/**
 * GC daemon expressed as a supervised daemon subsystem.
 *
 * Wraps the GC bootstrap logic (`bootstrapDaemon`, crash recovery, missed-run
 * recovery, and the node-cron schedule) in the uniform
 * `start → healthProbe → shutdown` lifecycle from `@cleocode/contracts/daemon`
 * so the `@cleocode/runtime` `SubsystemRegistry` can drive it identically to
 * every other long-running concern (Studio supervision, the web server, …).
 *
 * Design constraints
 * ------------------
 * `@cleocode/core` CANNOT depend on `@cleocode/runtime` (runtime already
 * depends on core). To remain dependency-cycle free this module imports only
 * the pure type contracts from `@cleocode/contracts` and returns a plain
 * frozen object that satisfies the `Subsystem<GcSubsystemContext>` interface
 * without calling `defineSubsystem()` (a runtime-layer factory). A caller that
 * holds a `SubsystemRegistry` (from `@cleocode/runtime/daemon`) simply calls
 * `registry.register(createGcSubsystem(cleoDir))` — the frozen shape is
 * identical to what `defineSubsystem` returns and the registry types accept it.
 *
 * Thread-through context
 * ----------------------
 * `start()` returns a {@link GcSubsystemContext} that is threaded into
 * `shutdown()` by the registry (same pattern as `GatewaySubsystemContext`
 * in `@cleocode/runtime/gateway`). This lets `shutdown()` cancel the exact
 * cron task that `start()` scheduled without requiring module-level mutable
 * state.
 *
 * @see packages/core/src/gc/daemon.ts — standalone bootstrap / spawn helpers
 * @see packages/runtime/src/daemon/define-subsystem.ts — `defineSubsystem` factory
 * @see packages/runtime/src/gateway/daemon-subsystem.ts — reference implementation
 *
 * @packageDocumentation
 * @module @cleocode/core/gc
 *
 * @task T11503 (R5-T1)
 * @task T11504 (R5-T2)
 * @epic T11256
 * @saga T11243 SG-RUNTIME-UNIFICATION
 */
import type { Subsystem } from '@cleocode/contracts';
/**
 * The live context `start()` returns and the registry threads into
 * `shutdown()`. Carries the scheduled cron task so `shutdown()` can destroy
 * exactly the task that `start()` created.
 */
export interface GcSubsystemContext {
    /** The OS pid of this daemon process (set at subsystem start). */
    readonly pid: number;
    /** The ISO-8601 timestamp when this subsystem started. */
    readonly startedAt: string;
    /**
     * The scheduled cron task. `ScheduledTask` is the node-cron return value.
     * Typed as the minimal destroy surface so callers do not need to import
     * node-cron types.
     */
    readonly cronTask: {
        destroy: () => void;
    };
    /** Count of GC runs performed since subsystem start. */
    runs: number;
}
/**
 * Create a GC cron-daemon expressed as a uniform daemon subsystem.
 *
 * The returned object is a frozen `Subsystem<GcSubsystemContext>` that any
 * `SubsystemRegistry` (from `@cleocode/runtime/daemon`) can `register()`.
 *
 * Lifecycle
 * ---------
 * - `start(cleoDir)` — reads gc-state.json, performs crash recovery
 *   (resumes `pendingPrune` if non-empty), performs missed-run recovery (runs
 *   GC immediately if elapsed > 24 h), then schedules the daily cron job.
 *   Returns a {@link GcSubsystemContext} for health-probe and shutdown.
 * - `healthProbe()` — reports a single {@link SubsystemHealth} row keyed on
 *   `child_id: 'gc'`; `running` while the cron task is active, with a `detail`
 *   summarising run count and last-run timestamp.
 * - `shutdown(context)` — destroys the cron task so the daemon process can
 *   exit cleanly.
 *
 * @param cleoDir - Absolute path to the `.cleo/` directory for this project.
 * @returns A frozen `Subsystem<GcSubsystemContext>`.
 *
 * @example
 * ```ts
 * // In the daemon process:
 * import { SubsystemRegistry } from '@cleocode/runtime/daemon';
 * import { createGcSubsystem } from '@cleocode/core/gc/gc-subsystem.js';
 *
 * const registry = new SubsystemRegistry();
 * registry.register(createGcSubsystem('/home/user/.local/share/cleo/project/abc/.cleo'));
 * await registry.startAll();
 * ```
 */
export declare function createGcSubsystem(cleoDir: string): Subsystem<GcSubsystemContext>;
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