possible checkpoint as the anchor block (from `cps`). If an anchor block
/// cannot be found, or the transaction is unconfirmed, [`None`] is returned.
///
/// [tx status](https://electrumx-spesmilo.readthedocs.io/en/latest/protocol-basics.html#status)
fn determine_tx_anchor(
    cps: &BTreeMap<u32, CheckPoint>,
    raw_height: i32,
    txid: Txid,
) -> Option<ConfirmationHeightAnchor> {
    // The electrum API has a weird quirk where an unconfirmed transaction is presented with a
    // height of 0. To avoid invalid representation in our data structures, we manually set
    // transactions residing in the genesis block to have height 0, then interpret a height of 0 as
    // unconfirmed for all other transactions.
    if txid
        == Txid::from_str("4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b")
            .expect("must deserialize genesis coinbase txid")
    {
        let anchor_block = cps.values().next()?.block_id();
        return Some(ConfirmationHeightAnchor {
            anchor_block,
            confirmation_height: 0,
        });
    }
    match raw_height {
        h if h <= 0 => {
            debug_assert!(h == 0 || h == -1, "unexpected height ({}) from electrum", h);
            None
        }
        h => {
            let h = h as u32;
            let anchor_block = cps.range(h..).next().map(|(_, cp)| cp.block_id())?;
            if h > anchor_block.height {
                None
            } else {
                Some(ConfirmationHeightAnchor {
                    anchor_block,
                    confirmation_height: h,
                })
            }
        }
    }
}

fn populate_with_outpoints<K>(
    client: &Client,
    cps: &BTreeMap<u32, CheckPoint>,
    update: &mut ElectrumUpdate<K, ConfirmationHeightAnchor>,
    outpoints: &mut impl Iterator<Item = OutPoint>,
) -> Result<HashMap<Txid, Transaction>, Error> {
    let mut full_txs = HashMap::new();
    for outpoint in outpoints {
        let txid = outpoint.txid;
        let tx = client.transaction_get(&txid)?;
        debug_assert_eq!(tx.txid(), txid);
        let txout = match tx.output.get(outpoint.vout as usize) {
            Some(txout) => txout,
            None => continue,
        };
        // attempt to find the following transactions (alongside their chain positions), and
        // add to our sparsechain `update`:
        let mut has_residing = false; // tx in which the outpoint resides
        let mut has_spending = false; // tx that spends the outpoint
        for res in client.script_get_history(&txout.script_pubkey)? {
            if has_residing && has_spending {
                break;
            }

            if res.tx_hash == txid {
                if has_residing {
                    continue;
                }
                has_residing = true;
                full_txs.insert(res.tx_hash, tx.clone());
            } else {
                if has_spending {
                    continue;
                }
                let res_tx = match full_txs.get(&res.tx_hash) {
                    Some(tx) => tx,
                    None => {
                        let res_tx = client.transaction_get(&res.tx_hash)?;
                        full_txs.insert(res.tx_hash, res_tx);
                        full_txs.get(&res.tx_hash).expect("just inserted")
                    }
                };
                has_spending = res_tx
                    .input
                    .iter()
                    .any(|txin| txin.previous_output == outpoint);
                if !has_spending {
                    continue;
                }
            };

            let anchor = determine_tx_anchor(cps, res.height, res.tx_hash);
            let tx_entry = update.graph_update.entry(res.tx_hash).or_default();
            if let Some(anchor) = anchor {
                tx_entry.insert(anchor);
            }
        }
    }
    Ok(full_txs)
}

fn populate_with_txids<K>(
    client: &Client,
    cps: &BTreeMap<u32, CheckPoint>,
    update: &mut ElectrumUpdate<K, ConfirmationHeightAnchor>,
    txids: &mut impl Iterator<Item = Txid>,
) -> Result<(), Error> {
    for txid in txids {
        let tx = match client.transaction_get(&txid) {
            Ok(tx) => tx,
            Err(electrum_client::Error::Protocol(_)) => continue,
            Err(other_err) => return Err(other_err),
        };

        let spk = tx
            .output
            .get(0)
            .map(|txo| &txo.script_pubkey)
            .expect("tx must have an output");

