import { Thread } from "./thread";
/** Pool event type. Specifies the type of each `PoolEvent`. */
export declare enum PoolEventType {
    initialized = "initialized",
    taskCanceled = "taskCanceled",
    taskCompleted = "taskCompleted",
    taskFailed = "taskFailed",
    taskQueued = "taskQueued",
    taskQueueDrained = "taskQueueDrained",
    taskStart = "taskStart",
    terminated = "terminated"
}
export declare type TaskRunFunction<ThreadType extends Thread, Return> = (worker: ThreadType) => Promise<Return>;
/** Pool event. Subscribe to those events using `pool.events()`. Useful for debugging. */
export declare type PoolEvent<ThreadType extends Thread> = {
    type: PoolEventType.initialized;
    size: number;
} | {
    type: PoolEventType.taskQueued;
    taskID: number;
} | {
    type: PoolEventType.taskQueueDrained;
} | {
    type: PoolEventType.taskStart;
    taskID: number;
    workerID: number;
} | {
    type: PoolEventType.taskCompleted;
    returnValue: any;
    taskID: number;
    workerID: number;
} | {
    type: PoolEventType.taskFailed;
    error: Error;
    taskID: number;
    workerID: number;
} | {
    type: PoolEventType.taskCanceled;
    taskID: number;
} | {
    type: PoolEventType.terminated;
    remainingQueue: Array<QueuedTask<ThreadType, any>>;
};
export interface WorkerDescriptor<ThreadType extends Thread> {
    init: Promise<ThreadType>;
    runningTasks: Array<Promise<any>>;
}
/**
 * Task that has been `pool.queued()`-ed.
 */
export interface QueuedTask<ThreadType extends Thread, Return> {
    /** @private */
    id: number;
    /** @private */
    run: TaskRunFunction<ThreadType, Return>;
    /**
     * Queued tasks can be cancelled until the pool starts running them on a worker thread.
     */
    cancel(): void;
    /**
     * `QueuedTask` is thenable, so you can `await` it.
     * Resolves when the task has successfully been executed. Rejects if the task fails.
     */
    then: Promise<Return>["then"];
}