emit after txn has been committed

to keep txn open for as short as possible,
and avoid any errors caused as part of emit aborting txn

doc/TODO.md

@@ -21,7 +21,7 @@
  - DONE: build a very basic interface with
  	- DONE: a start/stop sync button
  	- DONE: a room list sorted alphabetically
- - do some preprocessing on sync response which can then be used by persister, summary, timeline
+ - DONE: do some preprocessing on sync response which can then be used by persister, summary, timeline
  - support timeline
  	- clicking on a room list, you see messages (userId -> body)
  - send messages

src/matrix/room/room.js

@@ -12,9 +12,13 @@ export default class Room extends EventEmitter {
         this._emitCollectionChange = emitCollectionChange;
 	}
 
-	async applySync(roomResponse, membership, txn) {
+    persistSync(roomResponse, membership, txn) {
 		const changed = this._summary.applySync(roomResponse, membership, txn);
 		this._persister.persistSync(roomResponse, txn);
+        return changed;
+    }
+
+    emitSync(changed) {
         if (changed) {
             this.emit("change");
             (this._emitCollectionChange)(this);

src/matrix/sync.js

@@ -76,6 +76,7 @@ export default class Sync extends EventEmitter {
 			storeNames.roomTimeline,
 			storeNames.roomState,
 		]);
+        const roomChanges = [];
         try {
             this._session.applySync(syncToken, response.account_data, syncTxn);
             // to_device
@@ -87,7 +88,8 @@ export default class Sync extends EventEmitter {
 						room = this._session.createRoom(roomId);
 					}
 					console.log(` * applying sync response to room ${roomId} ...`);
-					room.applySync(roomResponse, membership, syncTxn);
+					const changes = room.persistSync(roomResponse, membership, syncTxn);
+                    roomChanges.push({room, changes});
 				});
 			}
 		} catch(err) {
@@ -104,6 +106,11 @@ export default class Sync extends EventEmitter {
 		} catch (err) {
 			throw new StorageError("unable to commit sync tranaction", err);
 		}
+        // emit room related events after txn has been closed
+        for(let {room, changes} of roomChanges) {
+            room.emitSync(changes);
+        }
+
 		return syncToken;
 	}