function check_nickname() {
    // focus on nickname field
    $('#nickname').focus();
    // find field nickname and check if the entered nickname is available via ajax
    $('#nickname').blur(function() {
        // now call ajax
        if ($(this).val().length > 0)
        {
            $.getJSON('/en/user/register/default.html?ajax=1&val=' + $(this).val(), function (data) {
                // update nickname class
                $('#nickname').attr('class', data['class']);
                if (data['class'] == 'taken') {
                    $('#nickname_error').attr('innerHTML', $('#trans_nickname_error_taken').attr('innerHTML'));
                    $('#nickname_error').show();
                }
                else if (data['class'] == 'error') {
                    $('#nickname_error').attr('innerHTML', $('#trans_nickname_error_chars').attr('innerHTML'));
                } else {
                    $('#nickname_error').hide();
                }
            });
        }
        else
        {
            $('#nickname_error').attr('innerHTML', $('#trans_nickname_error_emoty').attr('innerHTML'));

        }
    });
    
    // disable further clicks of the submit button
    $('#main_content form').submit(function() {
        $('button[@type=submit]', this).attr('disabled', 'disabled');
    });
}

$(document).ready(function(){
    check_nickname();
});