Implement Duplicate Upload Prevention

- Server: /upload rejects existing files with 409 Conflict
- Web: handleFileUpload skips duplicates with toast feedback
- Qt: upload_track blocks duplicate imports and uploads with dialog alert

script.js

@@ -1520,14 +1520,24 @@ async function handleFileUpload(event) {
     progressContainer.innerHTML = '<h3>UPLOADING TRACKS...</h3>';
     progressContainer.classList.add('active');
 
+    const existingFilenames = allSongs.map(s => s.file.split('/').pop().toLowerCase());
+
     const uploadPromises = files.map(async (file) => {
         const allowedExts = ['.mp3', '.m4a', '.wav', '.flac', '.ogg'];
         const ext = file.name.substring(file.name.lastIndexOf('.')).toLowerCase();
+        
         if (!allowedExts.includes(ext)) {
             console.warn(`${file.name} is not a supported audio file`);
             return;
         }
 
+        // Check for duplicates
+        if (existingFilenames.includes(file.name.toLowerCase())) {
+            console.log(`[UPLOAD] Skipping duplicate: ${file.name}`);
+            showToast(`Skipped duplicate: ${file.name}`, 'info');
+            return;
+        }
+
         const formData = new FormData();
         formData.append('file', file);
 

server.py

@@ -409,6 +409,9 @@ def setup_shared_routes(app, index_file='index.html'):
         
         filepath = os.path.join(MUSIC_FOLDER, filename)
         
+        if os.path.exists(filepath):
+            return jsonify({"success": False, "error": "File already exists in library"}), 409
+        
         try:
             file.save(filepath)
             print(f"UPLOADED: {filename}")

techdj_qt.py

@@ -2110,16 +2110,29 @@ class DJApp(QMainWindow):
             return
             
         if self.library_mode == "local":
+            filename = os.path.basename(file_path)
+            # Check for duplicates in local_library
+            if any(Path(track['path']).name.lower() == filename.lower() for track in self.local_library):
+                QMessageBox.information(self, "Import Skipped", f"'{filename}' is already in your local library.")
+                return
+
             # Copy to local music folder
-            dest = self.lib_path / os.path.basename(file_path)
+            dest = self.lib_path / filename
             try:
                 shutil.copy2(file_path, dest)
-                self.status_label.setText(f"Imported: {os.path.basename(file_path)}")
+                self.status_label.setText(f"Imported: {filename}")
                 self.load_library()
             except Exception as e:
                 QMessageBox.warning(self, "Import Error", f"Failed to import file: {e}")
         else:
             # Upload to server
+            filename = os.path.basename(file_path)
+            # Check for duplicates in server_library
+            if hasattr(self, 'server_library'):
+                if any(track['file'].split('/')[-1].lower() == filename.lower() for track in self.server_library):
+                    QMessageBox.information(self, "Upload Skipped", f"'{filename}' already exists on the server.")
+                    return
+
             try:
                 self.status_label.setText("Uploading to server...")
                 base_url = self.get_server_base_url()