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{} {
	if !this.next.isCursor() {
		return this.next.data
	}
	for pos := this.next; pos != this; pos = pos.next {
		if !pos.isCursor() {
			return pos.data
		}
	}
	return nil
}

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 {
	if this.next == this {
		return true
	}
	if !this.next.isCursor() {
		return false
	}
	for pos := this.next; pos != this; pos = pos.next {
		if !pos.isCursor() {
			return false
		}
	}
	return true
}

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

func (this *ListHead) Size() int32 {
	num := int32(0)
	this.ForEach(
		func(data interface{}) bool {
			num++
			return true
		})
	return num
}

func (this *ListHead) isCursor() bool {
	return this.data == this
}

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

func (this *ListHead) ForEach(cb ListHead_Foreach_Func) {
	for pos := this.next; pos != this; pos = pos.next {
		if !cb(pos.data) {
			break
		}
	}
	/*
		cursor := ListHead{}
		cursor.data = &cursor
		this.AddHead(&cursor)
		defer cursor.Del()
		for cursor.next != this {
			oldN := cursor.next
			if !cursor.next.isCursor() && !cb(cursor.next.data) {
				break
			}
			if cursor.next == oldN {
				oldN.Del()
				cursor.AddTail(oldN)
			}
		}*/
}

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