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/**
 * jQuery Form Validator Module: Security
 * ------------------------------------------
 * Created by Victor Jonsson <http://www.victorjonsson.se>
 *
 * This form validation module adds validators typically used on
 * websites in the UK. This module adds the following validators:
 *  - ukvatnumber
 *
 * @website http://formvalidator.net/#uk-validators
 * @license Dual licensed under the MIT or GPL Version 2 licenses
 * @version 2.2.beta.69
 */
$.formUtils.addValidator({
    name : 'ukvatnumber',
    validatorFunction : function(number) {

        // Code Adapted from http://www.codingforums.com/showthread.php?t=211967
        // TODO: Extra Checking for other VAT Numbers (Other countries and UK Government/Health Authorities)

        number = number.replace(/[^0-9]/g, '');

        //Check Length
        if(number.length < 9) {
                return false;
        }

        var valid = false;

        var VATsplit = [];
        VATsplit = number.split("");

        var checkDigits = Number(VATsplit[7] + VATsplit[8]);  // two final digits as a number

        var firstDigit = VATsplit[0];
        var secondDigit = VATsplit[1];
        if ((firstDigit == 0) && (secondDigit >0)) {
                return false;
        }

        var total = 0;
        for (var i=0; i<7; i++) {  // first 7 digits
                total += VATsplit[i]* (8-i);  // sum weighted cumulative total
        }

        var c = 0;
        var i = 0;

        for (var m = 8; m>=2; m--) {
                c += VATsplit[i]* m;
                i++;
        }

        // Traditional Algorithm for VAT numbers issued before 2010

        while (total > 0) {
                total -= 97; // deduct 97 repeatedly until total is negative
        }
        total = Math.abs(total);  // make positive

        if (checkDigits == total) {
                valid = true;
        }

        // If not valid try the new method (introduced November 2009) by subtracting 55 from the mod 97 check digit if we can - else add 42

        if (!valid) {
                total = total%97  // modulus 97

                if (total >= 55) {
                        total = total - 55
                } else {
                        total = total + 42
                }

                if (total == checkDigits) {
                        valid = true;
                }
        }

        return valid;
    },
    errorMessage : '',
    errorMessageKey: 'badUKVatAnswer'
});