puppeteer/lib/Page.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.
 */

const fs = require('fs');
const EventEmitter = require('events');
const mime = require('mime');
const {NetworkManager} = require('./NetworkManager');
const {Dialog} = require('./Dialog');
const {EmulationManager} = require('./EmulationManager');
const {FrameManager} = require('./FrameManager');
const {Keyboard, Mouse, Touchscreen} = require('./Input');
const Tracing = require('./Tracing');
const {helper, debugError, assert} = require('./helper');
const {Coverage} = require('./Coverage');
const {Worker} = require('./Worker');
const {createJSHandle} = require('./ExecutionContext');
const {Accessibility} = require('./Accessibility');
const writeFileAsync = helper.promisify(fs.writeFile);

class Page extends EventEmitter {
  /**
   * @param {!Puppeteer.CDPSession} client
   * @param {!Puppeteer.Target} target
   * @param {boolean} ignoreHTTPSErrors
   * @param {?Puppeteer.Viewport} defaultViewport
   * @param {!Puppeteer.TaskQueue} screenshotTaskQueue
   * @return {!Promise<!Page>}
   */
  static async create(client, target, ignoreHTTPSErrors, defaultViewport, screenshotTaskQueue) {

    await client.send('Page.enable');
    const {frameTree} = await client.send('Page.getFrameTree');
    const page = new Page(client, target, frameTree, ignoreHTTPSErrors, screenshotTaskQueue);

    await Promise.all([
      client.send('Target.setAutoAttach', {autoAttach: true, waitForDebuggerOnStart: false}),
      client.send('Page.setLifecycleEventsEnabled', { enabled: true }),
      client.send('Network.enable', {}),
      client.send('Runtime.enable', {}),
      client.send('Security.enable', {}),
      client.send('Performance.enable', {}),
      client.send('Log.enable', {}),
    ]);
    if (ignoreHTTPSErrors)
      await client.send('Security.setOverrideCertificateErrors', {override: true});
    // Initialize default page size.
    if (defaultViewport)
      await page.setViewport(defaultViewport);

    return page;
  }

  /**
   * @param {!Puppeteer.CDPSession} client
   * @param {!Puppeteer.Target} target
   * @param {!Protocol.Page.FrameTree} frameTree
   * @param {boolean} ignoreHTTPSErrors
   * @param {!Puppeteer.TaskQueue} screenshotTaskQueue
   */
  constructor(client, target, frameTree, ignoreHTTPSErrors, screenshotTaskQueue) {
    super();
    this._closed = false;
    this._client = client;
    this._target = target;
    this._keyboard = new Keyboard(client);
    this._mouse = new Mouse(client, this._keyboard);
    this._touchscreen = new Touchscreen(client, this._keyboard);
    this._accessibility = new Accessibility(client);
    this._networkManager = new NetworkManager(client);
    /** @type {!FrameManager} */
    this._frameManager = new FrameManager(client, frameTree, this, this._networkManager);
    this._networkManager.setFrameManager(this._frameManager);
    this._emulationManager = new EmulationManager(client);
    this._tracing = new Tracing(client);
    /** @type {!Map<string, Function>} */
    this._pageBindings = new Map();
    this._ignoreHTTPSErrors = ignoreHTTPSErrors;
    this._coverage = new Coverage(client);
    this._javascriptEnabled = true;
    /** @type {?Puppeteer.Viewport} */
    this._viewport = null;

    this._screenshotTaskQueue = screenshotTaskQueue;

    /** @type {!Map<string, Worker>} */
    this._workers = new Map();
    client.on('Target.attachedToTarget', event => {
      if (event.targetInfo.type !== 'worker') {
        // If we don't detach from service workers, they will never die.
        client.send('Target.detachFromTarget', {
          sessionId: event.sessionId
        }).catch(debugError);
        return;
      }
      const session = client._createSession(event.targetInfo.type, event.sessionId);
      const worker = new Worker(session, event.targetInfo.url, this._addConsoleMessage.bind(this), this._handleException.bind(this));
      this._workers.set(event.sessionId, worker);
      this.emit(Page.Events.WorkerCreated, worker);

