element.ts

import {By, error, ILocation, ISize, promise as wdpromise, WebDriver, WebElement, WebElementPromise} from 'selenium-webdriver';

import {ElementHelper} from './browser';
import {ProtractorBrowser} from './browser';
import {IError} from './exitCodes';
import {Locator} from './locators';
import {Logger} from './logger';

let webdriver = require('selenium-webdriver');
let clientSideScripts = require('./clientsidescripts');

let logger = new Logger('element');

let WEB_ELEMENT_FUNCTIONS = [
  'click', 'sendKeys', 'getTagName', 'getCssValue', 'getAttribute', 'getText', 'getSize',
  'getLocation', 'isEnabled', 'isSelected', 'submit', 'clear', 'isDisplayed', 'getOuterHtml',
  'getInnerHtml', 'getId', 'getRawId', 'serialize', 'takeScreenshot'
];

// Explicitly define webdriver.WebElement.
// TODO: extend WebElement from selenium-webdriver typings
export class WebdriverWebElement {
  getDriver: () => WebDriver;
  getId: () => wdpromise.Promise<any>;
  getRawId: () => wdpromise.Promise<string>;
  serialize: () => wdpromise.Promise<any>;
  findElement: (subLocator: Locator) => wdpromise.Promise<any>;
  click: () => wdpromise.Promise<void>;
  sendKeys: (...args: (string|wdpromise.Promise<string>)[]) => wdpromise.Promise<void>;
  getTagName: () => wdpromise.Promise<string>;
  getCssValue: (cssStyleProperty: string) => wdpromise.Promise<string>;
  getAttribute: (attributeName: string) => wdpromise.Promise<string>;
  getText: () => wdpromise.Promise<string>;
  getSize: () => wdpromise.Promise<ISize>;
  getLocation: () => wdpromise.Promise<ILocation>;
  isEnabled: () => wdpromise.Promise<boolean>;
  isSelected: () => wdpromise.Promise<boolean>;
  submit: () => wdpromise.Promise<void>;
  clear: () => wdpromise.Promise<void>;
  isDisplayed: () => wdpromise.Promise<boolean>;
  takeScreenshot: (opt_scroll?: boolean) => wdpromise.Promise<string>;
}

/**
 * ElementArrayFinder is used for operations on an array of elements (as opposed
 * to a single element).
 *
 * The ElementArrayFinder is used to set up a chain of conditions that identify
 * an array of elements. In particular, you can call all(locator) and
 * filter(filterFn) to return a new ElementArrayFinder modified by the
 * conditions, and you can call get(index) to return a single ElementFinder at
 * position 'index'.
 *
 * Similar to jquery, ElementArrayFinder will search all branches of the DOM
 * to find the elements that satisfy the conditions (i.e. all, filter, get).
 * However, an ElementArrayFinder will not actually retrieve the elements until
 * an action is called, which means it can be set up in helper files (i.e.
 * page objects) before the page is available, and reused as the page changes.
 *
 * You can treat an ElementArrayFinder as an array of WebElements for most
 * purposes, in particular, you may perform actions (i.e. click, getText) on
 * them as you would an array of WebElements. The action will apply to
 * every element identified by the ElementArrayFinder. ElementArrayFinder
 * extends Promise, and once an action is performed on an ElementArrayFinder,
 * the latest result can be accessed using then, and will be returned as an
 * array of the results; the array has length equal to the length of the
 * elements found by the ElementArrayFinder and each result represents the
 * result of performing the action on the element. Unlike a WebElement, an
 * ElementArrayFinder will wait for the angular app to settle before
 * performing finds or actions.
 *
 * @alias element.all(locator)
 * @view
 * <ul class="items">
 *   <li>First</li>
 *   <li>Second</li>
 *   <li>Third</li>
 * </ul>
 *
 * @example
 * element.all(by.css('.items li')).then(function(items) {
 *   expect(items.length).toBe(3);
 *   expect(items[0].getText()).toBe('First');
 * });
 *
 * @constructor
 * @param {ProtractorBrowser} browser A browser instance.
 * @param {function(): Array.<webdriver.WebElement>} getWebElements A function
 *    that returns a list of the underlying Web Elements.
 * @param {webdriver.Locator} locator The most relevant locator. It is only
 *    used for error reporting and ElementArrayFinder.locator.
 * @param {Array.<webdriver.promise.Promise>} opt_actionResults An array
 *    of promises which will be retrieved with then. Resolves to the latest
 *    action result, or null if no action has been called.
 * @returns {ElementArrayFinder}
 */
export class ElementArrayFinder extends WebdriverWebElement {
  constructor(
      public browser_: ProtractorBrowser,
      public getWebElements: () => wdpromise.Promise<WebElement[]> = null, public locator_?: any,
      public actionResults_: wdpromise.Promise<any> = null) {
    super();

