JSHandle.ts

/**
 * Copyright 2019 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.
 */

import { assert } from './assert';
import { helper, debugError } from './helper';
import { ExecutionContext } from './ExecutionContext';
import { Page } from './Page';
import { CDPSession } from './Connection';
import { KeyInput } from './USKeyboardLayout';
import { FrameManager, Frame } from './FrameManager';
import { getQueryHandlerAndSelector } from './QueryHandler';
import Protocol from '../protocol';

/**
 * @public
 */
export interface BoxModel {
  content: Array<{ x: number; y: number }>;
  padding: Array<{ x: number; y: number }>;
  border: Array<{ x: number; y: number }>;
  margin: Array<{ x: number; y: number }>;
  width: number;
  height: number;
}

/**
 * @public
 */
export interface BoundingBox {
  /**
   * the x coordinate of the element in pixels.
   */
  x: number;
  /**
   * the y coordinate of the element in pixels.
   */
  y: number;
  /**
   * the width of the element in pixels.
   */
  width: number;
  /**
   * the height of the element in pixels.
   */
  height: number;
}

/**
 * @internal
 */
export function createJSHandle(
  context: ExecutionContext,
  remoteObject: Protocol.Runtime.RemoteObject
): JSHandle {
  const frame = context.frame();
  if (remoteObject.subtype === 'node' && frame) {
    const frameManager = frame._frameManager;
    return new ElementHandle(
      context,
      context._client,
      remoteObject,
      frameManager.page(),
      frameManager
    );
  }
  return new JSHandle(context, context._client, remoteObject);
}

/**
 * @public
 */
export class JSHandle {
  _context: ExecutionContext;
  _client: CDPSession;
  _remoteObject: Protocol.Runtime.RemoteObject;
  _disposed = false;

  constructor(
    context: ExecutionContext,
    client: CDPSession,
    remoteObject: Protocol.Runtime.RemoteObject
  ) {
    this._context = context;
    this._client = client;
    this._remoteObject = remoteObject;
  }

  executionContext(): ExecutionContext {
    return this._context;
  }

  /**
   * This method passes this handle as the first argument to `pageFunction`.
   * If `pageFunction` returns a Promise, then `handle.evaluate` would wait
   * for the promise to resolve and return its value.
   *
   * @example
   * ```js
   * const tweetHandle = await page.$('.tweet .retweets');
   * expect(await tweetHandle.evaluate(node => node.innerText)).toBe('10');
   * ```
   */
  async evaluate<ReturnType extends any>(
    pageFunction: Function | string,
    ...args: unknown[]
  ): Promise<ReturnType> {
    return await this.executionContext().evaluate<ReturnType>(
      pageFunction,
      this,
      ...args
    );
  }

  /**
   * This method passes this handle as the first argument to `pageFunction`.
   *
   * @remarks
   *
   * The only difference between `evaluateHandle.evaluate` and
   * `evaluateHandle.evaluateHandle` is that `executionContext.evaluateHandle`
   * returns in-page object (JSHandle).
   *
   * If the function passed to the `evaluateHandle.evaluateHandle` returns a Promise,
   * then `evaluateHandle.evaluateHandle` would wait for the promise to resolve and
   * return its value.
   *
   * See {@link Page.evaluateHandle} for more details.
   */
  async evaluateHandle(
    pageFunction: Function | string,
    ...args: unknown[]
  ): Promise<JSHandle> {
    return await this.executionContext().evaluateHandle(
      pageFunction,
      this,
      ...args
    );
  }

  async getProperty(propertyName: string): Promise<JSHandle | undefined> {
    const objectHandle = await this.evaluateHandle(
      (object: HTMLElement, propertyName: string) => {
        const result = { __proto__: null };
        result[propertyName] = object[propertyName];
        return result;
      },
      propertyName
    );
    const properties = await objectHandle.getProperties();
    const result = properties.get(propertyName) || null;
    await objectHandle.dispose();
    return result;
  }

