/// <reference types="node" />
/**
 * An abstraction of a queue of operations used by the Batch Writer.
 */
export default interface IOperationQueue {
    /**
     * Places an operation at the tail of the queue.
     * If there is already an operation for the same DID, Sidetree Error is thrown with 'code': 'batch_writer_already_has_operation_for_did'.
     */
    enqueue(didUniqueSuffix: string, operationBuffer: Buffer): Promise<void>;
    /**
     * Removes the given count of operation buffers from the beginning of the queue.
     */
    dequeue(count: number): Promise<Buffer[]>;
    /**
     * Fetches the given count of operation buffers from the beginning of the queue without removing them.
     */
    peek(count: number): Promise<Buffer[]>;
    /**
     * Checks to see if the queue already contains an operation for the given DID unique suffix.
     */
    contains(didUniqueSuffix: string): Promise<boolean>;
}