        let anchor = match client
            .script_get_history(spk)?
            .into_iter()
            .find(|r| r.tx_hash == txid)
        {
            Some(r) => determine_tx_anchor(cps, r.height, txid),
            None => continue,
        };

        let tx_entry = update.graph_update.entry(txid).or_default();
        if let Some(anchor) = anchor {
            tx_entry.insert(anchor);
        }
    }
    Ok(())
}

fn populate_with_spks<K, I: Ord + Clone>(
    client: &Client,
    cps: &BTreeMap<u32, CheckPoint>,
    update: &mut ElectrumUpdate<K, ConfirmationHeightAnchor>,
    spks: &mut impl Iterator<Item = (I, ScriptBuf)>,
    stop_gap: usize,
    batch_size: usize,
) -> Result<BTreeMap<I, (ScriptBuf, bool)>, Error> {
    let mut unused_spk_count = 0_usize;
    let mut scanned_spks = BTreeMap::new();

    loop {
        let spks = (0..batch_size)
            .map_while(|_| spks.next())
            .collect::<Vec<_>>();
        if spks.is_empty() {
            return Ok(scanned_spks);
        }

        let spk_histories =
            client.batch_script_get_history(spks.iter().map(|(_, s)| s.as_script()))?;

        for ((spk_index, spk), spk_history) in spks.into_iter().zip(spk_histories) {
            if spk_history.is_empty() {
                scanned_spks.insert(spk_index, (spk, false));
                unused_spk_count += 1;
                if unused_spk_count > stop_gap {
                    return Ok(scanned_spks);
                }
                continue;
            } else {
                scanned_spks.insert(spk_index, (spk, true));
                unused_spk_count = 0;
            }

            for tx in spk_history {
                let tx_entry = update.graph_update.entry(tx.tx_hash).or_default();
                if let Some(anchor) = determine_tx_anchor(cps, tx.height, tx.tx_hash) {
                    tx_entry.insert(anchor);
                }
            }
        }
    }
}

