Gelir İdaresi Başkanlığının Verilerine Göre Gecikme Zammı Hesabı

gecikme_hesap.dart

import 'package:date_calc/date_calc.dart';
import 'package:test/test.dart';
import 'package:intl/intl.dart';

class DateDifference {
  int years;
  int months;
  int days;

  DateDifference(this.years, this.months, this.days);
}

extension DateDifferenceJodaStyle on DateCalc {
  DateDifference differenceJodaStyle(DateCalc otherDate) {
    var date1 = this;
    var date2 = otherDate;
    var yearDiff = date2.differenceValue(type: DateType.year, date: date1);
    date1 = date1.addYear(yearDiff);
    var monthDiff = date2.differenceValue(type: DateType.month, date: date1);
    date1 = date1.addMonth(monthDiff);
    var dayDiff = date2.differenceValue(type: DateType.day, date: date1);

    return DateDifference(yearDiff, monthDiff, dayDiff);
  }
}

class GecikmeData {
  DateCalc startDate;
  double rate;

  GecikmeData(this.startDate, this.rate);
}

double gecikmeHesapla(
    DateCalc sonOdemeTarih, DateCalc vadeTarih, double tutar) {
  var gecikmeData = List<GecikmeData>();
  var gecikme = 0.0;
  gecikmeData.add(GecikmeData(DateCalc(2000, 1, 20), 6.0));
  gecikmeData.add(GecikmeData(DateCalc(2000, 12, 2), 5.0));
  gecikmeData.add(GecikmeData(DateCalc(2001, 3, 29), 10.0));
  gecikmeData.add(GecikmeData(DateCalc(2002, 1, 31), 7.0));
  gecikmeData.add(GecikmeData(DateCalc(2003, 11, 12), 4.0));
  gecikmeData.add(GecikmeData(DateCalc(2004, 1, 2), 4.0));
  gecikmeData.add(GecikmeData(DateCalc(2005, 3, 2), 3.0));
  gecikmeData.add(GecikmeData(DateCalc(2006, 4, 21), 2.5));
  gecikmeData.add(GecikmeData(DateCalc(2009, 11, 20), 1.95));
  gecikmeData.add(GecikmeData(DateCalc(2010, 10, 19), 1.40));
  gecikmeData.add(GecikmeData(DateCalc(2018, 9, 5), 2.0));
  gecikmeData.add(GecikmeData(DateCalc(2019, 7, 1), 2.5));
  gecikmeData.add(GecikmeData(DateCalc(2019, 10, 2), 2.0));
  gecikmeData.add(GecikmeData(DateCalc(2019, 12, 30), 1.6));

  gecikmeData.removeWhere((tarih) =>
      tarih.startDate.isBefore(gecikmeData
          .where((t) => t.startDate.isBefore(sonOdemeTarih))
          .last
          .startDate) ||
      tarih.startDate.isAfter(vadeTarih));
  //ilk tarih ve son tarihi belirle

  gecikmeData.add(GecikmeData(vadeTarih, 0.0));
  gecikmeData.first = GecikmeData(sonOdemeTarih, gecikmeData.first.rate);

  var len = gecikmeData.length - 1;
  for (var i = 0; i < len; i++) {
    var start = gecikmeData[i].startDate;
    var end = gecikmeData[i + 1].startDate;
    var rate = gecikmeData[i].rate / 100.0;

    var diff = start.differenceJodaStyle(end);

    var localGecikme = 0.0;
    localGecikme += diff.years * 12 * rate * tutar;
    localGecikme += diff.months * rate * tutar;
    localGecikme += (diff.days / 30.0) * rate * tutar;
    gecikme += localGecikme;
  }

  return gecikme;
}