/**
 * 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 {totalmem} from 'os';
import {Worker} from 'worker_threads';
import mergeStream = require('merge-stream');
import {
  CHILD_MESSAGE_INITIALIZE,
  CHILD_MESSAGE_MEM_USAGE,
  ChildMessage,
  OnCustomMessage,
  OnEnd,
  OnStart,
  PARENT_MESSAGE_CLIENT_ERROR,
  PARENT_MESSAGE_CUSTOM,
  PARENT_MESSAGE_MEM_USAGE,
  PARENT_MESSAGE_OK,
  PARENT_MESSAGE_SETUP_ERROR,
  ParentMessage,
  WorkerInterface,
  WorkerOptions,
  WorkerStates,
} from '../types';
import WorkerAbstract from './WorkerAbstract';

export default class ExperimentalWorker
  extends WorkerAbstract
  implements WorkerInterface
{
  private _worker!: Worker;
  private readonly _options: WorkerOptions;

  private _request: ChildMessage | null;
  private _retries!: number;
  private _onProcessEnd!: OnEnd;
  private _onCustomMessage!: OnCustomMessage;

  private _stdout: ReturnType<typeof mergeStream> | null;
  private _stderr: ReturnType<typeof mergeStream> | null;

  private _memoryUsagePromise: Promise<number> | undefined;
  private _resolveMemoryUsage: ((arg0: number) => void) | undefined;

  private readonly _childWorkerPath: string;

  private _childIdleMemoryUsage: number | null;
  private readonly _childIdleMemoryUsageLimit: number | null;
  private _memoryUsageCheck = false;

  constructor(options: WorkerOptions) {
    super(options);

    this._options = options;

    this._request = null;

    this._stdout = null;
    this._stderr = null;

    this._childWorkerPath =
      options.childWorkerPath || require.resolve('./threadChild');

    this._childIdleMemoryUsage = null;
    this._childIdleMemoryUsageLimit = options.idleMemoryLimit || null;

    this.initialize();
  }

  initialize(): void {
    if (
      this.state === WorkerStates.OUT_OF_MEMORY ||
      this.state === WorkerStates.SHUTTING_DOWN ||
      this.state === WorkerStates.SHUT_DOWN
    ) {
      return;
    }

    if (this._worker) {
      this._worker.terminate();
    }

    this.state = WorkerStates.STARTING;

    this._worker = new Worker(this._childWorkerPath, {
      eval: false,
      resourceLimits: this._options.resourceLimits,
      stderr: true,
      stdout: true,
      workerData: this._options.workerData,
      ...this._options.forkOptions,
    });

    if (this._worker.stdout) {
      if (!this._stdout) {
        // We need to add a permanent stream to the merged stream to prevent it
        // from ending when the subprocess stream ends
        this._stdout = mergeStream(this._getFakeStream());
      }

      this._stdout.add(this._worker.stdout);
    }

    if (this._worker.stderr) {
      if (!this._stderr) {
        // We need to add a permanent stream to the merged stream to prevent it
        // from ending when the subprocess stream ends
        this._stderr = mergeStream(this._getFakeStream());
      }

      this._stderr.add(this._worker.stderr);
    }

    // This can be useful for debugging.
    if (!(this._options.silent ?? true)) {
      this._worker.stdout.setEncoding('utf8');
      // eslint-disable-next-line no-console
      this._worker.stdout.on('data', console.log);
      this._worker.stderr.setEncoding('utf8');
      this._worker.stderr.on('data', console.error);
    }

    this._worker.on('message', this._onMessage.bind(this));
    this._worker.on('exit', this._onExit.bind(this));
    this._worker.on('error', this._onError.bind(this));

    this._worker.postMessage([
      CHILD_MESSAGE_INITIALIZE,
      false,
      this._options.workerPath,
      this._options.setupArgs,
      String(this._options.workerId + 1), // 0-indexed workerId, 1-indexed JEST_WORKER_ID
    ]);

    this._retries++;

    // If we exceeded the amount of retries, we will emulate an error reply
    // coming from the child. This avoids code duplication related with cleaning
    // the queue, and scheduling the next call.
    if (this._retries > this._options.maxRetries) {
      const error = new Error('Call retries were exceeded');

      this._onMessage([
        PARENT_MESSAGE_CLIENT_ERROR,
        error.name,
        error.message,
        error.stack!,
        {type: 'WorkerError'},
      ]);
    }

    this.state = WorkerStates.OK;
    if (this._resolveWorkerReady) {
      this._resolveWorkerReady();
    }
  }

  private _onError(error: Error) {
    if (error.message.includes('heap out of memory')) {
      this.state = WorkerStates.OUT_OF_MEMORY;

      // Threads don't behave like processes, they don't crash when they run out of
      // memory. But for consistency we want them to behave like processes so we call
      // terminate to simulate a crash happening that was not planned
      this._worker.terminate();
    }
  }

  private _onMessage(response: ParentMessage) {
    // Ignore messages not intended for us
    if (!Array.isArray(response)) return;

    let error;

    switch (response[0]) {
      case PARENT_MESSAGE_OK:
        this._onProcessEnd(null, response[1]);
        break;

      case PARENT_MESSAGE_CLIENT_ERROR:
        error = response[4];

        if (error != null && typeof error === 'object') {
          const extra = error;
          // @ts-expect-error: no index
          const NativeCtor = globalThis[response[1]];
          const Ctor = typeof NativeCtor === 'function' ? NativeCtor : Error;

          error = new Ctor(response[2]);
          error.type = response[1];
          error.stack = response[3];

          for (const key in extra) {
            // @ts-expect-error: no index
            error[key] = extra[key];
          }
        }

        this._onProcessEnd(error, null);
        break;

      case PARENT_MESSAGE_SETUP_ERROR:
        error = new Error(`Error when calling setup: ${response[2]}`);

