server/bugfix: fix panic on invited rooms; expose v2 server url to client

- Expose `/client/server.json` so clients know the CS API base endpoint for things like media requests
  (and in future sending events, etc)
- Tidy up a few comments.

client/devtools.js

@@ -1,5 +1,7 @@
-// This file contains code to render the developer tools overlay (bandwidth, list visualisations, etc)
-// You don't need to read this file to understand sliding sync.
+/*
+ * This file contains code to render the developer tools overlay (bandwidth, list visualisations, etc)
+ * You don't need to read this file to understand sliding sync.
+ */
 
 /**
  * Set the bandwidth values on the devtools display.

client/index.js

@@ -1,4 +1,7 @@
-// This file contains the entry point for the client, as well as DOM interactions.
+/*
+ * This file contains the entry point for the client, as well as DOM interactions.
+ */
+
 import {
     SlidingList,
     SlidingSyncConnection,
@@ -9,6 +12,7 @@ import {
 import * as render from "./render.js";
 import * as devtools from "./devtools.js";
 
+let syncv2ServerUrl;
 let slidingSync;
 let syncConnection = new SlidingSyncConnection();
 let activeLists = [
@@ -202,14 +206,6 @@ const renderRoomContent = (roomId, refresh) => {
     if (roomId !== slidingSync.roomSubscription) {
         return;
     }
-    const container = document.getElementById("messages");
-    if (refresh) {
-        document.getElementById("selectedroomname").textContent = "";
-        // wipe all message entries
-        while (container.hasChildNodes()) {
-            container.removeChild(container.firstChild);
-        }
-    }
     let room = rooms.roomIdToRoom[slidingSync.roomSubscription];
     if (!room) {
         console.error(
@@ -218,6 +214,14 @@ const renderRoomContent = (roomId, refresh) => {
         );
         return;
     }
+    const container = document.getElementById("messages");
+    if (refresh) {
+        document.getElementById("selectedroomname").textContent = "";
+        // wipe all message entries
+        while (container.hasChildNodes()) {
+            container.removeChild(container.firstChild);
+        }
+    }
     document.getElementById("selectedroomname").textContent =
         room.name || room.room_id;
     if (room.avatar) {
@@ -485,11 +489,18 @@ const mxcToUrl = (mxc) => {
     if (!path) {
         return;
     }
-    // TODO: we should really use the proxy HS not matrix.org
-    return `https://matrix-client.matrix.org/_matrix/media/r0/thumbnail/${path}?width=64&height=64&method=crop`;
+    return `${syncv2ServerUrl}/_matrix/media/r0/thumbnail/${path}?width=64&height=64&method=crop`;
 };
 
-window.addEventListener("load", (event) => {
+window.addEventListener("load", async (event) => {
+    const v2ServerResp = await fetch("./server.json");
+    const syncv2ServerJson = await v2ServerResp.json();
+    if (!syncv2ServerJson || !syncv2ServerJson.server) {
+        console.error("failed to fetch v2 server url: ", v2ServerResp);
+        return;
+    }
+    syncv2ServerUrl = syncv2ServerJson.server.replace(/\/$/, ""); // remove trailing /
+
     const container = document.getElementById("roomlistcontainer");
     activeLists.forEach((list) => {
         const roomList = document.createElement("div");

client/render.js

@@ -1,6 +1,8 @@
-// This file contains code to map data structures to actual HTML elements.
-// It is mostly functional and boring and it does not include any sliding sync specific data.
-// In other words, if you want to learn about sliding sync, this isn't the file to look at.
+/*
+ * This file contains code to map data structures to actual HTML elements.
+ * It is mostly functional and boring and it does not include any sliding sync specific data.
+ * In other words, if you want to learn about sliding sync, this isn't the file to look at.
+ */
 
 const membershipChangeText = (ev) => {
     const prevContent = (ev.unsigned || {}).prev_content || {};

client/sync.js

@@ -1,4 +1,9 @@
-// This file contains the main sliding sync code.
+/*
+ * This file contains the main sliding sync code.
+ * It defines the core sliding sync types and contains code for handling list deltas.
+ * It doesn't concern itself with storing room data or updating the UI in any way, deferring
+ * to room/lifecycle callbacks for that.
+ */
 
