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| using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq; // .Net Framework 4.0
namespace TechScales
{
internal static class Luhn
{
/// <summary>
/// Luhn Algoritm.
/// </summary>
/// <param name="numbers">numbers to check</param>
internal static bool IsValid(string numbers)
{
int len = numbers.Length;
int dgt = 0, sum = 0;
int pos = 0; //the current process number (to calc odd/even proc)
for (int i = len - 1; i >= 0; i--)
{
//digit on right most
string rgt = numbers.Substring(i, 1);
//parse
if (!int.TryParse(rgt, out dgt)) { return false; }
//double value of every 2nd right most
//if value = 2digits, sum the digits by substract by 9
if (pos % 2 != 0) { if ((dgt *= 2) > 9) { dgt -= 9; } }
//increase the proc number
pos++;
//summarize the processed digits
sum += dgt;
}
//if sum is divisible by 10, return valid, else notValid
return (sum % 10 == 0);
}
/// <summary>
/// Luhn Algoritm.
/// </summary>
/// <param name="sidNum">numbers to check</param>
internal static bool IsValidA(string numbers)
{
int sum = 0, pos = 0;
// select numeric only
// reverse collection, need to sumarize from right most
var num = numbers.Where(c => "0123456789".Contains(c)).Reverse();
foreach(var n in num)
{
// multiply by 2 of every even digit value.
// if digit value > 9, substract it by 9.
// perform addition
var i = n - 48;
sum += pos % 2 != 0 ? ((i *= 2) > 9 ? (i - 9) : i) : i;
// next digit
pos++;
};
return sum % 10 == 0;
}
/// <summary>
/// extension: verify string by Luhn algorithm
/// </summary>
/// <param name="arg"></param>
/// <returns></returns>
internal static bool IsLuhnVerified(this string arg)
{
return !string.IsNullOrWhiteSpace(arg) ? IsValidA(arg) : false;
}
/// <summary>
/// extension: verify numbers by Luhn algorithm
/// </summary>
/// <param name="arg"></param>
/// <returns></returns>
internal static bool IsLuhnVerified(this long arg)
{
return
!string.IsNullOrWhiteSpace(arg.ToString()) ?
IsValidA(arg.ToString()) : false;
}
/// <summary>
/// get valid check digit of complete string numbers
/// using Luhn algorithm<para></para>
/// string cannot be empty/null value
/// </summary>
/// <param name="arg"></param>
/// <param name="numOnly">get number only</param>
/// <returns></returns>
internal static int ValidCheckDigit(string arg, bool numOnly = false)
{
int sum = 0, pos = 0;
var num = (!numOnly ?
arg :
arg.Where(c => "0123456789".Contains(c)))
.Reverse();
foreach (var n in num)
{
var i = n - 48;
sum += pos % 2 == 0 ? ((i *= 2) > 9 ? (i - 9) : i) : i;
pos++;
}
return ((int)Math.Ceiling(sum / 10d) * 10) - sum;
}
}
}
|
