flutter_application_1/lib/main.dart

import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter_application_1/enums.dart';
import 'package:flutter_application_1/translations.dart';
import 'package:flutter_application_1/utils.dart';
import 'package:flutter_application_1/widgets/input_widget.dart';
import 'package:flutter_application_1/widgets/interval_widget.dart';
import 'package:flutter_application_1/widgets/result_widget.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: CupertinoColors.white, background: CupertinoColors.white),
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Zinseszinsrechner',),
      debugShowCheckedModeBanner: false,
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});
  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final TextEditingController _initialCapitalController = TextEditingController();
  final TextEditingController _monthlySavingsRateController = TextEditingController();
  final TextEditingController _interestRateController = TextEditingController();
  final TextEditingController _timeController = TextEditingController();
  bool _isInitialCapitalEntered = false;
  bool _isMonthlySavingsRateEntered = false;
  bool _isInterestRateEntered = false;
  bool _isTimeEntered = false;
  final FocusNode _initialCapitalFocusNode = FocusNode();
  final FocusNode _monthlySavingsRateFocusNode = FocusNode();
  final FocusNode _interestRateFocusNode = FocusNode();
  final FocusNode _timeFocusNode = FocusNode();

  @override
  void initState() {
    super.initState();

    _initialCapitalController.addListener(() {
      setState(() {
        _isInitialCapitalEntered = _initialCapitalController.text.isNotEmpty &&
            isNumeric(_initialCapitalController.text);
        restoreDefaultValuesIfEmpty(_initialCapitalController);
      });
    });

    _monthlySavingsRateController.addListener(() {
      setState(() {
        _isMonthlySavingsRateEntered = _monthlySavingsRateController.text.isNotEmpty &&
            isNumeric(_monthlySavingsRateController.text);
        restoreDefaultValuesIfEmpty(_monthlySavingsRateController);
      });
    });

    _interestRateController.addListener(() {
      setState(() {
        _isInterestRateEntered = _interestRateController.text.isNotEmpty &&
            isNumeric(_interestRateController.text);
        restoreDefaultValuesIfEmpty(_interestRateController);
      });
    });

    _timeController.addListener(() {
      setState(() {
        _isTimeEntered = _timeController.text.isNotEmpty &&
            isNumeric(_timeController.text);
        restoreDefaultValuesIfEmpty(_timeController);
      });
    });

    _initialCapitalFocusNode.addListener(() {
      if (!_initialCapitalFocusNode.hasFocus) {
        roundToInteger(_initialCapitalController);
      }
    });

    _monthlySavingsRateFocusNode.addListener(() {
      if (!_monthlySavingsRateFocusNode.hasFocus) {
        roundToInteger(_monthlySavingsRateController);
      }
    });

    _interestRateFocusNode.addListener(() {
      if (!_interestRateFocusNode.hasFocus) {
        roundToInteger(_interestRateController);
      }
    });

    _timeFocusNode.addListener(() {
      if (!_timeFocusNode.hasFocus) {
        roundToInteger(_timeController);
      }
    });

    _initialCapitalController.text = '1000'; // Beispielwert für Anfangskapital
    _monthlySavingsRateController.text = '50'; // Beispielwert für monatliche Sparrate
    _interestRateController.text = '5'; // Beispielwert für jährlichen Zinssatz
    _timeController.text = '10'; // Beispielwert für Anlagezeitraum
  }


  double _initialCapital = 0.0; // Anfangskapital
  double _monthlySavingsRate = 0.0; // Monatliche Sparrate
  double _interestRate = 0.0; // Jährlicher Zinssatz
  double _time = 0.0; // Anlagezeitraum in Jahren
  double _investedMoney = 0.0; // Investiertes Geld ohne Zinsen
  List<double> _investedMoneyList = []; // Investiertes Geld ohne Zinsen (pro Jahr)
  PayoutInterval _payoutInterval = PayoutInterval.yearly; // Standardwert für das Ausschüttungsintervall
  double _compoundInterest = 0.0; // Investiertes Geld mit Zinsen
  List<double> _compoundInterestList = []; // Investiertes Geld mit Zinsen (pro Jahr)
  bool _calculationPerformed = false;

