300 lines
10 KiB
JavaScript
300 lines
10 KiB
JavaScript
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'use strict';
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const EventEmitter = require('events');
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const util = require('util');
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const formatUrl = require('url').format;
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const parseUrl = require('url').parse;
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const WebSocket = require('ws');
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const api = require('./api.js');
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const defaults = require('./defaults.js');
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const devtools = require('./devtools.js');
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class ProtocolError extends Error {
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constructor(request, response) {
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let {message} = response;
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if (response.data) {
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message += ` (${response.data})`;
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}
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super(message);
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// attach the original response as well
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this.request = request;
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this.response = response;
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}
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}
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class Chrome extends EventEmitter {
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constructor(options, notifier) {
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super();
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// options
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const defaultTarget = (targets) => {
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// prefer type = 'page' inspectable targets as they represents
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// browser tabs (fall back to the first inspectable target
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// otherwise)
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let backup;
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let target = targets.find((target) => {
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if (target.webSocketDebuggerUrl) {
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backup = backup || target;
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return target.type === 'page';
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} else {
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return false;
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}
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});
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target = target || backup;
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if (target) {
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return target;
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} else {
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throw new Error('No inspectable targets');
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}
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};
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options = options || {};
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this.host = options.host || defaults.HOST;
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this.port = options.port || defaults.PORT;
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this.secure = !!(options.secure);
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this.useHostName = !!(options.useHostName);
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this.alterPath = options.alterPath || ((path) => path);
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this.protocol = options.protocol;
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this.local = !!(options.local);
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this.target = options.target || defaultTarget;
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// locals
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this._notifier = notifier;
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this._callbacks = {};
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this._nextCommandId = 1;
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// properties
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this.webSocketUrl = undefined;
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// operations
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this._start();
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}
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// avoid misinterpreting protocol's members as custom util.inspect functions
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inspect(depth, options) {
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options.customInspect = false;
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return util.inspect(this, options);
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}
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send(method, params, sessionId, callback) {
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// handle optional arguments
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const optionals = Array.from(arguments).slice(1);
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params = optionals.find(x => typeof x === 'object');
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sessionId = optionals.find(x => typeof x === 'string');
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callback = optionals.find(x => typeof x === 'function');
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// return a promise when a callback is not provided
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if (typeof callback === 'function') {
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this._enqueueCommand(method, params, sessionId, callback);
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return undefined;
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} else {
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return new Promise((fulfill, reject) => {
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this._enqueueCommand(method, params, sessionId, (error, response) => {
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if (error) {
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const request = {method, params, sessionId};
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reject(
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error instanceof Error
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? error // low-level WebSocket error
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: new ProtocolError(request, response)
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);
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} else {
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fulfill(response);
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}
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});
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});
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}
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}
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close(callback) {
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const closeWebSocket = (callback) => {
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// don't close if it's already closed
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if (this._ws.readyState === 3) {
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callback();
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} else {
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// don't notify on user-initiated shutdown ('disconnect' event)
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this._ws.removeAllListeners('close');
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this._ws.once('close', () => {
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this._ws.removeAllListeners();
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callback();
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});
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this._ws.close();
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}
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};
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if (typeof callback === 'function') {
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closeWebSocket(callback);
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return undefined;
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} else {
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return new Promise((fulfill, reject) => {
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closeWebSocket(fulfill);
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});
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}
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}
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// initiate the connection process
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async _start() {
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const options = {
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host: this.host,
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port: this.port,
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secure: this.secure,
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useHostName: this.useHostName,
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alterPath: this.alterPath
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};
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try {
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// fetch the WebSocket debugger URL
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const url = await this._fetchDebuggerURL(options);
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// allow the user to alter the URL
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const urlObject = parseUrl(url);
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urlObject.pathname = options.alterPath(urlObject.pathname);
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this.webSocketUrl = formatUrl(urlObject);
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// update the connection parameters using the debugging URL
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options.host = urlObject.hostname;
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options.port = urlObject.port || options.port;
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// fetch the protocol and prepare the API
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const protocol = await this._fetchProtocol(options);
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api.prepare(this, protocol);
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// finally connect to the WebSocket
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await this._connectToWebSocket();
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// since the handler is executed synchronously, the emit() must be
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// performed in the next tick so that uncaught errors in the client code
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// are not intercepted by the Promise mechanism and therefore reported
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// via the 'error' event
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process.nextTick(() => {
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this._notifier.emit('connect', this);
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});
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} catch (err) {
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this._notifier.emit('error', err);
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}
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}
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// fetch the WebSocket URL according to 'target'
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async _fetchDebuggerURL(options) {
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const userTarget = this.target;
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switch (typeof userTarget) {
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case 'string': {
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let idOrUrl = userTarget;
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// use default host and port if omitted (and a relative URL is specified)
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if (idOrUrl.startsWith('/')) {
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idOrUrl = `ws://${this.host}:${this.port}${idOrUrl}`;
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}
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// a WebSocket URL is specified by the user (e.g., node-inspector)
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if (idOrUrl.match(/^wss?:/i)) {
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return idOrUrl; // done!
