import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

mobile/android/modules/Messaging.jsm

@@ -0,0 +1,183 @@
+/* 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 { classes: Cc, interfaces: Ci, utils: Cu } = Components;
+
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+Cu.import("resource://gre/modules/Task.jsm");
+
+this.EXPORTED_SYMBOLS = ["sendMessageToJava", "Messaging"];
+
+XPCOMUtils.defineLazyServiceGetter(this, "uuidgen",
+                                   "@mozilla.org/uuid-generator;1",
+                                   "nsIUUIDGenerator");
+
+function sendMessageToJava(aMessage, aCallback) {
+  Cu.reportError("sendMessageToJava is deprecated. Use Messaging API instead.");
+
+  if (aCallback) {
+    Messaging.sendRequestForResult(aMessage)
+      .then(result => aCallback(result, null),
+            error => aCallback(null, error));
+  } else {
+    Messaging.sendRequest(aMessage);
+  }
+}
+
+var Messaging = {
+  /**
+   * Add a listener for the given message.
+   *
+   * Only one request listener can be registered for a given message.
+   *
+   * Example usage:
+   *   // aData is data sent from Java with the request. The return value is
+   *   // used to respond to the request. The return type *must* be an instance
+   *   // of Object.
+   *   let listener = function (aData) {
+   *     if (aData == "foo") {
+   *       return { response: "bar" };
+   *     }
+   *     return {};
+   *   };
+   *   Messaging.addListener(listener, "Demo:Request");
+   *
+   * The listener may also be a generator function, useful for performing a
+   * task asynchronously. For example:
+   *   let listener = function* (aData) {
+   *     // Respond with "bar" after 2 seconds.
+   *     yield new Promise(resolve => setTimeout(resolve, 2000));
+   *     return { response: "bar" };
+   *   };
+   *   Messaging.addListener(listener, "Demo:Request");
+   *
+   * @param aListener Listener callback taking a single data parameter (see
+   *                  example usage above).
+   * @param aMessage  Event name that this listener should observe.
+   */
+  addListener: function (aListener, aMessage) {
+    requestHandler.addListener(aListener, aMessage);
+  },
+
+  /**
+   * Removes a listener for a given message.
+   *
+   * @param aMessage The event to stop listening for.
+   */
+  removeListener: function (aMessage) {
+    requestHandler.removeListener(aMessage);
+  },
+
+  /**
+   * Sends a request to Java.
+   *
+   * @param aMessage  Message to send; must be an object with a "type" property
+   */
+  sendRequest: function (aMessage) {
+    Services.androidBridge.handleGeckoMessage(aMessage);
+  },
+
+  /**
+   * Sends a request to Java, returning a Promise that resolves to the response.
+   *
+   * @param aMessage Message to send; must be an object with a "type" property
+   * @returns A Promise resolving to the response
+   */
+  sendRequestForResult: function (aMessage) {
+    return new Promise((resolve, reject) => {
+      let id = uuidgen.generateUUID().toString();
+      let obs = {
+        observe: function (aSubject, aTopic, aData) {
+          let data = JSON.parse(aData);
+          if (data.__guid__ != id) {
+            return;
+          }
+
+          Services.obs.removeObserver(obs, aMessage.type + ":Response");
+
+          if (data.status === "success") {
+            resolve(data.response);
+          } else {
+            reject(data.response);
+          }
+        }
+      };
+
+      aMessage.__guid__ = id;
+      Services.obs.addObserver(obs, aMessage.type + ":Response", false);
+
+      this.sendRequest(aMessage);
+    });
+  },
+
+  /**
+   * Handles a request from Java, using the given listener method.
+   * This is mainly an internal method used by the RequestHandler object, but can be
+   * used in nsIObserver.observe implmentations that fall outside the normal usage
+   * patterns.
+   *
+   * @param aTopic    The string name of the message
+   * @param aData     The data sent to the observe method from Java
+   * @param aListener A function that takes a JSON data argument and returns a
+   *                  response which is sent to Java.
+   */
+  handleRequest: Task.async(function* (aTopic, aData, aListener) {
+    let wrapper = JSON.parse(aData);
+
+    try {
+      let response = yield aListener(wrapper.data);
+      if (typeof response !== "object" || response === null) {
+        throw new Error("Gecko request listener did not return an object");
+      }
+
+      Messaging.sendRequest({
+        type: "Gecko:Request" + wrapper.id,
+        response: response
+      });
+    } catch (e) {
+      Cu.reportError("Error in Messaging handler for " + aTopic + ": " + e);
+
+      Messaging.sendRequest({
+        type: "Gecko:Request" + wrapper.id,
+        error: {
+          message: e.message || (e && e.toString()),
+          stack: e.stack || Components.stack.formattedStack,
+        }
+      });
+    }
+  })
+};
+
+var requestHandler = {
+  _listeners: {},
+
+  addListener: function (aListener, aMessage) {
+    if (aMessage in this._listeners) {
+      throw new Error("Error in addListener: A listener already exists for message " + aMessage);
+    }
+
+    if (typeof aListener !== "function") {
+      throw new Error("Error in addListener: Listener must be a function for message " + aMessage);
+    }
+
+    this._listeners[aMessage] = aListener;
+    Services.obs.addObserver(this, aMessage, false);
+  },
+
+  removeListener: function (aMessage) {
+    if (!(aMessage in this._listeners)) {
+      throw new Error("Error in removeListener: There is no listener for message " + aMessage);
+    }
+
+    delete this._listeners[aMessage];
+    Services.obs.removeObserver(this, aMessage);
+  },
+
+  observe: function(aSubject, aTopic, aData) {
+    let listener = this._listeners[aTopic];
+    Messaging.handleRequest(aTopic, aData, listener);
+  }
+};