1	use bdk_chain::{
2	bitcoin::{OutPoint, ScriptBuf, Transaction, Txid},
3	local_chain::{self, CheckPoint},
4	tx_graph::{self, TxGraph},
5	Anchor, BlockId, ConfirmationHeightAnchor, ConfirmationTimeAnchor,
6	};
7	use electrum_client::{Client, ElectrumApi, Error, HeaderNotification};
8	use std::{
9	collections::{BTreeMap, BTreeSet, HashMap, HashSet},
10	fmt::Debug,
11	str::FromStr,
12	};
13
14	/// We assume that a block of this depth and deeper cannot be reorged.
15	const ASSUME_FINAL_DEPTH: u32 = 8;
16
17	/// Represents an update fetched from an Electrum server, but excludes full
18	/// transactions.
19	///
20	/// To provide a complete update to [`TxGraph`], you'll need to call [`Self::missing_full_txs`] to
21	/// determine the full transactions missing from [`TxGraph`]. Then call [`Self::finalize`] to fetch
22	/// the full transactions from Electrum and finalize the update.
23	#[derive(Debug, Clone)]	×
24	pub struct ElectrumUpdate<K, A> {
25	/// Map of [`Txid`]s to associated [`Anchor`]s.
26	pub graph_update: HashMap<Txid, BTreeSet<A>>,
27	/// The latest chain tip, as seen by the Electrum server.
28	pub new_tip: local_chain::CheckPoint,
29	/// Last-used index update for [`KeychainTxOutIndex`](bdk_chain::keychain::KeychainTxOutIndex).
30	pub keychain_update: BTreeMap<K, u32>,
31	}
32
33	impl<K, A: Anchor> ElectrumUpdate<K, A> {
34	fn new(new_tip: local_chain::CheckPoint) -> Self {	×
35	Self {	×
36	new_tip,	×
37	graph_update: HashMap::new(),	×
38	keychain_update: BTreeMap::new(),	×
39	}	×
40	}	×
41
42	/// Determine the full transactions that are missing from `graph`.
43	///
44	/// Refer to [`ElectrumUpdate`].
45	pub fn missing_full_txs<A2>(&self, graph: &TxGraph<A2>) -> Vec<Txid> {	×
46	self.graph_update	×
47	.keys()	×
48	.filter(move \|&&txid\| graph.as_ref().get_tx(txid).is_none())	×
49	.cloned()	×
50	.collect()	×
51	}	×
52
53	/// Finalizes update with `missing` txids to fetch from `client`.
54	///
55	/// Refer to [`ElectrumUpdate`].
56	pub fn finalize(	×
57	self,	×
58	client: &Client,	×
59	seen_at: Option<u64>,	×
60	missing: Vec<Txid>,	×
61	) -> Result<(TxGraph<A>, BTreeMap<K, u32>, local_chain::CheckPoint), Error> {	×
62	let new_txs = client.batch_transaction_get(&missing)?;	×
63	let mut graph_update = TxGraph::<A>::new(new_txs);	×
64	for (txid, anchors) in self.graph_update {	×
65	if let Some(seen_at) = seen_at {	×
66	let _ = graph_update.insert_seen_at(txid, seen_at);	×
67	}	×
68	for anchor in anchors {	×
69	let _ = graph_update.insert_anchor(txid, anchor);	×
70	}	×
71	}
72	Ok((graph_update, self.keychain_update, self.new_tip))	×
73	}	×
74	}
75
76	impl<K> ElectrumUpdate<K, ConfirmationHeightAnchor> {
77	/// Finalizes the [`ElectrumUpdate`] with `new_txs` and anchors of type
78	/// [`ConfirmationTimeAnchor`].
79	///
80	/// Note: The confirmation time might not be precisely correct if there has been a reorg.
81	/// Electrum's API intends that we use the merkle proof API, we should change `bdk_electrum` to
82	/// use it.
83	pub fn finalize_as_confirmation_time(	×
84	self,	×
85	client: &Client,	×
86	seen_at: Option<u64>,	×
87	missing: Vec<Txid>,	×
88	) -> Result<	×
89	(	×
90	TxGraph<ConfirmationTimeAnchor>,	×
91	BTreeMap<K, u32>,	×
92	local_chain::CheckPoint,	×
93	),	×
94	Error,	×
95	> {	×
96	let (graph, keychain_update, update_tip) = self.finalize(client, seen_at, missing)?;	×
97
98	let relevant_heights = {	×
99	let mut visited_heights = HashSet::new();	×
100	graph	×
101	.all_anchors()	×
102	.iter()	×
103	.map(\|(a, _)\| a.confirmation_height_upper_bound())	×
