text: const assert            = require('assert');
  const Assert            = require('./assert');
  const Bluebird          = require('bluebird');
  const Tabs              = require('./tabs');
  const Console           = require('./console');
  const Cookies           = require('./cookies');
  const debug             = require('debug');
  const DOM               = require('./dom');
  const { EventEmitter }  = require('events');
  const EventLoop         = require('./eventloop');
  const { format }        = require('util');
  const Fetch             = require('./fetch');
  const File              = require('fs');
  const Mime              = require('mime');
  const ms                = require('ms');
  const Path              = require('path');
  const Pipeline          = require('./pipeline');
  const reroute           = require('./reroute');
  const Storages          = require('./storage');
  const Tough             = require('tough-cookie');
  const { Cookie }        = Tough;
  const URL               = require('url');
  const Utils             = require('jsdom/lib/jsdom/utils');
  
  
  // Version number.  We get this from package.json.
  const VERSION = require(`${__dirname}/../package.json`).version;
  
  // Browser options you can set when creating new browser, or on browser instance.
  const BROWSER_OPTIONS  = ['features', 'headers', 'waitDuration',
                            'proxy', 'referrer', 'silent', 'site', 'strictSSL', 'userAgent',
                            'language', 'runScripts', 'localAddress'];
  
  // These features are set on/off by default.
  // Note that default values are actually prescribed where they are used,
  // by calling hasFeature with name and default
  const DEFAULT_FEATURES  = 'scripts no-css no-img iframe';
  
  const MOUSE_EVENT_NAMES = ['mousedown', 'mousemove', 'mouseup'];
  
  
  // Use the browser to open up new windows and load documents.
  //
  // The browser maintains state for cookies and local storage.
  class Browser extends EventEmitter {
  
    constructor(options = {}) {
      super();
      // Used for assertions
      this.assert     = new Assert(this);
      this.cookies    = new Cookies();
      // Shared by all windows.
      this.console    = new Console(this);
      // Start with no this referrer.
      this.referrer   = null;
      // Open tabs.
      this.tabs       = new Tabs(this);
      // New pipeline for this browser.
      this.pipeline   = new Pipeline(this);
  
      // The browser event loop.
      this._eventLoop = new EventLoop(this);
  
      // Returns all errors reported while loading this window.
      this.errors     = [];
  
      this._storages  = new Storages();
  
      // The window that is currently in scope, some JS functions need this, e.g.
      // when closing a window, you need to determine whether caller (window in
      // scope) is same as window.opener
      this._windowInScope = null;
  
      this._debug         = Browser._debug;
  
      // Message written to window.console.  Level is log, info, error, etc.
      //
      // All output goes to stdout, except when browser.silent = true and output
      // only shown when debugging (DEBUG=zombie).
      this
        .on('console', (level, message)=> {
          if (this.silent)
            this._debug(`>> ${message}`);
          else
            console.log(message);
        })
        .on('log', (...args)=> {
          // Message written to browser.log.
          this._debug(format(...args));
        });
  
      // Logging resources
      this
        .on('request', (request)=> request)
        .on('response', (request, response)=> {
          this._debug('%s %s => %s', request.method, response.url, response.status);
        })
        .on('redirect', (request, response)=> {
          this._debug('%s %s => %s %s', request.method, request.url, response.status, response.headers.get('Location'));
        })
        .on('loaded', (document)=> {
          this._debug('Loaded document %s', document.location.href);
        })
        .on('xhr', (eventName, url)=> {
          this._debug('XHR %s %s', eventName, url);
        });
  
      // Logging windows/tabs/navigation
      this
        .on('opened', (window)=> {
          this._debug('Opened window %s %s', window.location.href, window.name || '');
        })
        .on('closed', (window)=> {
          this._debug('Closed window %s %s', window.location.href, window.name || '');
        });
  
      // Switching tabs/windows fires blur/focus event on active window/element
      this
        .on('active', (window)=> {
          // Window becomes inactive
          const winFocus = window.document.createEvent('HTMLEvents');
          winFocus.initEvent('focus', false, false);
          window.dispatchEvent(winFocus);
  
          if (window.document.activeElement) {
            const elemFocus = window.document.createEvent('HTMLEvents');
            elemFocus.initEvent('focus', false, false);
            window.document.activeElement.dispatchEvent(elemFocus);
          }
        })
        .on('inactive', (window)=> {
          // Window becomes inactive
          if (window.document.activeElement) {
            const elemBlur = window.document.createEvent('HTMLEvents');
            elemBlur.initEvent('blur', false, false);
            window.document.activeElement.dispatchEvent(elemBlur);
          }
          const winBlur = window.document.createEvent('HTMLEvents');
          winBlur.initEvent('blur', false, false);
          window.dispatchEvent(winBlur);
        });
  
      // Logging navigation
      this
        .on('link', (url)=> {
          this._debug('Follow link to %s', url);
        })
        .on('submit', (url)=> {
          this._debug('Submit form to %s', url);
        });
  
