puppeteer/lib/Connection.js

/**
 * 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.
 */

var EventEmitter = require('events');
var WebSocket = require('ws');
var http = require('http');
const COMMAND_TIMEOUT = 10000;

class Connection extends EventEmitter {
    /**
     * @param {number} port
     * @param {string} pageId
     * @param {!WebSocket} ws
     */
    constructor(port, pageId, ws) {
        super();
        this._port = port;
        this._pageId = pageId;
        this._lastId = 0;
        /** @type {!Map<number, {resolve: function(*), reject: function(*), method: string}>}*/
        this._callbacks = new Map();

        this._ws = ws;
        this._ws.on('message', this._onMessage.bind(this));
        this._ws.on('close', this._onClose.bind(this));
    }

    /**
     * @param {string} method
     * @param {(!Object|undefined)} params
     * @return {!Promise<?Object>}
     */
    send(method, params = {}) {
        var id = ++this._lastId;
        var message = JSON.stringify({id, method, params});
        this._ws.send(message);
        return new Promise((resolve, reject) => {
            this._callbacks.set(id, {resolve, reject, method});
        });
    }

    /**
     * @param {string} message
     */
    _onMessage(message) {
        var object = JSON.parse(message);
        if (object.id && this._callbacks.has(object.id)) {
            var callback = this._callbacks.get(object.id);
            this._callbacks.delete(object.id);
            if (object.error)
                callback.reject(new Error(`Protocol error (${callback.method}): ${object.error.message}`));
            else
                callback.resolve(object.result);
        } else {
            console.assert(!object.id);
            this.emit(object.method, object.params);
        }
    }

    _onClose() {
        this._ws.removeAllListeners();
        this._ws.close();
    }

    /**
     * @return {!Promise}
     */
    async dispose() {
        await runJsonCommand(this._port, `close/${this._pageId}`);
    }

    /**
     * @param {number} port
     * @return {!Promise<!Connection>}
     */
    static async create(port) {
        var newTab = await runJsonCommand(port, 'new');
        var url = newTab.webSocketDebuggerUrl;

        return new Promise((resolve, reject) => {
            var ws = new WebSocket(url, { perMessageDeflate: false });
            ws.on('open', () => resolve(new Connection(port, newTab.id, ws)));
            ws.on('error', reject);
        });
    }

    /**
     * @param {number} port
     * @return {!Promise<!Object>}
     */
    static version(port) {
        return runJsonCommand(port, 'version');
    }
}

/**
 * @param {number} port
 * @param {string} command
 * @return {!Promise<!Object>}
 */
function runJsonCommand(port, command) {
    var request = http.get({
        hostname: 'localhost',
        port: port,
        path: '/json/' + command
    }, onResponse);
    request.setTimeout(COMMAND_TIMEOUT, onTimeout);
    var resolve, reject;
    return new Promise((res, rej) => { resolve = res; reject = rej; });

    function onResponse(response) {
        var data = '';
        response.on('data', chunk => data += chunk);
        response.on('end', () => {
            if (response.statusCode !== 200) {
                reject(new Error(`Protocol JSON API error (${command}), status: ${response.statusCode}`));
                return;
            }
            // In the case of 'close' & 'activate' Chromium returns a string rather than JSON: goo.gl/7v27xD
            if (data === 'Target is closing' || data === 'Target activated') {
                resolve({message: data});
                return;
            }
            try {
              resolve(JSON.parse(data));
            } catch (e) {
              reject(e);
            }
        });
    }

    function onTimeout() {
        request.abort();
        // Reject on error with code specifically indicating timeout in connection setup.
        reject(new Error('Timeout waiting for initial Debugger Protocol connection.'));
    }
}

module.exports = Connection;