104	.filter(move \|&h\| visited_heights.insert(h))	×
105	.collect::<Vec<_>>()	×
106	};
107
108	let height_to_time = relevant_heights	×
109	.clone()	×
110	.into_iter()	×
111	.zip(	×
112	client	×
113	.batch_block_header(relevant_heights)?	×
114	.into_iter()	×
115	.map(\|bh\| bh.time as u64),	×
116	)	×
117	.collect::<HashMap<u32, u64>>();	×
118		×
119	let graph_changeset = {	×
120	let old_changeset = TxGraph::default().apply_update(graph.clone());	×
121	tx_graph::ChangeSet {	×
122	txs: old_changeset.txs,	×
123	txouts: old_changeset.txouts,	×
124	last_seen: old_changeset.last_seen,	×
125	anchors: old_changeset	×
126	.anchors	×
127	.into_iter()	×
128	.map(\|(height_anchor, txid)\| {	×
129	let confirmation_height = height_anchor.confirmation_height;	×
130	let confirmation_time = height_to_time[&confirmation_height];	×
131	let time_anchor = ConfirmationTimeAnchor {	×
132	anchor_block: height_anchor.anchor_block,	×
133	confirmation_height,	×
134	confirmation_time,	×
135	};	×
136	(time_anchor, txid)	×
137	})	×
138	.collect(),	×
139	}	×
140	};	×
141		×
142	let mut update = TxGraph::default();	×
143	update.apply_changeset(graph_changeset);	×
144		×
145	Ok((update, keychain_update, update_tip))	×
146	}	×
147	}
148
149	/// Trait to extend [`Client`] functionality.
150	pub trait ElectrumExt<A> {
151	/// Scan the blockchain (via electrum) for the data specified and returns a [`ElectrumUpdate`].
152	///
153	/// - `prev_tip`: the most recent blockchain tip present locally
154	/// - `keychain_spks`: keychains that we want to scan transactions for
155	/// - `txids`: transactions for which we want updated [`Anchor`]s
156	/// - `outpoints`: transactions associated with these outpoints (residing, spending) that we
157	/// want to included in the update
158	///
159	/// The scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
160	/// transactions. `batch_size` specifies the max number of script pubkeys to request for in a
161	/// single batch request.
162	fn scan<K: Ord + Clone>(
163	&self,
164	prev_tip: Option<CheckPoint>,
165	keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, ScriptBuf)>>,
166	txids: impl IntoIterator<Item = Txid>,
167	outpoints: impl IntoIterator<Item = OutPoint>,
168	stop_gap: usize,
169	batch_size: usize,
170	) -> Result<ElectrumUpdate<K, A>, Error>;
171
172	/// Convenience method to call [`scan`] without requiring a keychain.
173	///
174	/// [`scan`]: ElectrumExt::scan
175	fn scan_without_keychain(	×
176	&self,	×
177	prev_tip: Option<CheckPoint>,	×
178	misc_spks: impl IntoIterator<Item = ScriptBuf>,	×
179	txids: impl IntoIterator<Item = Txid>,	×
180	outpoints: impl IntoIterator<Item = OutPoint>,	×
181	batch_size: usize,	×
182	) -> Result<ElectrumUpdate<(), A>, Error> {	×
183	let spk_iter = misc_spks	×
184	.into_iter()	×
185	.enumerate()	×
186	.map(\|(i, spk)\| (i as u32, spk));	×
187		×
188	self.scan(	×
189	prev_tip,	×
190	[((), spk_iter)].into(),	×
191	txids,	×
192	outpoints,	×
193	usize::MAX,	×
194	batch_size,	×
195	)	×
196	}	×
197	}
198
199	impl ElectrumExt<ConfirmationHeightAnchor> for Client {
200	fn scan<K: Ord + Clone>(	×
201	&self,	×
202	prev_tip: Option<CheckPoint>,	×
203	keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, ScriptBuf)>>,	×
204	txids: impl IntoIterator<Item = Txid>,	×
205	outpoints: impl IntoIterator<Item = OutPoint>,	×
206	stop_gap: usize,	×
207	batch_size: usize,	×
208	) -> Result<ElectrumUpdate<K, ConfirmationHeightAnchor>, Error> {	×
209	let mut request_spks = keychain_spks	×
210	.into_iter()	×
211	.map(\|(k, s)\| (k, s.into_iter()))	×
212	.collect::<BTreeMap<K, _>>();	×