  /**
   * The method returns a map with property names as keys and JSHandle
   * instances for the property values.
   *
   * @example
   * ```js
   * const listHandle = await page.evaluateHandle(() => document.body.children);
   * const properties = await listHandle.getProperties();
   * const children = [];
   * for (const property of properties.values()) {
   *   const element = property.asElement();
   *   if (element)
   *     children.push(element);
   * }
   * children; // holds elementHandles to all children of document.body
   * ```
   */
  async getProperties(): Promise<Map<string, JSHandle>> {
    const response = await this._client.send('Runtime.getProperties', {
      objectId: this._remoteObject.objectId,
      ownProperties: true,
    });
    const result = new Map<string, JSHandle>();
    for (const property of response.result) {
      if (!property.enumerable) continue;
      result.set(property.name, createJSHandle(this._context, property.value));
    }
    return result;
  }

  /**
   * Returns a JSON representation of the object.
   *
   * @remarks
   *
   * The JSON is generated by running {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify | JSON.stringify}
   * on the object in page and consequent {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse | JSON.parse} in puppeteer.
   * **NOTE** The method will throw if the referenced object is not stringifiable.
   */
  async jsonValue(): Promise<{}> {
    if (this._remoteObject.objectId) {
      const response = await this._client.send('Runtime.callFunctionOn', {
        functionDeclaration: 'function() { return this; }',
        objectId: this._remoteObject.objectId,
        returnByValue: true,
        awaitPromise: true,
      });
      return helper.valueFromRemoteObject(response.result);
    }
    return helper.valueFromRemoteObject(this._remoteObject);
  }

  /* This always returns null but children can define this and return an ElementHandle */
  asElement(): ElementHandle | null {
    return null;
  }

  /**
   * The method stops referencing the element handle.
   */
  async dispose(): Promise<void> {
    if (this._disposed) return;
    this._disposed = true;
    await helper.releaseObject(this._client, this._remoteObject);
  }

  toString(): string {
    if (this._remoteObject.objectId) {
      const type = this._remoteObject.subtype || this._remoteObject.type;
      return 'JSHandle@' + type;
    }
    return 'JSHandle:' + helper.valueFromRemoteObject(this._remoteObject);
  }
}

/**
 * ElementHandle represents an in-page DOM element.
 *
 * @remarks
 *
 * ElementHandles can be created with the {@link Page.$} method.
 *
 * ```js
 * const puppeteer = require('puppeteer');
 *
 * (async () => {
 *  const browser = await puppeteer.launch();
 *  const page = await browser.newPage();
 *  await page.goto('https://example.com');
 *  const hrefElement = await page.$('a');
 *  await hrefElement.click();
 *  // ...
 * })();
 * ```
 *
 * ElementHandle prevents DOM element from garbage collection unless the handle is
 * {@link JSHandle.dispose | disposed}. ElementHandles are auto-disposed when their
 * origin frame gets navigated.
 *
 * ElementHandle instances can be used as arguments in {@link Page.$eval} and
 * {@link Page.evaluate} methods.
 *
 * @public
 */
export class ElementHandle extends JSHandle {
  private _page: Page;
  private _frameManager: FrameManager;

  /**
   * @internal
   */
  constructor(
    context: ExecutionContext,
    client: CDPSession,
    remoteObject: Protocol.Runtime.RemoteObject,
    page: Page,
    frameManager: FrameManager
  ) {
    super(context, client, remoteObject);
    this._client = client;
    this._remoteObject = remoteObject;
    this._page = page;
    this._frameManager = frameManager;
  }

  asElement(): ElementHandle | null {
    return this;
  }

  /**
   * Resolves to the content frame for element handles referencing
   * iframe nodes, or null otherwise
   */
  async contentFrame(): Promise<Frame | null> {
    const nodeInfo = await this._client.send('DOM.describeNode', {
      objectId: this._remoteObject.objectId,
    });
    if (typeof nodeInfo.node.frameId !== 'string') return null;
    return this._frameManager.frame(nodeInfo.node.frameId);
  }

