Start to build app skeleton

moneymgr_mobile/lib/providers/settings.dart

@@ -0,0 +1,37 @@
+import 'package:flutter/material.dart';
+import 'package:riverpod_annotation/riverpod_annotation.dart';
+
+import '../../../services/storage/prefs.dart';
+
+part 'settings.g.dart';
+
+/// The current theme mode of the app.
+///
+/// When this provider is first read, it will read the saved value from storage,
+/// and defaults to [ThemeMode.system] if the theme mode has not been set before.
+@riverpod
+class CurrentThemeMode extends _$CurrentThemeMode {
+  @override
+  ThemeMode build() {
+    final prefs = ref.watch(prefsProvider).requireValue;
+
+    // Load the saved theme mode setting from shared preferences.
+    final themeModeName = prefs.getString('themeMode');
+
+    // Return [ThemeMode] based on the saved setting, or [ThemeMode.system]
+    // if there's no saved setting yet.
+    return ThemeMode.values.singleWhere(
+          (themeMode) => themeMode.name == themeModeName,
+      orElse: () => ThemeMode.system,
+    );
+  }
+
+  void set(ThemeMode themeMode) {
+    final prefs = ref.read(prefsProvider).requireValue;
+
+    // Save the new theme mode to shared preferences.
+    prefs.setString('themeMode', themeMode.name);
+
+    ref.invalidateSelf();
+  }
+}