      // Logging event loop
      this._eventLoop
        .on('setTimeout', (fn, delay)=> {
          this._debug('Fired setTimeout after %dms delay', delay);
          this.emit('setTimeout', fn, delay);
        })
        .on('setInterval', (fn, interval)=> {
          this._debug('Fired setInterval every %dms', interval);
          this.emit('setInterval', fn, interval);
        })
        .on('serverEvent', ()=> {
          this._debug('Server initiated event');
          this.emit('serverEvent');
        })
        .on('idle', (timedOut)=> {
          if (timedOut)
            this._debug('Event loop timed out');
          else
            this._debug('Event loop is empty');
          this.emit('idle');
        })
        .on('error', (error)=> {
          this.emit('error', error);
        });
  
      // Make sure we don't blow up Node when we get a JS error, but dump error to console.  Also, catch any errors
      // reported while processing resources/JavaScript.
      this.on('error', (error)=> {
        this.errors.push(error);
        this._debug(error.stack);
      });
  
      // Sets the browser options.
      options = options || {};
      for (let name of BROWSER_OPTIONS) {
        this[name] = options.hasOwnProperty(name) ?
          options[name] :
          (Browser[name] || null);
      }
  
      // Last, run all extensions in order.
      for (let extension of Browser._extensions)
        extension(this);
    }
  
  
    // Returns true if the given feature is enabled.
    //
    // If the feature is listed, then it is enabled.  If the feature is listed
    // with "no-" prefix, then it is disabled.  If the feature is missing, return
    // the default value.
    hasFeature(name, defaultValue = true) {
      const features = (this.features || '').split(/\s+/);
      return ~features.indexOf(name) ? true :
             ~features.indexOf(`no-${name}`) ? false :
             defaultValue;
    }
  
  
    // Return a new browser with a snapshot of this browser's state.
    // Any changes to the forked browser's state do not affect this browser.
    fork() {
      throw new Error('Not implemented');
    }
  
  
    // Windows
    // -------
  
    // Returns the currently open window
    get window() {
      return this.tabs.current;
    }
  
    // Open new browser window.
    open({ url, name, referrer } = {}) {
      return this.tabs.open({ url, name, referrer });
    }
  
    // browser.error => Error
    //
    // Returns the last error reported while loading this window.
    get error() {
      return this.errors[this.errors.length - 1];
    }
  
  
    // Events
    // ------
  
    // Waits for the browser to complete loading resources and processing JavaScript events.
    //
    // Accepts two parameters, both optional:
    // options   - Options that determine how long to wait (see below)
    // callback  - Called with error or null and browser
    //
    // To determine how long to wait:
    // duration  - Do not wait more than this duration (milliseconds or string of
    //             the form "5s"). Defaults to "5s" (see Browser.waitDuration).
    // element   - Stop when this element(s) appear in the DOM.
    // function  - Stop when function returns true; this function is called with
    //             the active window and expected time to the next event (0 to
    //             Infinity).
    //
    // As a convenience you can also pass the duration directly.
    //
    // Without a callback, this method returns a promise.
    wait(options, callback) {
      assert(this.window, new Error('No window open'));
      if (arguments.length === 1 && typeof options === 'function')
        [callback, options] = [options, null];
      assert(!callback || typeof callback === 'function', 'Second argument expected to be a callback function or null');
  
      // Support all sort of shortcuts for options. Unofficial.
      const duration =
        (typeof options === 'number') ? options :
        (typeof options === 'string') ? options :
        (options && options.duration || this.waitDuration || '5s');
      // Support 500 (ms) as well as "5s"
      const waitDuration = ms(duration.toString());
  
      function completionFromElement(element) {
        return function(window) {
          return !!window.document.querySelector(element);
        };
      }
  
      const completionFunction =
        (typeof options === 'function') ? options :
        (options && options.element) ? completionFromElement(options.element) :
        (options && options.function);
  
      const { _eventLoop } = this;
      if (callback)
        _eventLoop.wait(waitDuration, completionFunction, callback);
      else
        return Bluebird.promisify(_eventLoop.wait.bind(_eventLoop))(waitDuration, completionFunction);
    }
  
  
    // Waits for the browser to get a single event from any EventSource,
    // then completes loading resources and processing JavaScript events.
    //
    // Accepts an optional callback which is called with error or nothing
    //
    // Without a callback, this method returns a promise.
    waitForServer(options, callback) {
      assert(this.window, new Error('No window open'));
      if (arguments.length === 1 && typeof options === 'function')
        [callback, options] = [options, null];
  
      if (callback) {
        this._eventLoop.once('serverEvent', ()=> {
          this.wait(options, callback);
        });
        return null;
      }
  
      return new Promise((resolve)=> {
        this._eventLoop.once('serverEvent', ()=> {
          resolve(this.wait(options, null));
        });
      });
    }
  
