using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace IBANNummerPrüfen
{
    public class IbanPrüfung
    {
        // Richtiges IBAN Format: DE68 2105 0170 0012 3456 78
        //private string? IBAN;
        private string? ibanCleared;
        private string? ibanSwapped;
        private string? sum;
        private string? iban;
        public void SetIbanPrüfungEntgegennehmen()
        {
            Console.Write("Bitte geben Sie ihre IBAN-Nummer ein: ");
            this.iban = Console.ReadLine();
            
            Console.WriteLine(IBANPrüfung());
        }

        /// <summary>
        /// Bestimmt ob die Checksumme einer IBAN gültig ist
        /// </summary>
        /// <param name="iban">Der zu prüfende IBAN (z.B: "DE68 2105 0170 0012 3456 78")</param>
        /// <returns><c>True</c>, wenn <paramref name="value"/> gültig ist. Andernfalls <c>False</c>.</returns>
        public bool IBANPrüfung()
        {
            if (this.iban != null)
            {
                this.ibanCleared = this.iban.ToUpper().Replace(" ", "").Replace("-", "").Replace(".", "");
                //Console.WriteLine(ibanCleared);
                this.ibanSwapped = ibanCleared.Substring(4) + ibanCleared.Substring(0, 4);
                //Console.WriteLine(ibanSwapped);
                this.sum = ibanSwapped.Aggregate("", (current, c) => current + (char.IsLetter(c) ? (c - 55).ToString() : c.ToString()));
                //Console.WriteLine(sum);
                //this.sum = ibanCleared.Aggregate("", (current, c) => current + (char.IsLetter(c) ? (c - 55).ToString() : c.ToString()));

                var d = decimal.Parse(sum);
                return ((d % 97) == 1);
            }
            return false;
        }

    }
}