package tools

import "errors"

var (
	NoElement = errors.New("no element in queue")
	QueueFull = errors.New("queue full")
)

type (
	// Queue 工具库，循环队列
	// TODO 使用模板重构
	Queue struct {
		maxsize   int
		head      int
		tail      int
		container []uint32
	}
)

func (q *Queue) Init(capacity int) {
	q.head = 0
	q.tail = 0
	q.maxsize = capacity + 1
	q.container = make([]uint32, q.maxsize)
}

func (q *Queue) Capacity() int {
	return q.maxsize - 1
}

func (q *Queue) Size() int {
	return (q.tail - q.head + q.maxsize) % q.maxsize
}

func (q *Queue) Full() bool {
	return (q.tail+1)%q.maxsize == q.head
}

func (q *Queue) Empty() bool {
	return q.head == q.tail
}

func (q *Queue) Top() (uint32, error) {
	if q.Empty() {
		return 0, NoElement
	}

	return q.container[q.head], nil
}

func (q *Queue) Pop() (uint32, error) {
	if q.Empty() {
		return 0, NoElement
	}

	elem := q.container[q.head]
	q.head = (q.head + 1) % q.maxsize

	return elem, nil
}

func (q *Queue) Push(element uint32) error {
	if q.Full() {
		return QueueFull
	}
	q.container[q.tail] = element
	q.tail = (q.tail + 1) % q.maxsize
	return nil
}

func (q *Queue) UnInit() {
	q.container = nil
	q.tail = 0
	q.tail = 0
	q.maxsize = 0
}