feat: add shared media assets and fix credit lifecycle

downloader.go

@@ -40,17 +40,17 @@ func (a *App) download(id uint) {
 	if ext == "" {
 		ext = "mp3"
 	}
-	filename := safe(t.Artist) + " - " + safe(t.Title) + "." + ext
-	local := filepath.Join(a.cfg.DownloadDir, filename)
-	t.Format, t.ResolvedQuality, t.ActualQuality, t.LocalPath = ext, info.Level, "", local
-
-	// Reuse only the path recorded on this task. Never borrow another task's quality.
-	if t.LocalPath != "" {
-		if fi, statErr := os.Stat(t.LocalPath); statErr == nil && fi.Size() > 0 {
-			a.finishExisting(&t, fi.Size())
-			return
-		}
+	t.Format, t.ResolvedQuality, t.ActualQuality = ext, info.Level, ""
+	asset, reused, err := a.acquireAsset(&t)
+	if err != nil {
+		a.fail(&t, err)
+		return
 	}
+	if reused {
+		a.finishExisting(&t, asset.Size)
+		return
+	}
+	a.db.Model(&t).Updates(map[string]any{"format": t.Format, "local_path": t.LocalPath})
 	a.downloadFile(&t, info)
 }
 
@@ -141,6 +141,13 @@ func (a *App) downloadFile(t *Task, info playInfo) {
 		t.Progress = 100
 	}
 	a.db.Save(t)
+	a.markAssetDone(t)
+	// The credit pays for the successful media download, not the later WebDAV sync.
+	// Commit before upload so a storage outage cannot turn a successful download into a free retry.
+	if err := a.commitCredit(t); err != nil {
+		a.fail(t, err)
+		return
+	}
 	a.upload(t)
 }