import { type ActivationKey, type EffectLedger, type SessionAdapter, type SessionCheckpoint, type SessionSeed } from "./adapter.ts";
import type { AppendedSessionEvent, SessionEvent } from "./events.ts";
import { type Clock, InMemorySessionLog, type SessionLog, type SqliteDb, SqliteSessionLog } from "./log.ts";
export interface SessionBackendOptions {
    /** Injectable clock for deterministic checkpoint timestamps. Default {@link systemClock}. */
    clock?: Clock;
    /** Injectable checkpoint-id generator (deterministic tests). Default `crypto.randomUUID`. */
    newCheckpointId?: () => string;
}
/**
 * A session adapter bound to one activation and one incarnation. Constructing it
 * takes the lease at `incarnation` (advancing the fence), so a re-lease at a
 * higher incarnation immediately fences every prior one — a subsequent `emit`
 * from an older adapter throws {@link StaleIncarnationError}.
 */
export declare class SessionBackend implements SessionAdapter {
    #private;
    readonly key: ActivationKey;
    readonly incarnation: number;
    constructor(log: SessionLog, key: ActivationKey, incarnation: number, options?: SessionBackendOptions);
    /** The offset the next `emit` will assign. */
    get nextOffset(): number;
    emit(event: SessionEvent): AppendedSessionEvent;
    checkpoint(commitSha: string, effectLedger: EffectLedger): SessionCheckpoint;
    restore(fromCheckpoint?: string): SessionSeed;
}
/**
 * Open a session adapter over an in-memory reference log. Pass a shared
 * {@link InMemorySessionLog} across incarnations of the same activation so the
 * fence and events persist across a re-lease (the reference resume scenario);
 * omit it for a throwaway single-incarnation log.
 */
export declare function openInMemorySession(key: ActivationKey, incarnation: number, options?: SessionBackendOptions & {
    log?: InMemorySessionLog;
}): {
    backend: SessionBackend;
    log: InMemorySessionLog;
};
/** Open a session adapter over the durable SQLite log. Applies the schema idempotently. */
export declare function openSqliteSession(db: SqliteDb, key: ActivationKey, incarnation: number, options?: SessionBackendOptions): {
    backend: SessionBackend;
    log: SqliteSessionLog;
};