1 files changed, 125 insertions, 0 deletions
diff --git a/devtools/server/actors/changes.js b/devtools/server/actors/changes.js
new file mode 100644
index 0000000000..16e24cb2e7
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+++ b/devtools/server/actors/changes.js
@@ -0,0 +1,125 @@
+/* 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 { Actor } = require("resource://devtools/shared/protocol.js");
+const { changesSpec } = require("resource://devtools/shared/specs/changes.js");
+
+const TrackChangeEmitter = require("resource://devtools/server/actors/utils/track-change-emitter.js");
+
+/**
+ * The ChangesActor stores a stack of changes made by devtools on
+ * the document in the associated tab.
+ */
+class ChangesActor extends Actor {
+  /**
+   * Create a ChangesActor.
+   *
+   * @param {DevToolsServerConnection} conn
+   *    The server connection.
+   * @param {TargetActor} targetActor
+   *    The top-level Actor for this tab.
+   */
+  constructor(conn, targetActor) {
+    super(conn, changesSpec);
+    this.targetActor = targetActor;
+
+    this.onTrackChange = this.pushChange.bind(this);
+    this.onWillNavigate = this.onWillNavigate.bind(this);
+
+    TrackChangeEmitter.on("track-change", this.onTrackChange);
+    this.targetActor.on("will-navigate", this.onWillNavigate);
+
+    this.changes = [];
+  }
+
+  destroy() {
+    // Stop trying to emit RDP event on destruction.
+    this._changesHaveBeenRequested = false;
+    this.clearChanges();
+    this.targetActor.off("will-navigate", this.onWillNavigate);
+    TrackChangeEmitter.off("track-change", this.onTrackChange);
+    super.destroy();
+  }
+
+  start() {
+    /**
+     * This function currently does nothing and returns nothing. It exists only
+     * so that the client can trigger the creation of the ChangesActor through
+     * the front, without triggering side effects, and with a sensible semantic
+     * meaning.
+     */
+  }
+
+  changeCount() {
+    return this.changes.length;
+  }
+
+  change(index) {
+    if (index >= 0 && index < this.changes.length) {
+      // Return a copy of the change at index.
+      return Object.assign({}, this.changes[index]);
+    }
+    // No change at that index -- return undefined.
+    return undefined;
+  }
+
+  allChanges() {
+    /**
+     * This function is called by all change event consumers on the client
+     * to get their initial state synchronized with the ChangesActor. We
+     * set a flag when this function is called so we know that it's worthwhile
+     * to send events.
+     */
+    this._changesHaveBeenRequested = true;
+    return this.changes.slice();
+  }
+
+  /**
+   * Handler for "will-navigate" event from the browsing context. The event is fired for
+   * the host page and any nested resources, like iframes. The list of changes should be
+   * cleared only when the host page navigates, ignoring any of its iframes.
+   *
+   * TODO: Clear changes made within sources in iframes when they navigate. Bug 1513940
+   *
+   * @param {Object} eventData
+   *        Event data with these properties:
+   *        {
+   *          window: Object      // Window DOM object of the event source page
+   *          isTopLevel: Boolean // true if the host page will navigate
+   *          newURI: String      // URI towards which the page will navigate
+   *          request: Object     // Request data.
+   *        }
+   */
+  onWillNavigate(eventData) {
+    if (eventData.isTopLevel) {
+      this.clearChanges();
+    }
+  }
+
+  pushChange(change) {
+    this.changes.push(change);
+    if (this._changesHaveBeenRequested) {
+      this.emit("add-change", change);
+    }
+  }
+
+  popChange() {
+    const change = this.changes.pop();
+    if (this._changesHaveBeenRequested) {
+      this.emit("remove-change", change);
+    }
+    return change;
+  }
+
+  clearChanges() {
+    this.changes.length = 0;
+    if (this._changesHaveBeenRequested) {
+      this.emit("clear-changes");
+    }
+  }
+}
+
+exports.ChangesActor = ChangesActor;