package ds

type ListRing[T any, L List[*T]] struct {
	list    L
	current int
}

var _ Ring[int] = &ListRing[int, List[*int]]{}

func NewListRing[T any, L List[*T]](list L, size int) *ListRing[T, L] {
	preAllocList[*T, List[*T]](list, nil, size)
	return &ListRing[T, L]{
		list:    list,
		current: 0,
	}
}

func (r *ListRing[T, L]) Next() Ring[T] {
	return &ListRing[T, L]{
		list:    r.list,
		current: modAbs(r.current+1, r.list.Size()),
	}
}

func (r *ListRing[T, L]) Prev() Ring[T] {
	return &ListRing[T, L]{
		list:    r.list,
		current: modAbs(r.current-1, r.list.Size()),
	}
}

func (r *ListRing[T, L]) Set(v T) {
	r.list.Set(r.current, &v)
}

func (r *ListRing[T, L]) Has() bool {
	return r.list.Get(r.current) != nil
}

func (r *ListRing[T, L]) Get() (T, bool) {
	if !r.Has() {
		return *new(T), false
	}
	return *r.list.Get(r.current), true
}

func (r *ListRing[T, L]) GetOrDefault(defaultValue T) T {
	value, ok := r.Get()
	if !ok {
		return defaultValue
	}
	return value
}

func (r *ListRing[T, L]) Each(f func(value *T)) {
	var t Ring[T] = r
	for i := 0; i < r.list.Size(); i++ {
		if value, ok := t.Get(); ok {
			f(&value)
		} else {
			f(nil)
		}
		t = t.Next()
	}
}