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Pull #1002

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Merge 7223adb9f into 81c761339

Pull Request Pull Request #1002: Implement linked-list `LocalChain` and add rpc-chain module/example

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0.0

/crates/electrum/src/electrum_ext.rs

use bdk_chain::{
    bitcoin::{hashes::hex::FromHex, OutPoint, Script, Transaction, Txid},
    keychain::LocalUpdate,
    local_chain::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,
};

/// 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 chain_update: 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(cp: CheckPoint) -> Self {
        Self {
            graph_update: HashMap::new(),
            chain_update: cp,
            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<LocalUpdate<K, A>, 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(LocalUpdate {
            keychain: self.keychain_update,
            graph: graph_update,
            tip: self.chain_update,
        })
    }
}

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<LocalUpdate<K, ConfirmationTimeAnchor>, Error> {
        let update = self.finalize(client, seen_at, missing)?;
        // client.batch_transaction_get(txid)

        let relevant_heights = {
            let mut visited_heights = HashSet::new();
            update
                .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_additions = {
            let old_additions = TxGraph::default().determine_additions(&update.graph);
            tx_graph::Additions {
                txs: old_additions.txs,
                txouts: old_additions.txouts,
                last_seen: old_additions.last_seen,
                anchors: old_additions
                    .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(),
            }
        };

        Ok(LocalUpdate {
            keychain: update.keychain,
            graph: {
                let mut graph = TxGraph::default();
                graph.apply_additions(graph_additions);
                graph
            },
            tip: 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, Script)>>,
        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 = Script>,
        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, Script)>>,
        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), (Script, 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
                .chain_update
                .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.extend(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_hex("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, Script)>,
    stop_gap: usize,
    batch_size: usize,
) -> Result<BTreeMap<I, (Script, 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))?;

