harn_session_store/
store.rs

1//! `SessionStore` trait + the shared types every backend speaks.
2
3use std::collections::BTreeMap;
4use std::sync::Arc;
5
6use async_trait::async_trait;
7use serde::{Deserialize, Serialize};
8
9use super::event::{AppendEvent, EventId, StoredEvent};
10use super::redaction::SharedEventRedactor;
11use super::retention::{RetentionPolicy, SharedArchiveSink, Tombstone};
12use super::search::{default_embedder, Embedder, SearchQuery, SearchResponse};
13use super::signing::SessionSigner;
14
15pub type SessionId = String;
16
17/// Result of a fork operation.
18#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
19pub struct ForkResult {
20    pub child_session_id: SessionId,
21    pub forked_from_event_id: EventId,
22    pub copied_event_count: usize,
23}
24
25#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
26pub struct TruncateResult {
27    pub kept_event_count: usize,
28    pub removed_event_count: usize,
29    pub new_tip_event_id: Option<EventId>,
30}
31
32/// Per-session retention/lifecycle state.
33#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
34#[serde(rename_all = "snake_case")]
35pub enum SessionStatus {
36    Open,
37    Closed,
38    /// Soft-deleted; will become `HardDeleted` once the grace window
39    /// elapses (enforced by retention sweeps; see [`crate::retention`]).
40    SoftDeleted,
41    HardDeleted,
42}
43
44#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
45#[serde(rename_all = "snake_case")]
46pub enum SessionType {
47    User,
48    Subagent,
49    Scheduled,
50}
51
52#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
53pub struct SessionMeta {
54    pub id: SessionId,
55    pub tenant_id: Option<String>,
56    pub persona: Option<String>,
57    pub parent_session_id: Option<SessionId>,
58    #[serde(default)]
59    pub title: Option<String>,
60    /// True when a person chose this title. Derived titles never overwrite it.
61    #[serde(default)]
62    pub title_pinned: bool,
63    #[serde(default)]
64    pub cwd: Option<String>,
65    #[serde(default)]
66    pub model: Option<String>,
67    #[serde(default)]
68    pub session_type: Option<SessionType>,
69    #[serde(default)]
70    pub project_scope: Option<String>,
71    #[serde(default)]
72    pub usage_input: u64,
73    #[serde(default)]
74    pub usage_output: u64,
75    /// Cost in millionths of a US dollar, avoiding floating-point drift.
76    #[serde(default)]
77    pub usage_cost_usd_micros: u64,
78    pub created_at_ms: i64,
79    pub created_at: String,
80    /// Last `append`/`fork` timestamp; refreshed on every mutation.
81    pub updated_at_ms: i64,
82    pub updated_at: String,
83    pub status: SessionStatus,
84    pub event_count: usize,
85    pub last_event_id: Option<EventId>,
86    pub chain_root_hash: Option<String>,
87    pub closed_at_ms: Option<i64>,
88    pub closed_at: Option<String>,
89    pub soft_deleted_at_ms: Option<i64>,
90    pub ttl_seconds: Option<u64>,
91    pub tags: Vec<String>,
92    pub attributes: BTreeMap<String, serde_json::Value>,
93}
94
95#[derive(Clone, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
96pub struct CreateSession {
97    #[serde(default)]
98    pub id: Option<SessionId>,
99    #[serde(default)]
100    pub tenant_id: Option<String>,
101    #[serde(default)]
102    pub persona: Option<String>,
103    #[serde(default)]
104    pub parent_session_id: Option<SessionId>,
105    #[serde(default)]
106    pub title: Option<String>,
107    /// Seed a session whose title is already a person's choice, so a rename
108    /// against a not-yet-persisted session survives its first derived write.
109    #[serde(default)]
110    pub title_pinned: bool,
111    #[serde(default)]
112    pub cwd: Option<String>,
113    #[serde(default)]
114    pub model: Option<String>,
115    #[serde(default)]
116    pub session_type: Option<SessionType>,
117    #[serde(default)]
118    pub project_scope: Option<String>,
119    #[serde(default)]
120    pub usage_input: u64,
121    #[serde(default)]
122    pub usage_output: u64,
123    #[serde(default)]
124    pub usage_cost_usd_micros: u64,
125    #[serde(default)]
126    pub ttl_seconds: Option<u64>,
127    #[serde(default)]
128    pub tags: Vec<String>,
129    #[serde(default)]
130    pub attributes: BTreeMap<String, serde_json::Value>,
131}
132
133/// Typed mutable facts for an existing session.