    // TODO(juliemr): might it be easier to combine this with our docs and just
    // wrap each one explicity with its own documentation?
    WEB_ELEMENT_FUNCTIONS.forEach((fnName: string) => {
      this[fnName] = (...args: any[]) => {
        let actionFn = (webElem: any) => {
          return webElem[fnName].apply(webElem, args);
        };
        return this.applyAction_(actionFn);
      };
    });
  }
  [key: string]: any;

  /**
   * Create a shallow copy of ElementArrayFinder.
   *
   * @returns {!ElementArrayFinder} A shallow copy of this.
   */
  clone(): ElementArrayFinder {
    // A shallow copy is all we need since the underlying fields can never be
    // modified. (Locator can be modified by the user, but that should
    // rarely/never happen and it doesn't affect functionalities).
    return new ElementArrayFinder(
        this.browser_, this.getWebElements, this.locator_, this.actionResults_);
  }

  /**
   * Calls to ElementArrayFinder may be chained to find an array of elements
   * using the current elements in this ElementArrayFinder as the starting
   * point. This function returns a new ElementArrayFinder which would contain
   * the children elements found (and could also be empty).
   *
   * @alias element.all(locator).all(locator)
   * @view
   * <div id='id1' class="parent">
   *   <ul>
   *     <li class="foo">1a</li>
   *     <li class="baz">1b</li>
   *   </ul>
   * </div>
   * <div id='id2' class="parent">
   *   <ul>
   *     <li class="foo">2a</li>
   *     <li class="bar">2b</li>
   *   </ul>
   * </div>
   *
   * @example
   * let foo = element.all(by.css('.parent')).all(by.css('.foo'))
   * expect(foo.getText()).toEqual(['1a', '2a'])
   * let baz = element.all(by.css('.parent')).all(by.css('.baz'))
   * expect(baz.getText()).toEqual(['1b'])
   * let nonexistent =
   * element.all(by.css('.parent')).all(by.css('.NONEXISTENT'))
   * expect(nonexistent.getText()).toEqual([''])
   *
   * @param {webdriver.Locator} subLocator
   * @returns {ElementArrayFinder}
   */
  all(locator: Locator): ElementArrayFinder {
    let ptor = this.browser_;
    let getWebElements = (): wdpromise.Promise<WebElement[]> => {
      if (this.getWebElements === null) {
        // This is the first time we are looking for an element
        return ptor.waitForAngular('Locator: ' + locator)
            .then((): wdpromise.Promise<webdriver.WebElement[]> => {
              if (locator.findElementsOverride) {
                return locator.findElementsOverride(ptor.driver, null, ptor.rootEl);
              } else {
                return ptor.driver.findElements(locator);
              }
            });
      } else {
        return this.getWebElements().then((parentWebElements: WebElement[]) => {
          // For each parent web element, find their children and construct
          // a list of Promise<List<child_web_element>>
          let childrenPromiseList =
              parentWebElements.map((parentWebElement: webdriver.WebElement) => {
                return locator.findElementsOverride ?
                    locator.findElementsOverride(ptor.driver, parentWebElement, ptor.rootEl) :
                    parentWebElement.findElements(locator);
              });

          // Resolve the list of Promise<List<child_web_elements>> and merge
          // into a single list
          return wdpromise.all(childrenPromiseList).then((resolved) => {
            return resolved.reduce((childrenList, resolvedE) => {
              return childrenList.concat(resolvedE);
            }, []);
          });
        });
      }
    };
    return new ElementArrayFinder(this.browser_, getWebElements, locator);
  }

  /**
   * Apply a filter function to each element within the ElementArrayFinder.
   * Returns a new ElementArrayFinder with all elements that pass the filter
   * function. The filter function receives the ElementFinder as the first
   * argument and the index as a second arg. This does not actually retrieve
   * the underlying list of elements, so it can be used in page objects.
   *
   * @alias element.all(locator).filter(filterFn)
   * @view
   * <ul class="items">
   *   <li class="one">First</li>
   *   <li class="two">Second</li>
   *   <li class="three">Third</li>
   * </ul>
   *
   * @example
   * element.all(by.css('.items li')).filter(function(elem, index) {
   *   return elem.getText().then(function(text) {
   *     return text === 'Third';
   *   });
   * }).first().click();
   *
   * @param {function(ElementFinder, number): webdriver.WebElement.Promise}
   * filterFn
   *     Filter function that will test if an element should be returned.
   *     filterFn can either return a boolean or a promise that resolves to a
   * boolean
   * @returns {!ElementArrayFinder} A ElementArrayFinder that represents an
   * array
   *     of element that satisfy the filter function.
   */
  filter(filterFn: Function): ElementArrayFinder {
    let getWebElements = (): wdpromise.Promise<WebElement[]> => {
      return this.getWebElements().then((parentWebElements: WebElement[]) => {
        let list = parentWebElements.map((parentWebElement: WebElement, index: number) => {
          let elementFinder =
              ElementFinder.fromWebElement_(this.browser_, parentWebElement, this.locator_);

