1 files changed, 236 insertions, 0 deletions
diff --git a/remote/shared/messagehandler/MessageHandlerRegistry.sys.mjs b/remote/shared/messagehandler/MessageHandlerRegistry.sys.mjs
new file mode 100644
index 0000000000..6a09173f50
--- /dev/null
+++ b/remote/shared/messagehandler/MessageHandlerRegistry.sys.mjs
@@ -0,0 +1,236 @@
+/* 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 { EventEmitter } from "resource://gre/modules/EventEmitter.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  Log: "chrome://remote/content/shared/Log.sys.mjs",
+  readSessionData:
+    "chrome://remote/content/shared/messagehandler/sessiondata/SessionDataReader.sys.mjs",
+  RootMessageHandler:
+    "chrome://remote/content/shared/messagehandler/RootMessageHandler.sys.mjs",
+  WindowGlobalMessageHandler:
+    "chrome://remote/content/shared/messagehandler/WindowGlobalMessageHandler.sys.mjs",
+});
+
+ChromeUtils.defineLazyGetter(lazy, "logger", () => lazy.Log.get());
+
+/**
+ * Map of MessageHandler type to MessageHandler subclass.
+ */
+ChromeUtils.defineLazyGetter(
+  lazy,
+  "MessageHandlerClasses",
+  () =>
+    new Map([
+      [lazy.RootMessageHandler.type, lazy.RootMessageHandler],
+      [lazy.WindowGlobalMessageHandler.type, lazy.WindowGlobalMessageHandler],
+    ])
+);
+
+/**
+ * Get the MessageHandler subclass corresponding to the provided type.
+
+ * @param {string} type
+ *     MessageHandler type, one of MessageHandler.type.
+ * @returns {Class}
+ *     A MessageHandler subclass
+ * @throws {Error}
+ *      Throws if no MessageHandler subclass is found for the provided type.
+ */
+export function getMessageHandlerClass(type) {
+  if (!lazy.MessageHandlerClasses.has(type)) {
+    throw new Error(`No MessageHandler class available for type "${type}"`);
+  }
+  return lazy.MessageHandlerClasses.get(type);
+}
+
+/**
+ * The MessageHandlerRegistry allows to create and retrieve MessageHandler
+ * instances for different session ids.
+ *
+ * A MessageHandlerRegistry instance is bound to a specific MessageHandler type
+ * and context. All MessageHandler instances created by the same registry will
+ * use the type and context of the registry, but each will be associated to a
+ * different session id.
+ *
+ * The registry is useful to retrieve the appropriate MessageHandler instance
+ * after crossing a technical boundary (eg process, thread...).
+ */
+export class MessageHandlerRegistry extends EventEmitter {
+  /*
+   * @param {String} type
+   *     MessageHandler type, one of MessageHandler.type.
+   * @param {Object} context
+   *     The context object, which depends on the type.
+   */
+  constructor(type, context) {
+    super();
+
+    this._messageHandlerClass = getMessageHandlerClass(type);
+    this._context = context;
+    this._type = type;
+
+    /**
+     * Map of session id to MessageHandler instance
+     */
+    this._messageHandlersMap = new Map();
+
+    this._onMessageHandlerDestroyed =
+      this._onMessageHandlerDestroyed.bind(this);
+    this._onMessageHandlerEvent = this._onMessageHandlerEvent.bind(this);
+  }
+
+  /**
+   * Create all message handlers for the current context, based on the content
+   * of the session data.
+   * This should typically be called when the context is ready to be used and
+   * to receive/send commands.
+   */
+  createAllMessageHandlers() {
+    const data = lazy.readSessionData();
+    for (const [sessionId, sessionDataItems] of data) {
+      // Create a message handler for this context for each active message
+      // handler session.
+      // TODO: In the future, to support debugging use cases we might want to
+      // only create a message handler if there is relevant data.
+      // For automation scenarios, this is less critical.
+      this._createMessageHandler(sessionId, sessionDataItems);
+    }
+  }
+
+  destroy() {
+    this._messageHandlersMap.forEach(messageHandler => {
+      messageHandler.destroy();
+    });
+  }
+
+  /**
+   * Retrieve all MessageHandler instances held in this registry, for all
+   * session IDs.