134///
135/// Omitted fields are preserved. Clearing metadata is deliberately not part of
136/// this contract; lifecycle operations own destructive state transitions.
137#[derive(Clone, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
138pub struct UpdateSession {
139    #[serde(default)]
140    pub title: Option<String>,
141    /// Whether `title` is a person's choice, which decides who may overwrite
142    /// whom. Leaving this `None` marks the write as *derived* — a title
143    /// generated from session content — and derived writes never overwrite a
144    /// pinned title. That default is what makes an auto-titling caller
145    /// fail-safe without having to know pinning exists.
146    ///
147    /// | `title` | `title_pinned` | effect |
148    /// |---|---|---|
149    /// | `Some` | `Some(true)` | rename: set the title and pin it |
150    /// | `Some` | `Some(false)` | retitle and release the pin |
151    /// | `None` | `Some(_)` | change the pin state, keep the title |
152    /// | `Some` | `None` | derived: applied only while unpinned |
153    /// | `None` | `None` | no title change |
154    #[serde(default)]
155    pub title_pinned: Option<bool>,
156    #[serde(default)]
157    pub cwd: Option<String>,
158    #[serde(default)]
159    pub model: Option<String>,
160    #[serde(default)]
161    pub parent_session_id: Option<SessionId>,
162    #[serde(default)]
163    pub session_type: Option<SessionType>,
164    #[serde(default)]
165    pub project_scope: Option<String>,
166    #[serde(default)]
167    pub usage_input: Option<u64>,
168    #[serde(default)]
169    pub usage_output: Option<u64>,
170    #[serde(default)]
171    pub usage_cost_usd_micros: Option<u64>,
172}
173
174/// One atomic, idempotent import into a new canonical session.
175///
176/// `source_id` names the external source independently of the target session;
177/// its receipt survives session deletion so retired sources cannot resurrect
178/// data. Reusing a source id with a different digest is a conflict.
179#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
180pub struct ImportSession {
181    pub source_id: String,
182    pub source_digest: String,
183    pub session: CreateSession,
184    #[serde(default)]
185    pub events: Vec<AppendEvent>,
186}
187
188impl ImportSession {
189    /// Validate the backend-independent import contract.
190    pub fn validate(&self) -> StoreResult<()> {
191        if self.source_id.trim().is_empty() || self.source_digest.trim().is_empty() {
192            return Err(StoreError::InvalidInput(
193                "import source_id and source_digest must be non-empty".to_string(),
194            ));
195        }
196        if self
197            .session
198            .id
199            .as_deref()
200            .is_none_or(|session_id| session_id.trim().is_empty())
201        {
202            return Err(StoreError::InvalidInput(
203                "import session id must be explicit and non-empty".to_string(),
204            ));
205        }
206        Ok(())
207    }
208}
209
210#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
211pub struct ImportResult {
212    pub source_id: String,
213    pub source_digest: String,
214    pub session_id: SessionId,
215    pub event_count: usize,
216    /// True only for the call that committed the import.
217    pub imported: bool,
218}
219
220#[derive(Clone, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
221pub struct ListFilter {
222    #[serde(default)]
223    pub tenant_id: Option<String>,
224    #[serde(default)]
225    pub persona: Option<String>,
226    #[serde(default)]
227    pub status: Option<SessionStatus>,
228    #[serde(default)]
229    pub tag: Option<String>,
230    #[serde(default)]
231    pub parent_session_id: Option<SessionId>,
232    #[serde(default)]
233    pub session_type: Option<SessionType>,
234    #[serde(default)]
235    pub project_scope: Option<String>,
236    /// Inclusive lower bound on `created_at_ms`.
237    #[serde(default)]
238    pub created_after_ms: Option<i64>,
239    /// Inclusive upper bound on `created_at_ms`.
240    #[serde(default)]
241    pub created_before_ms: Option<i64>,
242    #[serde(default)]
243    pub limit: Option<usize>,
244    #[serde(default)]
245    pub cursor: Option<String>,
246    /// Timestamp used to order and paginate matching sessions.
