using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using System.IO;
using System.Text;
using System.Xml;
using System.Xml.Linq;
using Microsoft.SqlServer.Server;
using Neo.Afx.ComponentModel;

namespace Neo.Afx.Validation
{
    /// <summary>
    /// The formatter.
    /// </summary>
    public class RsaIdValidation
    {
        /// <summary>
        /// Does check digit validation on an RSA id number
        /// </summary>
        /// <param name="idNumber">The ID number.</param>
        /// <returns>True/False</returns>
        [SqlFunction(
            IsDeterministic = true,
            IsPrecise = true,
            DataAccess = DataAccessKind.Read,
            SystemDataAccess = SystemDataAccessKind.Read
            )]
        public static SqlBoolean IsValidRsaIdNumber(SqlString idNumber)
        {
            var isValid = false;
            var idNumberToCheck = idNumber.Value;

            if (string.IsNullOrEmpty(idNumberToCheck) || idNumberToCheck.Length != 13)
            { 
                return  new SqlBoolean(isValid);
            }

            #region Check for 13 digits
            int i;
            for (i = 0; i < 13; i++)
                if (idNumberToCheck[i] < '0' || idNumberToCheck[i] > '9')
                {
                    return new SqlBoolean(isValid);
                }
            #endregion

            #region Check digit validation
            var digits = idNumberToCheck.ToCharArray();
            var checkDigit = Convert.ToInt32(digits[digits.Length - 1].ToString());
            var sumA = 0;
            var sumB = "";
            var sumC = 0;

            for (var counter = 0; counter < digits.Length - 1; counter++)
            {
                if ((counter + 1) % 2 != 0)
                {
                    sumA += Convert.ToInt32(digits[counter].ToString());
                }
                else
                {
                    if (digits[counter] != 0 || sumB != "")
                    {
                        sumB = sumB + digits[counter].ToString();
                    }
                }
            }

            sumC = Convert.ToInt32(sumB) * 2;
            var bSplit = sumC.ToString().ToCharArray();
            sumC = 0;

            for (var counter = 0; counter < bSplit.Length; counter++)
            {
                sumC += Convert.ToInt32(bSplit[counter].ToString());
            }

            sumC += sumA;

            var lastDigit = 10 - Convert.ToInt32(sumC.ToString().Substring(sumC.ToString().Length - 1));

            if (lastDigit.ToString().Length == 2)
            {
                if (Convert.ToInt32(lastDigit.ToString().Substring(1)) != checkDigit)
                {
                    return new SqlBoolean(false);
                }
            }
            else
            {
                if (Convert.ToInt32(lastDigit) != checkDigit)
                {
                    return new SqlBoolean(false);
                }
            } 
            #endregion

            return new SqlBoolean(true);
        }
    }
}