import type { IPicGo, MultipartCompletedPart, MultipartSession } from '../../../../types';
/**
 * Persistent storage for in-flight multipart upload sessions — used to support resume
 * across process crashes / restarts.
 *
 * Layout: a single JSON file `picgo-cloud-multipart-pending.json` under ctx.baseDir.
 * The top level carries a `v: 1` schema version for future migrations. Sessions are keyed
 * by `${userId}:${fingerprint}` so accounts switched on the same machine cannot collide.
 *
 * Design principle: missing file / corrupt JSON / write failure → silently degrade to
 * "no resume". Persistence is nice-to-have, never a hard requirement; storage failures
 * must never block the actual upload flow.
 */
export declare class MultipartStorage {
    private readonly ctx;
    constructor(ctx: IPicGo);
    /** Look up a session by (userId, fingerprint). Returns null if missing / expired / unreadable. */
    get(userId: string, fingerprint: string): MultipartSession | null;
    /** Write or replace a session. Write failures are swallowed (resume is not a hard requirement). */
    set(userId: string, fingerprint: string, session: MultipartSession): void;
    /** Remove a session by (userId, fingerprint). No-op if the entry doesn't exist. */
    remove(userId: string, fingerprint: string): void;
    /** Append a completed part; if the same partNumber already exists it is replaced (retry case). */
    appendCompletedPart(userId: string, fingerprint: string, part: MultipartCompletedPart): void;
    /** Sweep sessions whose createdAt is older than (now - 7d). Boundary: entries at exactly 7d are kept. */
    sweepExpired(now?: number): void;
    /** List every session for the given userId in insertion order. */
    listForUser(userId: string): Array<{
        fingerprint: string;
        session: MultipartSession;
    }>;
    private getFilePath;
    /** Read the file; missing / parse failure / schema mismatch all collapse to an empty store. */
    private read;
    /** Atomic write; failures swallowed (resume is not a hard requirement and must not block uploads). */
    private write;
}