// ===================================================================
// Author: Matt Kruse <matt@mattkruse.com>
// WWW: http://www.mattkruse.com/
//
// NOTICE: You may use this code for any purpose, commercial or
// private, without any further permission from the author. You may
// remove this notice from your final code if you wish, however it is
// appreciated by the author if at least my web site address is kept.
//
// You may *NOT* re-distribute this code in any way except through its
// use. That means, you can include it in your product, or your web
// site, or any other form where the code is actually being used. You
// may not put the plain javascript up on your site for download or
// include it in your javascript libraries for download. 
// If you wish to share this code with others, please just point them
// to the URL instead.
// Please DO NOT link directly to my .js files from your site. Copy
// the files to your server and use them there. Thank you.
// ===================================================================

// HISTORY
// ------------------------------------------------------------------
// May 17, 2003: Fixed bug in parseDate() for dates <1970
// March 11, 2003: Added parseDate() function
// March 11, 2003: Added "NNN" formatting option. Doesn't match up
//                 perfectly with SimpleDateFormat formats, but 
//                 backwards-compatability was required.

// ------------------------------------------------------------------
// These functions use the same 'format' strings as the 
// java.text.SimpleDateFormat class, with minor exceptions.
// The format string consists of the following abbreviations:
// 
// Field        | Full Form          | Short Form
// -------------+--------------------+-----------------------
// Year         | yyyy (4 digits)    | yy (2 digits), y (2 or 4 digits)
// Month        | MMM (name or abbr.)| MM (2 digits), M (1 or 2 digits)
//              | NNN (abbr.)        |
// Day of Month | dd (2 digits)      | d (1 or 2 digits)
// Day of Week  | EE (name)          | E (abbr)
// Hour (1-12)  | hh (2 digits)      | h (1 or 2 digits)
// Hour (0-23)  | HH (2 digits)      | H (1 or 2 digits)
// Hour (0-11)  | KK (2 digits)      | K (1 or 2 digits)
// Hour (1-24)  | kk (2 digits)      | k (1 or 2 digits)
// Minute       | mm (2 digits)      | m (1 or 2 digits)
// Second       | ss (2 digits)      | s (1 or 2 digits)
// AM/PM        | a                  |
//
// NOTE THE DIFFERENCE BETWEEN MM and mm! Month=MM, not mm!
// Examples:
//  "MMM d, y" matches: January 01, 2000
//                      Dec 1, 1900
//                      Nov 20, 00
//  "M/d/yy"   matches: 01/20/00
//                      9/2/00
//  "MMM dd, yyyy hh:mm:ssa" matches: "January 01, 2000 12:30:45AM"
// ------------------------------------------------------------------

var MONTH_NAMES = new Array('January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December', 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');
var DAY_NAMES = new Array('Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat');
function LZ(x)
{
  return (x < 0 || x > 9 ? "" : "0") + x;
}

// ------------------------------------------------------------------
// isDate ( date_string, format_string )
// Returns true if date string matches format of format string and
// is a valid date. Else returns false.
// It is recommended that you trim whitespace around the value before
// passing it to this function, as whitespace is NOT ignored!
// ------------------------------------------------------------------
function isDate(val, format)
{
  var date = getDateFromFormat(val, format);
  if(date == 0)
    return false;

  return true;
}

// -------------------------------------------------------------------
// compareDates(date1,date1format,date2,date2format)
//   Compare two date strings to see which is greater.
//   Returns:
//   1 if date1 is greater than date2
//   0 if date2 is greater than date1 of if they are the same
//  -1 if either of the dates is in an invalid format
// -------------------------------------------------------------------
function compareDates(date1, dateformat1, date2, dateformat2)
{
  var d1 = getDateFromFormat(date1, dateformat1);
  var d2 = getDateFromFormat(date2, dateformat2);
  if(d1 == 0 || d2 == 0)
    return -1;

  if(d1 > d2)
    return 1;

  return 0;
}

// ------------------------------------------------------------------
// formatDate (date_object, format)
// Returns a date in the output format specified.
// The format string uses the same abbreviations as in getDateFromFormat()
// ------------------------------------------------------------------
function formatDate(date, format)
{
  format = format + "";
  var result = "";
  var i_format = 0;
  var c = "";
  var token = "";
  var y = date.getYear() + "";
  var M = date.getMonth() + 1;
  var d = date.getDate();
  var E = date.getDay();
  var H = date.getHours();
  var m = date.getMinutes();
  var s = date.getSeconds();
  var yyyy, yy, MMM, MM, dd, hh, h, mm, ss, ampm, HH, H, KK, K, kk, k;

