better snapshots management

internal/server/server.go

@@ -126,21 +126,21 @@ func (s *Server) rotateSnapshots(clientID string) (int, int64) {
 		return 0, 0
 	}
 
-	// Select appropriate backend
-	var backend StorageBackend
-	if s.s3Backend != nil {
-		backend = s.s3Backend
-	} else if s.localBackend != nil {
-		backend = s.localBackend
-	} else {
-		log.Printf("No storage backend available for rotation")
-		return 0, 0
-	}
-
-	// Delete snapshots
+	// Delete snapshots - use correct backend based on each snapshot's storage type
 	ctx := context.Background()
 	for _, snap := range toDelete {
-		if err := backend.Delete(ctx, snap.StorageKey); err != nil {
+		// Determine which backend to use for this specific snapshot
+		var snapBackend StorageBackend
+		if snap.StorageType == "s3" && s.s3Backend != nil {
+			snapBackend = s.s3Backend
+		} else if snap.StorageType == "local" && s.localBackend != nil {
+			snapBackend = s.localBackend
+		} else {
+			log.Printf("No storage backend available for snapshot %s (type: %s)", snap.SnapshotID, snap.StorageType)
+			continue
+		}
+
+		if err := snapBackend.Delete(ctx, snap.StorageKey); err != nil {
 			log.Printf("Error deleting snapshot %s: %v", snap.StorageKey, err)
 			continue
 		}
@@ -326,6 +326,7 @@ func (s *Server) HandleUploadStream(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Save metadata to database
+	// Use actual storage type where snapshot was stored (not always s3)
 	metadata := &SnapshotMetadata{
 		ClientID:     clientID,
 		SnapshotID:   storageKey,
@@ -333,7 +334,7 @@ func (s *Server) HandleUploadStream(w http.ResponseWriter, r *http.Request) {
 		SizeBytes:    actualSize,
 		DatasetName:  datasetName,
 		StorageKey:   storageKey,
-		StorageType:  "s3",
+		StorageType:  client.StorageType, // Use actual storage type from client config
 		Compressed:   compressedStr == "true",
 		Incremental:  incrementalStr == "true",
 		BaseSnapshot: baseSnapshot,
@@ -450,15 +451,17 @@ func (s *Server) HandleDownload(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// Use snapshot's own storage_type to determine which backend to use
+	// This enables mixed storage scenarios (e.g., full on local, incrementals on S3)
 	ctx := context.Background()
 	var backend StorageBackend
 
-	if client.StorageType == "s3" && s.s3Backend != nil {
+	if targetSnapshot.StorageType == "s3" && s.s3Backend != nil {
 		backend = s.s3Backend
-	} else if s.localBackend != nil {
+	} else if targetSnapshot.StorageType == "local" && s.localBackend != nil {
 		backend = s.localBackend
 	} else {
-		http.Error(w, "No storage backend available", http.StatusInternalServerError)
+		http.Error(w, "No storage backend available for this snapshot's storage type", http.StatusInternalServerError)
 		return
 	}