Add an option to switch to Gemini Pro

[jacobsimionato]

Changes:

• Model Switching UI:
  • Added an overflow menu to the travel_app's AppBar allowing users to switch between "Gemini Flash" and "Gemini Pro"
    models.
  • The currently selected model is indicated with a tick box in the menu.
  • Refactored AiClient to use a ValueNotifier for reactive model switching, improving type safety and
    centralizing model name management.

Fixes: #28

[gemini-code-assist]

Code Review

This pull request introduces a model switching capability in the travel app, allowing users to choose between Gemini Flash and Pro. The implementation correctly uses a ValueNotifier for reactive UI updates. My review includes a high-severity fix to ensure the ValueNotifier instance is immutable to prevent listener issues, and a suggestion to refactor the UI code for better maintainability by reducing duplication.

[gemini-code-assist]

The model field should be final. A public, non-final field for a ValueNotifier allows the entire notifier instance to be replaced from outside the class. This is risky because any widgets listening to the original notifier instance would stop receiving updates, leading to a broken UI state. The ValueNotifier instance itself should be immutable after creation; only its internal value should change via model.value = ..., which the switchModel method correctly does.

  final ValueNotifier<GeminiModel> model;

[gemini-code-assist]

The code for creating PopupMenuItems is duplicated for each model. This can be made more concise and maintainable by iterating over GeminiModel.values. This avoids repetition and makes it easier to add new models in the future.

For even cleaner code, you could add a displayName property to the GeminiModel enum in pkgs/flutter_genui/lib/src/ai_client/ai_client.dart and use it here instead of the conditional logic for the text.

                itemBuilder: (BuildContext context) => [
                  for (final model in GeminiModel.values)
                    PopupMenuItem<GeminiModel>(
                      value: model,
                      child: Row(
                        mainAxisAlignment: MainAxisAlignment.spaceBetween,
                        children: [
                          Text(model == GeminiModel.flash ? 'Gemini Flash' : 'Gemini Pro'),
                          if (currentModel == model) const Icon(Icons.check),
                        ],
                      ),
                    ),
                ],