calorimeter/lib/food_entry/food_entry_bloc.dart

import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:calorimeter/storage/storage.dart';
import 'package:uuid/uuid.dart';

class FoodEntryBloc extends Bloc<FoodEvent, FoodEntryState> {
  final FoodEntryState initialState;
  final FoodStorage storage;
  final DateTime forDate;

  FoodEntryBloc(
      {required this.initialState,
      required this.forDate,
      required this.storage})
      : super(initialState) {
    on<FoodEntryEvent>(handleFoodEntryEvent);
    on<FoodDeletionEvent>(deleteFood);
    on<PageChangedEvent>(updateEntries);
  }

  void handleFoodEntryEvent(
      FoodEntryEvent event, Emitter<FoodEntryState> emit) async {
    FoodEntryState newState = FoodEntryState.from(state);
    newState.addEntry(event.entry);

    await storage.writeEntriesForDate(forDate, newState.foodEntries);
    storage.addFoodEntryToLookupDatabase(event.entry);

    emit(newState);
  }

  void deleteFood(FoodDeletionEvent event, Emitter<FoodEntryState> emit) async {
    state.foodEntries.removeWhere((entry) => entry.id == event.entryID);

    await storage.writeEntriesForDate(forDate, state.foodEntries);

    emit(FoodEntryState.from(state));
  }

  void updateEntries(
      PageChangedEvent event, Emitter<FoodEntryState> emit) async {
    var entries = await storage.getEntriesForDate(event.changedToDate);
    var newState = FoodEntryState(foodEntries: entries);
    emit(newState);
  }
}

class FoodEvent {}

class FoodEntryEvent extends FoodEvent {
  final FoodEntry entry;

  FoodEntryEvent({required this.entry});
}

class FoodDeletionEvent extends FoodEvent {
  final String entryID;

  FoodDeletionEvent({required this.entryID});
}

class PageChangedEvent extends FoodEvent {
  final DateTime changedToDate;

  PageChangedEvent({required this.changedToDate});
}

class FoodEntryState {
  final List<FoodEntry> foodEntries;

  FoodEntryState({required this.foodEntries});

  factory FoodEntryState.init() {
    return FoodEntryState(foodEntries: []);
  }

  static from(FoodEntryState state) {
    List<FoodEntry> newList = List.from(state.foodEntries);
    return FoodEntryState(foodEntries: newList);
  }

  void addEntry(FoodEntry entry) {
    foodEntries.add(entry);
  }
}

class FoodEntry {
  final String name;
  final double mass;
  final double kcalPerMass;
  final String id;

  FoodEntry({
    required this.name,
    required this.mass,
    required this.kcalPerMass,
  }) : id = const Uuid().v1();

  @override
  String toString() {
    //we use quotation marks around the name because the name might contain
    //commas and we want to store it in a csv file
    return '$id,"$name",$mass,$kcalPerMass';
  }
}