        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::{hashes::hex::FromHex, OutPoint, Script, Transaction, Txid},
3	keychain::LocalUpdate,
4	local_chain::CheckPoint,
5	tx_graph::{self, TxGraph},
6	Anchor, BlockId, ConfirmationHeightAnchor, ConfirmationTimeAnchor,
7	};
8	use electrum_client::{Client, ElectrumApi, Error, HeaderNotification};
9	use std::{
10	collections::{BTreeMap, BTreeSet, HashMap, HashSet},
11	fmt::Debug,
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 transactions.
18	///
19	/// To provide a complete update to [`TxGraph`], you'll need to call [`Self::missing_full_txs`] to
20	/// determine the full transactions missing from [`TxGraph`]. Then call [`Self::finalize`] to fetch
21	/// the full transactions from Electrum and finalize the update.
22	#[derive(Debug, Clone)]	×
23	pub struct ElectrumUpdate<K, A> {
24	/// Map of [`Txid`]s to associated [`Anchor`]s.
25	pub graph_update: HashMap<Txid, BTreeSet<A>>,
26	/// The latest chain tip, as seen by the Electrum server.
27	pub chain_update: CheckPoint,
28	/// Last-used index update for [`KeychainTxOutIndex`](bdk_chain::keychain::KeychainTxOutIndex).
29	pub keychain_update: BTreeMap<K, u32>,
30	}
31
32	impl<K, A: Anchor> ElectrumUpdate<K, A> {
33	fn new(cp: CheckPoint) -> Self {	×
34	Self {	×
35	graph_update: HashMap::new(),	×
36	chain_update: cp,	×
37	keychain_update: BTreeMap::new(),	×
38	}	×
39	}	×
40
41	/// Determine the full transactions that are missing from `graph`.
42	///
43	/// Refer to [`ElectrumUpdate`].
44	pub fn missing_full_txs<A2>(&self, graph: &TxGraph<A2>) -> Vec<Txid> {	×
45	self.graph_update	×
46	.keys()	×
47	.filter(move \|&&txid\| graph.as_ref().get_tx(txid).is_none())	×
48	.cloned()	×
49	.collect()	×
50	}	×
51
52	/// Finalizes update with `missing` txids to fetch from `client`.
53	///
54	/// Refer to [`ElectrumUpdate`].
55	pub fn finalize(	×
56	self,	×
57	client: &Client,	×
58	seen_at: Option<u64>,	×
59	missing: Vec<Txid>,	×
60	) -> Result<LocalUpdate<K, A>, Error> {	×
61	let new_txs = client.batch_transaction_get(&missing)?;	×
62	let mut graph_update = TxGraph::<A>::new(new_txs);	×
63	for (txid, anchors) in self.graph_update {	×
64	if let Some(seen_at) = seen_at {	×
65	let _ = graph_update.insert_seen_at(txid, seen_at);	×
66	}	×
67	for anchor in anchors {	×
68	let _ = graph_update.insert_anchor(txid, anchor);	×
69	}	×
70	}
71	Ok(LocalUpdate {	×
72	keychain: self.keychain_update,	×
73	graph: graph_update,	×
74	tip: self.chain_update,	×
75	})	×
76	}	×
77	}
78
79	impl<K> ElectrumUpdate<K, ConfirmationHeightAnchor> {
80	/// Finalizes the [`ElectrumUpdate`] with `new_txs` and anchors of type
81	/// [`ConfirmationTimeAnchor`].
82	///
83	/// Note: The confirmation time might not be precisely correct if there has been a reorg.
84	/// Electrum's API intends that we use the merkle proof API, we should change `bdk_electrum` to
85	/// use it.
86	pub fn finalize_as_confirmation_time(	×
87	self,	×
88	client: &Client,	×
89	seen_at: Option<u64>,	×
90	missing: Vec<Txid>,	×
91	) -> Result<LocalUpdate<K, ConfirmationTimeAnchor>, Error> {	×
92	let update = self.finalize(client, seen_at, missing)?;	×
93	// client.batch_transaction_get(txid)
94
95	let relevant_heights = {	×
96	let mut visited_heights = HashSet::new();	×
97	update	×
98	.graph	×
99	.all_anchors()	×
100	.iter()	×
101	.map(\|(a, _)\| a.confirmation_height_upper_bound())	×
102	.filter(move \|&h\| visited_heights.insert(h))	×
103	.collect::<Vec<_>>()	×
104	};
105
106	let height_to_time = relevant_heights	×
107	.clone()	×
108	.into_iter()	×