  // Convert real date parts into formatted versions
  var value = new Object();
  if(y.length < 4)
    y = "" + (y - 0 + 1900);

  value["y"] = "" + y;
  value["yyyy"] = y;
  value["yy"] = y.substring(2, 4);
  value["M"] = M;
  value["MM"] = LZ(M);
  value["MMM"] = MONTH_NAMES[M - 1];
  value["NNN"] = MONTH_NAMES[M + 11];
  value["d"] = d;
  value["dd"] = LZ(d);
  value["E"] = DAY_NAMES[E + 7];
  value["EE"] = DAY_NAMES[E];
  value["H"] = H;
  value["HH"] = LZ(H);
  if(H == 0)
    value["h"] = 12;
  else if(H > 12)
    value["h"] = H - 12;
  else
    value["h"] = H;
  value["hh"] = LZ(value["h"]);
  if(H > 11)
    value["K"] = H - 12;
  else
    value["K"] = H;
  value["k"] = H + 1;
  value["KK"] = LZ(value["K"]);
  value["kk"] = LZ(value["k"]);
  if(H > 11)
    value["a"] = "PM";
  else
    value["a"] = "AM";
  value["m"] = m;
  value["mm"] = LZ(m);
  value["s"] = s;
  value["ss"] = LZ(s);

  while(i_format < format.length)
  {
    c = format.charAt(i_format);
    token = "";
    while((format.charAt(i_format) == c) && (i_format < format.length))
      token += format.charAt(i_format++);

    if(value[token] != null)
      result = result + value[token];
    else
      result = result + token;
  }

  return result;
}
	
// ------------------------------------------------------------------
// Utility functions for parsing in getDateFromFormat()
// ------------------------------------------------------------------
function _isInteger(val)
{
  var digits = "1234567890";
  for(var i = 0; i < val.length; i++)
  {
    if(digits.indexOf(val.charAt(i)) == -1)
      return false;
  }

  return true;
}

function _getInt(str, i, minlength, maxlength)
{
  for(var x = maxlength; x >= minlength; x--)
  {
    var token = str.substring(i, i+x);
    if(token.length < minlength)
      return null;

    if(_isInteger(token))
      return token;
  }

  return null;
}
	
// ------------------------------------------------------------------
// getDateFromFormat( date_string , format_string )
//
// This function takes a date string and a format string. It matches
// If the date string matches the format string, it returns the 
// getTime() of the date. If it does not match, it returns 0.
// ------------------------------------------------------------------
function getDateFromFormat(val, format)
{
  val = val + "";
  format = format + "";
  var i_val = 0;
  var i_format = 0;
  var c = "";
  var token = "";
  var token2 = "";
  var x;
  var y;
  var now = new Date();
  var year = now.getYear();
  var month = now.getMonth()+1;
  var date = 1;
  var hh = now.getHours();
  var mm = now.getMinutes();
  var ss = now.getSeconds();
  var ampm = "";

  while(i_format < format.length)
  {
    // Get next token from format string
    c = format.charAt(i_format);
    token = "";
    while((format.charAt(i_format) == c) && (i_format < format.length))
      token += format.charAt(i_format++);

    // Extract contents of value based on format token
    if(token == "yyyy" || token == "yy" || token == "y")
    {
      if(token == "yyyy")
      {
      	x=4;
      	y=4;
      }
      else if(token == "yy")
      {
      	x=2;
      	y=2;
      }
      else if(token == "y")
      {
      	x=2;
      	y=4;
      }

      year = _getInt(val, i_val, x, y);
      if(year == null)
      	return 0;

      i_val += year.length;
      if(year.length == 2)
      {
        if(year > 30)
          year = 1900 + (year - 0);
        else
          year = 2000 + (year - 0);
      }
    }
    else if(token == "MMM" || token == "NNN")
    {
      month = 0;
      for(var i = 0; i < MONTH_NAMES.length; i++)
      {
      	var month_name = MONTH_NAMES[i];
      	if(val.substring(i_val, i_val + month_name.length).toLowerCase() == month_name.toLowerCase())
      	{
      	  if(token == "MMM" || (token == "NNN" && i > 11))
      	  {
      	    month = i + 1;
      	    if(month > 12)
      	      month -= 12;

      	    i_val += month_name.length;
      	    break;
      	  }
      	}
      }

      if((month < 1) || (month > 12))
        return 0;
    }
    else if(token == "EE" || token == "E")
    {
      for(var i = 0; i < DAY_NAMES.length; i++)
      {
        var day_name = DAY_NAMES[i];
        if(val.substring(i_val, i_val + day_name.length).toLowerCase() == day_name.toLowerCase())
        {
          i_val += day_name.length;
          break;
        }
      }
    }
    else if(token == "MM" || token == "M")
    {
      month = _getInt(val, i_val, token.length, 2);
      if(month == null || (month < 1) || (month > 12))
        return 0;

