Support for async request-respond through post-message

lib/PluginApi.js

@@ -1,3 +1,4 @@
+var xde = require('cross-domain-events');
 var data = {};
 var i = 0;
 
@@ -30,12 +31,64 @@ function publish (id, subject) {
     });
 }
 
+
+ /**
+ *
+ * Gardr.reqres
+ *
+ * Request-response pattern for sending messages
+ * between gardr hostplugins and ext banners and plugins.
+ */
+
+ // Sends a message to otherWindow with params
+ // waits for the response, and calls callback upon that.
+ function postMessage (subject, params, callback, otherWindow) {
+     otherWindow = otherWindow || window.top;
+
+     try {
+         xde.sendTo(otherWindow, 'gardr:' + subject, params);
+
+         xde.on('gardr:' + subject + ':response', function (evt) {
+             callback(null, evt.data);
+         });
+     } catch(e) {
+         callback(e);
+     }
+ }
+
+
+// listens to postmessages with subject
+// calls the given callback, and upon return
+// sends the result back
+function respondToPostMessage (subject, cb) {
+     xde.on('gardr:' + subject, onRespondToMsg(subject, cb))
+
+    function onRespondToMsg (subject, cb) {
+
+        return function (evt) {
+            // because cb can be async, it is responsible for
+            // triggering the _onCallbackComplete function
+            cb(evt.data, onCallbackComplete.bind(null, subject, evt));
+        }
+    }
+
+    function onCallbackComplete (subject, evt, res) {
+        xde.sendTo(evt.source, 'gardr:' + subject + ':response', res);
+    }
+}
+
+
 var PluginApi = function () {
     this.id = i++;
 
     set(this.id, 'listeners', {});
     this.on      = subscribe.bind(null, this.id);
-    this.trigger = publish.bind(null, this.id)
+    this.trigger = publish.bind(null, this.id);
+
+    // The reqres module enables gardr plugins to communicate after
+    // the banner has been document writed.
+    this.postMessage = postMessage;
+    this.respondToPostMessage = respondToPostMessage;
 
     this._reset = function () { set(this.id, 'listeners', {}); };
 };

package.json

@@ -26,5 +26,8 @@
     "karma": "~0.12.1",
     "karma-browserifast": "~0.4.1",
     "es5-shim": "~2.3.0"
+  },
+  "dependencies": {
+    "cross-domain-events": "0.0.2"
   }
 }

test/PluginApi.test.js

@@ -1,9 +1,20 @@
 /*jshint expr: true, nonew: false*/
-var PluginApi = require('../lib/PluginApi.js');
+var PluginApi = require('../lib/PluginApi.js'),
+          xde = require('cross-domain-events'),
+          api;
 
 describe('PluginApi', function () {
 
+    beforeEach(function () {
+        api = new PluginApi();
+    });
+
+    afterEach(function () {
+        api._reset();
+    });
+
     describe('constructor', function () {
+
         it('should not throw if no arguments', function () {
             expect(function () {
                 new PluginApi();
@@ -12,15 +23,6 @@ describe('PluginApi', function () {
     });
 
     describe('events', function () {
-        var api;
-
-        beforeEach(function () {
-            api = new PluginApi();
-        });
-
-        afterEach(function () {
-            api._reset();
-        });
 
         it('should exist', function () {
             expect(api.on).to.exist;
@@ -63,4 +65,46 @@ describe('PluginApi', function () {
             }).not.to.throw();
         });
     });
+
+    describe('reqres', function () {
+
+        describe('end-to-end', function () {
+            var evtName = 'yoer:bar';
+            var reqData = {fooInt : 1337};
+
+            it('should call request.callback with proper params when there is a responder', function (done) {
+                callRespondToPostMessage(api, evtName);
+                callPostMessage(api, evtName, reqData, 1338, done);
+            });
+        });
+
+        describe('errors', function () {
+            it('should catch xde errors', function () {
+                api.postMessage('test:event', {}, function (err) {
+                    expect(err).to.exist;
+                    expect(err.message).to.equal('otherWindow does not support postMessage');
+                }, 'not a window object');
+            });
+        })
+    });
 });
+
+
+function callRespondToPostMessage (api, evtName) {
+    api.respondToPostMessage(evtName, onResponseMsg);
+
+    function onResponseMsg (responseData, commCb) {
+        var result = responseData.fooInt + 1;
+        commCb({fooIntResult : result});
+    }
+}
+
+function callPostMessage (api, evtName, reqData, expectedResult, done) {
+    api.postMessage(evtName, reqData, onXdeCb, window);
+
+    function onXdeCb (err, responseData) {
+        expect(err).to.be.null;
+        expect(responseData.fooIntResult).to.equal(expectedResult);
+        done();
+    }
+}