  private async _scrollIntoViewIfNeeded(): Promise<void> {
    const error = await this.evaluate<Promise<string | false>>(
      async (element: HTMLElement, pageJavascriptEnabled: boolean) => {
        if (!element.isConnected) return 'Node is detached from document';
        if (element.nodeType !== Node.ELEMENT_NODE)
          return 'Node is not of type HTMLElement';
        // force-scroll if page's javascript is disabled.
        if (!pageJavascriptEnabled) {
          element.scrollIntoView({
            block: 'center',
            inline: 'center',
            // Chrome still supports behavior: instant but it's not in the spec
            // so TS shouts We don't want to make this breaking change in
            // Puppeteer yet so we'll ignore the line.
            // @ts-ignore
            behavior: 'instant',
          });
          return false;
        }
        const visibleRatio = await new Promise((resolve) => {
          const observer = new IntersectionObserver((entries) => {
            resolve(entries[0].intersectionRatio);
            observer.disconnect();
          });
          observer.observe(element);
        });
        if (visibleRatio !== 1.0) {
          element.scrollIntoView({
            block: 'center',
            inline: 'center',
            // Chrome still supports behavior: instant but it's not in the spec
            // so TS shouts We don't want to make this breaking change in
            // Puppeteer yet so we'll ignore the line.
            // @ts-ignore
            behavior: 'instant',
          });
        }
        return false;
      },
      this._page.isJavaScriptEnabled()
    );

    if (error) throw new Error(error);
  }

  private async _clickablePoint(): Promise<{ x: number; y: number }> {
    const [result, layoutMetrics] = await Promise.all([
      this._client
        .send('DOM.getContentQuads', {
          objectId: this._remoteObject.objectId,
        })
        .catch(debugError),
      this._client.send('Page.getLayoutMetrics'),
    ]);
    if (!result || !result.quads.length)
      throw new Error('Node is either not visible or not an HTMLElement');
    // Filter out quads that have too small area to click into.
    const { clientWidth, clientHeight } = layoutMetrics.layoutViewport;
    const quads = result.quads
      .map((quad) => this._fromProtocolQuad(quad))
      .map((quad) =>
        this._intersectQuadWithViewport(quad, clientWidth, clientHeight)
      )
      .filter((quad) => computeQuadArea(quad) > 1);
    if (!quads.length)
      throw new Error('Node is either not visible or not an HTMLElement');
    // Return the middle point of the first quad.
    const quad = quads[0];
    let x = 0;
    let y = 0;
    for (const point of quad) {
      x += point.x;
      y += point.y;
    }
    return {
      x: x / 4,
      y: y / 4,
    };
  }

  private _getBoxModel(): Promise<void | Protocol.DOM.getBoxModelReturnValue> {
    return this._client
      .send('DOM.getBoxModel', {
        objectId: this._remoteObject.objectId,
      })
      .catch((error) => debugError(error));
  }

  private _fromProtocolQuad(quad: number[]): Array<{ x: number; y: number }> {
    return [
      { x: quad[0], y: quad[1] },
      { x: quad[2], y: quad[3] },
      { x: quad[4], y: quad[5] },
      { x: quad[6], y: quad[7] },
    ];
  }

  private _intersectQuadWithViewport(
    quad: Array<{ x: number; y: number }>,
    width: number,
    height: number
  ): Array<{ x: number; y: number }> {
    return quad.map((point) => ({
      x: Math.min(Math.max(point.x, 0), width),
      y: Math.min(Math.max(point.y, 0), height),
    }));
  }

  /**
   * This method scrolls element into view if needed, and then
   * uses {@link Page.mouse} to hover over the center of the element.
   * If the element is detached from DOM, the method throws an error.
   */
  async hover(): Promise<void> {
    await this._scrollIntoViewIfNeeded();
    const { x, y } = await this._clickablePoint();
    await this._page.mouse.move(x, y);
  }