247    #[serde(default)]
248    pub sort_by: ListSortKey,
249    /// Direction for `sort_by`. Session ids remain ascending as the stable
250    /// tie-breaker in both directions.
251    #[serde(default)]
252    pub order: ListOrder,
253}
254
255#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
256#[serde(rename_all = "snake_case")]
257pub enum ListSortKey {
258    #[default]
259    CreatedAt,
260    UpdatedAt,
261}
262
263#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
264#[serde(rename_all = "snake_case")]
265pub enum ListOrder {
266    #[default]
267    Ascending,
268    Descending,
269}
270
271#[derive(Clone, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
272pub struct ReadRange {
273    /// Inclusive lower bound; `None` means start from the genesis event.
274    #[serde(default)]
275    pub from_event_id: Option<EventId>,
276    /// Inclusive upper bound; `None` means up to the latest event.
277    #[serde(default)]
278    pub to_event_id: Option<EventId>,
279    /// Maximum number of events to return. Capped at
280    /// [`MAX_READ_BATCH`] by the store; callers iterate by advancing
281    /// `from_event_id` on the returned cursor.
282    #[serde(default)]
283    pub limit: Option<usize>,
284}
285
286/// Page of events plus the cursor needed to continue reading.
287#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
288pub struct EventPage {
289    pub events: Vec<StoredEvent>,
290    /// Inclusive `from_event_id` to pass into the next read to resume.
291    /// `None` when the requested range was fully drained.
292    pub next_cursor: Option<EventId>,
293}
294
295#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
296pub struct SnapshotId(pub String);
297
298#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
299pub struct Snapshot {
300    pub id: SnapshotId,
301    pub session: SessionMeta,
302    pub events: Vec<StoredEvent>,
303    pub captured_at_ms: i64,
304    pub captured_at: String,
305}
306
307#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
308pub struct VerifyReport {
309    pub session_id: SessionId,
310    pub chain_root_hash: String,
311    pub event_count: usize,
312    pub signed_event_count: usize,
313    pub failures: Vec<VerifyFailure>,
314}
315
316#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
317pub struct VerifyFailure {
318    pub event_id: EventId,
319    pub reason: String,
320}
321
322/// Typed transient contention returned by a persistent backend.
323#[derive(Clone, Copy, Debug, PartialEq, Eq)]
324pub enum StoreContention {
325    /// Another SQLite connection owns the database write lock.
326    DatabaseBusy,
327    /// A shared-cache SQLite table lock blocks the operation.
328    DatabaseLocked,
329}
330
331impl std::fmt::Display for StoreContention {
332    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
333        match self {
334            Self::DatabaseBusy => f.write_str("database_busy"),
335            Self::DatabaseLocked => f.write_str("database_locked"),
336        }
337    }
338}
339
340/// Errors returned by every backend.
341#[derive(Clone, Debug, PartialEq, Eq)]
342pub enum StoreError {
343    NotFound(String),
344    AlreadyExists(String),
345    Conflict(String),
346    InvalidInput(String),
347    Tenant(String),
348    /// SQLite could not acquire a lock after applying its busy policy.
349    Contention {
350        /// Machine-readable lock-contention reason.
351        kind: StoreContention,
352        /// Backend diagnostic retained for operators.
353        message: String,
354    },
355    Backend(String),
356}
357
358impl std::fmt::Display for StoreError {
359    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
360        match self {
361            Self::NotFound(message) => write!(f, "not found: {message}"),
362            Self::AlreadyExists(message) => write!(f, "already exists: {message}"),
363            Self::Conflict(message) => write!(f, "conflict: {message}"),
364            Self::InvalidInput(message) => write!(f, "invalid input: {message}"),
365            Self::Tenant(message) => write!(f, "tenant: {message}"),
366            Self::Contention { kind, message } => {
367                write!(f, "retryable backend contention ({kind}): {message}")
368            }
369            Self::Backend(message) => write!(f, "backend error: {message}"),
370        }
371    }
372}
373
374impl std::error::Error for StoreError {}
375
376pub type StoreResult<T> = Result<T, StoreError>;
377
378/// Soft cap on a single page of events to keep response sizes bounded.
379/// Memory + sqlite backends apply this; callers iterate via cursors.
