1 files changed, 121 insertions, 0 deletions
diff --git a/browser/components/pagedata/PageDataChild.sys.mjs b/browser/components/pagedata/PageDataChild.sys.mjs
new file mode 100644
index 0000000000..51dc384526
--- /dev/null
+++ b/browser/components/pagedata/PageDataChild.sys.mjs
@@ -0,0 +1,121 @@
+/* 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/. */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  PageDataSchema: "resource:///modules/pagedata/PageDataSchema.sys.mjs",
+  PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
+});
+
+// We defer any attempt to check for page data for a short time after a page
+// loads to allow JS to operate.
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "READY_DELAY",
+  "browser.pagedata.readyDelay",
+  500
+);
+
+/**
+ * The actor responsible for monitoring a page for page data.
+ */
+export class PageDataChild extends JSWindowActorChild {
+  #isContentWindowPrivate = true;
+  /**
+   * Used to debounce notifications about a page being ready.
+   *
+   * @type {Timer | null}
+   */
+  #deferTimer = null;
+
+  /**
+   * Called when the actor is created for a new page.
+   */
+  actorCreated() {
+    this.#isContentWindowPrivate =
+      lazy.PrivateBrowsingUtils.isContentWindowPrivate(this.contentWindow);
+  }
+
+  /**
+   * Called when the page is destroyed.
+   */
+  didDestroy() {
+    if (this.#deferTimer) {
+      this.#deferTimer.cancel();
+    }
+  }
+
+  /**
+   * Called when the page has signalled it is done loading. This signal is
+   * debounced by READY_DELAY.
+   */
+  #deferReady() {
+    if (!this.#deferTimer) {
+      this.#deferTimer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+    }
+
+    // If the timer was already running this re-starts it.
+    this.#deferTimer.initWithCallback(
+      () => {
+        this.#deferTimer = null;
+        this.sendAsyncMessage("PageData:DocumentReady", {
+          url: this.document.documentURI,
+        });
+      },
+      lazy.READY_DELAY,
+      Ci.nsITimer.TYPE_ONE_SHOT_LOW_PRIORITY
+    );
+  }
+
+  /**
+   * Called when a message is received from the parent process.
+   *
+   * @param {ReceiveMessageArgument} msg
+   *   The received message.
+   *
+   * @returns {Promise | undefined}
+   *   A promise for the requested data or undefined if no data was requested.
+   */
+  receiveMessage(msg) {
+    if (this.#isContentWindowPrivate) {
+      return undefined;
+    }
+
+    switch (msg.name) {
+      case "PageData:CheckLoaded":
+        // The service just started in the parent. Check if this document is
+        // already loaded.
+        if (this.document.readystate == "complete") {
+          this.#deferReady();
+        }
+        break;
+      case "PageData:Collect":
+        return lazy.PageDataSchema.collectPageData(this.document);
+    }
+
+    return undefined;
+  }
+
+  /**
+   * DOM event handler.
+   *
+   * @param {Event} event
+   *   The DOM event.
+   */
+  handleEvent(event) {
+    if (this.#isContentWindowPrivate) {
+      return;
+    }
+
+    switch (event.type) {
+      case "DOMContentLoaded":
+      case "pageshow":
+        this.#deferReady();
+        break;
+    }
+  }
+}