  
    // Various methods use this with a callback, or return a lazy promise (e.g.
    // visit, click, fire)
    _wait(options, callback) {
      if (callback) {
        this.wait(options, callback);
        return null;
      }
  
      let promise = null;
      const lazyResolve = ()=> {
        if (!promise)
          promise = this.wait(options, null);
        return promise;
      };
      // Returns equivalent of a promise that only starts evaluating when you
      // call then() or catch() on it.
      return {
        then(resolved, rejected) {
          return lazyResolve().then(resolved, rejected);
        },
        catch(rejected) {
          return lazyResolve().then(null, rejected);
        }
      };
    }
  
  
    // Fire a DOM event.  You can use this to simulate a DOM event, e.g. clicking
    // a link.  These events will bubble up and can be cancelled.  Like `wait`
    // this method takes an optional callback and returns a promise.
    //
    // name - Even name (e.g `click`)
    // target - Target element (e.g a link)
    // callback - Called with error or nothing
    //
    // If called without callback, returns a promise
    fire(selector, eventName, callback) {
      assert(this.window, 'No window open');
      const target = this.query(selector);
      assert(target && target.dispatchEvent, 'No target element (note: call with selector/element, event name and callback)');
  
      const eventType = ~MOUSE_EVENT_NAMES.indexOf(eventName) ? 'MouseEvents' : 'HTMLEvents';
      const event = this.document.createEvent(eventType);
      event.initEvent(eventName, true, true);
      target.dispatchEvent(event);
      return this._wait(null, callback);
    }
  
    // Click on the element and returns a promise.
    //
    // selector - Element or CSS selector
    // callback - Called with error or nothing
    //
    // If called without callback, returns a promise
    click(selector, callback) {
      return this.fire(selector, 'click', callback);
    }
  
    // Dispatch asynchronously.  Returns true if preventDefault was set.
    dispatchEvent(selector, event) {
      assert(this.window, 'No window open');
      const target = this.query(selector);
      return target.dispatchEvent(event);
    }
  
  
    // Accessors
    // ---------
  
    // browser.queryAll(selector, context?) => Array
    //
    // Evaluates the CSS selector against the document (or context node) and return array of nodes.
    // (Unlike `document.querySelectorAll` that returns a node list).
    queryAll(selector = 'html', context = this.document) {
      assert(this.document && this.document.documentElement, 'No open window with an HTML document');
  
      if (Array.isArray(selector))
        return selector;
      if (selector instanceof DOM.Element)
        return [selector];
      if (selector) {
        const elements = context.querySelectorAll(selector);
        return Array.from(elements);
      } else
        return [];
    }
  
    // browser.query(selector, context?) => Element
    //
    // Evaluates the CSS selector against the document (or context node) and return an element.
    query(selector = 'html', context = this.document) {
      assert(this.document && this.document.documentElement, 'No open window with an HTML document');
  
      if (selector instanceof DOM.Element)
        return selector;
      return selector ? context.querySelector(selector) : context;
    }
  
    // WebKit offers this.
    $$(selector, context) {
      return this.query(selector, context);
    }
  
    // browser.querySelector(selector) => Element
    //
    // Select a single element (first match) and return it.
    //
    // selector - CSS selector
    //
    // Returns an Element or null
    querySelector(selector) {
      assert(this.document && this.document.documentElement, 'No open window with an HTML document');
      return this.document.querySelector(selector);
    }
  
    // browser.querySelectorAll(selector) => NodeList
    //
    // Select multiple elements and return a static node list.
    //
    // selector - CSS selector
    //
    // Returns a NodeList or null
    querySelectorAll(selector) {
      assert(this.document && this.document.documentElement, 'No open window with an HTML document');
      return this.document.querySelectorAll(selector);
    }
  
    // browser.text(selector, context?) => String
    //
    // Returns the text contents of the selected elements.
    //
    // selector - CSS selector (if missing, entire document)
    // context - Context element (if missing, uses document)
    //
    // Returns a string
    text(selector = 'html', context = this.document) {
      assert(this.document, 'No window open');
  
      if (this.document.documentElement)
        return this.queryAll(selector, context)
          .map(elem => elem.textContent)
          .join('')
          .trim()
          .replace(/\s+/g, ' ');
      else
        return (this.source ? this.source.toString : '');
    }
  
  
    // browser.html(selector?, context?) => String
    //
    // Returns the HTML contents of the selected elements.
    //
    // selector - CSS selector (if missing, entire document)
    // context - Context element (if missing, uses document)
    //
    // Returns a string
    html(selector = 'html', context = this.document) {
      assert(this.document, 'No window open');
  
      if (this.document.documentElement)
        return this.queryAll(selector, context)
          .map(elem => elem.outerHTML.trim())
          .join('');
      else
        return (this.source ? this.source.toString : '');
    }
  
