feat: start #279 (selection cubit + DI scaffold)

lib/core/utils/locator.dart

@@ -1,4 +1,5 @@
 import 'package:flutter_cache_manager/flutter_cache_manager.dart';
+import 'package:opennutritracker/features/add_meal/presentation/bloc/selected_meals_cubit.dart';
 import 'package:get_it/get_it.dart';
 import 'package:opennutritracker/core/data/data_source/config_data_source.dart';
 import 'package:opennutritracker/core/data/data_source/intake_data_source.dart';
@@ -114,6 +115,8 @@ Future<void> initLocator() async {
       .registerFactory<ProductsBloc>(() => ProductsBloc(locator(), locator()));
   locator.registerFactory<FoodBloc>(() => FoodBloc(locator(), locator()));
   locator.registerFactory(() => RecentMealBloc(locator(), locator()));
+locator.registerLazySingleton<SelectedMealsCubit>(() => SelectedMealsCubit());
+
 
   // UseCases
   locator.registerLazySingleton<GetConfigUsecase>(

lib/features/add_meal/presentation/bloc/selected_meals_cubit.dart

@@ -0,0 +1,196 @@
+import 'package:equatable/equatable.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:opennutritracker/core/utils/calc/unit_calc.dart';
+import 'package:opennutritracker/core/utils/id_generator.dart';
+import 'package:opennutritracker/features/add_meal/domain/entity/meal_entity.dart';
+import 'package:opennutritracker/features/add_meal/domain/entity/meal_nutriments_entity.dart';
+
+/// A single selected item with a normalized quantity in base units:
+/// - solids in grams (g)
+/// - liquids in milliliters (ml)
+class SelectedMealItem extends Equatable {
+  final MealEntity meal;
+  final double quantityBaseGml; // grams or milliliters in base unit
+
+  const SelectedMealItem({required this.meal, required this.quantityBaseGml});
+
+  SelectedMealItem copyWith({MealEntity? meal, double? quantityBaseGml}) =>
+      SelectedMealItem(
+        meal: meal ?? this.meal,
+        quantityBaseGml: quantityBaseGml ?? this.quantityBaseGml,
+      );
+
+  @override
+  List<Object?> get props => [meal, quantityBaseGml];
+}
+
+class SelectedMealsState extends Equatable {
+  final List<SelectedMealItem> items;
+  final bool selectionMode;
+
+  const SelectedMealsState({
+    this.items = const [],
+    this.selectionMode = false,
+  });
+
+  SelectedMealsState copyWith({
+    List<SelectedMealItem>? items,
+    bool? selectionMode,
+  }) =>
+      SelectedMealsState(
+        items: items ?? this.items,
+        selectionMode: selectionMode ?? this.selectionMode,
+      );
+
+  @override
+  List<Object?> get props => [items, selectionMode];
+}
+
+class SelectedMealsCubit extends Cubit<SelectedMealsState> {
+  SelectedMealsCubit() : super(const SelectedMealsState());
+
+  /// Turn selection mode on/off (e.g., when user taps a "Select" toggle).
+  void setSelectionMode(bool enabled) {
+    emit(state.copyWith(selectionMode: enabled));
+    if (!enabled) {
+      clear();
+    }
+  }
+
+  /// Toggle an item in the selection. If adding, we default to:
+  /// - 1 serving if the item has serving info
+  /// - otherwise 100 g (solids) or 100 ml (liquids/unknown)
+  void toggle(MealEntity meal) {
+    final exists = state.items.indexWhere((e) => e.meal.code == meal.code);
+    if (exists >= 0) {
+      final newItems = List<SelectedMealItem>.from(state.items)..removeAt(exists);
+      emit(state.copyWith(items: newItems));
+      return;
+    }
+
+    final defaultQty = meal.hasServingValues
+        ? (meal.servingQuantity ?? 1.0)
+        : 100.0; // sensible default
+
+    final normalized = _toBaseGml(meal, defaultQty,
+        meal.hasServingValues ? 'serving' : (meal.isSolid ? 'g' : 'ml'));
+
+    final newItems = List<SelectedMealItem>.from(state.items)
+      ..add(SelectedMealItem(meal: meal, quantityBaseGml: normalized));