          return filterFn(elementFinder, index);
        });
        return webdriver.promise.all(list).then((resolvedList: any) => {
          return parentWebElements.filter((parentWebElement: WebElement, index: number) => {
            return resolvedList[index];
          });
        });
      });
    };
    return new ElementArrayFinder(this.browser_, getWebElements, this.locator_);
  }

  /**
   * Get an element within the ElementArrayFinder by index. The index starts at
   * 0\. Negative indices are wrapped (i.e. -i means ith element from last)
   * This does not actually retrieve the underlying element.
   *
   * @alias element.all(locator).get(index)
   * @view
   * <ul class="items">
   *   <li>First</li>
   *   <li>Second</li>
   *   <li>Third</li>
   * </ul>
   *
   * @example
   * let list = element.all(by.css('.items li'));
   * expect(list.get(0).getText()).toBe('First');
   * expect(list.get(1).getText()).toBe('Second');
   *
   * @param {number|webdriver.promise.Promise} index Element index.
   * @returns {ElementFinder} finder representing element at the given index.
   */
  get(index: number): ElementFinder {
    let getWebElements = () => {
      return webdriver.promise.all([index, this.getWebElements()]).then((results: any) => {
        let i = results[0];
        let parentWebElements = results[1];

        if (i < 0) {
          // wrap negative indices
          i = parentWebElements.length + i;
        }
        if (i < 0 || i >= parentWebElements.length) {
          throw new error.NoSuchElementError(
              'Index out of bound. ' +
              'Trying to access element at index: ' + index + ', but there are ' +
              'only ' + parentWebElements.length + ' elements that match ' +
              'locator ' + this.locator_.toString());
        }
        return [parentWebElements[i]];
      });
    };
    return new ElementArrayFinder(this.browser_, getWebElements, this.locator_).toElementFinder_();
  }

  /**
   * Get the first matching element for the ElementArrayFinder. This does not
   * actually retrieve the underlying element.
   *
   * @alias element.all(locator).first()
   * @view
   * <ul class="items">
   *   <li>First</li>
   *   <li>Second</li>
   *   <li>Third</li>
   * </ul>
   *
   * @example
   * let first = element.all(by.css('.items li')).first();
   * expect(first.getText()).toBe('First');
   *
   * @returns {ElementFinder} finder representing the first matching element
   */
  first(): ElementFinder {
    return this.get(0);
  };

  /**
   * Get the last matching element for the ElementArrayFinder. This does not
   * actually retrieve the underlying element.
   *
   * @alias element.all(locator).last()
   * @view
   * <ul class="items">
   *   <li>First</li>
   *   <li>Second</li>
   *   <li>Third</li>
   * </ul>
   *
   * @example
   * let last = element.all(by.css('.items li')).last();
   * expect(last.getText()).toBe('Third');
   *
   * @returns {ElementFinder} finder representing the last matching element
   */
  last(): ElementFinder {
    return this.get(-1);
  }

  /**
   * Shorthand function for finding arrays of elements by css.
   *
   * @type {function(string): ElementArrayFinder}
   */
  $$(selector: string): ElementArrayFinder {
    return this.all(webdriver.By.css(selector));
  }

  /**
   * Returns an ElementFinder representation of ElementArrayFinder. It ensures
   * that the ElementArrayFinder resolves to one and only one underlying
   * element.
   *
   * @returns {ElementFinder} An ElementFinder representation
   * @private
   */
  toElementFinder_(): ElementFinder {
    return new ElementFinder(this.browser_, this);
  }

  /**
   * Count the number of elements represented by the ElementArrayFinder.
   *
   * @alias element.all(locator).count()
   * @view
   * <ul class="items">
   *   <li>First</li>
   *   <li>Second</li>
   *   <li>Third</li>
   * </ul>
   *
   * @example
   * let list = element.all(by.css('.items li'));
   * expect(list.count()).toBe(3);
   *
   * @returns {!webdriver.promise.Promise} A promise which resolves to the
   *     number of elements matching the locator.
   */
  count(): wdpromise.Promise<number> {
    return this.getWebElements().then(
        (arr: WebElement[]) => {
          return arr.length;
        },
        (err: IError) => {
          if (err.code && err.code == new webdriver.error.NoSuchElementError()) {
            return 0;
          } else {
            throw err;
          }
        });
  }