    });
    client.on('Target.detachedFromTarget', event => {
      const worker = this._workers.get(event.sessionId);
      if (!worker)
        return;
      this.emit(Page.Events.WorkerDestroyed, worker);
      this._workers.delete(event.sessionId);
    });

    this._frameManager.on(FrameManager.Events.FrameAttached, event => this.emit(Page.Events.FrameAttached, event));
    this._frameManager.on(FrameManager.Events.FrameDetached, event => this.emit(Page.Events.FrameDetached, event));
    this._frameManager.on(FrameManager.Events.FrameNavigated, event => this.emit(Page.Events.FrameNavigated, event));

    this._networkManager.on(NetworkManager.Events.Request, event => this.emit(Page.Events.Request, event));
    this._networkManager.on(NetworkManager.Events.Response, event => this.emit(Page.Events.Response, event));
    this._networkManager.on(NetworkManager.Events.RequestFailed, event => this.emit(Page.Events.RequestFailed, event));
    this._networkManager.on(NetworkManager.Events.RequestFinished, event => this.emit(Page.Events.RequestFinished, event));

    client.on('Page.domContentEventFired', event => this.emit(Page.Events.DOMContentLoaded));
    client.on('Page.loadEventFired', event => this.emit(Page.Events.Load));
    client.on('Runtime.consoleAPICalled', event => this._onConsoleAPI(event));
    client.on('Runtime.bindingCalled', event => this._onBindingCalled(event));
    client.on('Page.javascriptDialogOpening', event => this._onDialog(event));
    client.on('Runtime.exceptionThrown', exception => this._handleException(exception.exceptionDetails));
    client.on('Security.certificateError', event => this._onCertificateError(event));
    client.on('Inspector.targetCrashed', event => this._onTargetCrashed());
    client.on('Performance.metrics', event => this._emitMetrics(event));
    client.on('Log.entryAdded', event => this._onLogEntryAdded(event));
    this._target._isClosedPromise.then(() => {
      this.emit(Page.Events.Close);
      this._closed = true;
    });
  }

  /**
   * @param {!{longitude: number, latitude: number, accuracy: (number|undefined)}} options
   */
  async setGeolocation(options) {
    const { longitude, latitude, accuracy = 0} = options;
    if (longitude < -180 || longitude > 180)
      throw new Error(`Invalid longitude "${longitude}": precondition -180 <= LONGITUDE <= 180 failed.`);
    if (latitude < -90 || latitude > 90)
      throw new Error(`Invalid latitude "${latitude}": precondition -90 <= LATITUDE <= 90 failed.`);
    if (accuracy < 0)
      throw new Error(`Invalid accuracy "${accuracy}": precondition 0 <= ACCURACY failed.`);
    await this._client.send('Emulation.setGeolocationOverride', {longitude, latitude, accuracy});
  }

  /**
   * @return {!Puppeteer.Target}
   */
  target() {
    return this._target;
  }

  /**
   * @return {!Puppeteer.Browser}
   */
  browser() {
    return this._target.browser();
  }

  _onTargetCrashed() {
    this.emit('error', new Error('Page crashed!'));
  }

  /**
   * @param {!Protocol.Log.entryAddedPayload} event
   */
  _onLogEntryAdded(event) {
    const {level, text, args, source} = event.entry;
    if (args)
      args.map(arg => helper.releaseObject(this._client, arg));
    if (source !== 'worker')
      this.emit(Page.Events.Console, new ConsoleMessage(level, text));
  }

  /**
   * @return {!Puppeteer.Frame}
   */
  mainFrame() {
    return this._frameManager.mainFrame();
  }

  /**
   * @return {!Keyboard}
   */
  get keyboard() {
    return this._keyboard;
  }

  /**
   * @return {!Touchscreen}
   */
  get touchscreen() {
    return this._touchscreen;
  }

  /**
   * @return {!Coverage}
   */
  get coverage() {
    return this._coverage;
  }

  /**
   * @return {!Tracing}
   */
  get tracing() {
    return this._tracing;
  }

  /**
   * @return {!Accessibility}
   */
  get accessibility() {
    return this._accessibility;
  }

  /**
   * @return {!Array<Puppeteer.Frame>}
   */
  frames() {
    return this._frameManager.frames();
  }

  /**
   * @return {!Array<!Worker>}
   */
  workers() {
    return Array.from(this._workers.values());
  }

  /**
   * @param {boolean} value
   */
  async setRequestInterception(value) {
    return this._networkManager.setRequestInterception(value);
  }

  /**
   * @param {boolean} enabled
   */
  setOfflineMode(enabled) {
    return this._networkManager.setOfflineMode(enabled);
  }

  /**
   * @param {number} timeout
   */
  setDefaultNavigationTimeout(timeout) {
    this._frameManager.setDefaultNavigationTimeout(timeout);
  }

  /**
   * @param {!Protocol.Security.certificateErrorPayload} event
   */
  _onCertificateError(event) {
    if (!this._ignoreHTTPSErrors)
      return;
    this._client.send('Security.handleCertificateError', {
      eventId: event.eventId,
      action: 'continue'
    }).catch(debugError);
  }

