Connection.ts

/**
 * Copyright 2017 Google Inc. All rights reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
import {assert} from './assert.js';
import {debug} from './Debug.js';
const debugProtocolSend = debug('puppeteer:protocol:SEND ►');
const debugProtocolReceive = debug('puppeteer:protocol:RECV ◀');

import {Protocol} from 'devtools-protocol';
import {ProtocolMapping} from 'devtools-protocol/types/protocol-mapping.js';
import {ConnectionTransport} from './ConnectionTransport.js';
import {EventEmitter} from './EventEmitter.js';
import {ProtocolError} from './Errors.js';

/**
 * @public
 */
export {ConnectionTransport, ProtocolMapping};

/**
 * @public
 */
export interface ConnectionCallback {
  resolve(args: unknown): void;
  reject(args: unknown): void;
  error: ProtocolError;
  method: string;
}

/**
 * Internal events that the Connection class emits.
 *
 * @internal
 */
export const ConnectionEmittedEvents = {
  Disconnected: Symbol('Connection.Disconnected'),
} as const;

/**
 * @public
 */
export class Connection extends EventEmitter {
  #url: string;
  #transport: ConnectionTransport;
  #delay: number;
  #lastId = 0;
  #sessions: Map<string, CDPSession> = new Map();
  #closed = false;
  #callbacks: Map<number, ConnectionCallback> = new Map();

  constructor(url: string, transport: ConnectionTransport, delay = 0) {
    super();
    this.#url = url;
    this.#delay = delay;

    this.#transport = transport;
    this.#transport.onmessage = this.#onMessage.bind(this);
    this.#transport.onclose = this.#onClose.bind(this);
  }

  static fromSession(session: CDPSession): Connection | undefined {
    return session.connection();
  }

  /**
   * @internal
   */
  get _closed(): boolean {
    return this.#closed;
  }

  /**
   * @param sessionId - The session id
   * @returns The current CDP session if it exists
   */
  session(sessionId: string): CDPSession | null {
    return this.#sessions.get(sessionId) || null;
  }

  url(): string {
    return this.#url;
  }

  send<T extends keyof ProtocolMapping.Commands>(
    method: T,
    ...paramArgs: ProtocolMapping.Commands[T]['paramsType']
  ): Promise<ProtocolMapping.Commands[T]['returnType']> {
    // There is only ever 1 param arg passed, but the Protocol defines it as an
    // array of 0 or 1 items See this comment:
    // https://github.com/ChromeDevTools/devtools-protocol/pull/113#issuecomment-412603285
    // which explains why the protocol defines the params this way for better
    // type-inference.
    // So now we check if there are any params or not and deal with them accordingly.
    const params = paramArgs.length ? paramArgs[0] : undefined;
    const id = this._rawSend({method, params});
    return new Promise((resolve, reject) => {
      this.#callbacks.set(id, {
        resolve,
        reject,
        error: new ProtocolError(),
        method,
      });
    });
  }

  /**
   * @internal
   */
  _rawSend(message: Record<string, unknown>): number {
    const id = ++this.#lastId;
    const stringifiedMessage = JSON.stringify(Object.assign({}, message, {id}));
    debugProtocolSend(stringifiedMessage);
    this.#transport.send(stringifiedMessage);
    return id;
  }

  async #onMessage(message: string): Promise<void> {
    if (this.#delay) {
      await new Promise(f => {
        return setTimeout(f, this.#delay);
      });
    }
    debugProtocolReceive(message);
    const object = JSON.parse(message);
    if (object.method === 'Target.attachedToTarget') {
      const sessionId = object.params.sessionId;
      const session = new CDPSession(
        this,
        object.params.targetInfo.type,
        sessionId
      );
      this.#sessions.set(sessionId, session);
      this.emit('sessionattached', session);
      const parentSession = this.#sessions.get(object.sessionId);
      if (parentSession) {
        parentSession.emit('sessionattached', session);
      }
    } else if (object.method === 'Target.detachedFromTarget') {
      const session = this.#sessions.get(object.params.sessionId);
      if (session) {
        session._onClosed();
        this.#sessions.delete(object.params.sessionId);
        this.emit('sessiondetached', session);
        const parentSession = this.#sessions.get(object.sessionId);
        if (parentSession) {
          parentSession.emit('sessiondetached', session);
        }
      }
    }
    if (object.sessionId) {
      const session = this.#sessions.get(object.sessionId);
      if (session) {
        session._onMessage(object);
      }
    } else if (object.id) {
      const callback = this.#callbacks.get(object.id);
      // Callbacks could be all rejected if someone has called `.dispose()`.
      if (callback) {
        this.#callbacks.delete(object.id);
        if (object.error) {
          callback.reject(
            createProtocolError(callback.error, callback.method, object)
          );
        } else {
          callback.resolve(object.result);
        }
      }
    } else {
      this.emit(object.method, object.params);
    }
  }