380pub const MAX_READ_BATCH: usize = 1_000;
381
382/// Optional processors a host can plug in. Mutation hooks run inline before
383/// persistence; redaction is also reapplied to public retrieval projections
384/// as defense in depth for older stored data.
385#[derive(Clone)]
386pub struct StoreHooks {
387    /// Applied to event payloads and headers before persistence and again
388    /// when events are read, snapshotted, or replayed.
389    pub redaction: Option<SharedEventRedactor>,
390    /// If set, every event is signed at append time. Without a signer
391    /// only the `Receipt` event minted by [`SessionStore::close`] is
392    /// signed (which is enough to verify the chain end-to-end).
393    pub event_signer: Option<SessionSigner>,
394    /// Required to mint receipts on `close`. Without this, `close`
395    /// still finalises the chain root hash but emits an unsigned
396    /// `Receipt` event.
397    pub receipt_signer: Option<SessionSigner>,
398    /// Default retention policy applied to new sessions when their
399    /// meta does not override it.
400    pub retention: RetentionPolicy,
401    /// Optional durable archive destination. The default
402    /// [`SessionStore::sweep_retention`] writes archived sessions and
403    /// tombstones here before the rows leave primary storage; see
404    /// [`super::retention::ArchiveSink`].
405    pub archive_sink: Option<SharedArchiveSink>,
406    /// Embedding implementation used to index and rank canonical redacted
407    /// transcript rows. The default deterministic lexical floor is
408    /// cross-platform and requires no model asset.
409    pub embedder: Arc<dyn Embedder>,
410}
411
412impl Default for StoreHooks {
413    fn default() -> Self {
414        Self {
415            redaction: None,
416            event_signer: None,
417            receipt_signer: None,
418            retention: RetentionPolicy::default(),
419            archive_sink: None,
420            embedder: default_embedder(),
421        }
422    }
423}
424
425#[async_trait]
426pub trait SessionStore: Send + Sync {
427    /// Plug-in processors configured for this store. The default
428    /// [`Self::sweep_retention`] reads `hooks.archive_sink` so the
429    /// retention loop can hand archived sessions to durable storage
430    /// without callers wiring the sink explicitly.
431    fn hooks(&self) -> &StoreHooks;
432
433    async fn create(&self, request: CreateSession) -> StoreResult<SessionMeta>;
434    async fn update(&self, session_id: &str, request: UpdateSession) -> StoreResult<SessionMeta>;
435    async fn describe(&self, session_id: &str) -> StoreResult<SessionMeta>;
436    async fn list(&self, filter: ListFilter) -> StoreResult<Vec<SessionMeta>>;
437    async fn append(&self, session_id: &str, event: AppendEvent) -> StoreResult<StoredEvent>;
438    async fn read(&self, session_id: &str, range: ReadRange) -> StoreResult<EventPage>;
439    async fn fork(
440        &self,
441        session_id: &str,
442        at_event_id: EventId,
443        child_id: Option<SessionId>,
444    ) -> StoreResult<ForkResult>;
445    async fn truncate(&self, session_id: &str, at_event_id: EventId)
446        -> StoreResult<TruncateResult>;
447    async fn snapshot(&self, session_id: &str) -> StoreResult<Snapshot>;
448    async fn replay(&self, snapshot_id: &SnapshotId) -> StoreResult<Snapshot>;
449    async fn close(&self, session_id: &str) -> StoreResult<StoredEvent>;
450    async fn soft_delete(&self, session_id: &str) -> StoreResult<SessionMeta>;
451    async fn hard_delete(&self, session_id: &str) -> StoreResult<()>;
452    async fn verify(&self, session_id: &str) -> StoreResult<VerifyReport>;
453    async fn search(&self, query: SearchQuery) -> StoreResult<SearchResponse>;
454
455    /// Sweep retention. Backends with native scheduling can override
456    /// to skip the default loop; the default sweeps all sessions
457    /// against the configured [`RetentionPolicy`] and routes archived
458    /// sessions + tombstones through `hooks().archive_sink` when set.