  /**
   * @param {string} selector
   * @return {!Promise<?Puppeteer.ElementHandle>}
   */
  async $(selector) {
    return this.mainFrame().$(selector);
  }

  /**
   * @param {function()|string} pageFunction
   * @param {!Array<*>} args
   * @return {!Promise<!Puppeteer.JSHandle>}
   */
  async evaluateHandle(pageFunction, ...args) {
    const context = await this.mainFrame().executionContext();
    return context.evaluateHandle(pageFunction, ...args);
  }

  /**
   * @param {!Puppeteer.JSHandle} prototypeHandle
   * @return {!Promise<!Puppeteer.JSHandle>}
   */
  async queryObjects(prototypeHandle) {
    const context = await this.mainFrame().executionContext();
    return context.queryObjects(prototypeHandle);
  }

  /**
   * @param {string} selector
   * @param {function()|string} pageFunction
   * @param {!Array<*>} args
   * @return {!Promise<(!Object|undefined)>}
   */
  async $eval(selector, pageFunction, ...args) {
    return this.mainFrame().$eval(selector, pageFunction, ...args);
  }

  /**
   * @param {string} selector
   * @param {Function|string} pageFunction
   * @param {!Array<*>} args
   * @return {!Promise<(!Object|undefined)>}
   */
  async $$eval(selector, pageFunction, ...args) {
    return this.mainFrame().$$eval(selector, pageFunction, ...args);
  }

  /**
   * @param {string} selector
   * @return {!Promise<!Array<!Puppeteer.ElementHandle>>}
   */
  async $$(selector) {
    return this.mainFrame().$$(selector);
  }

  /**
   * @param {string} expression
   * @return {!Promise<!Array<!Puppeteer.ElementHandle>>}
   */
  async $x(expression) {
    return this.mainFrame().$x(expression);
  }

  /**
   * @param {!Array<string>} urls
   * @return {!Promise<!Array<Network.Cookie>>}
   */
  async cookies(...urls) {
    return (await this._client.send('Network.getCookies', {
      urls: urls.length ? urls : [this.url()]
    })).cookies;
  }

  /**
   * @param {Array<Network.CookieParam>} cookies
   */
  async deleteCookie(...cookies) {
    const pageURL = this.url();
    for (const cookie of cookies) {
      const item = Object.assign({}, cookie);
      if (!cookie.url && pageURL.startsWith('http'))
        item.url = pageURL;
      await this._client.send('Network.deleteCookies', item);
    }
  }

  /**
   * @param {Array<Network.CookieParam>} cookies
   */
  async setCookie(...cookies) {
    const pageURL = this.url();
    const startsWithHTTP = pageURL.startsWith('http');
    const items = cookies.map(cookie => {
      const item = Object.assign({}, cookie);
      if (!item.url && startsWithHTTP)
        item.url = pageURL;
      assert(
          item.url !== 'about:blank',
          `Blank page can not have cookie "${item.name}"`
      );
      assert(
          !String.prototype.startsWith.call(item.url || '', 'data:'),
          `Data URL page can not have cookie "${item.name}"`
      );
      return item;
    });
    await this.deleteCookie(...items);
    if (items.length)
      await this._client.send('Network.setCookies', { cookies: items });
  }

  /**
   * @param {Object} options
   * @return {!Promise<!Puppeteer.ElementHandle>}
   */
  async addScriptTag(options) {
    return this.mainFrame().addScriptTag(options);
  }

  /**
   * @param {Object} options
   * @return {!Promise<!Puppeteer.ElementHandle>}
   */
  async addStyleTag(options) {
    return this.mainFrame().addStyleTag(options);
  }

  /**
   * @param {string} name
   * @param {function(?)} puppeteerFunction
   */
  async exposeFunction(name, puppeteerFunction) {
    if (this._pageBindings.has(name))
      throw new Error(`Failed to add page binding with name ${name}: window['${name}'] already exists!`);
    this._pageBindings.set(name, puppeteerFunction);

    const expression = helper.evaluationString(addPageBinding, name);
    await this._client.send('Runtime.addBinding', {name: name});
    await this._client.send('Page.addScriptToEvaluateOnNewDocument', {source: expression});
    await Promise.all(this.frames().map(frame => frame.evaluate(expression).catch(debugError)));

    function addPageBinding(bindingName) {
      const binding = window[bindingName];
      window[bindingName] = async(...args) => {
        const me = window[bindingName];
        let callbacks = me['callbacks'];
        if (!callbacks) {
          callbacks = new Map();
          me['callbacks'] = callbacks;
        }
        const seq = (me['lastSeq'] || 0) + 1;
        me['lastSeq'] = seq;
        const promise = new Promise(fulfill => callbacks.set(seq, fulfill));
        binding(JSON.stringify({name: bindingName, seq, args}));
        return promise;
      };
    }
  }

