638 lines
29 KiB
TypeScript
638 lines
29 KiB
TypeScript
/**
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* Event-sourced session service: append-only session log, in-memory store, and
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* the derived LLM message history. Persistence is a plugin concern (subscribe
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* to `session/event`, drain on `session/flush`).
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*
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* @module @deepseek-ai/dsh-session
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*/
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import { Context, Service } from 'cordis'
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import { isAbsolute } from 'node:path'
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import { deepFreeze } from '@deepseek-ai/dsh-llm'
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import type { ContentBlock, Message, MessageSource } from '@deepseek-ai/dsh-llm'
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import { SESSION_FORMAT_VERSION, SessionId } from './types.ts'
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import type { ContextEnvelope, CreateSessionOptions, EpochHeader, SessionEvent, SessionEventMap, SessionEventType, SessionHeader, SurfaceIntent, SurfaceEventType } from './types.ts'
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import { isJsonValue } from './json.ts'
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import { SurfaceManager, isSurfaceEligibleType } from './surface.ts'
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import { foldRequestHeader } from './request-header.ts'
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export * from './types.ts'
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export { isJsonValue } from './json.ts'
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export type { JsonValue } from './json.ts'
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export { interruptedTurnClosers } from './repair.ts'
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export type { SurfaceNode } from './surface.ts'
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export { isSurfaceEvent, isSurfaceEligibleType } from './surface.ts'
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export { isToolPairingBalanced } from './tool-pairing.ts'
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export { applyHeaderDelta, canonicalHeader, diffHeader, foldRequestHeader, headerEquals } from './request-header.ts'
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declare module 'cordis' {
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interface Context {
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sessions: SessionStore
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}
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interface Events {
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/**
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* A session was created in the store.
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* @param session - the session just entered and announced.
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* @mode emit
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*/
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'session/created'(session: Session): void
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/**
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* An event was appended to a session log (sync, fire-and-forget). This is
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* the per-append feed a UI or invariant plugin tails.
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* @param session - the session whose log grew.
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* @param event - the appended event, exactly as recorded.
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* @mode emit
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*/
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'session/event'(session: Session, event: SessionEvent): void
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/**
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* Awaited durability checkpoint. The agent loop awaits
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* `ctx.parallel('session/flush', session)` at every turn end; persistence
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* plugins (JSONL, SQLite) drain their write-behind buffers here and on
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* fiber dispose. Awaited (parallel), not a waterfall: every listener runs
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* and the loop waits for all of them, but none can veto.
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* @param session - the session whose buffered events must reach durable storage.
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* @mode parallel
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*/
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'session/flush'(session: Session): Promise<void> | void
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}
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}
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/**
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* Renders a `context/message` or `steering/message` event as a tagged
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* synthetic user-role message (the system-reminder pattern: zero adapter
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* burden, models distinguish it from real user prompts by the envelope).
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*
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* Live-adapter review has validated the tagged-envelope rendering against
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* current DeepSeek behavior; provider-specific mismatches belong in that
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* adapter, not in the canonical session vocabulary.
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*/
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function renderTagged(tag: string, content: ContentBlock[], source: MessageSource): ContentBlock[] {
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const open = `<${tag} source=${JSON.stringify(source.kind)}>`
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const close = `</${tag}>`
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return [
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{ type: 'text', text: open },
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...content,
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{ type: 'text', text: close },
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]
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}
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/**
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* Render one context contribution exactly as it will appear in model history.
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* @param content - content blocks supplied by the context producer.
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* @param source - attribution used by the canonical context envelope.
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* @param envelope - canonical tagged framing or caller-owned raw framing.
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* @returns a detached block list ready for the derived model transcript.
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*/
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export function renderContextContent(
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content: ContentBlock[],
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source: MessageSource,
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envelope: ContextEnvelope = 'context',
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): ContentBlock[] {
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const cloned = structuredClone(content)
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return envelope === 'raw' ? cloned : renderTagged('context', cloned, source)
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}
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/**
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* An event-sourced session: an append-only log of {@link SessionEvent}s.
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*
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* Plain class (not a Service) — create instances via `ctx.sessions.create()`.
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* Seeding with an existing event log replays/forks a session.