  /**
   * This method scrolls element into view if needed, and then
   * uses {@link Page.mouse} to click in the center of the element.
   * If the element is detached from DOM, the method throws an error.
   */
  async click(options: ClickOptions = {}): Promise<void> {
    await this._scrollIntoViewIfNeeded();
    const { x, y } = await this._clickablePoint();
    await this._page.mouse.click(x, y, options);
  }

  /**
   * Triggers a `change` and `input` event once all the provided options have been
   * selected. If there's no `<select>` element matching `selector`, the method
   * throws an error.
   *
   * @example
   * ```js
   * handle.select('blue'); // single selection
   * handle.select('red', 'green', 'blue'); // multiple selections
   * ```
   * @param values - Values of options to select. If the `<select>` has the
   *    `multiple` attribute, all values are considered, otherwise only the first
   *    one is taken into account.
   */
  async select(...values: string[]): Promise<string[]> {
    for (const value of values)
      assert(
        helper.isString(value),
        'Values must be strings. Found value "' +
          value +
          '" of type "' +
          typeof value +
          '"'
      );

    /* TODO(jacktfranklin@): once ExecutionContext is TypeScript, and
     * its evaluate function is properly typed with generics we can
     * return here and remove the typecasting
     */
    return this.evaluate((element: HTMLSelectElement, values: string[]) => {
      if (element.nodeName.toLowerCase() !== 'select')
        throw new Error('Element is not a <select> element.');

      const options = Array.from(element.options);
      element.value = undefined;
      for (const option of options) {
        option.selected = values.includes(option.value);
        if (option.selected && !element.multiple) break;
      }
      element.dispatchEvent(new Event('input', { bubbles: true }));
      element.dispatchEvent(new Event('change', { bubbles: true }));
      return options
        .filter((option) => option.selected)
        .map((option) => option.value);
    }, values);
  }

  /**
   * This method expects `elementHandle` to point to an
   * {@link https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input | input element}.
   * @param filePaths - Sets the value of the file input to these paths.
   *    If some of the  `filePaths` are relative paths, then they are resolved
   *    relative to the {@link https://nodejs.org/api/process.html#process_process_cwd | current working directory}
   */
  async uploadFile(...filePaths: string[]): Promise<void> {
    const isMultiple = await this.evaluate<boolean>(
      (element: HTMLInputElement) => element.multiple
    );
    assert(
      filePaths.length <= 1 || isMultiple,
      'Multiple file uploads only work with <input type=file multiple>'
    );

    // This import is only needed for `uploadFile`, so keep it scoped here to avoid paying
    // the cost unnecessarily.
    // eslint-disable-next-line @typescript-eslint/no-var-requires
    const path = require('path');
    // eslint-disable-next-line @typescript-eslint/no-var-requires
    const fs = require('fs');
    // eslint-disable-next-line @typescript-eslint/no-var-requires
    const { promisify } = require('util');
    const access = promisify(fs.access);

    // Locate all files and confirm that they exist.
    const files = await Promise.all(
      filePaths.map(async (filePath) => {
        const resolvedPath: string = path.resolve(filePath);
        try {
          await access(resolvedPath, fs.constants.R_OK);
        } catch (error) {
          if (error.code === 'ENOENT')
            throw new Error(`${filePath} does not exist or is not readable`);
        }

        return resolvedPath;
      })
    );
    const { objectId } = this._remoteObject;
    const { node } = await this._client.send('DOM.describeNode', { objectId });
    const { backendNodeId } = node;

    // The zero-length array is a special case, it seems that DOM.setFileInputFiles does
    // not actually update the files in that case, so the solution is to eval the element
    // value to a new FileList directly.
    if (files.length === 0) {
      await this.evaluate((element: HTMLInputElement) => {
        element.files = new DataTransfer().files;