213	let mut scanned_spks = BTreeMap::<(K, u32), (ScriptBuf, bool)>::new();	×
214		×
215	let txids = txids.into_iter().collect::<Vec<_>>();	×
216	let outpoints = outpoints.into_iter().collect::<Vec<_>>();	×
217
218	let update = loop {	×
219	let (tip, _) = construct_update_tip(self, prev_tip.clone())?;	×
220	let mut update = ElectrumUpdate::<K, ConfirmationHeightAnchor>::new(tip.clone());	×
221	let cps = update	×
222	.new_tip	×
223	.iter()	×
224	.take(10)	×
225	.map(\|cp\| (cp.height(), cp))	×
226	.collect::<BTreeMap<u32, CheckPoint>>();	×
227		×
228	if !request_spks.is_empty() {	×
229	if !scanned_spks.is_empty() {	×
230	scanned_spks.append(&mut populate_with_spks(	×
231	self,	×
232	&cps,	×
233	&mut update,	×
234	&mut scanned_spks	×
235	.iter()	×
236	.map(\|(i, (spk, _))\| (i.clone(), spk.clone())),	×
237	stop_gap,	×
238	batch_size,	×
239	)?);	×
240	}	×
241	for (keychain, keychain_spks) in &mut request_spks {	×
242	scanned_spks.extend(
243	populate_with_spks(	×
244	self,	×
245	&cps,	×
246	&mut update,	×
247	keychain_spks,	×
248	stop_gap,	×
249	batch_size,	×
250	)?	×
251	.into_iter()	×
252	.map(\|(spk_i, spk)\| ((keychain.clone(), spk_i), spk)),	×
253	);
254	}
255	}	×
256
257	populate_with_txids(self, &cps, &mut update, &mut txids.iter().cloned())?;	×
258
259	let _txs =	×
260	populate_with_outpoints(self, &cps, &mut update, &mut outpoints.iter().cloned())?;	×
261
262	// check for reorgs during scan process
263	let server_blockhash = self.block_header(tip.height() as usize)?.block_hash();	×
264	if tip.hash() != server_blockhash {	×
265	continue; // reorg	×
266	}	×
267		×
268	update.keychain_update = request_spks	×
269	.into_keys()	×
270	.filter_map(\|k\| {	×
271	scanned_spks	×
272	.range((k.clone(), u32::MIN)..=(k.clone(), u32::MAX))	×
273	.rev()	×
274	.find(\|(_, (_, active))\| *active)	×
275	.map(\|((_, i), _)\| (k, *i))	×
276	})	×
277	.collect::<BTreeMap<_, _>>();	×
278	break update;	×
279	};	×
280		×
281	Ok(update)	×
282	}	×
283	}
284
285	/// Return a [`CheckPoint`] of the latest tip, that connects with `prev_tip`.
286	fn construct_update_tip(	×
287	client: &Client,	×
288	prev_tip: Option<CheckPoint>,	×
289	) -> Result<(CheckPoint, Option<u32>), Error> {	×
290	let HeaderNotification { height, .. } = client.block_headers_subscribe()?;	×
291	let new_tip_height = height as u32;	×
292
293	// If electrum returns a tip height that is lower than our previous tip, then checkpoints do
294	// not need updating. We just return the previous tip and use that as the point of agreement.
295	if let Some(prev_tip) = prev_tip.as_ref() {	×
296	if new_tip_height < prev_tip.height() {	×
297	return Ok((prev_tip.clone(), Some(prev_tip.height())));	×
298	}	×
299	}	×
300
301	// Atomically fetch the latest `ASSUME_FINAL_DEPTH` count of blocks from Electrum. We use this
302	// to construct our checkpoint update.
303	let mut new_blocks = {	×
304	let start_height = new_tip_height.saturating_sub(ASSUME_FINAL_DEPTH);	×
305	let hashes = client	×
306	.block_headers(start_height as _, ASSUME_FINAL_DEPTH as _)?	×
307	.headers
308	.into_iter()	×
309	.map(\|h\| h.block_hash());	×
310	(start_height..).zip(hashes).collect::<BTreeMap<u32, _>>()	×
311	};
312
313	// Find the "point of agreement" (if any).
314	let agreement_cp = {	×
315	let mut agreement_cp = Option::<CheckPoint>::None;	×
316	for cp in prev_tip.iter().flat_map(CheckPoint::iter) {	×
317	let cp_block = cp.block_id();	×
318	let hash = match new_blocks.get(&cp_block.height) {	×
319	Some(&hash) => hash,	×
320	None => {
321	assert!(	×