109	.zip(	×
110	client	×
111	.batch_block_header(relevant_heights)?	×
112	.into_iter()	×
113	.map(\|bh\| bh.time as u64),	×
114	)	×
115	.collect::<HashMap<u32, u64>>();	×
116		×
117	let graph_additions = {	×
118	let old_additions = TxGraph::default().determine_additions(&update.graph);	×
119	tx_graph::Additions {	×
120	txs: old_additions.txs,	×
121	txouts: old_additions.txouts,	×
122	last_seen: old_additions.last_seen,	×
123	anchors: old_additions	×
124	.anchors	×
125	.into_iter()	×
126	.map(\|(height_anchor, txid)\| {	×
127	let confirmation_height = height_anchor.confirmation_height;	×
128	let confirmation_time = height_to_time[&confirmation_height];	×
129	let time_anchor = ConfirmationTimeAnchor {	×
130	anchor_block: height_anchor.anchor_block,	×
131	confirmation_height,	×
132	confirmation_time,	×
133	};	×
134	(time_anchor, txid)	×
135	})	×
136	.collect(),	×
137	}	×
138	};	×
139		×
140	Ok(LocalUpdate {	×
141	keychain: update.keychain,	×
142	graph: {	×
143	let mut graph = TxGraph::default();	×
144	graph.apply_additions(graph_additions);	×
145	graph	×
146	},	×
147	tip: update.tip,	×
148	})	×
149	}	×
150	}
151
152	/// Trait to extend [`Client`] functionality.
153	pub trait ElectrumExt<A> {
154	/// Scan the blockchain (via electrum) for the data specified and returns a [`ElectrumUpdate`].
155	///
156	/// - `prev_tip`: the most recent blockchain tip present locally
157	/// - `keychain_spks`: keychains that we want to scan transactions for
158	/// - `txids`: transactions for which we want updated [`Anchor`]s
159	/// - `outpoints`: transactions associated with these outpoints (residing, spending) that we
160	/// want to included in the update
161	///
162	/// The scan for each keychain stops after a gap of `stop_gap` script pubkeys with no associated
163	/// transactions. `batch_size` specifies the max number of script pubkeys to request for in a
164	/// single batch request.
165	fn scan<K: Ord + Clone>(
166	&self,
167	prev_tip: Option<CheckPoint>,
168	keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, Script)>>,
169	txids: impl IntoIterator<Item = Txid>,
170	outpoints: impl IntoIterator<Item = OutPoint>,
171	stop_gap: usize,
172	batch_size: usize,
173	) -> Result<ElectrumUpdate<K, A>, Error>;
174
175	/// Convenience method to call [`scan`] without requiring a keychain.
176	///
177	/// [`scan`]: ElectrumExt::scan
178	fn scan_without_keychain(	×
179	&self,	×
180	prev_tip: Option<CheckPoint>,	×
181	misc_spks: impl IntoIterator<Item = Script>,	×
182	txids: impl IntoIterator<Item = Txid>,	×
183	outpoints: impl IntoIterator<Item = OutPoint>,	×
184	batch_size: usize,	×
185	) -> Result<ElectrumUpdate<(), A>, Error> {	×
186	let spk_iter = misc_spks	×
187	.into_iter()	×
188	.enumerate()	×
189	.map(\|(i, spk)\| (i as u32, spk));	×
190		×
191	self.scan(	×
192	prev_tip,	×
193	[((), spk_iter)].into(),	×
194	txids,	×
195	outpoints,	×
196	usize::MAX,	×
197	batch_size,	×
198	)	×
199	}	×
200	}
201
202	impl ElectrumExt<ConfirmationHeightAnchor> for Client {
203	fn scan<K: Ord + Clone>(	×
204	&self,	×
205	prev_tip: Option<CheckPoint>,	×
206	keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, Script)>>,	×
207	txids: impl IntoIterator<Item = Txid>,	×
208	outpoints: impl IntoIterator<Item = OutPoint>,	×
209	stop_gap: usize,	×
210	batch_size: usize,	×
211	) -> Result<ElectrumUpdate<K, ConfirmationHeightAnchor>, Error> {	×
212	let mut request_spks = keychain_spks	×
213	.into_iter()	×
214	.map(\|(k, s)\| (k, s.into_iter()))	×
215	.collect::<BTreeMap<K, _>>();	×