  /**
   * Returns the most relevant locator.
   *
   * @example
   * // returns by.css('#ID1')
   * $('#ID1').locator()
   *
   * // returns by.css('#ID2')
   * $('#ID1').$('#ID2').locator()
   *
   * // returns by.css('#ID1')
   * $$('#ID1').filter(filterFn).get(0).click().locator()
   *
   * @returns {webdriver.Locator}
   */
  locator(): Locator {
    return this.locator_;
  }

  /**
   * Apply an action function to every element in the ElementArrayFinder,
   * and return a new ElementArrayFinder that contains the results of the
   * actions.
   *
   * @param {function(ElementFinder)} actionFn
   *
   * @returns {ElementArrayFinder}
   * @private
   */
  // map<U>(callbackfn: (value: T, index: number, array: T[]) => U, thisArg?:
  // any): U[];
  applyAction_(actionFn: (value: WebElement, index: number, array: WebElement[]) => any):
      ElementArrayFinder {
    let callerError = new Error();
    let actionResults = this.getWebElements()
                            .then((arr: WebElement[]) => {
                              return webdriver.promise.all(arr.map(actionFn));
                            })
                            .then(null, (e: IError | string) => {
                              let noSuchErr: any;
                              let stack: string;
                              if (e instanceof Error) {
                                noSuchErr = e;
                                noSuchErr.stack = noSuchErr.stack + (callerError as IError).stack;
                              } else {
                                noSuchErr = new Error(e as string);
                                noSuchErr.stack = (callerError as IError).stack;
                              }
                              throw noSuchErr;
                            });
    return new ElementArrayFinder(this.browser_, this.getWebElements, this.locator_, actionResults);
  }

  /**
   * Represents the ElementArrayFinder as an array of ElementFinders.
   *
   * @returns {Array.<ElementFinder>} Return a promise, which resolves to a list
   *     of ElementFinders specified by the locator.
   */
  asElementFinders_(): wdpromise.Promise<any> {
    return this.getWebElements().then((arr: WebElement[]) => {
      return arr.map((webElem: WebElement) => {
        return ElementFinder.fromWebElement_(this.browser_, webElem, this.locator_);
      });
    });
  }

  /**
   * Retrieve the elements represented by the ElementArrayFinder. The input
   * function is passed to the resulting promise, which resolves to an
   * array of ElementFinders.
   *
   * @alias element.all(locator).then(thenFunction)
   * @view
   * <ul class="items">
   *   <li>First</li>
   *   <li>Second</li>
   *   <li>Third</li>
   * </ul>
   *
   * @example
   * element.all(by.css('.items li')).then(function(arr) {
   *   expect(arr.length).toEqual(3);
   * });
   *
   * @param {function(Array.<ElementFinder>)} fn
   * @param {function(Error)} errorFn
   *
   * @returns {!webdriver.promise.Promise} A promise which will resolve to
   *     an array of ElementFinders represented by the ElementArrayFinder.
   */
  then(fn?: (value: any) => any | wdpromise.IThenable<any>, errorFn?: (error: any) => any):
      wdpromise.Promise<any[]> {
    if (this.actionResults_) {
      return this.actionResults_.then(fn, errorFn);
    } else {
      return this.asElementFinders_().then(fn, errorFn);
    }
  }

  /**
   * Calls the input function on each ElementFinder represented by the
   * ElementArrayFinder.
   *
   * @alias element.all(locator).each(eachFunction)
   * @view
   * <ul class="items">
   *   <li>First</li>
   *   <li>Second</li>
   *   <li>Third</li>
   * </ul>
   *
   * @example
   * element.all(by.css('.items li')).each(function(element, index) {
   *   // Will print 0 First, 1 Second, 2 Third.
   *   element.getText().then(function (text) {
   *     console.log(index, text);
   *   });
   * });
   *
   * @param {function(ElementFinder)} fn Input function
   *
   * @returns {!webdriver.promise.Promise} A promise that will resolve when the
   *     function has been called on all the ElementFinders. The promise will
   *     resolve to null.
   */
  each(fn: (elementFinder?: ElementFinder, index?: number) => any): wdpromise.Promise<any> {
    return this.map(fn).then((): any => {
      return null;
    });
  }

