#region Copyright (c) 2006 Synerics Business Solutions

/*
(c) 2006 Synerics Business Solutions 
code@synerics.com
www.synerics.com

This software is provided 'as-is', without any warranty.
Permission is granted to anyone to use this software for any purpose.
This notice may not be removed from any source distribution; 
if you are using this software in a product, this notice should be 
included in materials distributed with your product.

*/

#endregion

using System;
using System.Text;
using System.Text.RegularExpressions;

namespace Foundation.Utils
{
	/// <summary>
	/// Validates a South African identity number.
	/// </summary>
	public class IDValidator
	{
		// constants
		const int VALID_LENGTH = 13;
		const int CONTROL_DIGIT_LOCATION = 12;
		const int CONTROL_DIGIT_CHECK_VALUE = 10;
		const int CONTROL_DIGIT_CHECK_EXCEPTION_VALUE = 9;
		const string REGEX_ID_PATTERN = "(?<Year>[0-9][0-9])(?<Month>([0][1-9])|([1][0-2]))(?<Day>([0-2][0-9])|([3][0-1]))(?<Gender>[0-9])(?<Series>[0-9]{3})(?<Citizenship>[0-9])(?<Uniform>[0-9])(?<Control>[0-9])";
		const bool VALID = true;
		const bool INVALID = false;

		// member variables
		private string id;

		// constructor
		public IDValidator(string id_)
		{
			id = id_;
		}

		public int GetAge() 
		{
			if (isValid()) 
			{
				DateTime birthDate = DateTime.ParseExact(id.Substring(0,2) + "/" + id.Substring(2,2) + "/" + id.Substring(4,2), "yy/MM/dd", System.Globalization.CultureInfo.InvariantCulture);
				int years = DateTime.Now.Year - birthDate.Year;

                if (years < 0)
                {
                    birthDate = DateTime.ParseExact("19" + id.Substring(0, 2) + "/" + id.Substring(2, 2) + "/" + id.Substring(4, 2), "yyyy/MM/dd", System.Globalization.CultureInfo.InvariantCulture);
                    years = DateTime.Now.Year - birthDate.Year;
                }

				if (DateTime.Now.Month < birthDate.Month ||
					(DateTime.Now.Month == birthDate.Month &&
					DateTime.Now.Day < birthDate.Day))
					years--;

				return years;
			} 
			else 
			{
				throw new Exception("Invalid ID");
			}
		}

		// SA citizen check
		public bool IsSACitizen() 
		{
			if (isValid()) 
			{
				if (int.Parse(id.Substring(10,1)) == 0) 
				{
					return true;
				}
				else 
				{
					return false;
				}
			} 
			else 
			{
				throw new Exception("Invalid ID");
			}
		}

		// gender check
		public bool IsFemale() 
		{
			if (isValid()) 
			{
				if (int.Parse(id.Substring(6,1)) < 5) 
				{
					return true;
				}
				else 
				{
					return false;
				}
			} 
			else 
			{
				throw new Exception("Invalid ID");
			}
		}

		// get date of birth
		public string GetDateOfBirth() 
		{
			if (isValid()) 
			{
				DateTime date = DateTime.ParseExact(id.Substring(0,2) + "/" + id.Substring(2,2) + "/" + id.Substring(4,2), "yy/MM/dd", System.Globalization.CultureInfo.InvariantCulture);

                int years = DateTime.Now.Year - date.Year;

                if (years < 0)
                {
                    date = DateTime.ParseExact("19" + id.Substring(0, 2) + "/" + id.Substring(2, 2) + "/" + id.Substring(4, 2), "yyyy/MM/dd", System.Globalization.CultureInfo.InvariantCulture);
                }

				return date.ToShortDateString();
			} 
			else 
			{
				throw new Exception("Invalid ID");
			}
		}

		public DateTime GetDateOfBirthAsDateTime() 
		{
			if (isValid()) 
			{
				DateTime date = DateTime.ParseExact(id.Substring(0,2) + "/" + id.Substring(2,2) + "/" + id.Substring(4,2), "yy/MM/dd", System.Globalization.CultureInfo.InvariantCulture);

                int years = DateTime.Now.Year - date.Year;

                if (years < 0)
                {
                    date = DateTime.ParseExact("19" + id.Substring(0, 2) + "/" + id.Substring(2, 2) + "/" + id.Substring(4, 2), "yyyy/MM/dd", System.Globalization.CultureInfo.InvariantCulture);
                }

				return date;
			} 
			else 
			{
				throw new Exception("Invalid ID");
			}
		}



		// check whether ID number is valid
		public bool isValid() 
		{
			// assume that the id number is invalid
			bool isValidPattern = false;
			bool isValidLength = false;
			bool isValidControlDigit = false;

			// check length
			if (id.Length == VALID_LENGTH) 
			{
				isValidLength = true;
			}

			// match regex pattern, only if length is valid
			if (isValidLength) 
			{
				Regex idPattern = new Regex(REGEX_ID_PATTERN);

				if (idPattern.IsMatch(id)) 
				{
                    //00 will slip through the regex and checksum
                    if (id.Substring(2, 2) != "00" && id.Substring(4, 2) != "00")
                    {
                        isValidPattern = true;
                    }					
				}
			}



			// check control digit, only if previous validations passed
			if (isValidLength && isValidPattern) 
			{
				int a = 0;
				int b = 0;
				int c = 0;
				int cDigit = -1;
				int tmp = 0;
				StringBuilder even = new StringBuilder();
				string evenResult = null;

				// sum odd digits
				for (int i=0; i<VALID_LENGTH-1; i=i+2) 
				{
					a = a + int.Parse(id[i].ToString());
				}

				// build a string containing even digits
				for (int i=1; i<VALID_LENGTH-1; i=i+2) 
				{
					even.Append(id[i]);
				}
				// multipy by 2
				tmp = int.Parse(even.ToString()) * 2;
				// convert to string again
				evenResult = tmp.ToString();
				// sum the digits in evenResult
				for (int i=0; i<evenResult.Length; i++) 
				{
					b = b + int.Parse(evenResult[i].ToString());
				}

				c = a + b;

				cDigit = CONTROL_DIGIT_CHECK_VALUE - int.Parse(c.ToString()[1].ToString());
				if (cDigit == int.Parse(id[CONTROL_DIGIT_LOCATION].ToString())) 
				{
					isValidControlDigit = true;
				} 
				else 
				{
					if (cDigit > CONTROL_DIGIT_CHECK_EXCEPTION_VALUE) 
					{
						if (0 == int.Parse(id[CONTROL_DIGIT_LOCATION].ToString())) 
						{
							isValidControlDigit = true;
						}
					}
				}
			}

			// final check
			if (isValidLength && isValidPattern && isValidControlDigit) 
			{
				return VALID;
			} 
			else 
			{
				return INVALID;
			}
		}
	}
}