+    emit(state.copyWith(items: newItems));
+  }
+
+  /// Update quantity for a given meal (quantity expressed in a UI unit).
+  /// [unit] accepted: 'g', 'ml', 'oz', 'fl.oz', 'serving'
+  void updateQuantity(MealEntity meal, double quantity, String unit) {
+    final idx = state.items.indexWhere((e) => e.meal.code == meal.code);
+    if (idx < 0) return;
+
+    final base = _toBaseGml(meal, quantity, unit);
+    final newItems = List<SelectedMealItem>.from(state.items)
+      ..[idx] = state.items[idx].copyWith(quantityBaseGml: base);
+
+    emit(state.copyWith(items: newItems));
+  }
+
+  void remove(MealEntity meal) {
+    final newItems =
+        state.items.where((e) => e.meal.code != meal.code).toList();
+    emit(state.copyWith(items: newItems));
+  }
+
+  void clear() => emit(state.copyWith(items: const []));
+
+  bool isSelected(MealEntity meal) =>
+      state.items.any((e) => e.meal.code == meal.code);
+
+  int get count => state.items.length;
+
+  /// Compose a single custom MealEntity by aggregating nutrients
+  /// weighted by each item's quantity in base units.
+  ///
+  /// Returns a MealEntity with:
+  ///  - per-100 g/ml nutrients = (sum nutrients) / (total qty) * 100
+  ///  - mealQuantity = total qty (as string), mealUnit = 'g/ml'
+  ///  - source = custom
+  MealEntity composeAsCustomMeal({String? name}) {
+    if (state.items.isEmpty) {
+      // Empty selection -> return a minimal custom meal
+      return MealEntity.empty();
+    }
+
+    double totalQty = 0.0;
+    double kcalSum = 0.0;
+    double carbsSum = 0.0;
+    double fatSum = 0.0;
+    double proteinSum = 0.0;
+
+    for (final item in state.items) {
+      final q = item.quantityBaseGml;
+      final n = item.meal.nutriments;
+
+      final energyPerUnit = n.energyPerUnit ?? 0.0;
+      final carbsPerUnit = n.carbohydratesPerUnit ?? 0.0;
+      final fatPerUnit = n.fatPerUnit ?? 0.0;
+      final proteinPerUnit = n.proteinsPerUnit ?? 0.0;
+
+      totalQty += q;
+      kcalSum += q * energyPerUnit;
+      carbsSum += q * carbsPerUnit;
+      fatSum += q * fatPerUnit;
+      proteinSum += q * proteinPerUnit;
+    }
+
+    // Derive per-100 g/ml values
+    double? per100(double sum) =>
+        totalQty > 0 ? (sum / totalQty) * 100.0 : null;
+
+    final nutriments = MealNutrimentsEntity(
+      energyKcal100: per100(kcalSum),
+      carbohydrates100: per100(carbsSum),
+      fat100: per100(fatSum),
+      proteins100: per100(proteinSum),
+      sugars100: null,
+      saturatedFat100: null,
+      fiber100: null,
+    );
+
+    return MealEntity(
+      code: IdGenerator.getUniqueID(),
+      name: name ?? 'Custom meal',
+      brands: null,
+      thumbnailImageUrl: null,
+      mainImageUrl: null,
+      url: null,
+      mealQuantity: totalQty.toStringAsFixed(0),
+      mealUnit: 'g/ml', // generic unit since we may mix solids & liquids
+      servingQuantity: null,
+      servingUnit: 'g/ml',
+      servingSize: '',
+      nutriments: nutriments,
+      source: MealSourceEntity.custom,
+    );
+  }
+
+  /// Normalize a [quantity] in [unit] to base g/ml for math.
+  /// - 'serving' -> multiply by servingQuantity if present
+  /// - 'oz' -> grams via UnitCalc
+  /// - 'fl.oz' -> ml via UnitCalc
+  /// - 'g' and 'ml' pass through
+  double _toBaseGml(MealEntity meal, double quantity, String unit) {
+    switch (unit) {
+      case 'serving':
+        final sq = meal.servingQuantity ?? 1.0;
+        return quantity * sq;
+      case 'oz':
+        return UnitCalc.ozToG(quantity);
+      case 'fl.oz':
+        return UnitCalc.flOzToMl(quantity);
+      case 'g':
+      case 'ml':
+      default:
+        return quantity;
+    }
+  }
+}
+