        // Dispatch events for this case because it should behave akin to a user action.
        element.dispatchEvent(new Event('input', { bubbles: true }));
        element.dispatchEvent(new Event('change', { bubbles: true }));
      });
    } else {
      await this._client.send('DOM.setFileInputFiles', {
        objectId,
        files,
        backendNodeId,
      });
    }
  }

  /**
   * This method scrolls element into view if needed, and then uses
   * {@link Touchscreen.tap} to tap in the center of the element.
   * If the element is detached from DOM, the method throws an error.
   */
  async tap(): Promise<void> {
    await this._scrollIntoViewIfNeeded();
    const { x, y } = await this._clickablePoint();
    await this._page.touchscreen.tap(x, y);
  }

  /**
   * Calls {@link https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/focus | focus} on the element.
   */
  async focus(): Promise<void> {
    await this.evaluate((element) => element.focus());
  }

  /**
   * Focuses the element, and then sends a `keydown`, `keypress`/`input`, and
   * `keyup` event for each character in the text.
   *
   * To press a special key, like `Control` or `ArrowDown`,
   * use {@link ElementHandle.press}.
   *
   * @example
   * ```js
   * await elementHandle.type('Hello'); // Types instantly
   * await elementHandle.type('World', {delay: 100}); // Types slower, like a user
   * ```
   *
   * @example
   * An example of typing into a text field and then submitting the form:
   *
   * ```js
   * const elementHandle = await page.$('input');
   * await elementHandle.type('some text');
   * await elementHandle.press('Enter');
   * ```
   */
  async type(text: string, options?: { delay: number }): Promise<void> {
    await this.focus();
    await this._page.keyboard.type(text, options);
  }

  /**
   * Focuses the element, and then uses {@link Keyboard.down} and {@link Keyboard.up}.
   *
   * @remarks
   * If `key` is a single character and no modifier keys besides `Shift`
   * are being held down, a `keypress`/`input` event will also be generated.
   * The `text` option can be specified to force an input event to be generated.
   *
   * **NOTE** Modifier keys DO affect `elementHandle.press`. Holding down `Shift`
   * will type the text in upper case.
   *
   * @param key - Name of key to press, such as `ArrowLeft`.
   *    See {@link KeyInput} for a list of all key names.
   */
  async press(key: KeyInput, options?: PressOptions): Promise<void> {
    await this.focus();
    await this._page.keyboard.press(key, options);
  }

  /**
   * This method returns the bounding box of the element (relative to the main frame),
   * or `null` if the element is not visible.
   */
  async boundingBox(): Promise<BoundingBox | null> {
    const result = await this._getBoxModel();

    if (!result) return null;

    const quad = result.model.border;
    const x = Math.min(quad[0], quad[2], quad[4], quad[6]);
    const y = Math.min(quad[1], quad[3], quad[5], quad[7]);
    const width = Math.max(quad[0], quad[2], quad[4], quad[6]) - x;
    const height = Math.max(quad[1], quad[3], quad[5], quad[7]) - y;

    return { x, y, width, height };
  }

  /**
   * This method returns boxes of the element, or `null` if the element is not visible.
   *
   * @remarks
   *
   * Boxes are represented as an array of points;
   * Each Point is an object `{x, y}`. Box points are sorted clock-wise.
   */
  async boxModel(): Promise<BoxModel | null> {
    const result = await this._getBoxModel();

    if (!result) return null;

    const { content, padding, border, margin, width, height } = result.model;
    return {
      content: this._fromProtocolQuad(content),
      padding: this._fromProtocolQuad(padding),
      border: this._fromProtocolQuad(border),
      margin: this._fromProtocolQuad(margin),
      width,
      height,
    };
  }