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*/
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export class Session {
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private log: SessionEvent[] = []
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/** Set by the store so appends are observable; undefined when detached. */
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onAppend: ((event: SessionEvent) => void) | undefined
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/**
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* Derived surface — a cached linked list of message-producing events.
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* Lazily rebuilt from `surfaceOp` markers in the log; processes only new
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* events (delta) on each access — the log is append-only, so prior events
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* never change.
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* `append`. Undefined until first accessed (including after fork/seed).
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*/
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private _surface: SurfaceManager | undefined
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/** The surface linked list over this session's event log. */
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get surface(): SurfaceManager {
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if (!this._surface) this._surface = new SurfaceManager(this.log)
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return this._surface
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}
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/**
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* Immutable creation metadata (format version, cwd, lineage, seed boundary).
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* Supplied by the store via `ctx.sessions.create()`. When a `Session` is
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* constructed bare (tests, ad-hoc replay), a minimal header is synthesized
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* (stamped with the current {@link SESSION_FORMAT_VERSION}) so
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* `session.header` is always present. Kept out of the event log — it is a
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* storage concern, not replayable conversation state.
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*/
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readonly header: SessionHeader
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constructor(public readonly id: SessionId, seed?: SessionEvent[], header?: SessionHeader) {
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if (seed) {
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// Validate the seed to the SAME invariants `append` enforces, so a
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// replay/fork (`ctx.sessions.create(id, { seed })`) cannot construct a
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// live log that no persistence backend could store: each event's `data`
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// must be JSON-serializable, and `seq` must be contiguous from 0 (the
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// `seq = log.length` contract the whole system relies on). Without this,
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// a bad seed would surface only later as a backend rejection or a silent
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// divergence between the live log and disk.
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seed.forEach((event, index) => {
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if (event.seq !== index) {
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throw new Error(`seed event at index ${index} has seq ${event.seq} (expected ${index}); seed must be contiguous from 0`)
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}
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if (!isJsonValue(event.data)) {
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throw new Error(`seed event "${event.type}" (seq ${event.seq}) carries non-JSON-serializable data`)
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}
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// Surface-eligible events MUST carry a surfaceOp marker — the surface is
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// the sole source of derived history, so a marker-less message event
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// would load fine yet vanish from deriveMessages(). `append` enforces
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// this at compile time via its typed overload; a seed arrives as raw
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// SessionEvent[] (replay/fork/load), bypassing that, so re-check at
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// runtime here rather than silently resuming with empty history.
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if (isSurfaceEligibleType(event.type)
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&& (event as SessionEvent<SurfaceEventType>).surfaceOp === undefined) {
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throw new Error(`seed event "${event.type}" (seq ${event.seq}) is surface-eligible but carries no surfaceOp marker`)
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}
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})
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// Deep-clone each seed event, NOT just the array: the seed events and
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// their `data` are still owned by the caller (or the source session of a
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// fork), so keeping the references would let a post-create mutation of the
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// original rewrite this session's durable log — or reintroduce a
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// non-JSON-serializable value AFTER the validation above. Snapshotting at
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// the boundary makes `session.events` independent and keeps it equal to
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// what was validated. Serializability is guaranteed by the check above, so
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// structuredClone can never hit a non-cloneable value here.
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this.log = seed.map(event => structuredClone(event))
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}
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this.header = header ?? { version: SESSION_FORMAT_VERSION, id, createdAt: Date.now() }
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}
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/**
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* The append-only event log, exposed live by reference (readonly-typed, not
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* a snapshot): later appends are visible through the same array.
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*/
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get events(): readonly SessionEvent[] {
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return this.log
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}
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/** The next event's sequence number — always the log length (the `seq = log.length` contiguity contract). */
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get seq(): number {
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return this.log.length
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}
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/**
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* Append one typed event to the log and synchronously notify observers via
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* `onAppend`. The hot path never blocks on I/O — persistence plugins buffer
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* asynchronously.
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*
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* @param type - The event type (key of {@link SessionEventMap}).
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* @param data - The event payload; must be JSON-serializable.
