package q5

type ListHead_Foreach_Func func(interface{}) bool

type ListHead struct {
	next *ListHead
	prev *ListHead
	data interface{}
}

func (this *ListHead) Init(data interface{}) {
	this.next = this
	this.prev = this
	this.data = data
}

func (this *ListHead) GetData() interface{} {
	return this.data
}

func (this *ListHead) Del() {
	this.next.prev = this.prev
	this.prev.next = this.next
}

func (this *ListHead) AddTail(pnew *ListHead) {
	prev := this.prev
	next := this

	next.prev = pnew
	pnew.next = next
	pnew.prev = prev
	prev.next = pnew
}

func (this *ListHead) AddHead(pnew *ListHead) {
	prev := this
	next := this.prev

	next.prev = pnew
	pnew.next = next
	pnew.prev = prev
	prev.next = pnew
}

func (this *ListHead) FirstEntry() interface{} {
	return this.next.data
}

func (this *ListHead) Replace(pnew *ListHead) {
	pnew.next = this.next
	pnew.next.prev = pnew
	pnew.prev = this.prev
	pnew.prev.next = pnew
}

func (this *ListHead) ReplaceInit(pnew *ListHead) {
	this.Replace(pnew)
	this.next = this
	this.prev = this
}

func (this *ListHead) Empty() bool {
	return this.next == this
}

func (this *ListHead) DelInit() {
	this.Del()
	this.next = this
	this.prev = this
}

func (this *ListHead) Next() *ListHead {
	return this.next
}

func (this *ListHead) ForEachFrom(from *ListHead,
	cb ListHead_Foreach_Func) {
	for pos := from; pos != this; pos = pos.next {
		if !cb(pos.data) {
			break
		}
	}
}

func (this *ListHead) ForEach(cb ListHead_Foreach_Func) {
	for pos := this.next; pos != this; pos = pos.next {
		if !cb(pos.data) {
			break
		}
	}
}

func (this *ListHead) ForEach_r(cb ListHead_Foreach_Func) {
	for pos := this.prev; pos != this; pos = pos.prev {
		if !cb(pos.data) {
			break
		}
	}
}

func MakeListHead () *ListHead{
	l := new(ListHead)
	l.Init(nil)
	return l
}