bsv_tracker/
tracker.rs

1use crate::{
2    ChainEvent, CheckError, Hash, Headers, Height, Input, Params, Reask, State, TxId, Word,
3};
4use std::collections::{BTreeMap, BTreeSet};
5
6/// A named result of an event on one affected transaction.
7#[derive(Clone, Debug, PartialEq, Eq)]
8pub struct ChainUpdate {
9    /// The transaction selected by an index, never by a chain scan.
10    pub txid: TxId,
11    /// The transition's result. The updated state's re-ask survives an error.
12    pub result: Result<(), CheckError>,
13    /// The next host action after the event.
14    pub reask: Option<Reask>,
15}
16
17/// A host's tracked transactions, with indexes for targeted chain events.
18/// Hints, ages and spend attempts name one transaction. A tip uses only the
19/// suspect set; reorgs, forks and splits use only the relevant mined height
20/// range.
21#[derive(Clone, Debug)]
22pub struct Tracker {
23    params: Params,
24    states: BTreeMap<TxId, State>,
25    mined: BTreeMap<Height, BTreeSet<TxId>>,
26    headers: BTreeMap<Hash, BTreeSet<TxId>>,
27    suspect: BTreeSet<TxId>,
28}
29
30#[derive(Debug, PartialEq, Eq)]
31struct Index {
32    height: Option<Height>,
33    header: Option<Hash>,
34    suspect: bool,
35}
36impl Index {
37    fn of(state: &State) -> Self {
38        Self {
39            height: state.word().height(),
40            header: match state.word() {
41                Word::Mined(m) => Some(m.checked().header().hash.clone()),
42                _ => None,
43            },
44            suspect: state.suspect(),
45        }
46    }
47}
48
49impl Tracker {
50    /// An empty host registry with explicit age parameters.
51    #[must_use]
52    pub fn new(params: Params) -> Self {
53        Self {
54            params,
55            states: BTreeMap::new(),
56            mined: BTreeMap::new(),
57            headers: BTreeMap::new(),
58            suspect: BTreeSet::new(),
59        }
60    }
61    /// Begin tracking one transaction; repeating this does not erase its state.
62    pub fn track(&mut self, txid: impl Into<TxId>) -> &State {
63        let txid = txid.into().to_ascii_lowercase();
64        self.states
65            .entry(txid.clone())
66            .or_insert_with(|| State::new(txid))
67    }
68    /// Hold a state restored by [`State::from_compact`] and index it as a
69    /// transition would; a restored `mined` word joins the suspect set, so the
70    /// next tip rechecks it. The state it replaces, if the txid was tracked.
71    pub fn restore(&mut self, state: State) -> Option<State> {
72        let txid = state.txid().to_owned();
73        let tracked = self.states.contains_key(&txid);
74        let mut previous = None;
75        // The transition only swaps the state; it cannot fail.
76        let _ = self.apply_transition(&txid, |_, slot| {
77            previous = Some(std::mem::replace(slot, state));
78            Ok(())
79        });
80        previous.filter(|_| tracked)
81    }
82    /// An immutable state, or none when the host does not track this txid.
83    #[must_use]
84    pub fn get(&self, txid: &str) -> Option<&State> {
85        self.states.get(&txid.to_ascii_lowercase())
86    }
87    /// Number of transactions this host tracks.
88    #[must_use]
89    pub fn len(&self) -> usize {
90        self.states.len()
91    }
92    /// Whether the registry is empty.
93    #[must_use]
94    pub fn is_empty(&self) -> bool {
95        self.states.is_empty()
96    }
97    /// Apply an input to one transaction and maintain the event indexes,
98    /// including after a failed proof or header lookup.
99    ///
100    /// # Errors
101    ///
102    /// The [`CheckError`] of [`State::step`] for that transaction.
103    pub fn apply<H: Headers + ?Sized>(
104        &mut self,
105        txid: &str,
106        headers: &H,
107        input: Input,
108    ) -> Result<(), CheckError> {
109        self.apply_transition(txid, |params, state| state.step(params, headers, input))
110    }
111    fn apply_transition(
112        &mut self,
113        txid: &str,
114        transition: impl FnOnce(&Params, &mut State) -> Result<(), CheckError>,
115    ) -> Result<(), CheckError> {
116        let txid = txid.to_ascii_lowercase();
117        let state = self
118            .states
119            .entry(txid.clone())
120            .or_insert_with(|| State::new(&txid));
121        let old = Index::of(state);
122        let result = transition(&self.params, state);
123        let new = Index::of(state);
124        if old != new {
125            if let Some(h) = old.height {
126                remove_index(&mut self.mined, &h, &txid);
127            }
128            if let Some(hash) = old.header {
129                remove_index(&mut self.headers, &hash, &txid);
130            }
131            self.suspect.remove(&txid);
132            if let Some(h) = new.height {
133                self.mined.entry(h).or_default().insert(txid.clone());
134            }
135            if let Some(hash) = new.header {
136                self.headers.entry(hash).or_default().insert(txid.clone());
137            }
138            if new.suspect {
139                self.suspect.insert(txid);
140            }
141        }
142        result
143    }
144    /// Deliver an evidence event only to the set it names. The output contains
145    /// every selected txid and each fault for the host to report.
146    // By reference would break the public API; a later minor (bsv-stack-lean #134).
147    #[allow(clippy::needless_pass_by_value)]
148    pub fn on_chain<H: Headers + ?Sized>(
149        &mut self,
150        headers: &H,
151        event: ChainEvent,
152    ) -> Vec<ChainUpdate> {
153        let targets: Vec<TxId> = match &event {
154            ChainEvent::Fork { height, .. } => self.at_or_above(*height),
155            ChainEvent::Reorg { fork_height, .. }
156            | ChainEvent::Split { fork_height, .. }
157            | ChainEvent::SplitResolved { fork_height, .. } => self.at_or_above(*fork_height),
158            ChainEvent::Invalidated { block_hash } => self
159                .headers
160                .get(block_hash)
161                .map(|ids| ids.iter().cloned().collect())
162                .unwrap_or_default(),
163            ChainEvent::Tip { .. } => self.suspect.iter().cloned().collect(),
164            ChainEvent::Frozen { .. } | ChainEvent::TipAge { .. } => vec![],
165        };
166        targets
167            .into_iter()
168            .map(|txid| {
169                let result =
170                    self.apply_transition(&txid, |_, state| state.on_chain(headers, &event));
171                let reask = self.states[&txid].reask().cloned();
172                ChainUpdate {
173                    txid,
174                    result,
175                    reask,
176                }
177            })
178            .collect()
179    }
180    fn at_or_above(&self, height: Height) -> Vec<TxId> {
181        self.mined
182            .range(height..)
183            .flat_map(|(_, ids)| ids.iter().cloned())
184            .collect()
185    }
186}
187
188fn remove_index<K: Ord>(index: &mut BTreeMap<K, BTreeSet<TxId>>, key: &K, txid: &str) {
189    if let Some(ids) = index.get_mut(key) {
190        ids.remove(txid);
191        if ids.is_empty() {
192            index.remove(key);
193        }
194    }
195}
bsv_tracker/tracker.rs

bsv_tracker/
tracker.rs
