Allow join prompt after paused YouTube sync

public/app.js

@@ -53,6 +53,7 @@ let applyingWatchStateUntil = 0;
 let pauseEnforcementUntil = 0;
 let syncedPlaybackRetryUntil = 0;
 let youtubeStartPromptAllowedUntil = 0;
+let allowJoinedYoutubeStartPrompt = false;
 let desiredYoutubePlaying = false;
 let youtubeReadyResolvers = [];
 let watchApplySequence = 0;
@@ -562,6 +563,7 @@ async function applyWatchState(state, { suppressEvents = true, allowStartPrompt
 
   if (!currentYoutubeVideoId) {
     desiredYoutubePlaying = false;
+    allowJoinedYoutubeStartPrompt = false;
     youtubePlaybackRequestId++;
     syncedPlaybackRetryUntil = 0;
     youtubeStartPromptAllowedUntil = 0;
@@ -900,7 +902,10 @@ async function handleSignal(message) {
     peerId = message.peerId;
     setStatus(`Joined the call as ${displayName}. ${message.peers.length} other participant(s).`);
     if (message.watchState) {
-      await applyWatchState(message.watchState, { allowStartPrompt: true });
+      const watchShouldPlay = message.watchState.action === "play" ||
+        (!message.watchState.action && Boolean(message.watchState.playing));
+      allowJoinedYoutubeStartPrompt = Boolean(message.watchState.videoId && !watchShouldPlay);
+      await applyWatchState(message.watchState, { allowStartPrompt: watchShouldPlay });
     }
     if (message.presentationState?.sharing) {
       setTimeout(() => {
@@ -936,7 +941,12 @@ async function handleSignal(message) {
   }
 
   if (message.type === "watch-state") {
-    await applyWatchState(message);
+    const watchShouldPlay = message.action === "play" || (!message.action && Boolean(message.playing));
+    const allowStartPrompt = allowJoinedYoutubeStartPrompt && watchShouldPlay;
+    if (allowStartPrompt) {
+      allowJoinedYoutubeStartPrompt = false;
+    }
+    await applyWatchState(message, { allowStartPrompt });
     setStatus(`${message.name || "Someone"} synced YouTube playback.`);
     return;
   }