  /**
   * Apply a map function to each element within the ElementArrayFinder. The
   * callback receives the ElementFinder as the first argument and the index as
   * a second arg.
   *
   * @alias element.all(locator).map(mapFunction)
   * @view
   * <ul class="items">
   *   <li class="one">First</li>
   *   <li class="two">Second</li>
   *   <li class="three">Third</li>
   * </ul>
   *
   * @example
   * let items = element.all(by.css('.items li')).map(function(elm, index) {
   *   return {
   *     index: index,
   *     text: elm.getText(),
   *     class: elm.getAttribute('class')
   *   };
   * });
   * expect(items).toEqual([
   *   {index: 0, text: 'First', class: 'one'},
   *   {index: 1, text: 'Second', class: 'two'},
   *   {index: 2, text: 'Third', class: 'three'}
   * ]);
   *
   * @param {function(ElementFinder, number)} mapFn Map function that
   *     will be applied to each element.
   * @returns {!webdriver.promise.Promise} A promise that resolves to an array
   *     of values returned by the map function.
   */
  map(mapFn: (elementFinder?: ElementFinder, index?: number) => any): wdpromise.Promise<any> {
    return this.asElementFinders_().then((arr: ElementFinder[]) => {
      let list = arr.map((elementFinder?: ElementFinder, index?: number) => {
        let mapResult = mapFn(elementFinder, index);
        // All nested arrays and objects will also be fully resolved.
        return wdpromise.fullyResolved(mapResult);
      });
      return wdpromise.all(list);
    });
  };

  /**
   * Apply a reduce function against an accumulator and every element found
   * using the locator (from left-to-right). The reduce function has to reduce
   * every element into a single value (the accumulator). Returns promise of
   * the accumulator. The reduce function receives the accumulator, current
   * ElementFinder, the index, and the entire array of ElementFinders,
   * respectively.
   *
   * @alias element.all(locator).reduce(reduceFn)
   * @view
   * <ul class="items">
   *   <li class="one">First</li>
   *   <li class="two">Second</li>
   *   <li class="three">Third</li>
   * </ul>
   *
   * @example
   * let value = element.all(by.css('.items li')).reduce(function(acc, elem) {
   *   return elem.getText().then(function(text) {
   *     return acc + text + ' ';
   *   });
   * }, '');
   *
   * expect(value).toEqual('First Second Third ');
   *
   * @param {function(number, ElementFinder, number, Array.<ElementFinder>)}
   *     reduceFn Reduce function that reduces every element into a single
   * value.
   * @param {*} initialValue Initial value of the accumulator.
   * @returns {!webdriver.promise.Promise} A promise that resolves to the final
   *     value of the accumulator.
   */
  reduce(reduceFn: Function, initialValue: any): wdpromise.Promise<any> {
    let valuePromise = wdpromise.fulfilled(initialValue);
    return this.asElementFinders_().then((arr: ElementFinder[]) => {
      return arr.reduce((valuePromise: any, elementFinder: ElementFinder, index: number) => {
        return valuePromise.then((value: any) => {
          return reduceFn(value, elementFinder, index, arr);
        });
      }, valuePromise);
    });
  }

  /**
   * Evaluates the input as if it were on the scope of the current underlying
   * elements.
   *
   * @view
   * <span class="foo">{{letiableInScope}}</span>
   *
   * @example
   * let value = element.all(by.css('.foo')).evaluate('letiableInScope');
   *
   * @param {string} expression
   *
   * @returns {ElementArrayFinder} which resolves to the
   *     evaluated expression for each underlying element.
   *     The result will be resolved as in
   *     {@link webdriver.WebDriver.executeScript}. In summary - primitives will
   *     be resolved as is, functions will be converted to string, and elements
   *     will be returned as a WebElement.
   */
  evaluate(expression: string): ElementArrayFinder {
    let evaluationFn = (webElem: WebElement) => {
      return webElem.getDriver().executeScript(clientSideScripts.evaluate, webElem, expression);
    };
    return this.applyAction_(evaluationFn);
  }

  /**
   * Determine if animation is allowed on the current underlying elements.
   * @param {string} value
   *
   * @example
   * // Turns off ng-animate animations for all elements in the <body>
   * element(by.css('body')).allowAnimations(false);
   *
   * @returns {ElementArrayFinder} which resolves to whether animation is
   * allowed.
   */
  allowAnimations(value: boolean): ElementArrayFinder {
    let allowAnimationsTestFn = (webElem: WebElement) => {
      return webElem.getDriver().executeScript(clientSideScripts.allowAnimations, webElem, value);
    };
    return this.applyAction_(allowAnimationsTestFn);
  }
}

