/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/* eslint-env browser */

"use strict";

const Services = require("Services");
const flags = require("devtools/shared/flags");
const { PureComponent } = require("devtools/client/shared/vendor/react");
const PropTypes = require("devtools/client/shared/vendor/react-prop-types");
const dom = require("devtools/client/shared/vendor/react-dom-factories");

const e10s = require("../utils/e10s");
const message = require("../utils/message");
const { getToplevelWindow } = require("../utils/window");

const FRAME_SCRIPT = "resource://devtools/client/responsive.html/browser/content.js";

class Browser extends PureComponent {
  /**
   * This component is not allowed to depend directly on frequently changing data (width,
   * height). Any changes in props would cause the <iframe> to be removed and added again,
   * throwing away the current state of the page.
   */
  static get propTypes() {
    return {
      swapAfterMount: PropTypes.bool.isRequired,
      userContextId: PropTypes.number.isRequired,
      onBrowserMounted: PropTypes.func.isRequired,
      onContentResize: PropTypes.func.isRequired,
    };
  }

  constructor(props) {
    super(props);
    this.onContentResize = this.onContentResize.bind(this);
  }

  /**
   * Before the browser is mounted, listen for `remote-browser-shown` so that we know when
   * the browser is fully ready.  Without waiting for an event such as this, we don't know
   * whether all frame state for the browser is fully initialized (since some happens
   * async after the element is added), and swapping browsers can fail if this state is
   * not ready.
   */
  componentWillMount() {
    this.browserShown = new Promise(resolve => {
      const handler = frameLoader => {
        if (frameLoader.ownerElement != this.browser) {
          return;
        }
        Services.obs.removeObserver(handler, "remote-browser-shown");
        resolve();
      };
      Services.obs.addObserver(handler, "remote-browser-shown");
    });
  }

  /**
   * Once the browser element has mounted, load the frame script and enable
   * various features, like floating scrollbars.
   */
  async componentDidMount() {
    // If we are not swapping browsers after mount, it's safe to start the frame
    // script now.
    if (!this.props.swapAfterMount) {
      await this.startFrameScript();
    }

    // Notify manager.js that this browser has mounted, so that it can trigger
    // a swap if needed and continue with the rest of its startup.
    await this.browserShown;
    this.props.onBrowserMounted();

    // If we are swapping browsers after mount, wait for the swap to complete
    // and start the frame script after that.
    if (this.props.swapAfterMount) {
      await message.wait(window, "start-frame-script");
      await this.startFrameScript();
      message.post(window, "start-frame-script:done");
    }

    // Stop the frame script when requested in the future.
    message.wait(window, "stop-frame-script").then(() => {
      this.stopFrameScript();
    });
  }

  onContentResize(msg) {
    const { onContentResize } = this.props;
    const { width, height } = msg.data;
    onContentResize({
      width,
      height,
    });
  }

  async startFrameScript() {
    const {
      browser,
      onContentResize,
    } = this;
    const mm = browser.frameLoader.messageManager;

    // Notify tests when the content has received a resize event.  This is not
    // quite the same timing as when we _set_ a new size around the browser,
    // since it still needs to do async work before the content is actually
    // resized to match.
    e10s.on(mm, "OnContentResize", onContentResize);

    const ready = e10s.once(mm, "ChildScriptReady");
    mm.loadFrameScript(FRAME_SCRIPT, true);
    await ready;

    const browserWindow = getToplevelWindow(window);
    const requiresFloatingScrollbars =
      !browserWindow.matchMedia("(-moz-overlay-scrollbars)").matches;

    await e10s.request(mm, "Start", {
      requiresFloatingScrollbars,
      // Tests expect events on resize to wait for various size changes
      notifyOnResize: flags.testing,
    });
  }

  async stopFrameScript() {
    const {
      browser,
      onContentResize,
    } = this;
    const mm = browser.frameLoader.messageManager;

    e10s.off(mm, "OnContentResize", onContentResize);
    await e10s.request(mm, "Stop");
    message.post(window, "stop-frame-script:done");
  }

  render() {
    const {
      userContextId,
    } = this.props;

    // In the case of @remote and @remoteType, the attribute must be set before the
    // element is added to the DOM to have any effect, which we are able to do with this
    // approach.
    //
    // @noisolation and @allowfullscreen are needed so that these frames have the same
    // access to browser features as regular browser tabs. The `swapFrameLoaders` platform
    // API we use compares such features before allowing the swap to proceed.
    return dom.iframe(
      {
        allowFullScreen: "true",
        className: "browser",
        height: "100%",
        mozbrowser: "true",
        noisolation: "true",
        remote: "true",
        remotetype: "web",
        src: "about:blank",
        usercontextid: userContextId,
        width: "100%",
        ref: browser => {
          this.browser = browser;
        },
      }
    );
  }
}

module.exports = Browser;
