CMS Sortable Models

# the javascript #
"""
    var position = -1;
    $(function(e) {
        $("#sortable").sortable({
            start: function(event, ui) {
                position = ui.item.index();
            },
            stop: function(event, ui) {
                //alert("New position: " + ui.item.index());
                if(position!=ui.item.index()) {
                    postData = {
                        old_position : position,
                        new_position : ui.item.index()
                    };

                    $.post('{% url change_article_position %}',
                        postData,
                        function(data) {
                            position = ui.item.index();
                            location.reload();
                        }
                    );

                }
            }
        });
        $("#sortable" ).disableSelection();
    });
"""

# urls.py
url(r'^admin/article/change/position/ajax/$', 'change_article_position', {}, name="change_article_position"),


# views.py
def change_article_position(request):
    return _change_model_position(request, Article)

def _change_model_position(request, model):
    if request.method == 'POST':
        old_position = int(request.POST.get('old_position')) + 1;
        new_position = int(request.POST.get('new_position')) + 1;

        current_item = model.objects.get(position=old_position)
        current_item.order = new_position
        current_item.save()

        if new_position < old_position:
            greater_items = model.objects.filter(
                                ~Q(pk=current_item.id), 
                                position__gte=current_item.order).order_by('position')
            ctr = current_item.order + 1
            for item in greater_items:
                item.position = ctr
                item.save()
                ctr += 1
        else:
            lesser_items = model.objects.filter(
                                ~Q(pk=current_item.id), 
                                position__lte=new_position).order_by('position')
            ctr = 1
            for item in lesser_items:
                item.position = ctr
                item.save()
                ctr += 1

            greater_items = model.objects.filter(
                                ~Q(pk=current_item.id), 
                                position__gt=new_position).order_by('position')
            ctr = new_position + 1
            for item in greater_items:
                item.position = ctr
                item.save()
                ctr += 1   

        messages.success(request, _('Position updated'))

    return HttpResponse('OK')