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* @param opts - Surface metadata: `surfaceOp` controls how the event enters
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* the surface linked list; `sourceEventSeqs` records provenance (the seq
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* numbers of events this one derives from). REQUIRED for
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* {@link SurfaceEventType} events (every message-producing event must
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* declare how it joins the surface, the sole source of derived history) and
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* rejected by the compiler for non-surface types like `turn/start` or
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* `assistant/chunk`.
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* @returns the logged event — its assigned `seq`/`time` plus the SNAPSHOT of
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* `data` that entered the log, so reading `event.data` back sees the logged
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* value, never the caller's still-mutable input.
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* @throws if `data` is not losslessly JSON-serializable (BigInt, function,
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* symbol, undefined, non-finite number, circular ref, or an exotic object
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* like Map/Set/Date). The event log is the durable source of truth, so this
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* invariant is enforced at the source — a bad event never enters the log,
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* keeping `session.events` always equal to what a backend can persist. The
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* throw surfaces at the buggy caller's append site, not asynchronously in a
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* backend flush.
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*/
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append<T extends SessionEventType>(
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type: T,
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data: SessionEventMap[T],
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...opts: T extends SurfaceEventType ? [opts: SurfaceIntent] : []
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): SessionEvent<T> {
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if (!isJsonValue(data)) {
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throw new Error(`session event "${type}" carries non-JSON-serializable data`)
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}
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const surfaceOpts: SurfaceIntent | undefined = opts[0]
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// Surface-eligible events MUST carry a surfaceOp marker — the surface is the
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// sole source of derived history, so a marker-less message event would be
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// logged yet vanish from deriveMessages(). The typed `opts` overload makes
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// the marker mandatory only when `T` is a SPECIFIC SurfaceEventType literal;
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// when `T` widens to the SessionEventType union (a caller iterating raw
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// events: `for (const e of log) append(e.type, e.data)`), the conditional
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// rest collapses to optional and the compiler stops enforcing it. Re-check
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// at runtime so that loophole can't silently drop history.
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if (isSurfaceEligibleType(type) && surfaceOpts?.surfaceOp === undefined) {
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throw new Error(`session event "${type}" is surface-eligible and requires a surfaceOp marker`)
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}
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// Snapshot `data` into the log, NOT the caller's reference: the validation
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// above proves it is JSON-serializable AT THIS MOMENT, but the caller still
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// owns the object and could mutate it afterwards (before a persistence
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// flush, or permanently in the in-memory history) — making `session.events`
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// diverge from the value that passed validation, or reintroducing a
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// non-serializable value. Cloning here keeps the log equal to what was
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// validated. structuredClone is safe because serializability was just
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// checked. The returned event carries the SAME snapshot, so a caller reading
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// back `event.data` sees the logged value, not its own mutable input.
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//
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// Surface metadata is snapshot separately: sourceEventSeqs (number[] —
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// primitives, so array spread is a complete copy) and surfaceOp (a string
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// primitive, or cloned if it's a replace object).
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// Build the event shape with conditional surface fields via spreading.
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// The result is cast through `unknown` because the conditional spreads
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// produce an intersection type that the assignability checker can't
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// narrow to a specific discriminated-union member when T is generic.
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// This is a safe internal boundary: data was validated above, and
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// surface metadata was snapshot from primitive/clone-safe values.
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const event = {
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type,
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seq: this.log.length,
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time: Date.now(),
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data: structuredClone(data),
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...surfaceOpts?.sourceEventSeqs !== undefined ? { sourceEventSeqs: [...surfaceOpts.sourceEventSeqs] } : {},
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...surfaceOpts?.surfaceOp !== undefined ? {
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surfaceOp: typeof surfaceOpts.surfaceOp === 'string' ? surfaceOpts.surfaceOp : structuredClone(surfaceOpts.surfaceOp),
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} : {},
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} as unknown as SessionEvent<T>
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this.log.push(event as unknown as SessionEvent)
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this.onAppend?.(event as unknown as SessionEvent)
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return event
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}
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/** Cached fold of the request-header events — see {@link requestHeader}. */
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private headerFold: EpochHeader | undefined
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/** Log position (events consumed) the header fold has reached. */
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private headerFoldSeq = 0
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/**
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* The {@link EpochHeader} in force after the log's last header event — the
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* header the NEXT request will be compared against — or undefined before
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* the first `request/header` snapshot. The live, incrementally-maintained
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* form of `foldRequestHeader(session.events)`: each header event is folded
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* once, when first seen, so a per-step read costs O(new events).