  /**
   * @param {?{username: string, password: string}} credentials
   */
  async authenticate(credentials) {
    return this._networkManager.authenticate(credentials);
  }

  /**
   * @param {!Object<string, string>} headers
   */
  async setExtraHTTPHeaders(headers) {
    return this._networkManager.setExtraHTTPHeaders(headers);
  }

  /**
   * @param {string} userAgent
   */
  async setUserAgent(userAgent) {
    return this._networkManager.setUserAgent(userAgent);
  }

  /**
   * @return {!Promise<!Object>}
   */
  async metrics() {
    const response = await this._client.send('Performance.getMetrics');
    return this._buildMetricsObject(response.metrics);
  }

  /**
   * @param {*} event
   */
  _emitMetrics(event) {
    this.emit(Page.Events.Metrics, {
      title: event.title,
      metrics: this._buildMetricsObject(event.metrics)
    });
  }

  /**
   * @param {?Array<!Protocol.Performance.Metric>} metrics
   * @return {!Object}
   */
  _buildMetricsObject(metrics) {
    const result = {};
    for (const metric of metrics || []) {
      if (supportedMetrics.has(metric.name))
        result[metric.name] = metric.value;
    }
    return result;
  }

  /**
   * @param {!Protocol.Runtime.ExceptionDetails} exceptionDetails
   */
  _handleException(exceptionDetails) {
    const message = helper.getExceptionMessage(exceptionDetails);
    const err = new Error(message);
    err.stack = ''; // Don't report clientside error with a node stack attached
    this.emit(Page.Events.PageError, err);
  }

  /**
   * @param {!Protocol.Runtime.consoleAPICalledPayload} event
   */
  async _onConsoleAPI(event) {
    const context = this._frameManager.executionContextById(event.executionContextId);
    const values = event.args.map(arg => createJSHandle(context, arg));
    this._addConsoleMessage(event.type, values);
  }

  /**
   * @param {!Protocol.Runtime.bindingCalledPayload} event
   */
  async _onBindingCalled(event) {
    const {name, seq, args} = JSON.parse(event.payload);
    const result = await this._pageBindings.get(name)(...args);
    const expression = helper.evaluationString(deliverResult, name, seq, result);
    this._client.send('Runtime.evaluate', { expression, contextId: event.executionContextId }).catch(debugError);

    function deliverResult(name, seq, result) {
      window[name]['callbacks'].get(seq)(result);
      window[name]['callbacks'].delete(seq);
    }
  }

  /**
   * @param {string} type
   * @param {!Array<!Puppeteer.JSHandle>} args
   */
  _addConsoleMessage(type, args) {
    if (!this.listenerCount(Page.Events.Console)) {
      args.forEach(arg => arg.dispose());
      return;
    }
    const textTokens = [];
    for (const arg of args) {
      const remoteObject = arg._remoteObject;
      if (remoteObject.objectId)
        textTokens.push(arg.toString());
      else
        textTokens.push(helper.valueFromRemoteObject(remoteObject));
    }
    const message = new ConsoleMessage(type, textTokens.join(' '), args);
    this.emit(Page.Events.Console, message);
  }

  _onDialog(event) {
    let dialogType = null;
    if (event.type === 'alert')
      dialogType = Dialog.Type.Alert;
    else if (event.type === 'confirm')
      dialogType = Dialog.Type.Confirm;
    else if (event.type === 'prompt')
      dialogType = Dialog.Type.Prompt;
    else if (event.type === 'beforeunload')
      dialogType = Dialog.Type.BeforeUnload;
    assert(dialogType, 'Unknown javascript dialog type: ' + event.type);
    const dialog = new Dialog(this._client, dialogType, event.message, event.defaultPrompt);
    this.emit(Page.Events.Dialog, dialog);
  }

  /**
   * @return {!string}
   */
  url() {
    return this.mainFrame().url();
  }

  /**
   * @return {!Promise<String>}
   */
  async content() {
    return await this._frameManager.mainFrame().content();
  }

  /**
   * @param {string} html
   */
  async setContent(html) {
    await this._frameManager.mainFrame().setContent(html);
  }