  
    // browser.xpath(expression, context?) => XPathResult
    //
    // Evaluates the XPath expression against the document (or context node) and return the XPath result.  Shortcut for
    // `document.evaluate`.
    xpath(expression, context = null) {
      return this.document.evaluate(expression, context || this.document.documentElement, null, DOM.XPathResult.ANY_TYPE);
    }
  
    // browser.document => Document
    //
    // Returns the main window's document. Only valid after opening a document (see `browser.open`).
    get document() {
      return this.window && this.window.document;
    }
  
    // browser.body => Element
    //
    // Returns the body Element of the current document.
    get body() {
      return this.querySelector('body');
    }
  
    // Element that has the current focus.
    get activeElement() {
      return this.document && this.document.activeElement;
    }
  
    // Close all windows, clean state, etc.  This doesn't do anything the garbage
    // collector doesn't already do, so you don't need to call this.
    //
    // But because it destroys the browser state, it's quite useful for detecting
    // weird behavior bugs, e.g. an event loop that keeps running.  That's why
    // the test suite uses this method.
    destroy() {
      if (this.tabs) {
        this.tabs.closeAll();
        this.tabs = null;
      }
    }
  
  
    // Navigation
    // ----------
  
    // browser.visit(url, callback?)
    //
    // Loads document from the specified URL, processes events and calls the callback, or returns a promise.
    visit(url, options, callback) {
      if (arguments.length < 3 && typeof options === 'function')
        [options, callback] = [{}, options];
  
      const site = /^(https?:|file:)/i.test(this.site) ? this.site : `http://${this.site || 'localhost'}/`;
      url = Utils.resolveHref(site, URL.format(url));
  
      if (this.window)
        this.tabs.close(this.window);
      this.errors = [];
      this.tabs.open({ url: url, referrer: this.referrer });
      return this._wait(options, callback);
    }
  
  
    // browser.load(html, callback)
    //
    // Loads the HTML, processes events and calls the callback.
    //
    // Without a callback, returns a promise.
    load(html, callback) {
      if (this.window)
        this.tabs.close(this.window);
      this.errors = [];
      this.tabs.open({ html: html });
      return this._wait(null, callback);
    }
  
  
    // browser.location => Location
    //
    // Return the location of the current document (same as `window.location`).
    get location() {
      return this.window && this.window.location;
    }
  
    // browser.location = url
    //
    // Changes document location, loads new document if necessary (same as setting `window.location`).
    set location(url) {
      if (this.window)
        this.window.location = url;
      else
        this.open({ url: url });
    }
  
    // browser.url => String
    //
    // Return the URL of the current document (same as `document.URL`).
    get url() {
      return this.window && this.window.location.href;
    }
  
    // browser.link(selector) : Element
    //
    // Finds and returns a link by its text content or selector.
    link(selector) {
      assert(this.document && this.document.documentElement, 'No open window with an HTML document');
      // If the link has already been queried, return itself
      if (selector instanceof DOM.Element)
        return selector;
  
      try {
        const link = this.querySelector(selector);
        if (link && link.tagName === 'A')
          return link;
      } catch (error) {
        /* eslint no-empty:0 */
      }
      for (let elem of Array.from(this.querySelectorAll('body a'))) {
        if (elem.textContent.trim() === selector)
          return elem;
      }
      return null;
    }
  
    // browser.clickLink(selector, callback)
    //
    // Clicks on a link. Clicking on a link can trigger other events, load new page, etc: use a callback to be notified of
    // completion.  Finds link by text content or selector.
    //
    // selector - CSS selector or link text
    // callback - Called with two arguments: error and browser
    clickLink(selector, callback) {
      const link = this.link(selector);
      assert(link, `No link matching '${selector}'`);
      return this.click(link, callback);
    }
  
    // Return the history object.
    get history() {
      if (!this.window)
        this.open();
      return this.window.history;
    }
  
    // Navigate back in history.
    back(callback) {
      this.window.history.back();
      return this._wait(null, callback);
    }
  
    // Reloads current page.
    reload(callback) {
      this.window.location.reload();
      return this._wait(null, callback);
    }
  
  
    // browser.saveHistory() => String
    //
    // Save history to a text string.  You can use this to load the data later on using `browser.loadHistory`.
    saveHistory() {
      return this.window.history.save();
    }
  
    // browser.loadHistory(String)
    //
    // Load history from a text string (e.g. previously created using `browser.saveHistory`.
    loadHistory(serialized) {
      this.window.history.load(serialized);
    }
  
  
    // Forms
    // -----
  
    // browser.field(selector) : Element
    //
    // Find and return an input field (`INPUT`, `TEXTAREA` or `SELECT`) based on a CSS selector, field name (its `name`
    // attribute) or the text value of a label associated with that field (case sensitive, but ignores leading/trailing
    // spaces).
    field(selector) {
      assert(this.document && this.document.documentElement, 'No open window with an HTML document');
      // If the field has already been queried, return itself
      if (selector instanceof DOM.Element)
        return selector;
  
      try {
        // Try more specific selector first.
        const field = this.query(selector);
        if (field && (field.tagName === 'INPUT' || field.tagName === 'TEXTAREA' || field.tagName === 'SELECT'))
          return field;
      } catch (error) {
        // Invalid selector, but may be valid field name
      }
  
