/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import {ForkOptions} from 'child_process';
import {ResourceLimits} from 'worker_threads';

declare const CHILD_MESSAGE_CALL = 1;

declare const CHILD_MESSAGE_CALL_SETUP = 4;

declare const CHILD_MESSAGE_END = 2;

declare const CHILD_MESSAGE_INITIALIZE = 0;

declare const CHILD_MESSAGE_MEM_USAGE = 3;

declare type ChildMessage =
  | ChildMessageInitialize
  | ChildMessageCall
  | ChildMessageEnd
  | ChildMessageMemUsage
  | ChildMessageCallSetup;

declare type ChildMessageCall = [
  type: typeof CHILD_MESSAGE_CALL,
  isProcessed: boolean,
  methodName: string,
  args: Array<unknown>,
];

declare type ChildMessageCallSetup = [type: typeof CHILD_MESSAGE_CALL_SETUP];

declare type ChildMessageEnd = [
  type: typeof CHILD_MESSAGE_END,
  isProcessed: boolean,
];

declare type ChildMessageInitialize = [
  type: typeof CHILD_MESSAGE_INITIALIZE,
  isProcessed: boolean,
  fileName: string,
  setupArgs: Array<unknown>,
  workerId: string | undefined,
];

declare type ChildMessageMemUsage = [type: typeof CHILD_MESSAGE_MEM_USAGE];

declare type ComputeTaskPriorityCallback = (
  method: string,
  ...args: Array<unknown>
) => number;

declare type ExcludeReservedKeys<K> = Exclude<K, ReservedKeys>;

/**
 * First-in, First-out task queue that manages a dedicated pool
 * for each worker as well as a shared queue. The FIFO ordering is guaranteed
 * across the worker specific and shared queue.
 */
export declare class FifoQueue implements TaskQueue {
  private _workerQueues;
  private readonly _sharedQueue;
  enqueue(task: QueueChildMessage, workerId?: number): void;
  dequeue(workerId: number): QueueChildMessage | null;
}

declare type FunctionLike = (...args: any) => unknown;

declare type HeapItem = {
  priority: number;
};

export declare type JestWorkerFarm<T extends Record<string, unknown>> =
  Worker_2 & WorkerModule<T>;

export declare function messageParent(
  message: unknown,
  parentProcess?: NodeJS.Process,
): void;

declare type MethodLikeKeys<T> = {
  [K in keyof T]: T[K] extends FunctionLike ? K : never;
}[keyof T];

declare class MinHeap<TItem extends HeapItem> {
  private readonly _heap;
  peek(): TItem | null;
  add(item: TItem): void;
  poll(): TItem | null;
}

declare type OnCustomMessage = (message: Array<unknown> | unknown) => void;

declare type OnEnd = (err: Error | null, result: unknown) => void;

declare type OnStart = (worker: WorkerInterface) => void;

declare type OnStateChangeHandler = (
  state: WorkerStates,
  oldState: WorkerStates,
) => void;

declare type PoolExitResult = {
  forceExited: boolean;
};

/**
 * Priority queue that processes tasks in natural ordering (lower priority first)
 * according to the priority computed by the function passed in the constructor.
 *
 * FIFO ordering isn't guaranteed for tasks with the same priority.
 *
 * Worker specific tasks with the same priority as a non-worker specific task
 * are always processed first.
 */
export declare class PriorityQueue implements TaskQueue {
  private readonly _computePriority;
  private _queue;
  private readonly _sharedQueue;
  constructor(_computePriority: ComputeTaskPriorityCallback);
  enqueue(task: QueueChildMessage, workerId?: number): void;
  _enqueue(task: QueueChildMessage, queue: MinHeap<QueueItem>): void;
  dequeue(workerId: number): QueueChildMessage | null;
  _getWorkerQueue(workerId: number): MinHeap<QueueItem>;
}

export declare interface PromiseWithCustomMessage<T> extends Promise<T> {
  UNSTABLE_onCustomMessage?: (listener: OnCustomMessage) => () => void;
}

declare type Promisify<T extends FunctionLike> =
  ReturnType<T> extends Promise<infer R>
    ? (...args: Parameters<T>) => Promise<R>
    : (...args: Parameters<T>) => Promise<ReturnType<T>>;

declare type QueueChildMessage = {
  request: ChildMessageCall;
  onStart: OnStart;
  onEnd: OnEnd;
  onCustomMessage: OnCustomMessage;
};

declare type QueueItem = {
  task: QueueChildMessage;
  priority: number;
};

declare type ReservedKeys =
  | 'end'
  | 'getStderr'
  | 'getStdout'
  | 'setup'
  | 'teardown';

export declare interface TaskQueue {
  /**
   * Enqueues the task in the queue for the specified worker or adds it to the
   * queue shared by all workers
   * @param task the task to queue
   * @param workerId the id of the worker that should process this task or undefined
   * if there's no preference.
   */
  enqueue(task: QueueChildMessage, workerId?: number): void;
  /**
   * Dequeues the next item from the queue for the specified worker
   * @param workerId the id of the worker for which the next task should be retrieved
   */
  dequeue(workerId: number): QueueChildMessage | null;
}