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}
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// a target id is specified by the user
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else {
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const targets = await devtools.List(options);
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const object = targets.find((target) => target.id === idOrUrl);
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return object.webSocketDebuggerUrl;
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}
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}
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case 'object': {
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const object = userTarget;
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return object.webSocketDebuggerUrl;
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}
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case 'function': {
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const func = userTarget;
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const targets = await devtools.List(options);
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const result = func(targets);
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const object = typeof result === 'number' ? targets[result] : result;
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return object.webSocketDebuggerUrl;
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}
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default:
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throw new Error(`Invalid target argument "${this.target}"`);
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}
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}
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// fetch the protocol according to 'protocol' and 'local'
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async _fetchProtocol(options) {
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// if a protocol has been provided then use it
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if (this.protocol) {
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return this.protocol;
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}
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// otherwise user either the local or the remote version
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else {
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options.local = this.local;
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return await devtools.Protocol(options);
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}
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}
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// establish the WebSocket connection and start processing user commands
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_connectToWebSocket() {
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return new Promise((fulfill, reject) => {
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// create the WebSocket
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try {
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if (this.secure) {
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this.webSocketUrl = this.webSocketUrl.replace(/^ws:/i, 'wss:');
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}
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this._ws = new WebSocket(this.webSocketUrl);
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} catch (err) {
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// handles bad URLs
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reject(err);
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return;
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}
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// set up event handlers
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this._ws.on('open', () => {
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fulfill();
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});
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this._ws.on('message', (data) => {
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const message = JSON.parse(data);
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this._handleMessage(message);
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});
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this._ws.on('close', (code) => {
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this.emit('disconnect');
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});
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this._ws.on('error', (err) => {
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reject(err);
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});
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});
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}
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// handle the messages read from the WebSocket
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_handleMessage(message) {
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// command response
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if (message.id) {
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const callback = this._callbacks[message.id];
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if (!callback) {
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return;
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}
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// interpret the lack of both 'error' and 'result' as success
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// (this may happen with node-inspector)
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if (message.error) {
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callback(true, message.error);
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} else {
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callback(false, message.result || {});
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}
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// unregister command response callback
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delete this._callbacks[message.id];
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// notify when there are no more pending commands
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if (Object.keys(this._callbacks).length === 0) {
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this.emit('ready');
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}
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}
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// event
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else if (message.method) {
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const {method, params, sessionId} = message;
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this.emit('event', message);
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this.emit(method, params, sessionId);
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this.emit(`${method}.${sessionId}`, params, sessionId);
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}
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}
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// send a command to the remote endpoint and register a callback for the reply
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_enqueueCommand(method, params, sessionId, callback) {
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const id = this._nextCommandId++;
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const message = {
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id,
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method,
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sessionId,
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params: params || {}
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};
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this._ws.send(JSON.stringify(message), (err) => {
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if (err) {
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// handle low-level WebSocket errors
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if (typeof callback === 'function') {
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callback(err);
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}
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} else {
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this._callbacks[id] = callback;
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}
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});
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}
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}
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module.exports = Chrome;
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