reflection2_8.go

type outExp struct {
	out    []reflect.Value
	expiry time.Time
}

func Cacher(f interface{}, expiration time.Duration) (interface{}, error) {
	ft := reflect.TypeOf(f)
	if ft.Kind() != reflect.Func {
		return nil, errors.New("Only for functions")
	}

	inType, err := buildInStruct(ft)
	if err != nil {
		return nil, err
	}

	if ft.NumOut() == 0 {
		return nil, errors.New("Must have at least one returned value")
	}

	m := map[interface{}]outExp{}
	fv := reflect.ValueOf(f)
	cacher := reflect.MakeFunc(ft, func(args []reflect.Value) []reflect.Value {
		iv := reflect.New(inType).Elem()
		for k, v := range args {
			iv.Field(k).Set(v)
		}
		ivv := iv.Interface()
		ov, ok := m[ivv]
		now := time.Now()
		if !ok || ov.expiry.Before(now) {
			ov.out = fv.Call(args)
			ov.expiry = now.Add(expiration)
			m[ivv] = ov
		}
		return ov.out
	})
	return cacher.Interface(), nil
}