FavoriteBloc

import 'dart:async';
import 'dart:collection';
import 'dart:convert';

import 'package:bloc_pattern/bloc_pattern.dart';
import 'package:rxdart/rxdart.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:tutorial_nox_vscode/models/Products.dart';

class FavoriteBloc extends BlocBase {
  ///
  /// Unique list of all favorite movies
  ///
  Set<ProductsModel> _favorites = Set<ProductsModel>();

  // ##########  STREAMS  ##############
  ///
  /// Interface that allows to add a new favorite product
  ///
  BehaviorSubject<ProductsModel> _favoriteAddController =
      BehaviorSubject<ProductsModel>();
  Sink<ProductsModel> get inAddFavorite => _favoriteAddController.sink;

  ///
  /// Interface that allows to remove a product from the list of favorites
  ///
  BehaviorSubject<ProductsModel> _favoriteRemoveController =
      BehaviorSubject<ProductsModel>();
  Sink<ProductsModel> get inRemoveFavorite => _favoriteRemoveController.sink;

  ///
  /// Interface that allows to get the total number of favorites
  ///
  BehaviorSubject<int> _favoriteTotalController =
      BehaviorSubject<int>.seeded(0);
  Sink<int> get _inTotalFavorites => _favoriteTotalController.sink;
  Stream<int> get outTotalFavorites => _favoriteTotalController.stream;

  ///
  /// Interface that allows to get the list of all favorite prdoducts
  ///
  final _favoritesController = BehaviorSubject<List<ProductsModel>>.seeded([]);
  Sink<List<ProductsModel>> get _inFavorites => _favoritesController.sink;
  Stream<List<ProductsModel>> get outFavorites => _favoritesController.stream;

  ///
  /// Constructor
  ///
  FavoriteBloc() {
    _favoriteAddController.listen(_handleAddFavorite);
    _favoriteRemoveController.listen(_handleRemoveFavorite);

    SharedPreferences.getInstance().then((prefs) {
      if (prefs.getKeys().contains('fav')) {
        _favorites = json.decode(prefs.getString('fav')).map((k, v) {
          return MapEntry(k, ProductsModel.fromJson(v));
        }).cast<String, ProductsModel>();
        _favoritesController.add(_favorites.toList());
      }
    });
  }

  void _saveFav() {
    SharedPreferences.getInstance().then((prefs) {
      prefs.setString('fav', json.encode(_favorites.toList()));
    });
  }

  void dispose() {
    _favoriteAddController.close();
    _favoriteRemoveController.close();
    _favoriteTotalController.close();
    _favoritesController.close();
    super.dispose();
  }

  // ############# HANDLING  #####################

  void _handleAddFavorite(ProductsModel product) {
    // Add the product to the list of favorite ones
    _favorites.add(product);
    _saveFav();

    _notify();
  }

  void _handleRemoveFavorite(ProductsModel product) {
    _favorites.remove(product);
    _saveFav();

    _notify();
  }

  void _notify() {
    // Send to whomever is interested...
    // The total number of favorites
    _inTotalFavorites.add(_favorites.length);

    // The new list of all favorite products
    _inFavorites.add(UnmodifiableListView(_favorites));
  }
}

// Buttons products_page
StreamBuilder<bool>(
 stream: favoritesBloc.outIsFavorite,
 initialData: false,
 builder: (context, snapshot) {
  return IconButton(
   icon: Icon(
    snapshot.data
    ? Icons.favorite
    : Icons.favorite_border),
   color: Colors.amber[500],
   onPressed: () {
    snapshot.data
    ? bloc.inRemoveFavorite.add(item)
    : bloc.inAddFavorite.add(item);
  },
 );
}),