      i_val += month.length;
    }
    else if(token == "dd" || token == "d")
    {
      date = _getInt(val, i_val, token.length, 2);
      if(date == null || (date < 1) || (date > 31))
        return 0;

      i_val += date.length;
    }
    else if(token == "hh" || token == "h")
    {
      hh = _getInt(val, i_val, token.length, 2);
      if(hh == null || (hh < 1) || (hh > 12))
        return 0;

      i_val += hh.length;
    }
    else if(token == "HH" || token == "H")
    {
      hh = _getInt(val, i_val, token.length, 2);
      if(hh == null || (hh < 0) || (hh > 23))
        return 0;

      i_val += hh.length;
    }
    else if(token == "KK" || token == "K")
    {
      hh = _getInt(val, i_val, token.length, 2);
      if(hh == null || (hh < 0) || (hh > 11))
        return 0;

      i_val += hh.length;
    }
    else if(token == "kk" || token == "k")
    {
      hh = _getInt(val, i_val, token.length, 2);
      if(hh == null || (hh < 1) || (hh > 24))
        return 0;

      i_val += hh.length;
      hh--;
    }
    else if(token == "mm" || token == "m")
    {
      mm = _getInt(val, i_val, token.length, 2);
      if(mm == null || (mm < 0) || (mm > 59))
        return 0;

      i_val += mm.length;
    }
    else if(token == "ss" || token == "s")
    {
      ss = _getInt(val, i_val, token.length, 2);
      if(ss == null || (ss < 0) || (ss > 59))
        return 0;

      i_val += ss.length;
    }
    else if(token == "a")
    {
      if(val.substring(i_val, i_val + 2).toLowerCase() == "am")
        ampm = "AM";
      else if(val.substring(i_val, i_val+2).toLowerCase() == "pm")
        ampm = "PM";
      else
        return 0;

      i_val += 2;
    }
    else
    {
      if(val.substring(i_val, i_val + token.length) != token)
        return 0;
      else
        i_val += token.length;
    }
  }

  // If there are any trailing characters left in the value, it doesn't match
  if(i_val != val.length)
    return 0;

  // Is date valid for month?
  if(month == 2)
  {
    // Check for leap year
    if(((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0))
    {
      // leap year
      if(date > 29)
        return 0;
    }
    else
    {
      if(date > 28)
        return 0;
    }
  }
  else if((month == 4) || (month == 6) || (month == 9) || (month == 11))
  {
    if(date > 30)
      return 0;
  }

  // Correct hours value
  if(hh < 12 && ampm == "PM")
    hh = hh - 0 + 12;
  else if(hh > 11 && ampm == "AM")
    hh -= 12;

  var newdate = new Date(year, month-1, date, hh, mm, ss);
  return newdate.getTime();
}

// ------------------------------------------------------------------
// parseDate( date_string [, prefer_euro_format] )
//
// This function takes a date string and tries to match it to a
// number of possible date formats to get the value. It will try to
// match against the following international formats, in this order:
// y-M-d   MMM d, y   MMM d,y   y-MMM-d   d-MMM-y  MMM d
// M/d/y   M-d-y      M.d.y     MMM-d     M/d      M-d
// d/M/y   d-M-y      d.M.y     d-MMM     d/M      d-M
// A second argument may be passed to instruct the method to search
// for formats like d/M/y (european format) before M/d/y (American).
// Returns a Date object or null if no patterns match.
// ------------------------------------------------------------------
function parseDate(val)
{
  var preferEuro = (arguments.length == 2) ? arguments[1] : false;
  generalFormats = new Array('y-M-d', 'MMM d, y', 'MMM d,y', 'y-MMM-d', 'd-MMM-y', 'MMM d');
  monthFirst = new Array('M/d/y', 'M-d-y', 'M.d.y', 'MMM-d', 'M/d','M-d');
  dateFirst = new Array('d/M/y', 'd-M-y', 'd.M.y', 'd-MMM', 'd/M', 'd-M');
  var checkList = new Array('generalFormats', preferEuro ? 'dateFirst' : 'monthFirst', preferEuro ? 'monthFirst' : 'dateFirst');
  var d=null;
  for(var i = 0; i < checkList.length; i++)
  {
    var l = window[checkList[i]];
    for(var j = 0; j < l.length; j++)
    {
      d = getDateFromFormat(val,l[j]);
      if(d != 0)
        return new Date(d);
    }
  }

  return null;
}

function SetDate(obj)
{
	if(IsEmpty(obj))
		return;

	var dt = parseDate(obj.value, true);
	if(dt == null)
	{
		alert("Invalid date");
		obj.focus();
		return;
	}

	obj.value = formatDate(dt, "dd-NNN-yyyy");
}