puppeteer/src/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 './helper';
import { Events } from './Events';
import * as debug from 'debug';
const debugProtocol = debug('puppeteer:protocol');

import Protocol from './protocol';
import { ConnectionTransport } from './ConnectionTransport';
import * as EventEmitter from 'events';

interface ConnectionCallback {
  resolve: Function;
  reject: Function;
  error: Error;
  method: string;
}

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 {
    return session._connection;
  }

  /**
   * @param {string} sessionId
   * @returns {?CDPSession}
   */
  session(sessionId: string): CDPSession | null {
    return this._sessions.get(sessionId) || null;
  }

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

  send<T extends keyof Protocol.CommandParameters>(
    method: T,
    params?: Protocol.CommandParameters[T]
  ): Promise<Protocol.CommandReturnValues[T]> {
    const id = this._rawSend({ method, params });
    return new Promise((resolve, reject) => {
      this._callbacks.set(id, { resolve, reject, error: new Error(), method });
    });
  }

  _rawSend(message: {}): number {
    const id = ++this._lastId;
    message = JSON.stringify(Object.assign({}, message, { id }));
    debugProtocol('SEND ► ' + message);
    this._transport.send(message);
    return id;
  }

  async _onMessage(message: string): Promise<void> {
    if (this._delay) await new Promise((f) => setTimeout(f, this._delay));
    debugProtocol('◀ RECV ' + 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);
    } else if (object.method === 'Target.detachedFromTarget') {
      const session = this._sessions.get(object.params.sessionId);
      if (session) {
        session._onClosed();
        this._sessions.delete(object.params.sessionId);
      }
    }
    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 = null;
    this._transport.onclose = null;
    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(Events.Connection.Disconnected);
  }

  dispose(): void {
    this._onClose();
    this._transport.close();
  }

  /**
   * @param {Protocol.Target.TargetInfo} targetInfo
   * @returns {!Promise<!CDPSession>}
   */
  async createSession(
    targetInfo: Protocol.Target.TargetInfo
  ): Promise<CDPSession> {
    const { sessionId } = await this.send('Target.attachToTarget', {
      targetId: targetInfo.targetId,
      flatten: true,
    });
    return this._sessions.get(sessionId);
  }
}

interface CDPSessionOnMessageObject {
  id?: number;
  method: string;
  params: {};
  error: { message: string; data: any };
  result?: any;
}
export class CDPSession extends EventEmitter {
  _connection: Connection;
  _sessionId: string;
  _targetType: string;
  _callbacks: Map<number, ConnectionCallback> = new Map();

  constructor(connection: Connection, targetType: string, sessionId: string) {
    super();
    this._connection = connection;
    this._targetType = targetType;
    this._sessionId = sessionId;
  }

  send<T extends keyof Protocol.CommandParameters>(
    method: T,
    params?: Protocol.CommandParameters[T]
  ): Promise<Protocol.CommandReturnValues[T]> {
    if (!this._connection)
      return Promise.reject(
        new Error(
          `Protocol error (${method}): Session closed. Most likely the ${this._targetType} has been closed.`
        )
      );

    const id = this._connection._rawSend({
      sessionId: this._sessionId,
      method,
      /* TODO(jacktfranklin@): once this Firefox bug is solved
       * we no longer need the `|| {}` check
       * https://bugzilla.mozilla.org/show_bug.cgi?id=1631570
       */
      params: params || {},
    });

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

  _onMessage(object: CDPSessionOnMessageObject): void {
    if (object.id && this._callbacks.has(object.id)) {
      const callback = this._callbacks.get(object.id);
      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);
    }
  }

  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,
    });
  }

  _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 = null;
    this.emit(Events.CDPSession.Disconnected);
  }
}

/**
 * @param {!Error} error
 * @param {string} method
 * @param {{error: {message: string, data: any}}} object
 * @returns {!Error}
 */
function createProtocolError(
  error: Error,
  method: string,
  object: { error: { message: string; data: any } }
): Error {
  let message = `Protocol error (${method}): ${object.error.message}`;
  if ('data' in object.error) message += ` ${object.error.data}`;
  return rewriteError(error, message);
}

/**
 * @param {!Error} error
 * @param {string} message
 * @returns {!Error}
 */
function rewriteError(error: Error, message: string): Error {
  error.message = message;
  return error;
}