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* @returns the folded header, or undefined when no header event exists yet.
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*/
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requestHeader(): EpochHeader | undefined {
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if (this.headerFoldSeq < this.log.length) {
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// Frozen on update: the fold is session state exposed by reference — a
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// consumer mutating it in place (instead of building a replacement)
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// would desync every later comparison against the log, so mutation
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// throws instead.
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this.headerFold = deepFreeze(foldRequestHeader(this.log.slice(this.headerFoldSeq), this.headerFold))
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this.headerFoldSeq = this.log.length
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}
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return this.headerFold
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}
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/** The derived-message cache: frozen projections, extended per unseen node. */
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private derived: Message[] = []
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/** Surface position (nodes projected) the cache has reached. */
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private derivedNodes = 0
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/** {@link SurfaceManager.replaceGeneration} the cache was built under. */
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private derivedGeneration = 0
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/**
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* Derive the LLM message history by walking the session surface — the linked
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* list of message-producing events maintained by `surfaceOp` markers. The
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* surface is the single source of derived history: every message-producing
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* append records its `surfaceOp`, so a raw event with no marker (a chunk, a
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* turn boundary) is correctly absent, and a compaction `replace` deletes the
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* shadowed nodes from the derivation. The projection rules are
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* {@link deriveEventMessage}, folded per node.
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*
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* CACHED: each surface node is projected exactly once, when first seen — a
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* call costs O(new nodes), and a surface rewrite (a `replace`;
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* {@link SurfaceManager.replaceGeneration}) rebuilds. The returned array is
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* a fresh snapshot per call (later appends never grow an array a caller
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* already holds); the `Message` objects in it are SHARED and **deep-frozen**
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* — cloned once off the log at projection time, so consumers can never
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* mutate logged data, and mutation attempts throw instead of silently
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* diverging replay from history.
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* @returns a fresh array of the shared, frozen derived history.
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*/
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deriveMessages(): Message[] {
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const nodes = this.surface.nodes
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const generation = this.surface.replaceGeneration
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if (generation !== this.derivedGeneration) {
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this.derived = []
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this.derivedNodes = 0
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this.derivedGeneration = generation
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}
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for (const node of nodes.slice(this.derivedNodes)) {
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// Surface nodes are built from this.log — node.seq is always a valid
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// index by construction. The non-null assertion expresses that invariant.
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// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
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const msg = this.deriveEventMessage(this.log[node.seq]!)
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// A surface node is one of the five message-producing types, but an
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// empty-content assistant/message (a max-tokens step that hosts only
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// usage) derives to null and must not enter the transcript.
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if (msg) this.derived.push(deepFreeze(msg))
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}
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this.derivedNodes = nodes.length
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return [...this.derived]
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}
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/**
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* Project a single event into the LLM message it derives to, or null when
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* it produces none — a non-surface event (chunk, boundary, log-only record)
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* or an empty-content assistant/message (which exists only to host usage).
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* The per-node pure function {@link deriveMessages} folds over the surface;
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* an external reconstructor (or the dev invariant) folds the same function
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* over a log prefix's surface to rebuild the exact messages any request was
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* built from (the reconstructability RFC). The returned `content` is
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* deep-cloned off the logged event: the log is append-only by contract, so
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* no live reference to logged data leaves this boundary.
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* @param event - the event to project.
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* @returns the derived message, or null when the event produces none.
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*/
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deriveEventMessage(event: SessionEvent): Message | null {
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// Intentionally non-exhaustive: only message-producing events derive
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// history; turn/step boundaries, chunks, usage, and errors are
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// trace/replay data.
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switch (event.type) {
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case 'user/message': {
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return { role: 'user', content: structuredClone(event.data.content) }
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}
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case 'assistant/message': {
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// Skip an empty-content assistant/message: it exists only to host a
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// max-tokens step's usage and must not inject a content-less assistant
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// turn into the provider transcript.
