time_from = lambda x : datetime.fromtimestamp(long(x is not None and x or '0'))
time_to = lambda x : x is not None and datetime.fromtimestamp(long(x)) or datetime.now()
void = lambda x : x

def param(key, default, validate):
    def decorator(view_func):
        @wraps(view_func, assigned = available_attrs(view_func))
        def _wrapped_view(request, *args, **kwargs):
            try:
                value = request.REQUEST.get(key, default)
                value = validate(value)

                if hasattr(request, 'DATA'):
                    dct = getattr(request, 'DATA')
                    dct.update({key : value})
                else:
                    dct = {key: value}
                
                setattr(request, 'DATA', dct)
                
            except ValueError, e:
                return JsonResponse(error = -3, error_msg = u'参数%s格式错误' % key)
            except TypeError, e:
                return JsonResponse(error = -4, error_msg = u'参数%s不能为空' % key)
            
            return view_func(request, *args, **kwargs)
        
        return _wrapped_view
    
    return decorator