/**
 * The ElementFinder simply represents a single element of an
 * ElementArrayFinder (and is more like a convenience object). As a result,
 * anything that can be done with an ElementFinder, can also be done using
 * an ElementArrayFinder.
 *
 * The ElementFinder can be treated as a WebElement for most purposes, in
 * particular, you may perform actions (i.e. click, getText) on them as you
 * would a WebElement. Once an action is performed on an ElementFinder, the
 * latest result from the chain can be accessed using the then method.
 * Unlike a WebElement, an ElementFinder will wait for angular to settle before
 * performing finds or actions.
 *
 * ElementFinder can be used to build a chain of locators that is used to find
 * an element. An ElementFinder does not actually attempt to find the element
 * until an action is called, which means they can be set up in helper files
 * before the page is available.
 *
 * @alias element(locator)
 * @view
 * <span>{{person.name}}</span>
 * <span ng-bind="person.email"></span>
 * <input type="text" ng-model="person.name"/>
 *
 * @example
 * // Find element with {{scopelet}} syntax.
 * element(by.binding('person.name')).getText().then(function(name) {
 *   expect(name).toBe('Foo');
 * });
 *
 * // Find element with ng-bind="scopelet" syntax.
 * expect(element(by.binding('person.email')).getText()).toBe('foo@bar.com');
 *
 * // Find by model.
 * let input = element(by.model('person.name'));
 * input.sendKeys('123');
 * expect(input.getAttribute('value')).toBe('Foo123');
 *
 * @constructor
 * @extends {webdriver.WebElement}
 * @param {ProtractorBrowser} browser_ A browser instance.
 * @param {ElementArrayFinder} elementArrayFinder The ElementArrayFinder
 *     that this is branched from.
 * @returns {ElementFinder}
 */
export class ElementFinder extends WebdriverWebElement {
  parentElementArrayFinder: ElementArrayFinder;
  elementArrayFinder_: ElementArrayFinder;
  then: (fn: Function, errorFn?: Function) => wdpromise.Promise<any> = null;

  constructor(public browser_: ProtractorBrowser, elementArrayFinder: ElementArrayFinder) {
    super();
    if (!elementArrayFinder) {
      throw new Error('BUG: elementArrayFinder cannot be empty');
    }
    this.parentElementArrayFinder = elementArrayFinder;

    // Only have a `then` method if the parent element array finder
    // has action results.
    if (this.parentElementArrayFinder.actionResults_) {
      /**
       * Access the underlying actionResult of ElementFinder.
       *
       * @param {function(webdriver.promise.Promise)} fn Function which takes
       *     the value of the underlying actionResult.
       * @param {function(Error)} errorFn
       *
       * @returns {webdriver.promise.Promise} Promise which contains the results
       * of
       *     evaluating fn.
       */
      this.then =
          (fn: (value: any) => {} | wdpromise.IThenable<{}>, errorFn?: (error: any) => any) => {
            return this.elementArrayFinder_.then((actionResults: any) => {
              if (!fn) {
                return actionResults[0];
              }
              return fn(actionResults[0]);
            }, errorFn);
          };
    }

    // This filter verifies that there is only 1 element returned by the
    // elementArrayFinder. It will warn if there are more than 1 element and
    // throw an error if there are no elements.
    let getWebElements = (): wdpromise.Promise<WebElement[]> => {
      return elementArrayFinder.getWebElements().then((webElements: WebElement[]) => {
        if (webElements.length === 0) {
          throw new error.NoSuchElementError(
              'No element found using locator: ' + elementArrayFinder.locator().toString());
        } else {
          if (webElements.length > 1) {
            logger.warn(
                'more than one element found for locator ' +
                elementArrayFinder.locator().toString() + ' - the first result will be used');
          }
          return [webElements[0]];
        }
      });
    };

    // Store a copy of the underlying elementArrayFinder, but with the more
    // restrictive getWebElements (which checks that there is only 1 element).
    this.elementArrayFinder_ = new ElementArrayFinder(
        this.browser_, getWebElements, elementArrayFinder.locator(),
        elementArrayFinder.actionResults_);

    WEB_ELEMENT_FUNCTIONS.forEach((fnName: string) => {
      (this)[fnName] = (...args: any[]) => {
        return (this.elementArrayFinder_)[fnName]
            .apply(this.elementArrayFinder_, args)
            .toElementFinder_();
      };
    });
  }
  [key: string]: any;

  static fromWebElement_(browser: ProtractorBrowser, webElem: WebElement, locator: Locator):
      ElementFinder {
    let getWebElements = () => {
      return wdpromise.fulfilled([webElem]);
    };
    return new ElementArrayFinder(browser, getWebElements, locator).toElementFinder_();
  }