459    async fn sweep_retention(
460        &self,
461        policy: &RetentionPolicy,
462        now_ms: i64,
463    ) -> StoreResult<SweepReport> {
464        use tracing::Instrument as _;
465        let span = tracing::info_span!(
466            "harn.session.sweep_retention",
467            harn.session.sweep.archive_sink_configured = self.hooks().archive_sink.is_some(),
468            harn.session.sweep.archived = tracing::field::Empty,
469            harn.session.sweep.soft_deleted = tracing::field::Empty,
470            harn.session.sweep.hard_deleted = tracing::field::Empty,
471        );
472        let span_for_record = span.clone();
473        let sink = self.hooks().archive_sink.clone();
474        let result = async move {
475            let mut report = SweepReport::default();
476            let sessions = self.list(ListFilter::default()).await?;
477            for session in sessions {
478                if policy.should_hard_delete(&session, now_ms) {
479                    if let Some(sink) = sink.as_ref() {
480                        let tombstone = Tombstone {
481                            session_id: session.id.clone(),
482                            tenant_id: session.tenant_id.clone(),
483                            deleted_at_ms: now_ms,
484                            deleted_at: super::event::ms_to_rfc3339(now_ms),
485                            final_chain_root_hash: session.chain_root_hash.clone(),
486                            final_event_id: session.last_event_id,
487                        };
488                        sink.tombstone(&tombstone).await?;
489                        report.tombstoned += 1;
490                    }
491                    self.hard_delete(&session.id).await?;
492                    report.hard_deleted += 1;
493                } else if policy.should_soft_delete(&session, now_ms) {
494                    if policy.should_archive(&session, now_ms) {
495                        if let Some(sink) = sink.as_ref() {
496                            let events = read_all_events(self, &session.id).await?;
497                            sink.archive(&session, &events).await?;
498                            report.archived += 1;
499                        }
500                    }
501                    self.soft_delete(&session.id).await?;
502                    report.soft_deleted += 1;
503                }
504            }
505            Ok::<_, StoreError>(report)
506        }
507        .instrument(span)
508        .await?;
509        span_for_record.record("harn.session.sweep.archived", result.archived as i64);
510        span_for_record.record(
511            "harn.session.sweep.soft_deleted",
512            result.soft_deleted as i64,
513        );
514        span_for_record.record(
515            "harn.session.sweep.hard_deleted",
516            result.hard_deleted as i64,
517        );
518        Ok(result)
519    }
520}
521
522/// Atomic, idempotent ingestion for stores that accept external session data.
523///
524/// This remains separate from [`SessionStore`] so downstream backends do not
525/// need to implement migration semantics unless they expose import support.
526#[async_trait]
527pub trait SessionImporter: SessionStore {
528    async fn import(&self, request: ImportSession) -> StoreResult<ImportResult>;
529}
530
531/// Drain every event for a session via repeated paginated reads. Used
532/// by [`SessionStore::sweep_retention`] when shipping a session to the
533/// [`super::retention::ArchiveSink`].
534async fn read_all_events<S: SessionStore + ?Sized>(
535    store: &S,
536    session_id: &str,
537) -> StoreResult<Vec<StoredEvent>> {
538    let mut all = Vec::new();
539    let mut cursor: Option<EventId> = None;
540    loop {
541        let page = store
542            .read(
543                session_id,
544                ReadRange {
545                    from_event_id: cursor,
546                    to_event_id: None,
547                    limit: Some(MAX_READ_BATCH),
548                },
549            )
550            .await?;
551        let next = page.next_cursor;
552        all.extend(page.events);
553        match next {
554            Some(next_cursor) => cursor = Some(next_cursor),
555            None => break,
556        }
557    }
558    Ok(all)
559}
560
561#[derive(Clone, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
562pub struct SweepReport {
563    pub soft_deleted: usize,
564    pub hard_deleted: usize,
565    /// Sessions handed to [`super::retention::ArchiveSink::archive`]
566    /// because they crossed `min_age_before_archive_seconds`.
567    pub archived: usize,
568    /// Hard-deleted sessions whose final state was emitted as a
569    /// [`super::retention::Tombstone`] to the archive sink.
570    pub tombstoned: usize,
571}
572
573/// Dyn-dispatch alias so adapters can keep one `Arc<dyn SessionStore>`
574/// in their state without naming the concrete backend everywhere.
575pub type SharedSessionStore = Arc<dyn SessionStore>;
harn_session_store/store.rs

harn_session_store/
store.rs
