import 'package:flutter_android_app/presentation/currency_bloc/currency_events.dart';
import 'package:flutter_android_app/presentation/currency_bloc/currency_state.dart';
import 'package:flutter_bloc/flutter_bloc.dart';
import 'package:shared_preferences/shared_preferences.dart';

class CurrencyBloc extends Bloc<CurrencyEvent, CurrencyState> {
  static const String _currencyPrefsKey = 'local_currency';
  static const List<String> _availableCurrencyIds = ['usd', 'rub'];
  static final String _defaultCurrencyId = _availableCurrencyIds[0];

  CurrencyBloc() : super(const CurrencyState()) {
    on<LoadLocalCurrencyEvent>(_onLoadLocalCurrency);
    on<ToggleLocalCurrencyEvent>(_onToggleLocalCurrency);
  }

  Future<void> _onLoadLocalCurrency(
      LoadLocalCurrencyEvent event, Emitter<CurrencyState> emit
  ) async {
    emit(state.copyWith(
      hasCurrencyLoaded: false,
    ));

    final prefs = await SharedPreferences.getInstance();
    final data = prefs.getString(_currencyPrefsKey);

    String currencyId = '';
    if (data != null) {
      currencyId = data;
    } else {
      currencyId = _defaultCurrencyId;
    }

    emit(state.copyWith(
      currencyId: currencyId,
      hasCurrencyLoaded: true,
    ));
  }

  Future<void> _onToggleLocalCurrency(
      ToggleLocalCurrencyEvent event, Emitter<CurrencyState> emit
  ) async {
    if (state.currencyId == null) {
      return;
    }

    final int oldCurrencyIdIdx = _availableCurrencyIds.indexOf(state.currencyId!);
    int newCurrencyIdIdx = oldCurrencyIdIdx + 1;
    if (newCurrencyIdIdx >= _availableCurrencyIds.length){
      newCurrencyIdIdx = 0;
    }

    final newCurrencyId = _availableCurrencyIds[newCurrencyIdIdx];

    final prefs = await SharedPreferences.getInstance();
    prefs.setString(_currencyPrefsKey, newCurrencyId);

    emit(state.copyWith(
      currencyId: newCurrencyId,
    ));
  }
}