 import * as devtools from "./devtools.js";
 

cmd/syncv3/main.go

@@ -39,5 +39,5 @@ func main() {
 	if err != nil {
 		panic(err)
 	}
-	syncv3.RunSyncV3Server(h, *flagBindAddr)
+	syncv3.RunSyncV3Server(h, *flagBindAddr, *flagDestinationServer)
 }

state/storage.go

@@ -95,11 +95,11 @@ func (s *Storage) MetadataForAllRooms() (map[string]internal.RoomMetadata, error
 	defer rows.Close()
 	result := make(map[string]internal.RoomMetadata)
 	for rows.Next() {
-		var hi internal.RoomMetadata
-		if err := rows.Scan(&hi.RoomID, &hi.JoinCount); err != nil {
+		var metadata internal.RoomMetadata
+		if err := rows.Scan(&metadata.RoomID, &metadata.JoinCount); err != nil {
 			return nil, err
 		}
-		result[hi.RoomID] = hi
+		result[metadata.RoomID] = metadata
 	}
 	// Select the invited member counts using the same style of query
 	rows, err = s.accumulator.db.Query(`
@@ -119,9 +119,9 @@ func (s *Storage) MetadataForAllRooms() (map[string]internal.RoomMetadata, error
 		if err := rows.Scan(&roomID, &inviteCount); err != nil {
 			return nil, err
 		}
-		hi := result[roomID]
-		hi.InviteCount = inviteCount
-		result[roomID] = hi
+		metadata := result[roomID]
+		metadata.InviteCount = inviteCount
+		result[roomID] = metadata
 	}
 
 	// work out latest timestamps
@@ -132,6 +132,9 @@ func (s *Storage) MetadataForAllRooms() (map[string]internal.RoomMetadata, error
 	for _, ev := range events {
 		metadata := result[ev.RoomID]
 		metadata.LastMessageTimestamp = gjson.ParseBytes(ev.JSON).Get("origin_server_ts").Uint()
+		// it's possible the latest event is a brand new room not caught by the first SELECT for joined
+		// rooms e.g when you're invited to a room so we need to make sure to se the metadata again here
+		metadata.RoomID = ev.RoomID
 		result[ev.RoomID] = metadata
 	}
 

sync3/globalcache.go

@@ -152,6 +152,8 @@ func (c *GlobalCache) Startup(roomIDToMetadata map[string]internal.RoomMetadata)
 	for roomID := range roomIDToMetadata {
 		metadata := roomIDToMetadata[roomID]
 		fmt.Printf("Room: %s - %s - %s \n", roomID, metadata.NameEvent, gomatrixserverlib.Timestamp(metadata.LastMessageTimestamp).Time())
+		internal.Assert("room ID is set", metadata.RoomID != "")
+		internal.Assert("last message timestamp exists", metadata.LastMessageTimestamp > 1)
 		c.roomIDToMetadata[roomID] = &metadata
 	}
 	return nil

v3.go

@@ -44,11 +44,20 @@ func allowCORS(next http.Handler) http.HandlerFunc {
 }
 
 // RunSyncV3Server is the main entry point to the server
-func RunSyncV3Server(h http.Handler, bindAddr string) {
+func RunSyncV3Server(h http.Handler, bindAddr, destV2Server string) {
 	// HTTP path routing
 	r := mux.NewRouter()
 	r.Handle("/_matrix/client/v3/sync", allowCORS(h))
 	r.Handle("/_matrix/client/unstable/org.matrix.msc3575/sync", allowCORS(h))
+
+	serverJSON, _ := json.Marshal(struct {
+		Server string `json:"server"`
+	}{destV2Server})
+	r.Handle("/client/server.json", allowCORS(http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+		rw.Header().Set("Content-Type", "application/json")
+		rw.WriteHeader(200)
+		rw.Write(serverJSON)
+	})))
 	r.PathPrefix("/client/").HandlerFunc(
 		allowCORS(
 			http.StripPrefix("/client/", http.FileServer(http.Dir("./client"))),