      // Use field name (case sensitive).
      for (let elem of this.queryAll('input[name],textarea[name],select[name]')) {
        if (elem.getAttribute('name') === selector)
          return elem;
      }
  
      // Try finding field from label.
      for (let label of this.queryAll('label')) {
        if (label.textContent.trim() === selector) {
          // nLabel can either reference field or enclose it
          const forAttr = label.getAttribute('for');
          return forAttr ?
            this.document.getElementById(forAttr) :
            label.querySelector('input,textarea,select');
        }
      }
      return null;
    }
  
  
    // browser.focus(selector) : Element
    //
    // Turns focus to the selected input field.  Shortcut for calling `field(selector).focus()`.
    focus(selector) {
      const field = this.field(selector) || this.query(selector);
      assert(field, `No form field matching '${selector}'`);
      field.focus();
      return this;
    }
  
  
    // browser.fill(selector, value) => this
    //
    // Fill in a field: input field or text area.
    //
    // selector - CSS selector, field name or text of the field label
    // value - Field value
    //
    // Returns this.
    fill(selector, value) {
      const field = this.field(selector);
      assert(field && (field.tagName === 'TEXTAREA' || (field.tagName === 'INPUT')), `No INPUT matching '${selector}'`);
      assert(!field.disabled, 'This INPUT field is disabled');
      assert(!field.readonly, 'This INPUT field is readonly');
  
      // Switch focus to field, change value and emit the input event (HTML5)
      field.focus();
      field.value = value;
      this.fire(field, 'input', false);
      // Switch focus out of field, if value changed, this will emit change event
      field.blur();
      return this;
    }
  
    _setCheckbox(selector, value) {
      const field = this.field(selector);
      assert(field && field.tagName === 'INPUT' && field.type === 'checkbox', `No checkbox INPUT matching '${selector}'`);
      assert(!field.disabled, 'This INPUT field is disabled');
      assert(!field.readonly, 'This INPUT field is readonly');
  
      if (field.checked ^ value)
        field.click();
      return this;
    }
  
    // browser.check(selector) => this
    //
    // Checks a checkbox.
    //
    // selector - CSS selector, field name or text of the field label
    //
    // Returns this.
    check(selector) {
      return this._setCheckbox(selector, true);
    }
  
    // browser.uncheck(selector) => this
    //
    // Unchecks a checkbox.
    //
    // selector - CSS selector, field name or text of the field label
    //
    // Returns this.
    uncheck(selector) {
      return this._setCheckbox(selector, false);
    }
  
    // browser.choose(selector) => this
    //
    // Selects a radio box option.
    //
    // selector - CSS selector, field value or text of the field label
    //
    // Returns this.
    choose(selector) {
      const field = this.field(selector) || this.field(`input[type=radio][value=\'${escape(selector)}\']`);
      assert(field && field.tagName === 'INPUT' && field.type === 'radio', `No radio INPUT matching '${selector}'`);
  
      field.click();
      return this;
    }
  
    _findOption(selector, value) {
      const field = this.field(selector);
      assert(field && field.tagName === 'SELECT', `No SELECT matching '${selector}'`);
      assert(!field.disabled, 'This SELECT field is disabled');
      assert(!field.readonly, 'This SELECT field is readonly');
  
      const options = Array.from(field.options);
      for (let option of options) {
        if (option.value === value)
          return option;
      }
      for (let option of options) {
        if (option.label === value)
          return option;
      }
      for (let option of options) {
        if (option.textContent.trim() === value)
          return option;
      }
      throw new Error(`No OPTION '${value}'`);
    }
  
    // browser.select(selector, value) => this
    //
    // Selects an option.
    //
    // selector - CSS selector, field name or text of the field label
    // value - Value (or label) or option to select
    //
    // Returns this.
    select(selector, value) {
      const option = this._findOption(selector, value);
      this.selectOption(option);
      return this;
    }
  
    // browser.selectOption(option) => this
    //
    // Selects an option.
    //
    // option - option to select
    //
    // Returns this.
    selectOption(selector) {
      const option = this.query(selector);
      if (option && !option.selected) {
        const select = this.xpath('./ancestor::select', option).iterateNext();
        option.selected = true;
        select.focus();
        this.fire(select, 'change', false);
      }
      return this;
    }
  
    // browser.unselect(selector, value) => this
    //
    // Unselects an option.
    //
    // selector - CSS selector, field name or text of the field label
    // value - Value (or label) or option to unselect
    //
    // Returns this.
    unselect(selector, value) {
      const option = this._findOption(selector, value);
      this.unselectOption(option);
      return this;
    }
  
