var defaultEmptyOK = false;
var whitespace = " \t\n\r";

//set up basic character groups
var digits = "0123456789";
var lowercaseLetters = "abcdefghijklmnopqrstuvwxyz";
var uppercaseLetters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
var whitespace = " \t\n\r";
var nameDelimiters = "-. ";
var decimalPointDelimiter = ".";
var daysInMonth = makeArrayFromString(31,29,31,30,31,30,31,31,30,31,30,31);

//electronic addresses
var validDomainNameChars = digits + uppercaseLetters + lowercaseLetters + "-_.";

function makeArrayFromString() {
   for (var i = 1; i <= makeArrayFromString.arguments.length; i++){
      this[i] = makeArrayFromString.arguments[i];
   }
   this[length] = makeArrayFromString.arguments.length;
   return this;
}

function isEmpty(s) {
    return ((s == null) || (s.length == 0))
}

function isWhitespace(s) {
    var i;

    if (isEmpty(s)) return true;
    for (i = 0; i < s.length; i++)
    {   
        var c = s.charAt(i);
        if (whitespace.indexOf(c) == -1) return false; // not whitespace
    }
    return true;
}

function isEmail (s){
    if (isEmpty(s)) {
       if (isEmail.arguments.length == 1) return defaultEmptyOK;
       else return (isEmail.arguments[1] == true); }
    if (isWhitespace(s)) return false;
    var i = 1;
    var sLength = s.length;
    while ((i < sLength) && (s.charAt(i) != "@"))
    { i++ }
    if ((i >= sLength) || (s.charAt(i) != "@")) return ("no @ sign");
    else atloc = i;
    j = i+1;
    i += 1;
    while ((j < sLength) && (validDomainNameChars.indexOf(s.charAt(j)) != -1))
    { j++ }
    if (j < sLength) return("invalid character in domain name: "+s.charAt(j));
    while ((i < sLength) && (s.charAt(i) != "."))
    { i++ }
    if (i == sLength) return("no . in domain name");
    if (i == (atloc +1)) return("not enough space between @ and .");
    k = atloc+1;
    while (k < sLength){
      if ((s.charAt(k) == ".") && (s.charAt(k+1) == ".")) return("too many .'s");
      k++
    }
    l = sLength;
    while ((i < sLength -2) && (l != i) && (s.charAt(l) != "."))
    { l = l-1 }
    if ((i >= sLength - 2) || (s.charAt(i) != ".") || (l >= sLength - 2)) return("not enough chars after .");
    else return true;
}

function checkEmail (theField, emptyOK){
    if (checkEmail.arguments.length == 1) emptyOK = defaultEmptyOK;
    if (theField.length > 0)
    {
		if ((emptyOK == true) && (isEmpty(theField))) return true;
		else {
		  emailStatus = isEmail(theField, false)
		  if (emailStatus != true) return false
		  else return true;
		}
	}
}