  /**
   * This method scrolls element into view if needed, and then uses
   * {@link Page.screenshot} to take a screenshot of the element.
   * If the element is detached from DOM, the method throws an error.
   */
  async screenshot(options = {}): Promise<string | Buffer | void> {
    let needsViewportReset = false;

    let boundingBox = await this.boundingBox();
    assert(boundingBox, 'Node is either not visible or not an HTMLElement');

    const viewport = this._page.viewport();

    if (
      viewport &&
      (boundingBox.width > viewport.width ||
        boundingBox.height > viewport.height)
    ) {
      const newViewport = {
        width: Math.max(viewport.width, Math.ceil(boundingBox.width)),
        height: Math.max(viewport.height, Math.ceil(boundingBox.height)),
      };
      await this._page.setViewport(Object.assign({}, viewport, newViewport));

      needsViewportReset = true;
    }

    await this._scrollIntoViewIfNeeded();

    boundingBox = await this.boundingBox();
    assert(boundingBox, 'Node is either not visible or not an HTMLElement');
    assert(boundingBox.width !== 0, 'Node has 0 width.');
    assert(boundingBox.height !== 0, 'Node has 0 height.');

    const {
      layoutViewport: { pageX, pageY },
    } = await this._client.send('Page.getLayoutMetrics');

    const clip = Object.assign({}, boundingBox);
    clip.x += pageX;
    clip.y += pageY;

    const imageData = await this._page.screenshot(
      Object.assign(
        {},
        {
          clip,
        },
        options
      )
    );

    if (needsViewportReset) await this._page.setViewport(viewport);

    return imageData;
  }

  /**
   * The method runs `element.querySelector` within the page. If no element matches
   * the selector, the return value resolves to `null`.
   */
  async $(selector: string): Promise<ElementHandle | null> {
    const defaultHandler = (element: Element, selector: string) =>
      element.querySelector(selector);
    const { updatedSelector, queryHandler } = getQueryHandlerAndSelector(
      selector,
      defaultHandler
    );

    const handle = await this.evaluateHandle(queryHandler, updatedSelector);
    const element = handle.asElement();
    if (element) return element;
    await handle.dispose();
    return null;
  }

  /**
   * The method runs `element.querySelectorAll` within the page. If no elements match
   * the selector, the return value resolves to `[]`.
   */
  async $$(selector: string): Promise<ElementHandle[]> {
    const defaultHandler = (element: Element, selector: string) =>
      element.querySelectorAll(selector);
    const { updatedSelector, queryHandler } = getQueryHandlerAndSelector(
      selector,
      defaultHandler
    );

    const arrayHandle = await this.evaluateHandle(
      queryHandler,
      updatedSelector
    );
    const properties = await arrayHandle.getProperties();
    await arrayHandle.dispose();
    const result = [];
    for (const property of properties.values()) {
      const elementHandle = property.asElement();
      if (elementHandle) result.push(elementHandle);
    }
    return result;
  }

  /**
   * This method runs `document.querySelector` within the element and passes it as
   * the first argument to `pageFunction`. If there's no element matching `selector`,
   * the method throws an error.
   *
   * If `pageFunction` returns a Promise, then `frame.$eval` would wait for the promise
   * to resolve and return its value.
   *
   * @example
   * ```js
   * const tweetHandle = await page.$('.tweet');
   * expect(await tweetHandle.$eval('.like', node => node.innerText)).toBe('100');
   * expect(await tweetHandle.$eval('.retweets', node => node.innerText)).toBe('10');
   * ```
   */
  async $eval<ReturnType extends any>(
    selector: string,
    pageFunction: Function | string,
    ...args: unknown[]
  ): Promise<ReturnType> {
    const elementHandle = await this.$(selector);
    if (!elementHandle)
      throw new Error(
        `Error: failed to find element matching selector "${selector}"`
      );
    const result = await elementHandle.evaluate<ReturnType>(
      pageFunction,
      ...args
    );
    await elementHandle.dispose();
    return result;
  }

