export interface JsonRepoOptions<T> {
    filePath: string;
    defaultValue: () => T;
    /** Optional migration function. Called on every disk read; use to normalise legacy shapes without zod. */
    migrate?: (raw: unknown) => T;
}
export declare class JsonRepository<T> {
    private readonly opts;
    private cache;
    private readonly mutex;
    /** Fires the first-call orphan sweep exactly once per instance, on the first I/O op. */
    private sweepPromise;
    constructor(opts: JsonRepoOptions<T>);
    /**
     * Delete any `<basename>.tmp.*` siblings of filePath.
     * `atomicWrite` (tmp → rename) can orphan its tmp when the process is SIGTERM'd mid-write
     * (e.g., daemon hot-reload landing during a long write). On next boot this sweeper clears them.
     * Runs lazily on the first read/mutate so repos that are constructed but never used pay nothing.
     */
    private sweepOrphans;
    private ensureSwept;
    /**
     * Return the current value.
     * Cache hit: zero I/O. Cache miss: reads file, parses JSON, applies migrate if present.
     * Missing file returns and caches defaultValue().
     */
    read(): Promise<T>;
    /**
     * Atomically persist `next` and update the in-memory cache.
     * Does not hold the mutex — callers that need serialization should use mutate().
     */
    write(next: T): Promise<void>;
    /**
     * Wait until any in-flight `mutate()` has fully completed (tmp written + rename landed).
     * Acquire-release the mutex without doing any work; FIFO ordering guarantees that once this
     * resolves, every operation enqueued before flush() has finished.
     * Intended for graceful SIGTERM handlers to drain writes before `process.exit(0)`.
     */
    flush(): Promise<void>;
    /**
     * Mutex-serialized read-modify-write.
     * `fn` receives the current value and must return `{ next, result }`.
     * Returns the `result` value from `fn`.
     */
    mutate<R>(fn: (cur: T) => {
        next: T;
        result: R;
    }): Promise<R>;
    /** Drop the in-memory cache so the next read() fetches from disk. */
    invalidate(): void;
}