package q5

import (
	"sync"
)

type Queue struct {
	msgMutex sync.Mutex
	msgList  ListHead
	WorkList ListHead
}

func (this *Queue) Init() {
	this.msgList.Init(nil)
	this.WorkList.Init(nil)
}

func (this *Queue) Push(node *ListHead) {
	this.msgMutex.Lock()
	defer this.msgMutex.Unlock()
	this.msgList.AddTail(node)
}

func (this *Queue) Fetch() {
	if this.WorkList.Empty() {
		this.msgMutex.Lock()
		defer this.msgMutex.Unlock()
		if !this.msgList.Empty() {
			this.msgList.ReplaceInit(&this.WorkList)
		}
	}
}

func (this *Queue) IsEmpty() bool {
	if !this.WorkList.Empty() {
		return false
	}
	this.msgMutex.Lock()
	defer this.msgMutex.Unlock()
	return this.msgList.Empty()
}