216	let mut scanned_spks = BTreeMap::<(K, u32), (Script, bool)>::new();	×
217		×
218	let txids = txids.into_iter().collect::<Vec<_>>();	×
219	let outpoints = outpoints.into_iter().collect::<Vec<_>>();	×
220
221	let update = loop {	×
222	let (tip, _) = construct_update_tip(self, prev_tip.clone())?;	×
223	let mut update = ElectrumUpdate::<K, ConfirmationHeightAnchor>::new(tip.clone());	×
224	let cps = update	×
225	.chain_update	×
226	.iter()	×
227	.take(10)	×
228	.map(\|cp\| (cp.height(), cp))	×
229	.collect::<BTreeMap<u32, CheckPoint>>();	×
230		×
231	if !request_spks.is_empty() {	×
232	if !scanned_spks.is_empty() {	×
233	scanned_spks.append(&mut populate_with_spks(	×
234	self,	×
235	&cps,	×
236	&mut update,	×
237	&mut scanned_spks	×
238	.iter()	×
239	.map(\|(i, (spk, _))\| (i.clone(), spk.clone())),	×
240	stop_gap,	×
241	batch_size,	×
242	)?);	×
243	}	×
244	for (keychain, keychain_spks) in &mut request_spks {	×
245	scanned_spks.extend(
246	populate_with_spks(	×
247	self,	×
248	&cps,	×
249	&mut update,	×
250	keychain_spks,	×
251	stop_gap,	×
252	batch_size,	×
253	)?	×
254	.into_iter()	×
255	.map(\|(spk_i, spk)\| ((keychain.clone(), spk_i), spk)),	×
256	);
257	}
258	}	×
259
260	populate_with_txids(self, &cps, &mut update, &mut txids.iter().cloned())?;	×
261
262	let _txs =	×
263	populate_with_outpoints(self, &cps, &mut update, &mut outpoints.iter().cloned())?;	×
264
265	// check for reorgs during scan process
266	let server_blockhash = self.block_header(tip.height() as usize)?.block_hash();	×
267	if tip.hash() != server_blockhash {	×
268	continue; // reorg	×
269	}	×
270		×
271	update.keychain_update = request_spks	×
272	.into_keys()	×
273	.filter_map(\|k\| {	×
274	scanned_spks	×
275	.range((k.clone(), u32::MIN)..=(k.clone(), u32::MAX))	×
276	.rev()	×
277	.find(\|(_, (_, active))\| *active)	×
278	.map(\|((_, i), _)\| (k, *i))	×
279	})	×
280	.collect::<BTreeMap<_, _>>();	×
281	break update;	×
282	};	×
283		×
284	Ok(update)	×
285	}	×
286	}
287
288	/// Return a [`CheckPoint`] of the latest tip, that connects with `prev_tip`.
289	fn construct_update_tip(	×
290	client: &Client,	×
291	prev_tip: Option<CheckPoint>,	×
292	) -> Result<(CheckPoint, Option<u32>), Error> {	×
293	let HeaderNotification { height, .. } = client.block_headers_subscribe()?;	×
294	let new_tip_height = height as u32;	×
295
296	// If electrum returns a tip height that is lower than our previous tip, then checkpoints do
297	// not need updating. We just return the previous tip and use that as the point of agreement.
298	if let Some(prev_tip) = prev_tip.as_ref() {	×
299	if new_tip_height < prev_tip.height() {	×
300	return Ok((prev_tip.clone(), Some(prev_tip.height())));	×
301	}	×
302	}	×
303
304	// Atomically fetch the latest `ASSUME_FINAL_DEPTH` count of blocks from Electrum. We use this
305	// to construct our checkpoint update.
306	let mut new_blocks = {	×
307	let start_height = new_tip_height.saturating_sub(ASSUME_FINAL_DEPTH);	×
308	let hashes = client	×
309	.block_headers(start_height as _, ASSUME_FINAL_DEPTH as _)?	×
310	.headers
311	.into_iter()	×
312	.map(\|h\| h.block_hash());	×
313	(start_height..).zip(hashes).collect::<BTreeMap<u32, _>>()	×
314	};
315
316	// Find the "point of agreement" (if any).
317	let agreement_cp = {	×
318	let mut agreement_cp = Option::<CheckPoint>::None;	×
319	for cp in prev_tip.iter().flat_map(CheckPoint::iter) {	×
320	let cp_block = cp.block_id();	×
321	let hash = match new_blocks.get(&cp_block.height) {	×
322	Some(&hash) => hash,	×
323	None => {
324	assert!(	×
325	new_tip_height >= cp_block.height,	×