322	new_tip_height >= cp_block.height,	×
323	"already checked that electrum's tip cannot be smaller"	×
324	);
325	let hash = client.block_header(cp_block.height as _)?.block_hash();	×
326	new_blocks.insert(cp_block.height, hash);	×
327	hash	×
328	}
329	};
330	if hash == cp_block.hash {	×
331	agreement_cp = Some(cp);	×
332	break;	×
333	}	×
334	}
335	agreement_cp	×
336	};	×
337		×
338	let agreement_height = agreement_cp.as_ref().map(CheckPoint::height);	×
339		×
340	let new_tip = new_blocks	×
341	.into_iter()	×
342	// Prune `new_blocks` to only include blocks that are actually new.	×
343	.filter(\|(height, _)\| Some(*height) > agreement_height)	×
344	.map(\|(height, hash)\| BlockId { height, hash })	×
345	.fold(agreement_cp, \|prev_cp, block\| {	×
346	Some(match prev_cp {	×
347	Some(cp) => cp.push(block).expect("must extend checkpoint"),	×
348	None => CheckPoint::new(block),	×
349	})
350	})	×
351	.expect("must have at least one checkpoint");	×
352		×
353	Ok((new_tip, agreement_height))	×
354	}	×
355
356	/// A [tx status] comprises of a concatenation of `tx_hash:height:`s. We transform a single one of
357	/// these concatenations into a [`ConfirmationHeightAnchor`] if possible.
358	///
359	/// We use the lowest possible checkpoint as the anchor block (from `cps`). If an anchor block
360	/// cannot be found, or the transaction is unconfirmed, [`None`] is returned.
361	///
362	/// [tx status](https://electrumx-spesmilo.readthedocs.io/en/latest/protocol-basics.html#status)
363	fn determine_tx_anchor(	×
364	cps: &BTreeMap<u32, CheckPoint>,	×
365	raw_height: i32,	×
366	txid: Txid,	×
367	) -> Option<ConfirmationHeightAnchor> {	×
368	// The electrum API has a weird quirk where an unconfirmed transaction is presented with a	×
369	// height of 0. To avoid invalid representation in our data structures, we manually set	×
370	// transactions residing in the genesis block to have height 0, then interpret a height of 0 as	×
371	// unconfirmed for all other transactions.	×
372	if txid	×
373	== Txid::from_str("4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b")	×
374	.expect("must deserialize genesis coinbase txid")	×
375	{
376	let anchor_block = cps.values().next()?.block_id();	×
377	return Some(ConfirmationHeightAnchor {	×
378	anchor_block,	×
379	confirmation_height: 0,	×
380	});	×
381	}	×
382	match raw_height {	×
383	h if h <= 0 => {	×
384	debug_assert!(h == 0 \|\| h == -1, "unexpected height ({}) from electrum", h);	×
385	None	×
386	}
387	h => {	×
388	let h = h as u32;	×
389	let anchor_block = cps.range(h..).next().map(\|(_, cp)\| cp.block_id())?;	×
390	if h > anchor_block.height {	×
391	None	×
392	} else {
393	Some(ConfirmationHeightAnchor {	×
394	anchor_block,	×
395	confirmation_height: h,	×
396	})	×
397	}
398	}
399	}
400	}	×
401
402	fn populate_with_outpoints<K>(	×
403	client: &Client,	×
404	cps: &BTreeMap<u32, CheckPoint>,	×
405	update: &mut ElectrumUpdate<K, ConfirmationHeightAnchor>,	×
406	outpoints: &mut impl Iterator<Item = OutPoint>,	×
407	) -> Result<HashMap<Txid, Transaction>, Error> {	×
408	let mut full_txs = HashMap::new();	×
409	for outpoint in outpoints {	×
410	let txid = outpoint.txid;	×
411	let tx = client.transaction_get(&txid)?;	×
412	debug_assert_eq!(tx.txid(), txid);	×
413	let txout = match tx.output.get(outpoint.vout as usize) {	×
414	Some(txout) => txout,	×
415	None => continue,	×
416	};
417	// attempt to find the following transactions (alongside their chain positions), and
418	// add to our sparsechain `update`:
419	let mut has_residing = false; // tx in which the outpoint resides	×
