export declare const DEFAULT_EXPIRY: number;
export interface Options {
    /**
     * The delay in ms before a lock expires.
     *
     * This delay exists to ensure that locks held by tabs which have since been
     * closed or are frozen (eg. for performance reasons) do not prevent other
     * tabs from acquiring the lock.
     *
     * Defaults to DEFAULT_EXPIRY
     */
    expiry?: number;
    /**
     * The name of the object store in the database to use.
     *
     * If an existing database is passed to the constructor, that database must
     * have an object store of this name.
     *
     * Defaults to 'mutexes'.
     */
    objectStoreName?: string;
    /**
     * The amount of time to wait in ms between attempts to lock if the lock is
     * contended.
     *
     * Note that `lock()` does not spin at all if the lock is not currently held.
     *
     * Defaults to 50ms.
     */
    spinDelay?: number;
}
/**
 * A mutex for coordinating cross-tab activities.
 */
export default class Mutex {
    private _db;
    private _objectStoreName;
    private _name;
    private _id;
    private _expiry;
    private _spinDelay;
    /**
     * Initialize the mutex.
     *
     * @param name - Name of the mutex.
     * @param db - Existing database to use. If null, an IndexedDB database named
     *   'idb-mutex' is created. If an existing database is provided it must have
     *   an object store name matching `options.objectStoreName`.
     * @param options
     */
    constructor(name: string, db?: Promise<IDBDatabase> | null, options?: Options);
    /**
     * Acquire the lock.
     *
     * If no other instance currently holds the lock, the previous lock has expired
     * or the current instance already holds the lock, then this resolves
     * immediately.
     *
     * Otherwise `lock()` waits until the current lock owner releases the lock or
     * it expires.
     *
     * Returns a Promise that resolves when the lock has been acquired.
     */
    lock(): Promise<void>;
    /**
     * Release the lock.
     *
     * Releases the lock, regardless of who currently owns it or whether it is
     * currently locked.
     */
    unlock(): Promise<{}>;
    private _initDb(objectStoreName);
    private _tryLock();
}