(function ($) {
    $.fn.prepopulate = function (dependencies, maxLength) {
        /*
         Depends on urlify.js
         Populates a selected field with the values of the dependent fields,
         URLifies and shortens the string.
         dependencies - array of dependent fields id's
         maxLength - maximum length of the URLify'd string
         */
        return this.each(function () {
            var field = $(this);

            field.data('_changed', false);
            field.change(function () {
                field.data('_changed', true);
            });

            var populate = function () {
                // Bail if the fields value has changed
                if (field.data('_changed') == true) return;

                var values = [];
                $.each(dependencies, function (i, field) {
                    if ($(field).val().length > 0) {
                        values.push($(field).val());
                    }
                })
                field.val(URLify(values.join(' '), maxLength));
            };

            $(dependencies.join(',')).keyup(populate).change(populate).focus(populate);
        });
    };
})(django.jQuery);