  /**
   * This method runs `document.querySelectorAll` within the element and passes it as
   * the first argument to `pageFunction`. If there's no element matching `selector`,
   * the method throws an error.
   *
   * If `pageFunction` returns a Promise, then `frame.$$eval` would wait for the
   * promise to resolve and return its value.
   *
   * @example
   * ```html
   * <div class="feed">
   *   <div class="tweet">Hello!</div>
   *   <div class="tweet">Hi!</div>
   * </div>
   * ```
   *
   * @example
   * ```js
   * const feedHandle = await page.$('.feed');
   * expect(await feedHandle.$$eval('.tweet', nodes => nodes.map(n => n.innerText)))
   *  .toEqual(['Hello!', 'Hi!']);
   * ```
   */
  async $$eval<ReturnType extends any>(
    selector: string,
    pageFunction: Function | string,
    ...args: unknown[]
  ): Promise<ReturnType> {
    const defaultHandler = (element: Element, selector: string) =>
      Array.from(element.querySelectorAll(selector));
    const { updatedSelector, queryHandler } = getQueryHandlerAndSelector(
      selector,
      defaultHandler
    );

    const arrayHandle = await this.evaluateHandle(
      queryHandler,
      updatedSelector
    );
    const result = await arrayHandle.evaluate<ReturnType>(
      pageFunction,
      ...args
    );
    await arrayHandle.dispose();
    return result;
  }

  /**
   * The method evaluates the XPath expression relative to the elementHandle.
   * If there are no such elements, the method will resolve to an empty array.
   * @param expression - Expression to {@link https://developer.mozilla.org/en-US/docs/Web/API/Document/evaluate | evaluate}
   */
  async $x(expression: string): Promise<ElementHandle[]> {
    const arrayHandle = await this.evaluateHandle((element, expression) => {
      const document = element.ownerDocument || element;
      const iterator = document.evaluate(
        expression,
        element,
        null,
        XPathResult.ORDERED_NODE_ITERATOR_TYPE
      );
      const array = [];
      let item;
      while ((item = iterator.iterateNext())) array.push(item);
      return array;
    }, expression);
    const properties = await arrayHandle.getProperties();
    await arrayHandle.dispose();
    const result = [];
    for (const property of properties.values()) {
      const elementHandle = property.asElement();
      if (elementHandle) result.push(elementHandle);
    }
    return result;
  }

  /**
   * Resolves to true if the element is visible in the current viewport.
   */
  async isIntersectingViewport(): Promise<boolean> {
    return await this.evaluate<Promise<boolean>>(async (element) => {
      const visibleRatio = await new Promise((resolve) => {
        const observer = new IntersectionObserver((entries) => {
          resolve(entries[0].intersectionRatio);
          observer.disconnect();
        });
        observer.observe(element);
      });
      return visibleRatio > 0;
    });
  }
}

/**
 * @public
 */
export interface ClickOptions {
  /**
   * Time to wait between `mousedown` and `mouseup` in milliseconds.
   *
   * @defaultValue 0
   */
  delay?: number;
  /**
   * @defaultValue 'left'
   */
  button?: 'left' | 'right' | 'middle';
  /**
   * @defaultValue 1
   */
  clickCount?: number;
}

/**
 * @public
 */
export interface PressOptions {
  /**
   * Time to wait between `keydown` and `keyup` in milliseconds. Defaults to 0.
   */
  delay?: number;
  /**
   * If specified, generates an input event with this text.
   */
  text?: string;
}

function computeQuadArea(quad: Array<{ x: number; y: number }>): number {
  // Compute sum of all directed areas of adjacent triangles
  // https://en.wikipedia.org/wiki/Polygon#Simple_polygons
  let area = 0;
  for (let i = 0; i < quad.length; ++i) {
    const p1 = quad[i];
    const p2 = quad[(i + 1) % quad.length];
    area += (p1.x * p2.y - p2.x * p1.y) / 2;
  }
  return Math.abs(area);
}