fixed refactored code

src/embeddingbuddy/ui/callbacks/data_processing.py

@@ -9,30 +9,52 @@ class DataProcessingCallbacks:
 
     def _register_callbacks(self):
         @callback(
-            Output("processed-data", "data"),
+            [
+                Output("processed-data", "data", allow_duplicate=True),
+                Output("upload-error-alert", "children", allow_duplicate=True),
+                Output("upload-error-alert", "is_open", allow_duplicate=True),
+                Output("upload-success-alert", "children", allow_duplicate=True),
+                Output("upload-success-alert", "is_open", allow_duplicate=True),
+            ],
             Input("upload-data", "contents"),
             State("upload-data", "filename"),
+            prevent_initial_call=True,
         )
         def process_uploaded_file(contents, filename):
             if contents is None:
-                return None
+                return None, "", False, "", False
 
             processed_data = self.processor.process_upload(contents, filename)
 
             if processed_data.error:
-                return {"error": processed_data.error}
+                error_message = self._format_error_message(processed_data.error, filename)
+                return (
+                    {"error": processed_data.error},
+                    error_message,
+                    True,  # Show error alert
+                    "",
+                    False,  # Hide success alert
+                )
 
-            return {
-                "documents": [
-                    self._document_to_dict(doc) for doc in processed_data.documents
-                ],
-                "embeddings": processed_data.embeddings.tolist(),
-            }
+            success_message = f"Successfully loaded {len(processed_data.documents)} documents from {filename or 'file'}"
+            return (
+                {
+                    "documents": [
+                        self._document_to_dict(doc) for doc in processed_data.documents
+                    ],
+                    "embeddings": processed_data.embeddings.tolist(),
+                },
+                "",
+                False,  # Hide error alert
+                success_message,
+                True,   # Show success alert
+            )
 
         @callback(
-            Output("processed-prompts", "data"),
+            Output("processed-prompts", "data", allow_duplicate=True),
             Input("upload-prompts", "contents"),
             State("upload-prompts", "filename"),
+            prevent_initial_call=True,
         )
         def process_uploaded_prompts(contents, filename):
             if contents is None:
@@ -60,3 +82,40 @@ class DataProcessingCallbacks:
             "subcategory": doc.subcategory,
             "tags": doc.tags,
         }
+
+    @staticmethod
+    def _format_error_message(error: str, filename: str | None = None) -> str:
+        """Format error message with helpful guidance for users."""
+        file_part = f" in file '{filename}'" if filename else ""
+        
+        # Check for common error patterns and provide helpful messages
+        if "embedding" in error.lower() and ("key" in error.lower() or "required field" in error.lower()):
+            return (
+                f"❌ Missing 'embedding' field{file_part}. "
+                "Each line must contain an 'embedding' field with a list of numbers."
+            )
+        elif "text" in error.lower() and ("key" in error.lower() or "required field" in error.lower()):
+            return (
+                f"❌ Missing 'text' field{file_part}. "
+                "Each line must contain a 'text' field with the document content."
+            )
+        elif "json" in error.lower() and "decode" in error.lower():
+            return (
+                f"❌ Invalid JSON format{file_part}. "
+                "Please check that each line is valid JSON with proper syntax (quotes, braces, etc.)."
+            )
+        elif "unicode" in error.lower() or "decode" in error.lower():
+            return (
+                f"❌ File encoding issue{file_part}. "
+                "Please ensure the file is saved in UTF-8 format and contains no binary data."
+            )
+        elif "array" in error.lower() or "list" in error.lower():
+            return (
+                f"❌ Invalid embedding format{file_part}. "
+                "Embeddings must be arrays/lists of numbers, not strings or other types."
+            )
+        else:
+            return (
+                f"❌ Error processing file{file_part}: {error}. "
+                "Please check that your file is valid NDJSON with required 'text' and 'embedding' fields."
+            )