    // browser.unselectOption(option) => this
    //
    // Unselects an option.
    //
    // selector - selector or option to unselect
    //
    // Returns this.
    unselectOption(selector) {
      const option = this.query(selector);
      if (option && option.selected) {
        const select = this.xpath('./ancestor::select', option).iterateNext();
        assert(select.multiple, 'Cannot unselect in single select');
        option.selected = false;
        select.focus();
        this.fire(select, 'change', false);
      }
      return this;
    }
  
    // browser.attach(selector, filename) => this
    //
    // Attaches a file to the specified input field.  The second argument is the file name.
    //
    // Returns this.
    attach(selector, filename) {
      const field = this.field(selector);
      assert(field && field.tagName === 'INPUT' && field.type === 'file', `No file INPUT matching '${selector}'`);
  
      if (filename) {
        const stat = File.statSync(filename);
        const file = new (this.window.File)();
        file.name = Path.basename(filename);
        file.type = Mime.lookup(filename);
        file.size = stat.size;
  
        field.value = filename;
        field.files = field.files || [];
        field.files.push(file);
      }
      field.focus();
      this.fire(field, 'change', false);
      return this;
    }
  
    // browser.button(selector) : Element
    //
    // Finds a button using CSS selector, button name or button text (`BUTTON` or `INPUT` element).
    //
    // selector - CSS selector, button name or text of BUTTON element
    button(selector) {
      assert(this.document && this.document.documentElement, 'No open window with an HTML document');
      // If the button has already been queried, return itself
      if (selector instanceof DOM.Element)
        return selector;
  
      try {
        const button = this.querySelector(selector);
        if (button && (button.tagName === 'BUTTON' || button.tagName === 'INPUT'))
          return button;
      } catch (error) {
      }
      for (let elem of Array.from(this.querySelectorAll('button'))) {
        if (elem.textContent.trim() === selector)
          return elem;
      }
  
      const inputs = Array.from(this.querySelectorAll('input[type=submit],button'));
      for (let input of inputs) {
        if (input.name === selector)
          return input;
      }
      for (let input of inputs) {
        if (input.value === selector)
          return input;
      }
      return null;
    }
  
    // browser.pressButton(selector, callback)
    //
    // Press a button (button element or input of type `submit`).  Typically this will submit the form.  Use the callback
    // to wait for the from submission, page to load and all events run their course.
    //
    // selector - CSS selector, button name or text of BUTTON element
    // callback - Called with two arguments: null and browser
    pressButton(selector, callback) {
      const button = this.button(selector);
      assert(button, `No BUTTON '${selector}'`);
      assert(!button.disabled, 'This button is disabled');
      button.focus();
      return this.fire(button, 'click', callback);
    }
  
  
    // -- Cookies --
  
  
    // Returns cookie that best matches the identifier.
    //
    // identifier - Identifies which cookie to return
    // allProperties - If true, return all cookie properties, other just the value
    //
    // Identifier is either the cookie name, in which case the cookie domain is
    // determined from the currently open Web page, and the cookie path is "/".
    //
    // Or the identifier can be an object specifying:
    // name   - The cookie name
    // domain - The cookie domain (defaults to hostname of currently open page)
    // path   - The cookie path (defaults to "/")
    //
    // Returns cookie value, or cookie object (see setCookie).
    getCookie(identifier, allProperties) {
      identifier = this._cookieIdentifier(identifier);
      assert(identifier.name, 'Missing cookie name');
      assert(identifier.domain, 'No domain specified and no open page');
  
      const cookie = this.cookies.select(identifier)[0];
      return cookie ?
        (allProperties ?
          this._cookieProperties(cookie) :
          cookie.value) :
        null;
    }
  
    // Deletes cookie that best matches the identifier.
    //
    // identifier - Identifies which cookie to return
    //
    // Identifier is either the cookie name, in which case the cookie domain is
    // determined from the currently open Web page, and the cookie path is "/".
    //
    // Or the identifier can be an object specifying:
    // name   - The cookie name
    // domain - The cookie domain (defaults to hostname of currently open page)
    // path   - The cookie path (defaults to "/")
    //
    // Returns true if cookie delete.
    deleteCookie(identifier) {
      identifier = this._cookieIdentifier(identifier);
      assert(identifier.name, 'Missing cookie name');
      assert(identifier.domain, 'No domain specified and no open page');
  
      const cookie = this.cookies.select(identifier)[0];
      if (cookie)
        this.cookies.delete(cookie);
      return !!cookie;
    }
  