  /**
   * @param {string} url
   * @param {!Object=} options
   * @return {!Promise<?Puppeteer.Response>}
   */
  async goto(url, options = {}) {
    return await this._frameManager.mainFrame().goto(url, options);
  }

  /**
   * @param {!Object=} options
   * @return {!Promise<?Puppeteer.Response>}
   */
  async reload(options) {
    const [response] = await Promise.all([
      this.waitForNavigation(options),
      this._client.send('Page.reload')
    ]);
    return response;
  }

  /**
   * @param {!Object=} options
   * @return {!Promise<?Puppeteer.Response>}
   */
  async waitForNavigation(options = {}) {
    return await this._frameManager.mainFrame().waitForNavigation(options);
  }

  /**
   * @param {(string|Function)} urlOrPredicate
   * @param {!Object=} options
   * @return {!Promise<!Puppeteer.Request>}
   */
  async waitForRequest(urlOrPredicate, options = {}) {
    const timeout = typeof options.timeout === 'number' ? options.timeout : 30000;
    return helper.waitForEvent(this._networkManager, NetworkManager.Events.Request, request => {
      if (helper.isString(urlOrPredicate))
        return (urlOrPredicate === request.url());
      if (typeof urlOrPredicate === 'function')
        return !!(urlOrPredicate(request));
      return false;
    }, timeout);
  }

  /**
   * @param {(string|Function)} urlOrPredicate
   * @param {!Object=} options
   * @return {!Promise<!Puppeteer.Response>}
   */
  async waitForResponse(urlOrPredicate, options = {}) {
    const timeout = typeof options.timeout === 'number' ? options.timeout : 30000;
    return helper.waitForEvent(this._networkManager, NetworkManager.Events.Response, response => {
      if (helper.isString(urlOrPredicate))
        return (urlOrPredicate === response.url());
      if (typeof urlOrPredicate === 'function')
        return !!(urlOrPredicate(response));
      return false;
    }, timeout);
  }

  /**
   * @param {!Object=} options
   * @return {!Promise<?Puppeteer.Response>}
   */
  async goBack(options) {
    return this._go(-1, options);
  }

  /**
   * @param {!Object=} options
   * @return {!Promise<?Puppeteer.Response>}
   */
  async goForward(options) {
    return this._go(+1, options);
  }

  /**
   * @param {!Object=} options
   * @return {!Promise<?Puppeteer.Response>}
   */
  async _go(delta, options) {
    const history = await this._client.send('Page.getNavigationHistory');
    const entry = history.entries[history.currentIndex + delta];
    if (!entry)
      return null;
    const [response] = await Promise.all([
      this.waitForNavigation(options),
      this._client.send('Page.navigateToHistoryEntry', {entryId: entry.id}),
    ]);
    return response;
  }

  async bringToFront() {
    await this._client.send('Page.bringToFront');
  }

  /**
   * @param {!Object} options
   */
  async emulate(options) {
    return Promise.all([
      this.setViewport(options.viewport),
      this.setUserAgent(options.userAgent)
    ]);
  }

  /**
   * @param {boolean} enabled
   */
  async setJavaScriptEnabled(enabled) {
    if (this._javascriptEnabled === enabled)
      return;
    this._javascriptEnabled = enabled;
    await this._client.send('Emulation.setScriptExecutionDisabled', { value: !enabled });
  }

  /**
   * @param {boolean} enabled
   */
  async setBypassCSP(enabled) {
    await this._client.send('Page.setBypassCSP', { enabled });
  }

  /**
   * @param {?string} mediaType
   */
  async emulateMedia(mediaType) {
    assert(mediaType === 'screen' || mediaType === 'print' || mediaType === null, 'Unsupported media type: ' + mediaType);
    await this._client.send('Emulation.setEmulatedMedia', {media: mediaType || ''});
  }

  /**
   * @param {!Puppeteer.Viewport} viewport
   */
  async setViewport(viewport) {
    const needsReload = await this._emulationManager.emulateViewport(viewport);
    this._viewport = viewport;
    if (needsReload)
      await this.reload();
  }

  /**
   * @return {?Puppeteer.Viewport}
   */
  viewport() {
    return this._viewport;
  }

  /**
   * @param {function()|string} pageFunction
   * @param {!Array<*>} args
   * @return {!Promise<*>}
   */
  async evaluate(pageFunction, ...args) {
    return this._frameManager.mainFrame().evaluate(pageFunction, ...args);
  }

  /**
   * @param {function()|string} pageFunction
   * @param {!Array<*>} args
   */
  async evaluateOnNewDocument(pageFunction, ...args) {
    const source = helper.evaluationString(pageFunction, ...args);
    await this._client.send('Page.addScriptToEvaluateOnNewDocument', { source });
  }