  void setInitialCapital() {
    setState(() {
      _initialCapital = double.parse(_initialCapitalController.text);
    });
  }

  void setMonthlySavingsRate() {
    setState(() {
      _monthlySavingsRate = double.parse(_monthlySavingsRateController.text);
    });
  }

  void setInterestRate() {
    setState(() {
      _interestRate = double.parse(_interestRateController.text);
    });
  }

  void setTime() {
    setState(() {
      _time = double.parse(_timeController.text);
    });
  }

  void _calculateInvestedMoney() {
    setState(() {
      _investedMoneyList.clear();
      _investedMoney = _initialCapital;
      for (int i = 0; i < _time; i++) {
        _investedMoney += _monthlySavingsRate * 12;
        _investedMoney = _investedMoney.roundToDouble();
        _investedMoneyList.add(_investedMoney);
      }
      _calculationPerformed = true;
    });
  }

  void _calculateCompoundInterest() {
    setState(() {
      _compoundInterestList.clear();
      _compoundInterest = _initialCapital;
      if(_payoutInterval == PayoutInterval.yearly){
        for(int i = 0; i < _time; i++){
          _compoundInterest += _compoundInterest * (_interestRate / 100) + _monthlySavingsRate * 12;
          _compoundInterest = _compoundInterest.roundToDouble();
          _compoundInterestList.add(_compoundInterest - _investedMoneyList[i]);
        }
      }
      else{
        for(int i = 0; i < _time; i++){
          for(int j = 0; j < 12; j++){
            _compoundInterest += _compoundInterest * ((_interestRate / 100) / 12) + _monthlySavingsRate;
            _compoundInterest = _compoundInterest.roundToDouble();
          }
          _compoundInterestList.add(_compoundInterest - _investedMoneyList[i]);
        }
      }
      _calculationPerformed = true;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SingleChildScrollView(
        child: Padding(
          padding: const EdgeInsets.all(20.0),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: <Widget>[
              buildInputWidget('Anfangskapital', _initialCapitalController, _initialCapitalFocusNode, _isInitialCapitalEntered, '€', 'Das Anfangskapital ist der Betrag, den Sie zu Beginn Ihrer Anlage haben.'),
              buildInputWidget('Monatliche Sparrate', _monthlySavingsRateController, _monthlySavingsRateFocusNode, _isMonthlySavingsRateEntered, '€', 'Die monatliche Sparrate ist der Betrag, den Sie jeden Monat zu Ihrer Investition hinzufügen.'),
              buildInputWidget('Jährlicher Zinssatz', _interestRateController, _interestRateFocusNode, _isInterestRateEntered, '%', 'Der jährliche Zinssatz ist der Prozentsatz, zu dem Ihr investiertes Kapital jedes Jahr wächst.'),
              buildInputWidget('Anlagezeitraum', _timeController, _timeFocusNode, _isTimeEntered, 'Jahre', 'Der Anlagezeitraum ist die Zeitspanne, für die Sie planen, Ihr Geld anzulegen.'),
              IntervalWidget(
                selectedInterval: translateInterval(_payoutInterval),
                onChanged: (newInterval) {
                  setState(() {
                    _payoutInterval = newInterval == 'jährlich' ? PayoutInterval.yearly : PayoutInterval.monthly;
                  });
                },
              ),
              ElevatedButton(
                onPressed: () {
                  setInitialCapital();
                  setMonthlySavingsRate();
                  setInterestRate();
                  setTime();
                  _calculateInvestedMoney();
                  _calculateCompoundInterest();
                },
                style: ButtonStyle(
                  backgroundColor: MaterialStateProperty.all<Color>(CupertinoColors.black),
                  foregroundColor: MaterialStateProperty.all<Color>(CupertinoColors.white),
                ),
                child: const Text(
                  'Berechnen',
                  style: TextStyle(
                    fontWeight: FontWeight.bold,
                  ),
                ),
              ),
              const SizedBox(height: 20),
              if(_calculationPerformed)
                buildResultWidget('$_compoundInterest', '$_investedMoney', '$_time', '$_monthlySavingsRate', '$_interestRate', _payoutInterval, _investedMoneyList, _compoundInterestList),
                
            ],
          ),
        )
      )
    );
  }
}