326	"already checked that electrum's tip cannot be smaller"	×
327	);
328	let hash = client.block_header(cp_block.height as _)?.block_hash();	×
329	new_blocks.insert(cp_block.height, hash);	×
330	hash	×
331	}
332	};
333	if hash == cp_block.hash {	×
334	agreement_cp = Some(cp);	×
335	break;	×
336	}	×
337	}
338	agreement_cp	×
339	};	×
340		×
341	let agreement_height = agreement_cp.as_ref().map(CheckPoint::height);	×
342		×
343	let new_tip = new_blocks	×
344	.into_iter()	×
345	// Prune `new_blocks` to only include blocks that are actually new.	×
346	.filter(\|(height, _)\| Some(*height) > agreement_height)	×
347	.map(\|(height, hash)\| BlockId { height, hash })	×
348	.fold(agreement_cp, \|prev_cp, block\| {	×
349	Some(match prev_cp {	×
350	Some(cp) => cp.extend(block).expect("must extend checkpoint"),	×
351	None => CheckPoint::new(block),	×
352	})
353	})	×
354	.expect("must have at least one checkpoint");	×
355		×
356	Ok((new_tip, agreement_height))	×
357	}	×
358
359	/// A [tx status] comprises of a concatenation of `tx_hash:height:`s. We transform a single one of
360	/// these concatenations into a [`ConfirmationHeightAnchor`] if possible.
361	///
362	/// We use the lowest possible checkpoint as the anchor block (from `cps`). If an anchor block
363	/// cannot be found, or the transaction is unconfirmed, [`None`] is returned.
364	///
365	/// [tx status](https://electrumx-spesmilo.readthedocs.io/en/latest/protocol-basics.html#status)
366	fn determine_tx_anchor(	×
367	cps: &BTreeMap<u32, CheckPoint>,	×
368	raw_height: i32,	×
369	txid: Txid,	×
370	) -> Option<ConfirmationHeightAnchor> {	×
371	// The electrum API has a weird quirk where an unconfirmed transaction is presented with a	×
372	// height of 0. To avoid invalid representation in our data structures, we manually set	×
373	// transactions residing in the genesis block to have height 0, then interpret a height of 0 as	×
374	// unconfirmed for all other transactions.	×
375	if txid	×
376	== Txid::from_hex("4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b")	×
377	.expect("must deserialize genesis coinbase txid")	×
378	{
379	let anchor_block = cps.values().next()?.block_id();	×
380	return Some(ConfirmationHeightAnchor {	×
381	anchor_block,	×
382	confirmation_height: 0,	×
383	});	×
384	}	×
385	match raw_height {	×
386	h if h <= 0 => {	×
387	debug_assert!(h == 0 \|\| h == -1, "unexpected height ({}) from electrum", h);	×
388	None	×
389	}
390	h => {	×
391	let h = h as u32;	×
392	let anchor_block = cps.range(h..).next().map(\|(_, cp)\| cp.block_id())?;	×
393	if h > anchor_block.height {	×
394	None	×
395	} else {
396	Some(ConfirmationHeightAnchor {	×
397	anchor_block,	×
398	confirmation_height: h,	×
399	})	×
400	}
401	}
402	}
403	}	×
404
405	fn populate_with_outpoints<K>(	×
406	client: &Client,	×
407	cps: &BTreeMap<u32, CheckPoint>,	×
408	update: &mut ElectrumUpdate<K, ConfirmationHeightAnchor>,	×
409	outpoints: &mut impl Iterator<Item = OutPoint>,	×
410	) -> Result<HashMap<Txid, Transaction>, Error> {	×
411	let mut full_txs = HashMap::new();	×
412	for outpoint in outpoints {	×
413	let txid = outpoint.txid;	×
414	let tx = client.transaction_get(&txid)?;	×
415	debug_assert_eq!(tx.txid(), txid);	×
416	let txout = match tx.output.get(outpoint.vout as usize) {	×
417	Some(txout) => txout,	×
418	None => continue,	×
419	};
420	// attempt to find the following transactions (alongside their chain positions), and
421	// add to our sparsechain `update`:
422	let mut has_residing = false; // tx in which the outpoint resides	×