  /**
   * @param {Boolean} enabled
   * @returns {!Promise}
   */
  async setCacheEnabled(enabled = true) {
    await this._client.send('Network.setCacheDisabled', {cacheDisabled: !enabled});
  }

  /**
   * @param {!Object=} options
   * @return {!Promise<!Buffer|!String>}
   */
  async screenshot(options = {}) {
    let screenshotType = null;
    // options.type takes precedence over inferring the type from options.path
    // because it may be a 0-length file with no extension created beforehand (i.e. as a temp file).
    if (options.type) {
      assert(options.type === 'png' || options.type === 'jpeg', 'Unknown options.type value: ' + options.type);
      screenshotType = options.type;
    } else if (options.path) {
      const mimeType = mime.getType(options.path);
      if (mimeType === 'image/png')
        screenshotType = 'png';
      else if (mimeType === 'image/jpeg')
        screenshotType = 'jpeg';
      assert(screenshotType, 'Unsupported screenshot mime type: ' + mimeType);
    }

    if (!screenshotType)
      screenshotType = 'png';

    if (options.quality) {
      assert(screenshotType === 'jpeg', 'options.quality is unsupported for the ' + screenshotType + ' screenshots');
      assert(typeof options.quality === 'number', 'Expected options.quality to be a number but found ' + (typeof options.quality));
      assert(Number.isInteger(options.quality), 'Expected options.quality to be an integer');
      assert(options.quality >= 0 && options.quality <= 100, 'Expected options.quality to be between 0 and 100 (inclusive), got ' + options.quality);
    }
    assert(!options.clip || !options.fullPage, 'options.clip and options.fullPage are exclusive');
    if (options.clip) {
      assert(typeof options.clip.x === 'number', 'Expected options.clip.x to be a number but found ' + (typeof options.clip.x));
      assert(typeof options.clip.y === 'number', 'Expected options.clip.y to be a number but found ' + (typeof options.clip.y));
      assert(typeof options.clip.width === 'number', 'Expected options.clip.width to be a number but found ' + (typeof options.clip.width));
      assert(typeof options.clip.height === 'number', 'Expected options.clip.height to be a number but found ' + (typeof options.clip.height));
    }
    return this._screenshotTaskQueue.postTask(this._screenshotTask.bind(this, screenshotType, options));
  }

  /**
   * @param {"png"|"jpeg"} format
   * @param {!Object=} options
   * @return {!Promise<!Buffer|!String>}
   */
  async _screenshotTask(format, options) {
    await this._client.send('Target.activateTarget', {targetId: this._target._targetId});
    let clip = options.clip ? Object.assign({}, options['clip']) : undefined;
    if (clip)
      clip.scale = 1;

    if (options.fullPage) {
      const metrics = await this._client.send('Page.getLayoutMetrics');
      const width = Math.ceil(metrics.contentSize.width);
      const height = Math.ceil(metrics.contentSize.height);

      // Overwrite clip for full page at all times.
      clip = { x: 0, y: 0, width, height, scale: 1 };
      const {
        isMobile = false,
        deviceScaleFactor = 1,
        isLandscape = false
      } = this._viewport || {};
      /** @type {!Protocol.Emulation.ScreenOrientation} */
      const screenOrientation = isLandscape ? { angle: 90, type: 'landscapePrimary' } : { angle: 0, type: 'portraitPrimary' };
      await this._client.send('Emulation.setDeviceMetricsOverride', { mobile: isMobile, width, height, deviceScaleFactor, screenOrientation });
    }
    const shouldSetDefaultBackground = options.omitBackground && format === 'png';
    if (shouldSetDefaultBackground)
      await this._client.send('Emulation.setDefaultBackgroundColorOverride', { color: { r: 0, g: 0, b: 0, a: 0 } });
    const result = await this._client.send('Page.captureScreenshot', { format, quality: options.quality, clip });
    if (shouldSetDefaultBackground)
      await this._client.send('Emulation.setDefaultBackgroundColorOverride');

    if (options.fullPage && this._viewport)
      await this.setViewport(this._viewport);

    const buffer = options.encoding === 'base64' ? result.data : Buffer.from(result.data, 'base64');
    if (options.path)
      await writeFileAsync(options.path, buffer);
    return buffer;
  }

