notes how to implement reconnecting and status reporting

doc/impl-thoughts/RECONNECTING.md

@@ -1 +1,34 @@
 # Reconnecting
+
+`HomeServerApi` notifies `Reconnecter` of network call failure
+
+`Reconnecter` listens for online/offline event
+
+`Reconnecter` polls `/versions` with a `RetryDelay` (implemented as ExponentialRetryDelay, also used by SendScheduler if no retry_after_ms is given)
+
+`Reconnecter` emits an event when sync and message sending should retry
+
+`Sync` listen to `Reconnecter`
+`Sync` notifies when the catchup sync has happened
+
+`Reconnecter` has state:
+    - disconnected (and retrying at x seconds from timestamp)
+    - reconnecting (call /versions, and if successful /sync)
+    - connected
+
+`Reconnecter` has a method to try to connect now
+
+`SessionStatus` can be:
+    - disconnected (and retrying at x seconds from timestamp)
+    - reconnecting
+    - connected (and syncing)
+
+    - doing catchup sync
+    - sending x / y messages
+
+rooms should report how many messages they have queued up, and each time they sent one?
+
+`SendReporter` (passed from `Session` to `Room`, passed down to `SendQueue`), with:
+ - setPendingEventCount(roomId, count)
+
+`Session` listens to `Reconnecter` to update it's status, but perhaps we wait to send messages until catchup sync is done