423	let mut has_spending = false; // tx that spends the outpoint	×
424	for res in client.script_get_history(&txout.script_pubkey)? {	×
425	if has_residing && has_spending {	×
426	break;	×
427	}	×
428		×
429	if res.tx_hash == txid {	×
430	if has_residing {	×
431	continue;	×
432	}	×
433	has_residing = true;	×
434	full_txs.insert(res.tx_hash, tx.clone());	×
435	} else {
436	if has_spending {	×
437	continue;	×
438	}	×
439	let res_tx = match full_txs.get(&res.tx_hash) {	×
440	Some(tx) => tx,	×
441	None => {
442	let res_tx = client.transaction_get(&res.tx_hash)?;	×
443	full_txs.insert(res.tx_hash, res_tx);	×
444	full_txs.get(&res.tx_hash).expect("just inserted")	×
445	}
446	};
447	has_spending = res_tx	×
448	.input	×
449	.iter()	×
450	.any(\|txin\| txin.previous_output == outpoint);	×
451	if !has_spending {	×
452	continue;	×
453	}	×
454	};
455
456	let anchor = determine_tx_anchor(cps, res.height, res.tx_hash);	×
457		×
458	let tx_entry = update.graph_update.entry(res.tx_hash).or_default();	×
459	if let Some(anchor) = anchor {	×
460	tx_entry.insert(anchor);	×
461	}	×
462	}
463	}
464	Ok(full_txs)	×
465	}	×
466
467	fn populate_with_txids<K>(	×
468	client: &Client,	×
469	cps: &BTreeMap<u32, CheckPoint>,	×
470	update: &mut ElectrumUpdate<K, ConfirmationHeightAnchor>,	×
471	txids: &mut impl Iterator<Item = Txid>,	×
472	) -> Result<(), Error> {	×
473	for txid in txids {	×
474	let tx = match client.transaction_get(&txid) {	×
475	Ok(tx) => tx,	×
476	Err(electrum_client::Error::Protocol(_)) => continue,	×
477	Err(other_err) => return Err(other_err),	×
478	};
479
480	let spk = tx	×
481	.output	×
482	.get(0)	×
483	.map(\|txo\| &txo.script_pubkey)	×
484	.expect("tx must have an output");	×
485
486	let anchor = match client	×
487	.script_get_history(spk)?	×
488	.into_iter()	×
489	.find(\|r\| r.tx_hash == txid)	×
490	{
491	Some(r) => determine_tx_anchor(cps, r.height, txid),	×
492	None => continue,	×
493	};
494
495	let tx_entry = update.graph_update.entry(txid).or_default();	×
496	if let Some(anchor) = anchor {	×
497	tx_entry.insert(anchor);	×
498	}	×
499	}
500	Ok(())	×
501	}	×
502
503	fn populate_with_spks<K, I: Ord + Clone>(	×
504	client: &Client,	×
505	cps: &BTreeMap<u32, CheckPoint>,	×
506	update: &mut ElectrumUpdate<K, ConfirmationHeightAnchor>,	×
507	spks: &mut impl Iterator<Item = (I, Script)>,	×
508	stop_gap: usize,	×
509	batch_size: usize,	×
510	) -> Result<BTreeMap<I, (Script, bool)>, Error> {	×
511	let mut unused_spk_count = 0_usize;	×
512	let mut scanned_spks = BTreeMap::new();	×
513
514	loop {	×
515	let spks = (0..batch_size)	×
516	.map_while(\|_\| spks.next())	×
517	.collect::<Vec<_>>();	×
518	if spks.is_empty() {	×
519	return Ok(scanned_spks);	×
520	}	×
521
522	let spk_histories = client.batch_script_get_history(spks.iter().map(\|(_, s)\| s))?;	×
523
524	for ((spk_index, spk), spk_history) in spks.into_iter().zip(spk_histories) {	×
525	if spk_history.is_empty() {	×
526	scanned_spks.insert(spk_index, (spk, false));	×
527	unused_spk_count += 1;	×
528	if unused_spk_count > stop_gap {	×
529	return Ok(scanned_spks);	×
530	}	×
531	continue;	×
532	} else {	×
533	scanned_spks.insert(spk_index, (spk, true));	×
534	unused_spk_count = 0;	×
535	}	×
536
537	for tx in spk_history {	×
538	let tx_entry = update.graph_update.entry(tx.tx_hash).or_default();	×
539	if let Some(anchor) = determine_tx_anchor(cps, tx.height, tx.tx_hash) {	×
540	tx_entry.insert(anchor);	×
541	}	×
542	}
543	}
544	}
545	}	×

bitcoindevkit / bdk / 5472795873

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