    // Sets a cookie.
    //
    // You can call this function with two arguments to set a session cookie: the
    // cookie value and cookie name.  The domain is determined from the current
    // page URL, and the path is always "/".
    //
    // Or you can call it with a single argument, with all cookie options:
    // name     - Name of the cookie
    // value    - Value of the cookie
    // domain   - The cookie domain (e.g example.com, .example.com)
    // path     - The cookie path
    // expires  - Time when cookie expires
    // maxAge   - How long before cookie expires
    // secure   - True for HTTPS only cookie
    // httpOnly - True if cookie not accessible from JS
    setCookie(nameOrOptions, value) {
      const domain = this.location && this.location.hostname;
      if (typeof nameOrOptions === 'string')
        this.cookies.set({
          name:     nameOrOptions,
          value:    value || '',
          domain:   domain,
          path:     '/',
          secure:   false,
          httpOnly: false
        });
      else {
        assert(nameOrOptions.name, 'Missing cookie name');
        this.cookies.set({
          name:       nameOrOptions.name,
          value:      nameOrOptions.value || value || '',
          domain:     nameOrOptions.domain || domain,
          path:       nameOrOptions.path || '/',
          secure:     !!nameOrOptions.secure,
          httpOnly:   !!nameOrOptions.httpOnly,
          expires:    nameOrOptions.expires,
          'max-age':  nameOrOptions['max-age']
        });
      }
    }
  
    // Deletes all cookies.
    deleteCookies() {
      this.cookies.deleteAll();
    }
  
    // Save cookies to a text string.  You can use this to load them back
    // later on using `Browser.loadCookies`.
    saveCookies() {
      const serialized = [`# Saved on ${new Date().toISOString()}`];
      for (let cookie of this.cookies.sort(Tough.cookieCompare))
        serialized.push(cookie.toString());
      return serialized.join('\n') + '\n';
    }
  
    // Load cookies from a text string (e.g. previously created using
    // `Browser.saveCookies`.
    loadCookies(serialized) {
      for (let line of serialized.split(/\n+/)) {
        line = line.trim();
        if (line && line[0] !== `#`)
          this.cookies.push(Cookie.parse(line));
      }
    }
  
    // Converts Tough Cookie object into Zombie cookie representation.
    _cookieProperties(cookie) {
      const properties = {
        name:   cookie.key,
        value:  cookie.value,
        domain: cookie.domain,
        path:   cookie.path
      };
      if (cookie.secure)
        properties.secure = true;
      if (cookie.httpOnly)
        properties.httpOnly = true;
      if (cookie.expires && cookie.expires < Infinity)
        properties.expires = cookie.expires;
      return properties;
    }
  
    // Converts cookie name/identifier into an identifier object.
    _cookieIdentifier(identifier) {
      const location = this.location;
      const domain = location && location.hostname;
      const path   = location && location.pathname || '/';
      return {
        name:   identifier.name || identifier,
        domain: identifier.domain || domain,
        path:   identifier.path || path
      };
    }
  
  
    // -- Local/Session Storage --
  
  
    // Returns local Storage based on the document origin (hostname/port). This is the same storage area you can access
    // from any document of that origin.
    localStorage(host) {
      return this._storages.local(host);
    }
  
    // Returns session Storage based on the document origin (hostname/port). This is the same storage area you can access
    // from any document of that origin.
    sessionStorage(host) {
      return this._storages.session(host);
    }
  
    // Save local/session storage to a text string.  You can use this to load the data later on using
    // `browser.loadStorage`.
    saveStorage() {
      return this._storages.save();
    }
  
    // Load local/session storage from a text string (e.g. previously created using `browser.saveStorage`.
    loadStorage(serialized) {
      this._storages.load(serialized);
    }
  
  
    // Scripts
    // -------
  
    // Evaluates a JavaScript expression in the context of the current window and returns the result.  When evaluating
    // external script, also include filename.
    //
    // You can also use this to evaluate a function in the context of the window: for timers and asynchronous callbacks
    // (e.g. XHR).
    evaluate(code, filename) {
      if (!this.window)
        this.open();
      return this.window._evaluate(code, filename);
    }
  
  
    // Resources
    // ---------
  
    fetch(input, init) {
      return this.pipeline._fetch(input, init);
    }
  
    // Returns all resources loaded by currently open window.
    get resources() {
      return this.window && this.window.resources;
    }
  
    // Get Request associated with currently open window
    get request() {
      return this.window && this.window._request || null;
    }
  
    // Get Response associated with currently open window
    get response() {
      return this.window && this.window._response || null;
    }
  
    // Get the status code of the response associated with this window
    get status() {
      const { response } = this;
      return response ? response.status : 0;
    }
  
    get statusCode() {
      return this.status;
    }
  
    // Return true if last response had status code 200 .. 299
    get success() {
      const { status } = this;
      return status >= 200 && status < 300;
    }
  
    // Returns true if the last response followed a redirect
    get redirected() {
      const { request } = this;
      return request ? (request._redirectCount > 0) : false;
    }
  
    // Get the source HTML for the last response
    get source() {
      const { response } = this;
      return response ? response.body : null;
    }
  
  
    // Debugging
    // ---------
  
    // Enable debugging.  You can do this in code instead of setting DEBUG environment variable.
    debug() {
      this._debug = Browser._enableDebugging();
    }
  
  
  