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if (event.data.content.length === 0) return null
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return { role: 'assistant', content: structuredClone(event.data.content) }
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}
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case 'tool/result': {
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const { callId, content, isError } = event.data
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return {
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role: 'user',
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content: [{ type: 'tool-result', toolCallId: callId, content: structuredClone(content), isError }],
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}
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}
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case 'context/message': {
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const { content, source, envelope } = event.data
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return { role: 'user', content: renderContextContent(content, source, envelope) }
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}
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case 'steering/message': {
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const { content, source } = event.data
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return { role: 'user', content: renderTagged('steering', structuredClone(content), source) }
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}
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default:
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// A non-surface event (boundary, chunk, log-only record) projects to
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// no message. Merge-extensible union: no assertNever here.
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return null
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}
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}
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}
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/** A fork source: either the live session object or its live store id. */
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export type SessionForkSource = Session | SessionId
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/**
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* Rejection codes for session forking: the fork source id is unknown to the
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* live store (`SESSION_NOT_FOUND`) or names a session object that is not the
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* store's live instance (`SESSION_NOT_LIVE`); the requested child id is
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* already taken (`SESSION_ALREADY_EXISTS`); the boundary is not a contiguous
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* existing seq (`INVALID_BOUNDARY`); or the boundary event is not a
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* `turn/end` — a fork must cut on a closed turn (`OPEN_TURN`).
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*/
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export type SessionForkErrorCode =
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| 'SESSION_NOT_FOUND'
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| 'SESSION_NOT_LIVE'
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| 'SESSION_ALREADY_EXISTS'
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| 'INVALID_BOUNDARY'
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| 'OPEN_TURN'
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/** Typed error for session fork rejections. */
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export class SessionForkError extends Error {
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constructor(message: string, public readonly code: SessionForkErrorCode) {
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super(message)
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this.name = 'SessionForkError'
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}
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}
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/**
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* In-memory session store (`ctx.sessions`).
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*
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* Persistence is intentionally not implemented here — persistence plugins
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* subscribe to `session/event` and flush on `session/flush` / dispose.
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*/
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export class SessionStore extends Service {
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private store = new Map<SessionId, Session>()
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private counter = 0
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constructor(ctx: Context) {
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super(ctx, 'sessions')
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}
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/**
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* Create a session owned by the calling fiber: disposing that fiber stops
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* event notification and removes the session from the store. `options.seed`
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* populates the session with a copy of those events (replay/fork);
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* `options.meta` attaches creation metadata (validated absolute `cwd`,
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* `parentSession` lineage) as the immutable {@link SessionHeader} (the store
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* fills `version`/`id`/`createdAt`).
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*
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* For an agent whose session must be torn down IN ORDER with its loop (so the
|
|
* loop's final flush is captured before `onAppend` detaches), do NOT use this
|
|
* — fold the session lifecycle into the agent's own effect via
|
|
* {@link prepare} + {@link enter} + {@link announce} (see `dsh-agent-loop`'s
|
|
* `startOwned`).
|
|
*
|
|
* @param id - the session id; omitted, the store mints `session-<n>`.
|
|
* @param options - seed events and/or creation metadata for the header.
|
|
* @returns the live session, already entered and announced.
|
|
* @throws if a session with `id` already exists, or if `meta.cwd` is a
|
|
* non-absolute path (storage backends key directories off it).
|
|
*/
|
|
create(id?: SessionId, options?: CreateSessionOptions): Session {
|
|
const session = this.prepare(id, options)
|
|
// Single effect owned by the calling fiber. Yield the detach BEFORE
|
|
// announcing so a throwing `session/created` listener rolls the attach back
|
|
// (the generator effect disposes already-yielded disposers on a throw)
|
|
// instead of leaking the store entry + onAppend.
|
|
this.ctx.effect(function* (this: SessionStore) {
|
|
yield this.enter(session)
|
|
this.announce(session)
|
|
}.bind(this), 'sessions.create()')
|
|
return session
|
|
}
|
|
|
|
/**
|
|
* Build a session WITHOUT entering it into the store — validate the id/cwd and
|
|
* construct the {@link Session} (with its immutable {@link SessionHeader}).