  /**
   * Create a shallow copy of ElementFinder.
   *
   * @returns {!ElementFinder} A shallow copy of this.
   */
  clone(): ElementFinder {
    // A shallow copy is all we need since the underlying fields can never be
    // modified
    return new ElementFinder(this.browser_, this.parentElementArrayFinder);
  }

  /**
   * @see ElementArrayFinder.prototype.locator
   *
   * @returns {webdriver.Locator}
   */
  locator(): any {
    return this.elementArrayFinder_.locator();
  }

  /**
   * Returns the WebElement represented by this ElementFinder.
   * Throws the WebDriver error if the element doesn't exist.
   *
   * @alias element(locator).getWebElement()
   * @view
   * <div class="parent">
   *   some text
   * </div>
   *
   * @example
   * // The following three expressions are equivalent.
   * element(by.css('.parent')).getWebElement();
   * browser.driver.findElement(by.css('.parent'));
   * browser.findElement(by.css('.parent'));
   *
   * @returns {webdriver.WebElement}
   */
  getWebElement(): WebElementPromise {
    let id = this.elementArrayFinder_.getWebElements().then(
        (parentWebElements: webdriver.WebElement[]) => {
          return parentWebElements[0];
        });
    return new WebElementPromise(this.browser_.driver, id);
  }

  /**
   * Calls to {@code all} may be chained to find an array of elements within a
   * parent.
   *
   * @alias element(locator).all(locator)
   * @view
   * <div class="parent">
   *   <ul>
   *     <li class="one">First</li>
   *     <li class="two">Second</li>
   *     <li class="three">Third</li>
   *   </ul>
   * </div>
   *
   * @example
   * let items = element(by.css('.parent')).all(by.tagName('li'))
   *
   * @param {webdriver.Locator} subLocator
   * @returns {ElementArrayFinder}
   */
  all(subLocator: Locator): ElementArrayFinder {
    return this.elementArrayFinder_.all(subLocator);
  }

  /**
   * Calls to {@code element} may be chained to find elements within a parent.
   *
   * @alias element(locator).element(locator)
   * @view
   * <div class="parent">
   *   <div class="child">
   *     Child text
   *     <div>{{person.phone}}</div>
   *   </div>
   * </div>
   *
   * @example
   * // Chain 2 element calls.
   * let child = element(by.css('.parent')).
   *     element(by.css('.child'));
   * expect(child.getText()).toBe('Child text\n555-123-4567');
   *
   * // Chain 3 element calls.
   * let triple = element(by.css('.parent')).
   *     element(by.css('.child')).
   *     element(by.binding('person.phone'));
   * expect(triple.getText()).toBe('555-123-4567');
   *
   * @param {webdriver.Locator} subLocator
   * @returns {ElementFinder}
   */
  element(subLocator: Locator): ElementFinder {
    return this.all(subLocator).toElementFinder_();
  }

  /**
   * Calls to {@code $$} may be chained to find an array of elements within a
   * parent.
   *
   * @alias element(locator).all(selector)
   * @view
   * <div class="parent">
   *   <ul>
   *     <li class="one">First</li>
   *     <li class="two">Second</li>
   *     <li class="three">Third</li>
   *   </ul>
   * </div>
   *
   * @example
   * let items = element(by.css('.parent')).$$('li')
   *
   * @param {string} selector a css selector
   * @returns {ElementArrayFinder}
   */
  $$(selector: string): ElementArrayFinder {
    return this.all(webdriver.By.css(selector));
  }

  /**
   * Calls to {@code $} may be chained to find elements within a parent.
   *
   * @alias element(locator).$(selector)
   * @view
   * <div class="parent">
   *   <div class="child">
   *     Child text
   *     <div>{{person.phone}}</div>
   *   </div>
   * </div>
   *
   * @example
   * // Chain 2 element calls.
   * let child = element(by.css('.parent')).
   *     $('.child');
   * expect(child.getText()).toBe('Child text\n555-123-4567');
   *
   * // Chain 3 element calls.
   * let triple = element(by.css('.parent')).
   *     $('.child').
   *     element(by.binding('person.phone'));
   * expect(triple.getText()).toBe('555-123-4567');
   *
   * @param {string} selector A css selector
   * @returns {ElementFinder}
   */
  $(selector: string): ElementFinder {
    return this.element(webdriver.By.css(selector));
  }