  /**
   * @param {!Object=} options
   * @return {!Promise<!Buffer>}
   */
  async pdf(options = {}) {
    const scale = options.scale || 1;
    const displayHeaderFooter = !!options.displayHeaderFooter;
    const headerTemplate = options.headerTemplate || '';
    const footerTemplate = options.footerTemplate || '';
    const printBackground = !!options.printBackground;
    const landscape = !!options.landscape;
    const pageRanges = options.pageRanges || '';

    let paperWidth = 8.5;
    let paperHeight = 11;
    if (options.format) {
      const format = Page.PaperFormats[options.format.toLowerCase()];
      assert(format, 'Unknown paper format: ' + options.format);
      paperWidth = format.width;
      paperHeight = format.height;
    } else {
      paperWidth = convertPrintParameterToInches(options.width) || paperWidth;
      paperHeight = convertPrintParameterToInches(options.height) || paperHeight;
    }

    const marginOptions = options.margin || {};
    const marginTop = convertPrintParameterToInches(marginOptions.top) || 0;
    const marginLeft = convertPrintParameterToInches(marginOptions.left) || 0;
    const marginBottom = convertPrintParameterToInches(marginOptions.bottom) || 0;
    const marginRight = convertPrintParameterToInches(marginOptions.right) || 0;
    const preferCSSPageSize = options.preferCSSPageSize || false;

    const result = await this._client.send('Page.printToPDF', {
      landscape: landscape,
      displayHeaderFooter: displayHeaderFooter,
      headerTemplate: headerTemplate,
      footerTemplate: footerTemplate,
      printBackground: printBackground,
      scale: scale,
      paperWidth: paperWidth,
      paperHeight: paperHeight,
      marginTop: marginTop,
      marginBottom: marginBottom,
      marginLeft: marginLeft,
      marginRight: marginRight,
      pageRanges: pageRanges,
      preferCSSPageSize: preferCSSPageSize
    });
    const buffer = Buffer.from(result.data, 'base64');
    if (options.path)
      await writeFileAsync(options.path, buffer);
    return buffer;
  }

  /**
   * @return {!Promise<string>}
   */
  async title() {
    return this.mainFrame().title();
  }

  /**
   * @param {!{runBeforeUnload: (boolean|undefined)}=} options
   */
  async close(options = {runBeforeUnload: undefined}) {
    assert(!!this._client._connection, 'Protocol error: Connection closed. Most likely the page has been closed.');
    const runBeforeUnload = !!options.runBeforeUnload;
    if (runBeforeUnload) {
      await this._client.send('Page.close');
    } else {
      await this._client._connection.send('Target.closeTarget', { targetId: this._target._targetId });
      await this._target._isClosedPromise;
    }
  }

  /**
   * @return {boolean}
   */
  isClosed() {
    return this._closed;
  }

  /**
   * @return {!Mouse}
   */
  get mouse() {
    return this._mouse;
  }

  /**
   * @param {string} selector
   * @param {!Object=} options
   */
  click(selector, options = {}) {
    return this.mainFrame().click(selector, options);
  }

  /**
   * @param {string} selector
   */
  focus(selector) {
    return this.mainFrame().focus(selector);
  }

  /**
   * @param {string} selector
   */
  hover(selector) {
    return this.mainFrame().hover(selector);
  }

  /**
   * @param {string} selector
   * @param {!Array<string>} values
   * @return {!Promise<!Array<string>>}
   */
  select(selector, ...values) {
    return this.mainFrame().select(selector, ...values);
  }

  /**
   * @param {string} selector
   */
  tap(selector) {
    return this.mainFrame().tap(selector);
  }

  /**
   * @param {string} selector
   * @param {string} text
   * @param {{delay: (number|undefined)}=} options
   */
  type(selector, text, options) {
    return this.mainFrame().type(selector, text, options);
  }

  /**
   * @param {(string|number|Function)} selectorOrFunctionOrTimeout
   * @param {!Object=} options
   * @param {!Array<*>} args
   * @return {!Promise}
   */
  waitFor(selectorOrFunctionOrTimeout, options = {}, ...args) {
    return this.mainFrame().waitFor(selectorOrFunctionOrTimeout, options, ...args);
  }

  /**
   * @param {string} selector
   * @param {!Object=} options
   * @return {!Promise}
   */
  waitForSelector(selector, options = {}) {
    return this.mainFrame().waitForSelector(selector, options);
  }

  /**
   * @param {string} xpath
   * @param {!Object=} options
   * @return {!Promise}
   */
  waitForXPath(xpath, options = {}) {
    return this.mainFrame().waitForXPath(xpath, options);
  }

