/**
 * GC State — Persistent crash-recovery state for the autonomous GC daemon.
 *
 * Stored in `.cleo/gc-state.json` (plain JSON, not SQLite) to avoid
 * SQLite WAL conflicts between the long-running daemon process and the
 * main CLEO CLI process. Human-readable for debugging.
 *
 * The file is gitignored (see .gitignore §.cleo/ section) and created empty
 * by `cleo init`. It is NOT included in `cleo backup restore` scope because
 * it is ephemeral operational state — only the `daemonPid` and `lastRunAt`
 * fields survive between process restarts.
 *
 * @see ADR-047 — Autonomous GC and Disk Safety
 * @task T731
 * @epic T726
 */
/** Schema version for gc-state.json. Bump on breaking field changes. */
export declare const GC_STATE_SCHEMA_VERSION: "1.0";
/**
 * Persistent GC daemon state written to `.cleo/gc-state.json`.
 *
 * Design principles:
 * - `pendingPrune` enables idempotent crash recovery: populate BEFORE deletion,
 *   clear each entry AFTER successful deletion, clear entirely when job completes.
 * - `diskThresholdBreached` is a sticky flag: cleared only when disk drops
 *   below the WATCH tier (70%).
 * - `escalationNeeded` is set by the daemon when disk is in WARN/URGENT range;
 *   cleared by the CLI after displaying the escalation banner.
 */
export interface GCState {
    /** JSON schema version for forward-compatibility checks. */
    schemaVersion: typeof GC_STATE_SCHEMA_VERSION;
    /** ISO-8601 timestamp of last COMPLETED GC run. null = never run. */
    lastRunAt: string | null;
    /** Outcome of the last GC run. */
    lastRunResult: 'success' | 'partial' | 'failed' | null;
    /** Bytes freed in the last completed GC run. */
    lastRunBytesFreed: number;
    /**
     * Paths queued for deletion but not yet deleted.
     * Written BEFORE starting deletion; cleared entry-by-entry on success.
     * Enables idempotent crash recovery on daemon restart.
     */
    pendingPrune: string[] | null;
    /** Number of consecutive GC failures. Triggers escalation banner after 3. */
    consecutiveFailures: number;
    /** Sticky flag: true when disk is ≥ WATCH tier (70%). Cleared when disk < 70%. */
    diskThresholdBreached: boolean;
    /** Current disk usage percentage (0–100) from the last GC run. */
    lastDiskUsedPct: number | null;
    /**
     * Escalation banner flag. Set by daemon when disk is in WARN+ range.
     * Cleared by CLI after displaying the banner to the user.
     */
    escalationNeeded: boolean;
    /** Escalation reason shown in the CLI banner. */
    escalationReason: string | null;
    /** PID of the currently running daemon process. null = daemon not running. */
    daemonPid: number | null;
    /** ISO-8601 timestamp when the daemon was last started. */
    daemonStartedAt: string | null;
}
/** Default (empty) GC state for fresh initialisation. */
export declare const DEFAULT_GC_STATE: GCState;
/**
 * Read the GC state from disk.
 *
 * Returns the default state if the file does not exist or is malformed.
 * Never throws — GC state file absence is not an error condition.
 *
 * @param statePath - Absolute path to gc-state.json
 * @returns Parsed GC state, merged with defaults for any missing fields
 */
export declare function readGCState(statePath: string): Promise<GCState>;
/**
 * Write the GC state to disk atomically via tmp-then-rename.
 *
 * Atomic write prevents partial reads if the daemon crashes mid-write.
 * Idempotent: safe to call multiple times.
 *
 * @param statePath - Absolute path to gc-state.json
 * @param state - GC state to persist
 */
export declare function writeGCState(statePath: string, state: GCState): Promise<void>;
/**
 * Patch a subset of fields in the GC state file.
 *
 * Convenience wrapper: reads current state, merges patch, writes back.
 *
 * @param statePath - Absolute path to gc-state.json
 * @param patch - Partial state to merge over the existing state
 */
export declare function patchGCState(statePath: string, patch: Partial<GCState>): Promise<GCState>;
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