/**
 * Reference: Sandeep V. Tamhankar (stamhankar@hotmail.com),
 * http://javascript.internet.com,
 * JBilling
 */
function checkEmail(emailStr) {
    if (emailStr.length == 0) {
        return true;
    }
    var emailPat = /^(.+)@(.+)$/;
    var specialChars = "\\(\\)<>@,;:\\\\\\\"\\.\\[\\]";
    var validChars = "\[^\\s" + specialChars + "\]";
    var quotedUser = "(\"[^\"]*\")";
    var ipDomainPat = /^(\d{1,3})[.](\d{1,3})[.](\d{1,3})[.](\d{1,3})$/;
    var atom = validChars + '+';
    var word = "(" + atom + "|" + quotedUser + ")";
    var userPat = new RegExp("^" + word + "(\\." + word + ")*$");
    var domainPat = new RegExp("^" + atom + "(\\." + atom + ")*$");
    var matchArray = emailStr.match(emailPat);
    if (matchArray == null) {
        return false;
    }

    var user = matchArray[1];
    var domain = matchArray[2];
    if (user.match(userPat) == null) {
        return false;
    }

    var IPArray = domain.match(ipDomainPat);
    if (IPArray != null) {
        for (var i = 1; i <= 4; i++) {
            if (IPArray[i] > 255) {
                return false;
            }
        }
        return true;
    }

    var domainArray = domain.match(domainPat);
    if (domainArray == null) {
        return false;
    }

    var atomPat = new RegExp(atom, "g");
    var domArr = domain.match(atomPat);
    var len = domArr.length;
    if ((domArr[domArr.length - 1].length < 2) ||
        (domArr[domArr.length - 1].length > 3)) {
        return false;
    }

    return len >= 2;
}

function luhnCheck(cardNumber) {
    if (isLuhnNum(cardNumber)) {
        cardNumber = cardNumber.value.toString();
        var no_digit = cardNumber.length;
        var oddoeven = no_digit & 1;
        var sum = 0;
        for (var count = 0; count < no_digit; count++) {
            var digit = parseInt(cardNumber.charAt(count));
            if (!((count & 1) ^ oddoeven)) {
                digit *= 2;
                if (digit > 9) digit -= 9;
            }
            ;
            sum += digit;
        }
        ;
        if (sum == 0) return false;
        if (sum % 10 == 0) return true;
    }
    ;
    return false;
}

function isLuhnNum(argvalue) {
    argvalue = argvalue.value.toString();
    if (argvalue.length == 0) {
        return false;
    }
    for (var n = 0; n < argvalue.length; n++) {
        if ((argvalue.substring(n, n + 1) < "0") ||
            (argvalue.substring(n, n + 1) > "9")) {
            return false;
        }
    }
    return true;
}