|
|
* Pairs with {@link enter} + {@link announce}: a caller that owns a composite
|
|
* `ctx.effect` (the agent factory) folds the session lifecycle into that ONE
|
|
* effect so a fiber unload tears the session + agent down as a single ORDERED
|
|
* chain rather than as racing sibling effects — which would detach `onAppend`
|
|
* before the loop's closing `session/flush`, dropping the closing events.
|
|
*
|
|
* @param id - the session id; omitted, the store mints `session-<n>`.
|
|
* @param options - seed events and/or creation metadata for the header.
|
|
* @returns the constructed session, NOT yet in the store.
|
|
* @throws if a session with `id` already exists, or if `meta.cwd` is a
|
|
* non-absolute path.
|
|
*/
|
|
prepare(id?: SessionId, options?: CreateSessionOptions): Session {
|
|
const sessionId = SessionId(id ?? `session-${++this.counter}`)
|
|
if (this.store.has(sessionId)) throw new Error(`session "${sessionId}" already exists`)
|
|
const cwd = options?.meta?.cwd
|
|
if (cwd !== undefined && !isAbsolute(cwd)) {
|
|
throw new Error(`session cwd must be an absolute path, got "${cwd}"`)
|
|
}
|
|
const header: SessionHeader = {
|
|
version: SESSION_FORMAT_VERSION,
|
|
id: sessionId,
|
|
createdAt: options?.meta?.createdAt ?? Date.now(),
|
|
...cwd !== undefined ? { cwd } : {},
|
|
...options?.meta?.parentSession !== undefined ? { parentSession: options.meta.parentSession } : {},
|
|
...options?.meta?.seedLength !== undefined ? { seedLength: options.meta.seedLength } : {},
|
|
}
|
|
return new Session(sessionId, options?.seed, header)
|
|
}
|
|
|
|
/**
|
|
* Enter a {@link prepare}d session into the store: wire `onAppend` →
|
|
* `session/event` and add it to the store. Returns the DETACH disposer
|
|
* (`onAppend = undefined` + store removal). Does NOT emit `session/created` —
|
|
* the caller yields this disposer inside its effect and THEN calls
|
|
* {@link announce}, so a throwing `session/created` listener rolls the attach
|
|
* back instead of leaking it.
|
|
*
|
|
* Re-checks the id for a duplicate: `prepare` and `enter` are public
|
|
* cross-package primitives and a caller may interleave arbitrary work (or
|
|
* another create) between them, so a stale prepared session must NOT overwrite
|
|
* a live store entry of the same id — its detach disposer would later delete
|
|
* the REAL session. The {@link create} convenience and the agent factory call
|
|
* the two back-to-back so they never trip this, but the public seam cannot
|
|
* assume that.
|
|
*
|
|
* @param session - a {@link prepare}d session not yet in the store.
|
|
* @returns the detach disposer (`onAppend = undefined` + store removal).
|
|
* @throws if a session with this id is already in the store.
|
|
*/
|
|
enter(session: Session): () => void {
|
|
if (this.store.has(session.id)) throw new Error(`session "${session.id}" already exists`)
|
|
session.onAppend = (event) => { this.ctx.emit('session/event', session, event) }
|
|
this.store.set(session.id, session)
|
|
return () => {
|
|
session.onAppend = undefined
|
|
this.store.delete(session.id)
|
|
}
|
|
}
|
|
|
|
/** Emit `session/created` for an {@link enter}ed session. Separate from
|
|
* {@link enter} so the caller can yield the detach disposer first (rollback
|
|
* safety — see {@link enter}).
|
|
* @param session - the entered session to announce to listeners. */
|
|
announce(session: Session): void {
|
|
this.ctx.emit('session/created', session)
|
|
}
|
|
|
|
/**
|
|
* Look up a live session.
|
|
* @param id - the session id to look up.
|
|
* @returns the session, or undefined when no live session has that id.
|
|
*/
|
|
get(id: SessionId): Session | undefined {
|
|
return this.store.get(id)
|
|
}
|
|
|
|
/**
|
|
* All live sessions, in creation order.
|
|
* @returns a fresh array; mutating it does not affect the store.