    // Zombie can spit out messages to help you figure out what's going on as your code executes.
    //
    // To spit a message to the console when running in debug mode, call this method with one or more values (same as
    // `console.log`).  You can also call it with a function that will be evaluated only when running in debug mode.
    //
    // For example:
    //     browser.log('Opening page:', url);
    //     browser.log(function() { return 'Opening page: ' + url });
    log(...args) {
      if (typeof args[0] === 'function')
        args = [args[0]()];
      this.emit('log', format(...args));
    }
  
    // Dump information to the console: Zombie version, current URL, history, cookies, event loop, etc.  Useful for
    // debugging and submitting error reports.
    dump(output = process.stdout) {
      function indent(lines) {
        return lines.map(line => `  ${line}\n`).join('');
      }
      output.write(`Zombie: ${Browser.VERSION}\n`);
      output.write(`URL:    ${this.window.location.href}\n`);
      output.write(`\nHistory:\n`);
      this.history.dump(output);
      output.write(`\nCookies:\n`);
      this.cookies.dump(output);
      output.write(`\nStorage:\n`);
  
      if (this.document) {
        const html  = this.html();
        const slice = (html.length > 497) ? `${html.slice(0, 497)}...` : html;
        output.write(`Document:\n${indent(slice.split('\n'))}\n`);
      } else
        output.write('No document\n');
  
      output.write('\n');
      this._eventLoop.dump(output);
    }
  
  
    // -- Static methods ---
  
    // ### zombie.visit(url, callback)
    // ### zombie.visit(url, options? callback)
    //
    // Creates a new Browser, opens window to the URL and calls the callback when
    // done processing all events.
    //
    // * url -- URL of page to open
    // * callback -- Called with error, browser
    static visit(url, options, callback) {
      if (arguments.length === 2 && typeof options === 'function')
        [options, callback] = [null, options];
      const browser = new Browser(options);
      if (callback)
        browser.visit(url, (error)=> callback(error, browser));
      else
        return browser.visit(url).then(()=> browser);
    }
  
    // Allows you to make requests against a named domain and HTTP/S port, and
    // will route it to the test server running on localhost and unprivileged
    // port.
    static localhost(source, target) {
      reroute(source, target);
      if (!this.site) {
        const [ hostname ] = source.split(':');
        this.site = hostname.replace(/^\*\./, '');
      }
    }
  
    // Register a browser extension.
    //
    // Browser extensions are called for each newly created browser object, and
    // can be used to change browser options, register listeners, add methods,
    // etc.
    static extend(extension) {
      this._extensions.push(extension);
    }
  
    // Call this to return a debug() instance with debugging enabled.
    static _enableDebugging() {
      // With debugging enabled, every time we call debug('zombie') we get a new
      // instance which outputs with a different color.  This can be confusing, so
      // if debugging is already enabled (DEBUG=zombie) we want to use the current
      // instance.  Otherwise, we want to create a new instance (_debugEnabled)
      // and reuse it every time someone calls browser.debug().
      if (this._debug.enabled)
        return this._debug.enabled;
  
      if (!this._debugEnabled) {
        debug.enable('zombie');
        this._debugEnabled = debug('zombie');
      }
      return this._debugEnabled;
    }
  
  
    // -- Static properties --
  
    static VERSION  = VERSION
  
    static Assert   = Assert
    static Pipeline = Pipeline
    static Headers  = Fetch.Headers
    static Request  = Fetch.Request
    static Response = Fetch.Response
  
  
    // -- These defaults are used in any new browser instance --
  
    // Which features are enabled.
    static features = DEFAULT_FEATURES
  
    // Proxy URL.
    //
    // Example
    //   Browser.proxy = 'http://myproxy:8080'
    static proxy = null
  
    // If true, suppress `console.log` output from scripts (ignored when DEBUG=zombie)
    static silent = false
  
    // You can use visit with a path, and it will make a request relative to this host/URL.
    static site = null
  
    // Check SSL certificates against CA.  False by default since you're likely
    // testing with a self-signed certificate.
    static strictSSL = false
  
    // Sets the outgoing IP address in case there is more than on available.
    // Defaults to 0.0.0.0 which should select default interface
    static localAddress = '0.0.0.0'
  
    // User agent string sent to server.
    static userAgent = `Mozilla/5.0 Chrome/10.0.613.0 Safari/534.15 Zombie.js/${VERSION}`
  
    // Navigator language code
    static language = 'en-US'
  
    // Default time to wait (visit, wait, etc).
    static waitDuration = '5s'
  
    // Indicates whether or not to validate and execute JavaScript, default true.
    static runScripts = true
  
  
    // -- Internal properties --
  
    // Debug instance.  Create new instance when enabling debugging with Zombie.debug
    static _debug = debug('zombie')
  
    // Set after calling _enableDebugging
    static _debugEnabled = null
  
    // Browser extensions;
    static _extensions = []
  }
  
  
  module.exports = Browser;
  
  