Update app.py via AI Editor

app.py

@@ -141,6 +141,15 @@ app = dash.Dash(__name__, external_stylesheets=external_stylesheets, suppress_ca
 server = app.server
 app.title = "Intelligent PDF Splitter"
 
+def get_split_results_placeholder():
+    # Always render split-btn (disabled) so Dash Input/Output registration never fails
+    return dbc.Row([
+        dbc.Col(
+            dbc.Button("Split PDF", id='split-btn', color='primary', className='mb-3 mt-2', n_clicks=0, style={'width': '180px', 'fontWeight': 'bold'}, disabled=True),
+            width=12, style={'display': 'flex', 'justifyContent': 'center'}
+        )
+    ])
+
 app.layout = dbc.Container(
     [
         dcc.Store(id='session-store', storage_type='session'),
@@ -172,7 +181,7 @@ app.layout = dbc.Container(
                                     dbc.Button("Clear Session", id='clear-session', color='secondary', className='mt-2 mb-2'),
                                     dcc.Loading(
                                         id="loading", type="default",
-                                        children=[html.Div(id='split-results')]
+                                        children=[html.Div(id='split-results', children=get_split_results_placeholder())]
                                     )
                                 ]
                             )
@@ -214,13 +223,12 @@ def handle_upload(contents, filename, clear_n, delete_upload_n_list, split_n, se
     if trigger == 'clear-session':
         clean_session(session_id)
         resp_data = {}
-        return "", "", resp_data
+        return "", get_split_results_placeholder(), resp_data
 
     # Handle Delete Upload (detect ANY delete button press)
     delete_pressed = False
     if isinstance(trigger, dict) and trigger.get('type') == 'delete-upload-btn':
         delete_pressed = True
-    # Also handle if delete_upload_n_list is not None and has a value >0
     if not delete_pressed and delete_upload_n_list is not None and len(delete_upload_n_list) > 0:
         if any(n is not None and n > 0 for n in delete_upload_n_list):
             delete_pressed = True
@@ -234,15 +242,15 @@ def handle_upload(contents, filename, clear_n, delete_upload_n_list, split_n, se
         if os.path.exists(session_dir):
             for file in os.listdir(session_dir):
                 os.remove(os.path.join(session_dir, file))
-        return "", "", {}
+        return "", get_split_results_placeholder(), {}
 
     # Handle Upload
     if trigger == 'upload-pdf':
         if not contents:
-            return "", "", {}
+            return "", get_split_results_placeholder(), {}
 
         if not allowed_file(filename):
-            return html.Div("Only .pdf files are allowed.", style={'color': 'red'}), "", {}
+            return html.Div("Only .pdf files are allowed.", style={'color': 'red'}), get_split_results_placeholder(), {}
 
         try:
             header, b64data = contents.split(',', 1)
@@ -273,7 +281,7 @@ def handle_upload(contents, filename, clear_n, delete_upload_n_list, split_n, se
             return file_info, split_results, session_data
         except Exception as e:
             logging.error(f"Error processing PDF: {e}")
-            return html.Div(f"Error: {e}", style={'color': 'red'}), "", {}
+            return html.Div(f"Error: {e}", style={'color': 'red'}), get_split_results_placeholder(), {}
 
     # Restore after upload (before split)
     if session_data.get('orig_filename') and not session_data.get('split_files'):
@@ -296,10 +304,10 @@ def handle_upload(contents, filename, clear_n, delete_upload_n_list, split_n, se
     if trigger == 'split-btn':
         orig_filename = session_data.get('orig_filename')
         if not orig_filename:
-            return html.Div("No file to split.", style={'color': 'red'}), "", session_data
+            return html.Div("No file to split.", style={'color': 'red'}), get_split_results_placeholder(), session_data
         pdf_path = os.path.join(session_dir, orig_filename)
         if not os.path.exists(pdf_path):
-            return html.Div("Uploaded file not found. Please upload again.", style={'color': 'red'}), "", {}
+            return html.Div("Uploaded file not found. Please upload again.", style={'color': 'red'}), get_split_results_placeholder(), {}
         try:
             with lock:
                 split_files = intelligent_pdf_split(pdf_path, session_dir)
@@ -331,7 +339,7 @@ def handle_upload(contents, filename, clear_n, delete_upload_n_list, split_n, se
             return file_info, results, session_data
         except Exception as e:
             logging.error(f"Error splitting PDF: {e}")
-            return html.Div(f"Error: {e}", style={'color': 'red'}), "", session_data
+            return html.Div(f"Error: {e}", style={'color': 'red'}), get_split_results_placeholder(), session_data
 
     # Restore after split
     if session_data.get('split_files'):
@@ -360,7 +368,7 @@ def handle_upload(contents, filename, clear_n, delete_upload_n_list, split_n, se
         ]
         return file_info, results, session_data
 
-    return "", "", session_data
+    return "", get_split_results_placeholder(), session_data
 
 @app.server.route('/download_zip/<session_id>/<filename>')
 def download_zip_file(session_id, filename):