1 files changed, 145 insertions, 0 deletions
diff --git a/devtools/client/shared/workers-listener.js b/devtools/client/shared/workers-listener.js
new file mode 100644
index 0000000000..7d544481d8
--- /dev/null
+++ b/devtools/client/shared/workers-listener.js
@@ -0,0 +1,145 @@
+/* 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";
+
+/**
+ * Listening to worker updates requires watching various sources. This class provides
+ * a single addListener/removeListener API that will aggregate all possible worker update
+ * events.
+ *
+ * Only supports one listener at a time.
+ */
+class WorkersListener {
+  constructor(rootFront, { registrationsOnly = false } = {}) {
+    this.rootFront = rootFront;
+    this.registrationsOnly = registrationsOnly;
+
+    // bind handlers
+    this._onContentProcessTargetAvailable =
+      this._onContentProcessTargetAvailable.bind(this);
+    this._onServiceWorkerRegistrationAvailable =
+      this._onServiceWorkerRegistrationAvailable.bind(this);
+    this._onProcessDescriptorAvailable =
+      this._onProcessDescriptorAvailable.bind(this);
+    this._onContentProcessTargetDestroyed =
+      this._onContentProcessTargetDestroyed.bind(this);
+    this._onServiceWorkerRegistrationDestroyed =
+      this._onServiceWorkerRegistrationDestroyed.bind(this);
+    this._onProcessDescriptorDestroyed =
+      this._onProcessDescriptorDestroyed.bind(this);
+
+    // Array of contentProcessTarget fronts on which we will listen for worker events.
+    this._contentProcessFronts = [];
+    this._serviceWorkerRegistrationFronts = [];
+    this._processDescriptors = [];
+    this._listener = null;
+  }
+
+  addListener(listener) {
+    if (this._listener) {
+      throw new Error("WorkersListener addListener called twice.");
+    }
+
+    this._listener = listener;
+    if (!this.registrationsOnly) {
+      this.rootFront.on("workerListChanged", this._listener);
+      this.rootFront.watchFronts(
+        "processDescriptor",
+        this._onProcessDescriptorAvailable,
+        this._onProcessDescriptorDestroyed
+      );
+      this.rootFront.on("processListChanged", this._listener);
+    }
+
+    this.rootFront.watchFronts(
+      "serviceWorkerRegistration",
+      this._onServiceWorkerRegistrationAvailable,
+      this._onServiceWorkerRegistrationDestroyed
+    );
+
+    this.rootFront.on("serviceWorkerRegistrationListChanged", this._listener);
+  }
+
+  removeListener(listener) {
+    if (!this._listener) {
+      return;
+    }
+
+    this.rootFront.off("workerListChanged", this._listener);
+    this.rootFront.off("serviceWorkerRegistrationListChanged", this._listener);
+    this.rootFront.off("processListChanged", this._listener);
+
+    for (const front of this._contentProcessFronts) {
+      front.off("workerListChanged", this._listener);
+    }
+
+    for (const front of this._serviceWorkerRegistrationFronts) {
+      front.off("push-subscription-modified", this._listener);
+      front.off("registration-changed", this._listener);
+    }
+
+    for (const processFront of this._processDescriptors) {
+      processFront.unwatchFronts(
+        "contentProcessTarget",
+        this._onContentProcessTargetAvailable
+      );
+    }
+
+    this.rootFront.unwatchFronts(
+      "processDescriptor",
+      this._onProcessDescriptorAvailable,
+      this._onProcessDescriptorDestroyed
+    );
+    this.rootFront.unwatchFronts(
+      "serviceWorkerRegistration",
+      this._onServiceWorkerRegistrationAvailable,
+      this._onServiceWorkerRegistrationDestroyed
+    );
+
+    this._contentProcessFronts = [];
+    this._serviceWorkerRegistrationFronts = [];
+    this._processDescriptors = [];
+    this._listener = null;
+  }
+
+  _onContentProcessTargetAvailable(front) {
+    this._contentProcessFronts.push(front);
+    front.on("workerListChanged", this._listener);
+  }
+
+  _onContentProcessTargetDestroyed(front) {
+    this._contentProcessFronts = this._contentProcessFronts.filter(
+      f => f !== front
+    );
+  }
+
+  _onServiceWorkerRegistrationAvailable(front) {
+    this._serviceWorkerRegistrationFronts.push(front);
+    front.on("push-subscription-modified", this._listener);
+    front.on("registration-changed", this._listener);
+  }
+
+  _onServiceWorkerRegistrationDestroyed(front) {
+    this._serviceWorkerRegistrationFronts =
+      this._serviceWorkerRegistrationFronts.filter(f => f !== front);
+  }
+
+  _onProcessDescriptorAvailable(processFront) {
+    this._processDescriptors.push(processFront);
+    processFront.watchFronts(
+      "contentProcessTarget",
+      this._onContentProcessTargetAvailable,
+      this._onContentProcessTargetDestroyed
+    );
+  }
+
+  _onProcessDescriptorDestroyed(processFront) {
+    this._processDescriptors = this._processDescriptors.filter(
+      f => f !== processFront
+    );
+  }
+}
+
+exports.WorkersListener = WorkersListener;