  #onClose(): void {
    if (this.#closed) {
      return;
    }
    this.#closed = true;
    this.#transport.onmessage = undefined;
    this.#transport.onclose = undefined;
    for (const callback of this.#callbacks.values()) {
      callback.reject(
        rewriteError(
          callback.error,
          `Protocol error (${callback.method}): Target closed.`
        )
      );
    }
    this.#callbacks.clear();
    for (const session of this.#sessions.values()) {
      session._onClosed();
    }
    this.#sessions.clear();
    this.emit(ConnectionEmittedEvents.Disconnected);
  }

  dispose(): void {
    this.#onClose();
    this.#transport.close();
  }

  /**
   * @param targetInfo - The target info
   * @returns The CDP session that is created
   */
  async createSession(
    targetInfo: Protocol.Target.TargetInfo
  ): Promise<CDPSession> {
    const {sessionId} = await this.send('Target.attachToTarget', {
      targetId: targetInfo.targetId,
      flatten: true,
    });
    const session = this.#sessions.get(sessionId);
    if (!session) {
      throw new Error('CDPSession creation failed.');
    }
    return session;
  }
}

/**
 * @public
 */
export interface CDPSessionOnMessageObject {
  id?: number;
  method: string;
  params: Record<string, unknown>;
  error: {message: string; data: any; code: number};
  result?: any;
}

/**
 * Internal events that the CDPSession class emits.
 *
 * @internal
 */
export const CDPSessionEmittedEvents = {
  Disconnected: Symbol('CDPSession.Disconnected'),
} as const;

/**
 * The `CDPSession` instances are used to talk raw Chrome Devtools Protocol.
 *
 * @remarks
 *
 * Protocol methods can be called with {@link CDPSession.send} method and protocol
 * events can be subscribed to with `CDPSession.on` method.
 *
 * Useful links: {@link https://chromedevtools.github.io/devtools-protocol/ | DevTools Protocol Viewer}
 * and {@link https://github.com/aslushnikov/getting-started-with-cdp/blob/HEAD/README.md | Getting Started with DevTools Protocol}.
 *
 * @example
 * ```js
 * const client = await page.target().createCDPSession();
 * await client.send('Animation.enable');
 * client.on('Animation.animationCreated', () => console.log('Animation created!'));
 * const response = await client.send('Animation.getPlaybackRate');
 * console.log('playback rate is ' + response.playbackRate);
 * await client.send('Animation.setPlaybackRate', {
 *   playbackRate: response.playbackRate / 2
 * });
 * ```
 *
 * @public
 */
export class CDPSession extends EventEmitter {
  #sessionId: string;
  #targetType: string;
  #callbacks: Map<number, ConnectionCallback> = new Map();
  #connection?: Connection;

  /**
   * @internal
   */
  constructor(connection: Connection, targetType: string, sessionId: string) {
    super();
    this.#connection = connection;
    this.#targetType = targetType;
    this.#sessionId = sessionId;
  }

  connection(): Connection | undefined {
    return this.#connection;
  }

  send<T extends keyof ProtocolMapping.Commands>(
    method: T,
    ...paramArgs: ProtocolMapping.Commands[T]['paramsType']
  ): Promise<ProtocolMapping.Commands[T]['returnType']> {
    if (!this.#connection) {
      return Promise.reject(
        new Error(
          `Protocol error (${method}): Session closed. Most likely the ${
            this.#targetType
          } has been closed.`
        )
      );
    }

    // See the comment in Connection#send explaining why we do this.
    const params = paramArgs.length ? paramArgs[0] : undefined;

    const id = this.#connection._rawSend({
      sessionId: this.#sessionId,
      method,
      params,
    });

    return new Promise((resolve, reject) => {
      this.#callbacks.set(id, {
        resolve,
        reject,
        error: new ProtocolError(),
        method,
      });
    });
  }

  /**
   * @internal
   */
  _onMessage(object: CDPSessionOnMessageObject): void {
    const callback = object.id ? this.#callbacks.get(object.id) : undefined;
    if (object.id && callback) {
      this.#callbacks.delete(object.id);
      if (object.error) {
        callback.reject(
          createProtocolError(callback.error, callback.method, object)
        );
      } else {
        callback.resolve(object.result);
      }
    } else {
      assert(!object.id);
      this.emit(object.method, object.params);
    }
  }

  /**
   * Detaches the cdpSession from the target. Once detached, the cdpSession object
   * won't emit any events and can't be used to send messages.
   */
  async detach(): Promise<void> {
    if (!this.#connection) {
      throw new Error(
        `Session already detached. Most likely the ${
          this.#targetType
        } has been closed.`
      );
    }
    await this.#connection.send('Target.detachFromTarget', {
      sessionId: this.#sessionId,
    });
  }

  /**
   * @internal
   */
  _onClosed(): void {
    for (const callback of this.#callbacks.values()) {
      callback.reject(
        rewriteError(
          callback.error,
          `Protocol error (${callback.method}): Target closed.`
        )
      );
    }
    this.#callbacks.clear();
    this.#connection = undefined;
    this.emit(CDPSessionEmittedEvents.Disconnected);
  }

  /**
   * Returns the session's id.
   */
  id(): string {
    return this.#sessionId;
  }
}

function createProtocolError(
  error: ProtocolError,
  method: string,
  object: {error: {message: string; data: any; code: number}}
): Error {
  let message = `Protocol error (${method}): ${object.error.message}`;
  if ('data' in object.error) {
    message += ` ${object.error.data}`;
  }
  return rewriteError(error, message, object.error.message);
}

function rewriteError(
  error: ProtocolError,
  message: string,
  originalMessage?: string
): Error {
  error.message = message;
  error.originalMessage = originalMessage ?? error.originalMessage;
  return error;
}