/**
 * The Jest farm (publicly called "Worker") is a class that allows you to queue
 * methods across multiple child processes, in order to parallelize work. This
 * is done by providing an absolute path to a module that will be loaded on each
 * of the child processes, and bridged to the main process.
 *
 * Bridged methods are specified by using the "exposedMethods" property of the
 * "options" object. This is an array of strings, where each of them corresponds
 * to the exported name in the loaded module.
 *
 * You can also control the amount of workers by using the "numWorkers" property
 * of the "options" object, and the settings passed to fork the process through
 * the "forkOptions" property. The amount of workers defaults to the amount of
 * CPUS minus one.
 *
 * Queueing calls can be done in two ways:
 *   - Standard method: calls will be redirected to the first available worker,
 *     so they will get executed as soon as they can.
 *
 *   - Sticky method: if a "computeWorkerKey" method is provided within the
 *     config, the resulting string of this method will be used as a key.
 *     Every time this key is returned, it is guaranteed that your job will be
 *     processed by the same worker. This is specially useful if your workers
 *     are caching results.
 */
declare class Worker_2 {
  private _ending;
  private readonly _farm;
  private readonly _options;
  private readonly _workerPool;
  constructor(workerPath: string | URL, options?: WorkerFarmOptions);
  private _bindExposedWorkerMethods;
  private _callFunctionWithArgs;
  getStderr(): NodeJS.ReadableStream;
  getStdout(): NodeJS.ReadableStream;
  start(): Promise<void>;
  end(): Promise<PoolExitResult>;
}
export {Worker_2 as Worker};

declare type WorkerCallback = (
  workerId: number,
  request: ChildMessage,
  onStart: OnStart,
  onEnd: OnEnd,
  onCustomMessage: OnCustomMessage,
) => void;

declare enum WorkerEvents {
  STATE_CHANGE = 'state-change',
}

export declare type WorkerFarmOptions = {
  computeWorkerKey?: (method: string, ...args: Array<unknown>) => string | null;
  enableWorkerThreads?: boolean;
  exposedMethods?: ReadonlyArray<string>;
  forkOptions?: ForkOptions;
  maxRetries?: number;
  numWorkers?: number;
  resourceLimits?: ResourceLimits;
  setupArgs?: Array<unknown>;
  taskQueue?: TaskQueue;
  WorkerPool?: new (
    workerPath: string,
    options?: WorkerPoolOptions,
  ) => WorkerPoolInterface;
  workerSchedulingPolicy?: WorkerSchedulingPolicy;
  idleMemoryLimit?: number;
};

declare interface WorkerInterface {
  get state(): WorkerStates;
  send(
    request: ChildMessage,
    onProcessStart: OnStart,
    onProcessEnd: OnEnd,
    onCustomMessage: OnCustomMessage,
  ): void;
  waitForExit(): Promise<void>;
  forceExit(): void;
  getWorkerId(): number;
  getStderr(): NodeJS.ReadableStream | null;
  getStdout(): NodeJS.ReadableStream | null;
  /**
   * Some system level identifier for the worker. IE, process id, thread id, etc.
   */
  getWorkerSystemId(): number;
  getMemoryUsage(): Promise<number | null>;
  /**
   * Checks to see if the child worker is actually running.
   */
  isWorkerRunning(): boolean;
  /**
   * When the worker child is started and ready to start handling requests.
   *
   * @remarks
   * This mostly exists to help with testing so that you don't check the status
   * of things like isWorkerRunning before it actually is.
   */
  waitForWorkerReady(): Promise<void>;
}

declare type WorkerModule<T> = {
  [K in keyof T as Extract<
    ExcludeReservedKeys<K>,
    MethodLikeKeys<T>
  >]: T[K] extends FunctionLike ? Promisify<T[K]> : never;
};

declare type WorkerOptions_2 = {
  forkOptions: ForkOptions;
  resourceLimits: ResourceLimits;
  setupArgs: Array<unknown>;
  maxRetries: number;
  workerId: number;
  workerData?: unknown;
  workerPath: string;
  /**
   * After a job has executed the memory usage it should return to.
   *
   * @remarks
   * Note this is different from ResourceLimits in that it checks at idle, after
   * a job is complete. So you could have a resource limit of 500MB but an idle
   * limit of 50MB. The latter will only trigger if after a job has completed the
   * memory usage hasn't returned back down under 50MB.
   */
  idleMemoryLimit?: number;
  /**
   * This mainly exists so the path can be changed during testing.
   * https://github.com/jestjs/jest/issues/9543
   */
  childWorkerPath?: string;
  /**
   * This is useful for debugging individual tests allowing you to see
   * the raw output of the worker.
   */
  silent?: boolean;
  /**
   * Used to immediately bind event handlers.
   */
  on?: {
    [WorkerEvents.STATE_CHANGE]:
      | OnStateChangeHandler
      | ReadonlyArray<OnStateChangeHandler>;
  };
};

export declare interface WorkerPoolInterface {
  getStderr(): NodeJS.ReadableStream;
  getStdout(): NodeJS.ReadableStream;
  getWorkers(): Array<WorkerInterface>;
  createWorker(options: WorkerOptions_2): WorkerInterface;
  send: WorkerCallback;
  start(): Promise<void>;
  end(): Promise<PoolExitResult>;
}

export declare type WorkerPoolOptions = {
  setupArgs: Array<unknown>;
  forkOptions: ForkOptions;
  resourceLimits: ResourceLimits;
  maxRetries: number;
  numWorkers: number;
  enableWorkerThreads: boolean;
  idleMemoryLimit?: number;
};

declare type WorkerSchedulingPolicy = 'round-robin' | 'in-order';

declare enum WorkerStates {
  STARTING = 'starting',
  OK = 'ok',
  OUT_OF_MEMORY = 'oom',
  RESTARTING = 'restarting',
  SHUTTING_DOWN = 'shutting-down',
  SHUT_DOWN = 'shut-down',
}

export {};
