Handle accountData events from TagOrderStore

This introduces a generic way to register certain events emitted by
the js-sdk as those that should be propagated through as dispatched
actions.

This allows the store to treat the js-sdk as the "Server" in the
Flux data flow model. It also allows for stores to not be aware
specifically of the matrix client if they are only reading from it.

src/actions/actionCreators.js

@@ -16,6 +16,16 @@ limitations under the License.
 
 import dis from '../dispatcher';
 
+/**
+ * Create an action creator that will dispatch actions asynchronously that
+ * indicate the current status of promise returned by the given function, fn.
+ * @param {string} id the id to give the dispatched actions. This is given a
+ *                   suffix determining whether it is pending, successful or
+ *                   a failure.
+ * @param {function} fn the function to call with arguments given to the
+ *                   returned function. This function should return a Promise.
+ * @returns a function that dispatches asynchronous actions when called.
+ */
 export function createPromiseActionCreator(id, fn) {
     return (...args) => {
         dis.dispatch({action: id + '.pending'});
@@ -26,3 +36,37 @@ export function createPromiseActionCreator(id, fn) {
         })
     }
 }
+
+/**
+ * Create an action creator that will listen to events of type eventId emitted
+ * by matrixClient and dispatch a corresponding action of the following shape:
+ *     {
+ *         action: 'MatrixActions.' + eventId,
+ *         event: matrixEvent,
+ *         event_type: matrixEvent.getType(),
+ *         event_content: matrixEvent.getContent(),
+ *     }
+ * @param matrixClient{MatrixClient} the matrix client with which to register
+ *                                   a listener.
+ * @param eventId{string} the ID of the event that hen emitted will cause the
+ *                        an action to be dispatched.
+ * @returns a function that, when called, will begin to listen to dispatches
+ *          from matrixClient. The result from that function can be called to
+ *          stop listening.
+ */
+export function createMatrixActionCreator(matrixClient, eventId) {
+    const listener = (matrixEvent) => {
+        dis.dispatch({
+            action: 'MatrixActions.' + eventId,
+            event: matrixEvent,
+            event_type: matrixEvent.getType(),
+            event_content: matrixEvent.getContent(),
+        });
+    };
+    return () => {
+        matrixClient.on(eventId, listener);
+        return () => {
+            matrixClient.removeListener(listener);
+        }
+    }
+}