  /**
   * @param {function()} pageFunction
   * @param {!Object=} options
   * @param {!Array<*>} args
   * @return {!Promise}
   */
  waitForFunction(pageFunction, options = {}, ...args) {
    return this.mainFrame().waitForFunction(pageFunction, options, ...args);
  }
}

/** @type {!Set<string>} */
const supportedMetrics = new Set([
  'Timestamp',
  'Documents',
  'Frames',
  'JSEventListeners',
  'Nodes',
  'LayoutCount',
  'RecalcStyleCount',
  'LayoutDuration',
  'RecalcStyleDuration',
  'ScriptDuration',
  'TaskDuration',
  'JSHeapUsedSize',
  'JSHeapTotalSize',
]);

/** @enum {!{width: number, height: number}} */
Page.PaperFormats = {
  letter: {width: 8.5, height: 11},
  legal: {width: 8.5, height: 14},
  tabloid: {width: 11, height: 17},
  ledger: {width: 17, height: 11},
  a0: {width: 33.1, height: 46.8 },
  a1: {width: 23.4, height: 33.1 },
  a2: {width: 16.5, height: 23.4 },
  a3: {width: 11.7, height: 16.5 },
  a4: {width: 8.27, height: 11.7 },
  a5: {width: 5.83, height: 8.27 },
  a6: {width: 4.13, height: 5.83 },
};

const unitToPixels = {
  'px': 1,
  'in': 96,
  'cm': 37.8,
  'mm': 3.78
};

/**
 * @param {(string|number|undefined)} parameter
 * @return {(number|undefined)}
 */
function convertPrintParameterToInches(parameter) {
  if (typeof parameter === 'undefined')
    return undefined;
  let pixels;
  if (helper.isNumber(parameter)) {
    // Treat numbers as pixel values to be aligned with phantom's paperSize.
    pixels = /** @type {number} */ (parameter);
  } else if (helper.isString(parameter)) {
    const text = /** @type {string} */ (parameter);
    let unit = text.substring(text.length - 2).toLowerCase();
    let valueText = '';
    if (unitToPixels.hasOwnProperty(unit)) {
      valueText = text.substring(0, text.length - 2);
    } else {
      // In case of unknown unit try to parse the whole parameter as number of pixels.
      // This is consistent with phantom's paperSize behavior.
      unit = 'px';
      valueText = text;
    }
    const value = Number(valueText);
    assert(!isNaN(value), 'Failed to parse parameter value: ' + text);
    pixels = value * unitToPixels[unit];
  } else {
    throw new Error('page.pdf() Cannot handle parameter type: ' + (typeof parameter));
  }
  return pixels / 96;
}

Page.Events = {
  Close: 'close',
  Console: 'console',
  Dialog: 'dialog',
  DOMContentLoaded: 'domcontentloaded',
  Error: 'error',
  // Can't use just 'error' due to node.js special treatment of error events.
  // @see https://nodejs.org/api/events.html#events_error_events
  PageError: 'pageerror',
  Request: 'request',
  Response: 'response',
  RequestFailed: 'requestfailed',
  RequestFinished: 'requestfinished',
  FrameAttached: 'frameattached',
  FrameDetached: 'framedetached',
  FrameNavigated: 'framenavigated',
  Load: 'load',
  Metrics: 'metrics',
  WorkerCreated: 'workercreated',
  WorkerDestroyed: 'workerdestroyed',
};


/**
 * @typedef {Object} Network.Cookie
 * @property {string} name
 * @property {string} value
 * @property {string} domain
 * @property {string} path
 * @property {number} expires
 * @property {number} size
 * @property {boolean} httpOnly
 * @property {boolean} secure
 * @property {boolean} session
 * @property {("Strict"|"Lax")=} sameSite
 */


/**
 * @typedef {Object} Network.CookieParam
 * @property {string} name
 * @property {string} value
 * @property {string=} url
 * @property {string=} domain
 * @property {string=} path
 * @property {number=} expires
 * @property {boolean=} httpOnly
 * @property {boolean=} secure
 * @property {("Strict"|"Lax")=} sameSite
 */

class ConsoleMessage {
  /**
   * @param {string} type
   * @param {string} text
   * @param {!Array<!Puppeteer.JSHandle>} args
   */
  constructor(type, text, args = []) {
    this._type = type;
    this._text = text;
    this._args = args;
  }

  /**
   * @return {string}
   */
  type() {
    return this._type;
  }

  /**
   * @return {string}
   */
  text() {
    return this._text;
  }

  /**
   * @return {!Array<!Puppeteer.JSHandle>}
   */
  args() {
    return this._args;
  }
}


module.exports = {Page};
helper.tracePublicAPI(Page);