(function ($) {
    $.fn.liveCheck = function () {
        return this.each(function () {
            var $$ = $(this);
            var t = this;
            
            var url = $$.parents('form:first').attr('action');
            
            var infospan = $$.parent().find('span');
            if (!infospan.length) {
                infospan = $$.after(' <span></span>').next();
            }
            
            $$.keyup(function () {
                // prevent tabbing in to the field firing an ajax hit
                if (t.value == '' && (t.lastValue == undefined)) return true;
                
                if (t.value != t.lastValue) {
                    if (this.timer) clearTimeout(this.timer);
                    infospan.removeClass('error').html('<img src="/images/ajax-loader.gif" height="16" width="16" /> validating...');
                    this.timer = setTimeout(function () {
                        $.ajax({
                            url: url,
                            data: t.name + '=' + t.value,
                            dataType: 'json',
                            type: 'post',
                            success: function (j) {
                                infospan.toggleClassIf(!j.ok, 'error').html(j.msg);
                            }
                        });
                    }, 200);
                    t.lastValue = t.value;
                }
            });
        });
    };
    
    $.fn.toggleClassIf = function (v, c) {
        return v ? this.addClass(c) : this.removeClass(c);
    };
    
})(jQuery);