fix: radio fill lock prevents concurrent fills; random fallback when similar songs exhausted

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/player.js

@@ -243,9 +243,11 @@ window.NSPlayer = {
     setPlayIcon(false);
     if (S.radioMode) {
       const prevLen = S.queue.length;
-      // fillRadioQueue sends addToQueue to native internally — only trigger play here.
       fillRadioQueue().then(() => {
-        if (S.queue.length > prevLen) _nsBridge('play');
+        if (S.queue.length > prevLen) { _nsBridge('play'); return; }
+        // fillRadioQueue was locked by a concurrent fill — wait for it to finish
+        // then trigger play so native doesn't stay stopped after queue end.
+        if (_radioFilling) setTimeout(() => { if (S.queue.length > prevLen) _nsBridge('play'); }, 3000);
       });
     }
   },
@@ -320,6 +322,7 @@ let _queueGen = 0;
 
 export function playQueue(songs, startIdx) {
   _queueGen++;
+  _radioFilling = false; // cancel any in-flight radio fill for the old queue
   S.queue = songs.map(s => ({...s}));
   S.qIdx  = startIdx;
   _clearPreload();
@@ -675,8 +678,11 @@ export async function toggleRadioMode() {
   if(S.radioMode) await fillRadioQueue();
 }
 
+let _radioFilling = false;
+
 export async function fillRadioQueue() {
-  if(!S.radioMode) return;
+  if (!S.radioMode || _radioFilling) return;
+  _radioFilling = true;
   const gen = _queueGen;
   try {
     const seed = S.queue[S.qIdx];
@@ -697,21 +703,30 @@ export async function fillRadioQueue() {
     if (gen !== _queueGen) return;
     if (!newSongs.length) return;
 
-    // Deduplicate only against the last 50 queued songs so the radio never
-    // stalls on a small library. Songs cycle back after ~50 tracks rather than
-    // blocking forever once they've been seen once.
     const recentIds = new Set(S.queue.slice(-50).map(s => s.id));
     const deduped   = newSongs.filter(s => !recentIds.has(s.id));
-    // If every candidate was a recent duplicate (very small library), allow
-    // repeats rather than letting the queue run dry and music stop.
-    newSongs = deduped.length > 0 ? deduped : newSongs.slice(0, 5);
 
+    if (deduped.length === 0) {
+      // All similar songs recently played (small library) — try random as final fallback
+      if (gen !== _queueGen) return;
+      const rr = await api('getRandomSongs', '&size=20');
+      const randomFresh = (rr.randomSongs?.song || []).filter(s => !recentIds.has(s.id));
+      // If random is also exhausted, allow repeats to keep music playing
+      newSongs = randomFresh.length > 0 ? randomFresh : newSongs.slice(0, 5);
+    } else {
+      newSongs = deduped;
+    }
+
+    if (gen !== _queueGen) return;
     const prevLen = S.queue.length;
     S.queue.push(...newSongs);
     renderQueue();
     // Append-only: never call setQueue here (that resets position to 0).
     S.queue.slice(prevLen).forEach(s => _nsBridge('addToQueue', JSON.stringify(_trackToNative(s)), -1));
-  } catch {}
+  } catch {
+  } finally {
+    _radioFilling = false;
+  }
 }
 
 // ─── PROGRESS & SCRUBBING ─────────────────────────────────────────────────