420	let mut has_spending = false; // tx that spends the outpoint	×
421	for res in client.script_get_history(&txout.script_pubkey)? {	×
422	if has_residing && has_spending {	×
423	break;	×
424	}	×
425		×
426	if res.tx_hash == txid {	×
427	if has_residing {	×
428	continue;	×
429	}	×
430	has_residing = true;	×
431	full_txs.insert(res.tx_hash, tx.clone());	×
432	} else {
433	if has_spending {	×
434	continue;	×
435	}	×
436	let res_tx = match full_txs.get(&res.tx_hash) {	×
437	Some(tx) => tx,	×
438	None => {
439	let res_tx = client.transaction_get(&res.tx_hash)?;	×
440	full_txs.insert(res.tx_hash, res_tx);	×
441	full_txs.get(&res.tx_hash).expect("just inserted")	×
442	}
443	};
444	has_spending = res_tx	×
445	.input	×
446	.iter()	×
447	.any(\|txin\| txin.previous_output == outpoint);	×
448	if !has_spending {	×
449	continue;	×
450	}	×
451	};
452
453	let anchor = determine_tx_anchor(cps, res.height, res.tx_hash);	×
454	let tx_entry = update.graph_update.entry(res.tx_hash).or_default();	×
455	if let Some(anchor) = anchor {	×
456	tx_entry.insert(anchor);	×
457	}	×
458	}
459	}
460	Ok(full_txs)	×
461	}	×
462
463	fn populate_with_txids<K>(	×
464	client: &Client,	×
465	cps: &BTreeMap<u32, CheckPoint>,	×
466	update: &mut ElectrumUpdate<K, ConfirmationHeightAnchor>,	×
467	txids: &mut impl Iterator<Item = Txid>,	×
468	) -> Result<(), Error> {	×
469	for txid in txids {	×
470	let tx = match client.transaction_get(&txid) {	×
471	Ok(tx) => tx,	×
472	Err(electrum_client::Error::Protocol(_)) => continue,	×
473	Err(other_err) => return Err(other_err),	×
474	};
475
476	let spk = tx	×
477	.output	×
478	.get(0)	×
479	.map(\|txo\| &txo.script_pubkey)	×
480	.expect("tx must have an output");	×
481
482	let anchor = match client	×
483	.script_get_history(spk)?	×
484	.into_iter()	×
485	.find(\|r\| r.tx_hash == txid)	×
486	{
487	Some(r) => determine_tx_anchor(cps, r.height, txid),	×
488	None => continue,	×
489	};
490
491	let tx_entry = update.graph_update.entry(txid).or_default();	×
492	if let Some(anchor) = anchor {	×
493	tx_entry.insert(anchor);	×
494	}	×
495	}
496	Ok(())	×
497	}	×
498
499	fn populate_with_spks<K, I: Ord + Clone>(	×
500	client: &Client,	×
501	cps: &BTreeMap<u32, CheckPoint>,	×
502	update: &mut ElectrumUpdate<K, ConfirmationHeightAnchor>,	×
503	spks: &mut impl Iterator<Item = (I, ScriptBuf)>,	×
504	stop_gap: usize,	×
505	batch_size: usize,	×
506	) -> Result<BTreeMap<I, (ScriptBuf, bool)>, Error> {	×
507	let mut unused_spk_count = 0_usize;	×
508	let mut scanned_spks = BTreeMap::new();	×
509
510	loop {	×
511	let spks = (0..batch_size)	×
512	.map_while(\|_\| spks.next())	×
513	.collect::<Vec<_>>();	×
514	if spks.is_empty() {	×
515	return Ok(scanned_spks);	×
516	}	×
517
518	let spk_histories =	×
519	client.batch_script_get_history(spks.iter().map(\|(_, s)\| s.as_script()))?;	×
520
521	for ((spk_index, spk), spk_history) in spks.into_iter().zip(spk_histories) {	×
522	if spk_history.is_empty() {	×
523	scanned_spks.insert(spk_index, (spk, false));	×
524	unused_spk_count += 1;	×
525	if unused_spk_count > stop_gap {	×
526	return Ok(scanned_spks);	×
527	}	×
528	continue;	×
529	} else {	×
530	scanned_spks.insert(spk_index, (spk, true));	×
531	unused_spk_count = 0;	×
532	}	×
533
534	for tx in spk_history {	×
535	let tx_entry = update.graph_update.entry(tx.tx_hash).or_default();	×
536	if let Some(anchor) = determine_tx_anchor(cps, tx.height, tx.tx_hash) {	×
537	tx_entry.insert(anchor);	×
538	}	×
539	}
540	}
541	}
542	}	×

bitcoindevkit / bdk / 5984736767

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