/* vim: set ts=2 sw=2 et tw=80: */
/* 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/. */

"use strict";

const EXPORTED_SYMBOLS = [
  "LinkClickHandlerChild",
  "StrictLinkClickHandlerChild",
];

const { XPCOMUtils } = ChromeUtils.importESModule(
  "resource://gre/modules/XPCOMUtils.sys.mjs"
);

const lazy = {};

XPCOMUtils.defineLazyServiceGetter(
  lazy,
  "protocolSvc",
  "@mozilla.org/uriloader/external-protocol-service;1",
  "nsIExternalProtocolService"
);

/**
 * Extract the href from the link click event.
 * We look for HTMLAnchorElement, HTMLAreaElement, HTMLLinkElement,
 * HTMLInputElement.form.action, and nested anchor tags.
 * If the clicked element was a HTMLInputElement or HTMLButtonElement
 * we return the form action.
 *
 * @returns the url and the text for the link being clicked.
 */
function hRefForClickEvent(aEvent) {
  let target = aEvent.target;

  if (
    HTMLImageElement.isInstance(target) &&
    target.hasAttribute("overflowing")
  ) {
    // Click on zoomed image.
    return [null, null];
  }

  let href = null;
  if (
    HTMLAnchorElement.isInstance(target) ||
    HTMLAreaElement.isInstance(target) ||
    HTMLLinkElement.isInstance(target)
  ) {
    if (target.hasAttribute("href") && !target.download) {
      href = target.href;
    }
  } else {
    // We may be nested inside of a link node.
    let linkNode = aEvent.target;
    while (linkNode && !HTMLAnchorElement.isInstance(linkNode)) {
      linkNode = linkNode.parentNode;
    }

    if (linkNode && !linkNode.download) {
      href = linkNode.href;
    }
  }
  return href;
}

/**
 * Listens for click events and, if the click would result in loading a page
 * on a different base domain from the current page, cancels the click event,
 * redirecting the URI to an external browser, effectively creating a
 * single-site browser.
 *
 * This actor applies to browsers in the "single-site" message manager group.
 */
class LinkClickHandlerChild extends JSWindowActorChild {
  handleEvent(event) {
    // Don't handle events that:
    //   a) are in the parent process (handled by onclick),
    //   b) aren't trusted,
    //   c) have already been handled or
    //   d) aren't left-click.
    if (
      this.manager.isInProcess ||
      !event.isTrusted ||
      event.defaultPrevented ||
      event.button
    ) {
      return;
    }

    let eventHRef = hRefForClickEvent(event);
    if (!eventHRef) {
      return;
    }

    let pageURI = Services.io.newURI(this.document.location.href);
    let eventURI = Services.io.newURI(eventHRef);

    try {
      if (pageURI.host == eventURI.host) {
        // Avoid using the eTLD service, and this also works for IP addresses.
        return;
      }

      try {
        if (
          Services.eTLD.getBaseDomain(eventURI) ==
          Services.eTLD.getBaseDomain(pageURI)
        ) {
          return;
        }
      } catch (ex) {
        if (ex.result != Cr.NS_ERROR_HOST_IS_IP_ADDRESS) {
          console.error(ex);
        }
      }
    } catch (ex) {
      // The page or link might be from a host-less URL scheme such as about,
      // blob, or data. The host is never going to match, carry on.
    }

    if (
      !lazy.protocolSvc.isExposedProtocol(eventURI.scheme) ||
      eventURI.schemeIs("http") ||
      eventURI.schemeIs("https")
    ) {
      event.preventDefault();
      this.sendAsyncMessage("openLinkExternally", eventHRef);
    }
  }
}

/**
 * Listens for click events and, if the click would result in loading a
 * different page from the current page, cancels the click event, redirecting
 * the URI to an external browser, effectively creating a single-page browser.
 *
 * This actor applies to browsers in the "single-page" message manager group.
 */
class StrictLinkClickHandlerChild extends JSWindowActorChild {
  handleEvent(event) {
    // Don't handle events that:
    //   a) are in the parent process (handled by onclick),
    //   b) aren't trusted,
    //   c) have already been handled or
    //   d) aren't left-click.
    if (
      this.manager.isInProcess ||
      !event.isTrusted ||
      event.defaultPrevented ||
      event.button
    ) {
      return;
    }

    let eventHRef = hRefForClickEvent(event);
    if (!eventHRef) {
      return;
    }

    let pageURI = Services.io.newURI(this.document.location.href);
    let eventURI = Services.io.newURI(eventHRef);
    if (eventURI.specIgnoringRef == pageURI.specIgnoringRef) {
      return;
    }

    if (
      !lazy.protocolSvc.isExposedProtocol(eventURI.scheme) ||
      eventURI.schemeIs("http") ||
      eventURI.schemeIs("https")
    ) {
      event.preventDefault();
      this.sendAsyncMessage("openLinkExternally", eventHRef);
    }
  }
}