|
|
*/
|
|
list(): Session[] {
|
|
return [...this.store.values()]
|
|
}
|
|
|
|
/**
|
|
* Create a live child session from a turn-enclosed prefix of a live source.
|
|
* `boundary` is an inclusive source event seq; omitted means the source's
|
|
* current last event. A non-empty selected slice must end at `turn/end`.
|
|
*
|
|
* @param source - Live source session object or id.
|
|
* @param boundary - Inclusive source event seq to fork through; omitted means
|
|
* the source's current last event, and omitted on an empty source forks an
|
|
* empty child.
|
|
* @param childSessionId - Optional child session id; omitted delegates to
|
|
* `SessionStore`'s id policy.
|
|
* @returns The created live child session.
|
|
*/
|
|
fork(source: SessionForkSource, boundary?: number, childSessionId?: SessionId): Session {
|
|
if (childSessionId !== undefined && this.get(childSessionId) !== undefined) {
|
|
throw new SessionForkError(`session "${childSessionId}" already exists`, 'SESSION_ALREADY_EXISTS')
|
|
}
|
|
const liveSource = this._resolveForkSource(source)
|
|
const seed = this._forkSeed(liveSource, boundary)
|
|
return this.create(childSessionId, {
|
|
seed,
|
|
meta: {
|
|
...liveSource.header.cwd !== undefined ? { cwd: liveSource.header.cwd } : {},
|
|
parentSession: liveSource.id,
|
|
seedLength: seed.length,
|
|
},
|
|
})
|
|
}
|
|
|
|
private _forkSeed(session: Session, requestedBoundary: number | undefined): SessionEvent[] {
|
|
const events = session.events
|
|
const lastEvent = events.at(-1)
|
|
let boundary: number
|
|
if (requestedBoundary !== undefined) {
|
|
boundary = requestedBoundary
|
|
} else {
|
|
if (lastEvent === undefined) return []
|
|
boundary = lastEvent.seq
|
|
}
|
|
if (!Number.isSafeInteger(boundary) || boundary < 0) {
|
|
throw new SessionForkError(
|
|
`fork boundary for session "${session.id}" must be a non-negative safe integer, got ${String(boundary)}`,
|
|
'INVALID_BOUNDARY',
|
|
)
|
|
}
|
|
if (boundary >= events.length) {
|
|
const lastSeq = events.at(-1)?.seq
|
|
throw new SessionForkError(
|
|
`fork boundary ${boundary} does not exist in session "${session.id}" (last seq: ${lastSeq ?? 'none'})`,
|
|
'INVALID_BOUNDARY',
|
|
)
|
|
}
|
|
|
|
const boundaryEvent = events[boundary]
|
|
if (boundaryEvent === undefined || boundaryEvent.seq !== boundary) {
|
|
throw new SessionForkError(
|
|
`fork boundary ${boundary} does not match a contiguous event seq in session "${session.id}"`,
|
|
'INVALID_BOUNDARY',
|
|
)
|
|
}
|
|
if (boundaryEvent.type !== 'turn/end') {
|
|
throw new SessionForkError(
|
|
`fork boundary ${boundary} in session "${session.id}" must be turn/end, got ${boundaryEvent.type}`,
|
|
'OPEN_TURN',
|
|
)
|
|
}
|
|
|
|
return events.slice(0, boundary + 1).map(event => structuredClone(event))
|
|
}
|
|
|
|
private _resolveForkSource(source: SessionForkSource): Session {
|
|
if (typeof source === 'string') {
|
|
const session = this.get(source)
|
|
if (session === undefined) throw new SessionForkError(`session "${source}" not found`, 'SESSION_NOT_FOUND')
|
|
return session
|
|
}
|
|
|
|
const live = this.get(source.id)
|
|
if (live === undefined) {
|
|
throw new SessionForkError(`session "${source.id}" not found`, 'SESSION_NOT_FOUND')
|
|
}
|
|
if (live !== source) throw new SessionForkError(`session "${source.id}" is not the live store instance`, 'SESSION_NOT_LIVE')
|
|
return source
|
|
}
|
|
|
|
}
|
|
|
|
export default SessionStore
|