from django.http import HttpResponseRedirect

def check_allowed(view_func):
    
        def _view(request, *args, **kwargs):

            code = request.GET.get('code')
            if code:
                # just change if we can
                try:
                    ensemble = request.session.get('registered', {})[code.replace('-', '')]
                    request.session['ensemble'] = ensemble
                except KeyError:
                    # need to register this code
                    return HttpResponseRedirect('/register?code=' + code)
               
            request.ensemble_id = request.session.get('ensemble')

            if request.ensemble_id is None:
                return HttpResponseRedirect('/register')

            return view_func(request, *args, **kwargs)

        _view.__name__ = view_func.__name__
        _view.__dict__ = view_func.__dict__
        _view.__doc__ = view_func.__doc__

        return _view