+   *
+   * @returns {Iterable.<MessageHandler>}
+   *     Iterator of MessageHandler instances
+   */
+  getAllMessageHandlers() {
+    return this._messageHandlersMap.values();
+  }
+
+  /**
+   * Retrieve an existing MessageHandler instance matching the provided session
+   * id. Returns null if no MessageHandler was found.
+   *
+   * @param {string} sessionId
+   *     ID of the session the handler is used for.
+   * @returns {MessageHandler=}
+   *     A MessageHandler instance, null if not found.
+   */
+  getExistingMessageHandler(sessionId) {
+    return this._messageHandlersMap.get(sessionId);
+  }
+
+  /**
+   * Retrieve the MessageHandler instance registered for the provided session
+   * id. Will create and register a MessageHander if no instance was found.
+   *
+   * @param {string} sessionId
+   *     ID of the session the handler is used for.
+   * @returns {MessageHandler}
+   *     A MessageHandler instance.
+   */
+  getOrCreateMessageHandler(sessionId) {
+    let messageHandler = this.getExistingMessageHandler(sessionId);
+    if (!messageHandler) {
+      messageHandler = this._createMessageHandler(sessionId);
+    }
+
+    return messageHandler;
+  }
+
+  /**
+   * Retrieve an already registered RootMessageHandler instance matching the
+   * provided sessionId.
+   *
+   * @param {string} sessionId
+   *     ID of the session the handler is used for.
+   * @returns {RootMessageHandler}
+   *     A RootMessageHandler instance.
+   * @throws {Error}
+   *     If no root MessageHandler can be found for the provided session id.
+   */
+  getRootMessageHandler(sessionId) {
+    const rootMessageHandler = this.getExistingMessageHandler(
+      sessionId,
+      lazy.RootMessageHandler.type
+    );
+    if (!rootMessageHandler) {
+      throw new Error(
+        `Unable to find a root MessageHandler for session id ${sessionId}`
+      );
+    }
+    return rootMessageHandler;
+  }
+
+  toString() {
+    return `[object ${this.constructor.name}]`;
+  }
+
+  /**
+   * Create a new MessageHandler instance.
+   *
+   * @param {string} sessionId
+   *     ID of the session the handler will be used for.
+   * @param {Array<SessionDataItem>=} sessionDataItems
+   *     Optional array of session data items to be applied automatically to the
+   *     MessageHandler.
+   * @returns {MessageHandler}
+   *     A new MessageHandler instance.
+   */
+  _createMessageHandler(sessionId, sessionDataItems) {
+    const messageHandler = new this._messageHandlerClass(
+      sessionId,
+      this._context,
+      this
+    );
+
+    messageHandler.on(
+      "message-handler-destroyed",
+      this._onMessageHandlerDestroyed
+    );
+    messageHandler.on("message-handler-event", this._onMessageHandlerEvent);
+
+    messageHandler.initialize(sessionDataItems);
+
+    this._messageHandlersMap.set(sessionId, messageHandler);
+
+    lazy.logger.trace(
+      `Created MessageHandler ${this._type} for session ${sessionId}`
+    );
+
+    return messageHandler;
+  }
+
+  // Event handlers
+
+  _onMessageHandlerDestroyed(eventName, messageHandler) {
+    messageHandler.off(
+      "message-handler-destroyed",
+      this._onMessageHandlerDestroyed
+    );
+    messageHandler.off("message-handler-event", this._onMessageHandlerEvent);
+    this._messageHandlersMap.delete(messageHandler.sessionId);
+
+    lazy.logger.trace(
+      `Unregistered MessageHandler ${messageHandler.constructor.type} for session ${messageHandler.sessionId}`
+    );
+  }
+
+  _onMessageHandlerEvent(eventName, messageHandlerEvent) {
+    // The registry simply re-emits MessageHandler events so that consumers
+    // don't have to attach listeners to individual MessageHandler instances.
+    this.emit("message-handler-registry-event", messageHandlerEvent);
+  }
+}