Promote active screen shares

server.js

@@ -8,6 +8,7 @@ const host = process.env.HOST || "127.0.0.1";
 const publicDir = join(process.cwd(), "public");
 const rooms = new Map();
 const watchStates = new Map();
+const presentationStates = new Map();
 const defaultRoomId = "main";
 
 const mimeTypes = {
@@ -76,10 +77,15 @@ function removePeer(roomId, peerId) {
 
   room.delete(peerId);
   broadcast(roomId, peerId, { type: "peer-left", peerId });
+  if (presentationStates.get(roomId)?.peerId === peerId) {
+    presentationStates.delete(roomId);
+    broadcast(roomId, peerId, { type: "presentation-state", from: peerId, sharing: false });
+  }
 
   if (room.size === 0) {
     rooms.delete(roomId);
     watchStates.delete(roomId);
+    presentationStates.delete(roomId);
   }
 }
 
@@ -140,7 +146,8 @@ const server = http.createServer(async (req, res) => {
           peerId,
           name: displayName,
           peers: existingPeers,
-          watchState: watchStates.get(roomId) || null
+          watchState: watchStates.get(roomId) || null,
+          presentationState: presentationStates.get(roomId) || null
         })}\n\n`
       );
       broadcast(roomId, peerId, { type: "peer-joined", peerId, name: displayName });
@@ -156,6 +163,34 @@ const server = http.createServer(async (req, res) => {
       return;
     }
 
+    if (req.method === "POST" && url.pathname.startsWith("/room-event/")) {
+      const roomId = url.pathname.split("/").at(-1) || defaultRoomId;
+      const payload = await parseJson(req);
+
+      if (!payload.from || payload.type !== "presentation-state") {
+        sendJson(res, 400, { error: "Room events require from and type=presentation-state." });
+        return;
+      }
+
+      const event = {
+        type: "presentation-state",
+        from: payload.from,
+        name: normalizeName(payload.name),
+        sharing: Boolean(payload.sharing),
+        updatedAt: Date.now()
+      };
+
+      if (event.sharing) {
+        presentationStates.set(roomId, { ...event, peerId: payload.from });
+      } else if (presentationStates.get(roomId)?.peerId === payload.from) {
+        presentationStates.delete(roomId);
+      }
+
+      broadcast(roomId, payload.from, event);
+      sendJson(res, 202, { ok: true });
+      return;
+    }
+
     if (req.method === "POST" && url.pathname.startsWith("/signal/")) {
       const roomId = url.pathname.split("/").at(-1);
       const payload = await parseJson(req);