        // @ts-expect-error: adding custom properties to errors.
        error.type = response[1];
        error.stack = response[3];

        this._onProcessEnd(error, null);
        break;

      case PARENT_MESSAGE_CUSTOM:
        this._onCustomMessage(response[1]);
        break;

      case PARENT_MESSAGE_MEM_USAGE:
        this._childIdleMemoryUsage = response[1];

        if (this._resolveMemoryUsage) {
          this._resolveMemoryUsage(response[1]);

          this._resolveMemoryUsage = undefined;
          this._memoryUsagePromise = undefined;
        }

        this._performRestartIfRequired();
        break;

      default:
        // Ignore messages not intended for us
        break;
    }
  }

  private _onExit(exitCode: number) {
    this._workerReadyPromise = undefined;
    this._resolveWorkerReady = undefined;

    if (exitCode !== 0 && this.state === WorkerStates.OUT_OF_MEMORY) {
      this._onProcessEnd(
        new Error('Jest worker ran out of memory and crashed'),
        null,
      );

      this._shutdown();
    } else if (
      (exitCode !== 0 &&
        this.state !== WorkerStates.SHUTTING_DOWN &&
        this.state !== WorkerStates.SHUT_DOWN) ||
      this.state === WorkerStates.RESTARTING
    ) {
      this.initialize();

      if (this._request) {
        this._worker.postMessage(this._request);
      }
    } else {
      // If the worker thread exits while a request is still pending, throw an
      // error. This is unexpected and tests may not have run to completion.
      const isRequestStillPending = !!this._request;
      if (isRequestStillPending) {
        this._onProcessEnd(
          new Error(
            'A Jest worker thread exited unexpectedly before finishing tests for an unknown reason. One of the ways this can happen is if process.exit() was called in testing code.',
          ),
          null,
        );
      }

      this._shutdown();
    }
  }

  waitForExit(): Promise<void> {
    return this._exitPromise;
  }

  forceExit(): void {
    this.state = WorkerStates.SHUTTING_DOWN;
    this._worker.terminate();
  }

  send(
    request: ChildMessage,
    onProcessStart: OnStart,
    onProcessEnd: OnEnd | null,
    onCustomMessage: OnCustomMessage,
  ): void {
    onProcessStart(this);
    this._onProcessEnd = (...args) => {
      const hasRequest = !!this._request;

      // Clean the request to avoid sending past requests to workers that fail
      // while waiting for a new request (timers, unhandled rejections...)
      this._request = null;

      if (this._childIdleMemoryUsageLimit && hasRequest) {
        this.checkMemoryUsage();
      }

      const res = onProcessEnd?.(...args);

      // Clean up the reference so related closures can be garbage collected.
      onProcessEnd = null;

      return res;
    };

    this._onCustomMessage = (...arg) => onCustomMessage(...arg);

    this._request = request;
    this._retries = 0;

    this._worker.postMessage(request);
  }

  getWorkerId(): number {
    return this._options.workerId;
  }

  getStdout(): NodeJS.ReadableStream | null {
    return this._stdout;
  }

  getStderr(): NodeJS.ReadableStream | null {
    return this._stderr;
  }

  private _performRestartIfRequired(): void {
    if (this._memoryUsageCheck) {
      this._memoryUsageCheck = false;

      let limit = this._childIdleMemoryUsageLimit;

      // TODO: At some point it would make sense to make use of
      // stringToBytes found in jest-config, however as this
      // package does not have any dependencies on an other jest
      // packages that can wait until some other time.
      if (limit && limit > 0 && limit <= 1) {
        limit = Math.floor(totalmem() * limit);
      } else if (limit) {
        limit = Math.floor(limit);
      }

      if (
        limit &&
        this._childIdleMemoryUsage &&
        this._childIdleMemoryUsage > limit
      ) {
        this.state = WorkerStates.RESTARTING;

        this._worker.terminate();
      }
    }
  }

  /**
   * Gets the last reported memory usage.
   *
   * @returns Memory usage in bytes.
   */
  getMemoryUsage(): Promise<number | null> {
    if (!this._memoryUsagePromise) {
      let rejectCallback!: (err: Error) => void;

      const promise = new Promise<number>((resolve, reject) => {
        this._resolveMemoryUsage = resolve;
        rejectCallback = reject;
      });
      this._memoryUsagePromise = promise;

      if (!this._worker.threadId) {
        rejectCallback(new Error('Child process is not running.'));

        this._memoryUsagePromise = undefined;
        this._resolveMemoryUsage = undefined;

        return promise;
      }

      try {
        this._worker.postMessage([CHILD_MESSAGE_MEM_USAGE]);
      } catch (err: any) {
        this._memoryUsagePromise = undefined;
        this._resolveMemoryUsage = undefined;

        rejectCallback(err);
      }

      return promise;
    }

    return this._memoryUsagePromise;
  }

  /**
   * Gets updated memory usage and restarts if required
   */
  checkMemoryUsage(): void {
    if (this._childIdleMemoryUsageLimit) {
      this._memoryUsageCheck = true;
      this._worker.postMessage([CHILD_MESSAGE_MEM_USAGE]);
    } else {
      console.warn(
        'Memory usage of workers can only be checked if a limit is set',
      );
    }
  }

  /**
   * Gets the thread id of the worker.
   *
   * @returns Thread id.
   */
  getWorkerSystemId(): number {
    return this._worker.threadId;
  }

  isWorkerRunning(): boolean {
    return this._worker.threadId >= 0;
  }
}
