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connection.js
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connection.js
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/**
* @license
* Copyright 2016 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.
*/
'use strict';
const EventEmitter = require('events').EventEmitter;
const log = require('../../lib/log.js');
const MessageLog = require('./message-log');
class Connection {
constructor() {
this._lastCommandId = 0;
/** @type {!Map<number, {resolve: function(*), reject: function(*), method: string}>}*/
this._callbacks = new Map();
this._eventEmitter = new EventEmitter();
this.log = new MessageLog();
}
/**
* @return {!Promise}
*/
connect() {
return Promise.reject(new Error('Not implemented'));
}
/**
* @return {!Promise}
*/
disconnect() {
return Promise.reject(new Error('Not implemented'));
}
/**
* Call protocol methods
* @param {!string} method
* @param {!Object} params
* @return {!Promise}
*/
sendCommand(method, params = {}) {
log.formatProtocol('method => browser', {method, params}, 'verbose');
const id = ++this._lastCommandId;
const message = JSON.stringify({id, method, params});
this.sendRawMessage(message);
return new Promise((resolve, reject) => {
this._callbacks.set(id, {resolve, reject, method});
});
}
/**
* Bind listeners for connection events
* @param {!string} eventName
* @param {function(...)} cb
*/
on(eventName, cb) {
if (eventName !== 'notification') {
throw new Error('Only supports "notification" events');
}
this._eventEmitter.on(eventName, cb);
}
/* eslint-disable no-unused-vars */
/**
* @param {string} message
* @return {!Promise}
* @protected
*/
sendRawMessage(message) {
return Promise.reject(new Error('Not implemented'));
}
/* eslint-enable no-unused-vars */
/**
* @param {string} message
* @return {!Promise}
* @protected
*/
handleRawMessage(message) {
const object = JSON.parse(message);
// Remote debugging protocol is JSON RPC 2.0 compiant. In terms of that transport,
// responses to the commands carry "id" property, while notifications do not.
if (object.id) {
const callback = this._callbacks.get(object.id);
this._callbacks.delete(object.id);
// handleRawError returns or throws synchronously; wrap to put into promise chain.
return callback.resolve(Promise.resolve().then(_ => {
if (object.error) {
log.formatProtocol('method <= browser ERR', {method: callback.method}, 'error');
throw new Error(`Protocol error (${callback.method}): ${object.error.message}`);
}
log.formatProtocol('method <= browser OK',
{method: callback.method, params: object.result}, 'verbose');
return object.result;
}));
}
this.log.record(object);
log.formatProtocol('<= event',
{method: object.method, params: object.params}, 'verbose');
this.emitNotification(object.method, object.params);
}
/**
* @param {!string} method
* @param {!Object} params
* @protected
*/
emitNotification(method, params) {
this._eventEmitter.emit('notification', {method, params});
}
/**
* @protected
*/
dispose() {
this._eventEmitter.removeAllListeners();
this._eventEmitter = null;
}
}
module.exports = Connection;