Add onCancelCallback, onFailureCallback in LLM Chat View

CHANGELOG.md

@@ -3,6 +3,7 @@
 * Require Dart 3.5 or later.
 * Remove dependency on `package:gap`.
 * fixed #40: Unrecoverable Black screen
+* implements #37: Custom Callback on Prompt/Response Error
 
 ## 0.6.7
 

example/lib/callbacks/on_cancel.dart

@@ -0,0 +1,48 @@
+// Copyright 2024 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_ai_toolkit/flutter_ai_toolkit.dart';
+import 'package:google_generative_ai/google_generative_ai.dart';
+
+import '../gemini_api_key.dart';
+
+void main() => runApp(const App());
+
+class App extends StatelessWidget {
+  static const title = 'Example: Welcome Message';
+
+  const App({super.key});
+
+  @override
+  Widget build(BuildContext context) => const MaterialApp(
+        title: title,
+        home: ChatPage(),
+      );
+}
+
+class ChatPage extends StatelessWidget {
+  const ChatPage({super.key});
+
+  void _onCancel(BuildContext context) {
+    ScaffoldMessenger.of(context).showSnackBar(
+      const SnackBar(content: Text('Chat cancelled')),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) => Scaffold(
+        appBar: AppBar(title: const Text(App.title)),
+        body: LlmChatView(
+          onCancelCallback: _onCancel,
+          cancelMessage: 'Request cancelled',
+          provider: GeminiProvider(
+            model: GenerativeModel(
+              model: 'gemini-1.5-flash',
+              apiKey: geminiApiKey,
+            ),
+          ),
+        ),
+      );
+}

example/lib/callbacks/on_error.dart

@@ -0,0 +1,48 @@
+// Copyright 2024 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_ai_toolkit/flutter_ai_toolkit.dart';
+import 'package:google_generative_ai/google_generative_ai.dart';
+
+import '../gemini_api_key.dart';
+
+void main() => runApp(const App());
+
+class App extends StatelessWidget {
+  static const title = 'Example: Welcome Message';
+
+  const App({super.key});
+
+  @override
+  Widget build(BuildContext context) => const MaterialApp(
+        title: title,
+        home: ChatPage(),
+      );
+}
+
+class ChatPage extends StatelessWidget {
+  const ChatPage({super.key});
+
+  void _onError(BuildContext context, LlmException error) {
+    ScaffoldMessenger.of(context).showSnackBar(
+      SnackBar(content: Text('Error: ${error.message}')),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) => Scaffold(
+        appBar: AppBar(title: const Text(App.title)),
+        body: LlmChatView(
+          onErrorCallback: _onError,
+          errorMessage: 'An error occurred',
+          provider: GeminiProvider(
+            model: GenerativeModel(
+              model: 'gemini-1.5-flash',
+              apiKey: geminiApiKey,
+            ),
+          ),
+        ),
+      );
+}

lib/src/views/llm_chat_view/llm_chat_view.dart

@@ -65,13 +65,27 @@ class LlmChatView extends StatefulWidget {
   ///   when the chat history is empty. Defaults to an empty list.
   /// - [welcomeMessage]: Optional. A welcome message to display when the chat
   ///   is first opened.
+  /// - [onCancelCallback]: Optional. The action to perform when the user
+  ///   cancels a chat operation. By default, a snackbar is displayed with the
+  ///   canceled message.
+  /// - [onErrorCallback]: Optional. The action to perform when an
+  ///   error occurs during a chat operation. By default, an alert dialog is
+  ///   displayed with the error message.
+  /// - [cancelMessage]: Optional. The message to display when the user cancels
+  ///   a chat operation. Defaults to 'CANCEL'.
+  /// - [errorMessage]: Optional. The message to display when an error occurs
+  ///   during a chat operation. Defaults to 'ERROR'.
   LlmChatView({
     required LlmProvider provider,
     LlmChatViewStyle? style,
     ResponseBuilder? responseBuilder,
     LlmStreamGenerator? messageSender,
     this.suggestions = const [],
     String? welcomeMessage,
+    this.onCancelCallback,
+    this.onErrorCallback,
+    this.cancelMessage = 'CANCEL',
+    this.errorMessage = 'ERROR',
     super.key,
   }) : viewModel = ChatViewModel(
           provider: provider,
@@ -95,6 +109,27 @@ class LlmChatView extends StatefulWidget {
   /// It encapsulates the core data and functionality needed for the chat view.
   late final ChatViewModel viewModel;
 
+  /// The action to perform when the user cancels a chat operation.
+  ///
+  /// By default, a snackbar is displayed with the canceled message.
+  final void Function(BuildContext context)? onCancelCallback;
+
+  /// The action to perform when an error occurs during a chat operation.
+  ///
+  /// By default, an alert dialog is displayed with the error message.
+  final void Function(BuildContext context, LlmException error)?
+      onErrorCallback;
+
+  /// The text message to display when the user cancels a chat operation.
+  ///
+  /// Defaults to 'CANCEL'.
+  final String cancelMessage;
+
+  /// The text message to display when an error occurs during a chat operation.
+  ///
+  /// Defaults to 'ERROR'.
+  final String errorMessage;
+
   @override
   State<LlmChatView> createState() => _LlmChatViewState();
 }
@@ -280,19 +315,32 @@ class _LlmChatViewState extends State<LlmChatView>
     // empty LLM message.
     final llmMessage = widget.viewModel.provider.history.last;
     if (llmMessage.text == null) {
-      llmMessage.append(error is LlmCancelException ? 'CANCEL' : 'ERROR');
+      llmMessage.append(
+        error is LlmCancelException
+            ? widget.cancelMessage
+            : widget.errorMessage,
+      );
     }
 
     switch (error) {
       case LlmCancelException():
-        AdaptiveSnackBar.show(context, 'LLM operation canceled by user');
+        if (widget.onCancelCallback != null) {
+          widget.onCancelCallback!(context);
+        } else {
+          AdaptiveSnackBar.show(context, 'LLM operation canceled by user');
+        }
+        break;
       case LlmFailureException():
       case LlmException():
-        await AdaptiveAlertDialog.show(
-          context: context,
-          content: Text(error.toString()),
-          showOK: true,
-        );
+        if (widget.onErrorCallback != null) {
+          widget.onErrorCallback!(context, error);
+        } else {
+          await AdaptiveAlertDialog.show(
+            context: context,
+            content: Text(error.toString()),
+            showOK: true,
+          );
+        }
     }
   }