  /**
   * Determine whether the element is present on the page.
   *
   * @view
   * <span>{{person.name}}</span>
   *
   * @example
   * // Element exists.
   * expect(element(by.binding('person.name')).isPresent()).toBe(true);
   *
   * // Element not present.
   * expect(element(by.binding('notPresent')).isPresent()).toBe(false);
   *
   * @returns {webdriver.promise.Promise<boolean>} which resolves to whether
   *     the element is present on the page.
   */
  isPresent(): wdpromise.Promise<boolean> {
    return this.parentElementArrayFinder.getWebElements().then(
        (arr: any[]) => {
          if (arr.length === 0) {
            return false;
          }
          return arr[0].isEnabled().then(
              () => {
                return true;  // is present, whether it is enabled or not
              },
              (err: any) => {
                if (err.code == webdriver.error.ErrorCode.STALE_ELEMENT_REFERENCE) {
                  return false;
                } else {
                  throw err;
                }
              });
        },
        (err: any) => {
          if (err.code == webdriver.error.ErrorCode.NO_SUCH_ELEMENT) {
            return false;
          } else {
            throw err;
          }
        });
  }

  /**
   * Same as ElementFinder.isPresent(), except this checks whether the element
   * identified by the subLocator is present, rather than the current element
   * finder. i.e. `element(by.css('#abc')).element(by.css('#def')).isPresent()`
   * is identical to `element(by.css('#abc')).isElementPresent(by.css('#def'))`.
   *
   * @see ElementFinder.isPresent
   *
   * @param {webdriver.Locator} subLocator Locator for element to look for.
   * @returns {webdriver.promise.Promise<boolean>} which resolves to whether
   *     the subelement is present on the page.
   */
  isElementPresent(subLocator: Locator): wdpromise.Promise<boolean> {
    if (!subLocator) {
      throw new Error(
          'SubLocator is not supplied as a parameter to ' +
          '`isElementPresent(subLocator)`. You are probably looking for the ' +
          'function `isPresent()`.');
    }
    return this.element(subLocator).isPresent();
  }

  /**
   * Evaluates the input as if it were on the scope of the current element.
   * @see ElementArrayFinder.prototype.evaluate
   *
   * @view
   * <span id="foo">{{letiableInScope}}</span>
   *
   * @example
   * let value = element(by.id('foo')).evaluate('letiableInScope');
   *
   * @param {string} expression
   *
   * @returns {ElementFinder} which resolves to the evaluated expression.
   */
  evaluate(expression: string): ElementFinder {
    return this.elementArrayFinder_.evaluate(expression).toElementFinder_();
  }

  /**
   * @see ElementArrayFinder.prototype.allowAnimations.
   * @param {string} value
   *
   * @returns {ElementFinder} which resolves to whether animation is allowed.
   */
  allowAnimations(value: boolean): ElementFinder {
    return this.elementArrayFinder_.allowAnimations(value).toElementFinder_();
  }

  /**
   * Compares an element to this one for equality.
   *
   * @param {!ElementFinder|!webdriver.WebElement} The element to compare to.
   *
   * @returns {!webdriver.promise.Promise.<boolean>} A promise that will be
   *     resolved to whether the two WebElements are equal.
   */
  equals(element: ElementFinder|WebElement): wdpromise.Promise<any> {
    return WebElement.equals(
        this.getWebElement(), (element as any).getWebElement ?
            (element as ElementFinder).getWebElement() :
            element as WebElement);
  }
}

/**
 * Shortcut for querying the document directly with css.
 * `element(by.css('.abc'))` is equivalent to `$('.abc')`
 *
 *
 * @alias $(cssSelector)
 * @view
 * <div class="count">
 *   <span class="one">First</span>
 *   <span class="two">Second</span>
 * </div>
 *
 * @example
 * let item = $('.count .two');
 * expect(item.getText()).toBe('Second');
 *
 * @param {string} selector A css selector
 * @returns {ElementFinder} which identifies the located
 *     {@link webdriver.WebElement}
 */
export let build$ = (element: ElementHelper, by: typeof By) => {
  return (selector: string) => {
    return element(by.css(selector));
  };
};

/**
 * Shortcut for querying the document directly with css.
 * `element.all(by.css('.abc'))` is equivalent to `$$('.abc')`
 *
 * @alias $$(cssSelector)
 * @view
 * <div class="count">
 *   <span class="one">First</span>
 *   <span class="two">Second</span>
 * </div>
 *
 * @example
 * // The following protractor expressions are equivalent.
 * let list = element.all(by.css('.count span'));
 * expect(list.count()).toBe(2);
 *
 * list = $$('.count span');
 * expect(list.count()).toBe(2);
 * expect(list.get(0).getText()).toBe('First');
 * expect(list.get(1).getText()).toBe('Second');
 *
 * @param {string} selector a css selector
 * @returns {ElementArrayFinder} which identifies the
 *     array of the located {@link webdriver.WebElement}s.
 */
export let build$$ = (element: ElementHelper, by: typeof By) => {
  return (selector: string) => {
    return element.all(by.css(selector));
  };
};