package main

import "sync"

type queue struct {
	buf    []interface{}
	length int
	mux    *sync.RWMutex
}

func newQueue() *queue {
	return &queue{make([]interface{}, 0), 0, &sync.RWMutex{}}
}

func (q *queue) rPush(e interface{}) {
	q.mux.Lock()
	defer q.mux.Unlock()

	q.buf = append(q.buf, e)
	q.length += 1

}

func (q *queue) rPushs(elements ...interface{}) {
	q.mux.Lock()
	defer q.mux.Unlock()

	q.buf = append(q.buf, elements...)
	q.length += len(elements)
}

func (q *queue) lPush(e interface{}) {
	q.mux.Lock()
	defer q.mux.Unlock()

	q.buf = append([]interface{}{e}, q.buf...)
	q.length += 1
}

func (q *queue) rPop() interface{} {
	q.mux.Lock()

	if q.length == 0 {
		return nil
	}

	n := q.buf[q.length-1]

	q.buf = q.buf[:q.length-1]
	q.length -= 1

	q.mux.Unlock()
	return n
}

func (q *queue) lPop() interface{} {
	q.mux.Lock()

	if q.length == 0 {
		return nil
	}

	n := q.buf[0]

	q.buf = q.buf[1:]
	q.length -= 1

	q.mux.Unlock()
	return n
}

func (q *queue) lGet() interface{} {
	q.mux.RLock()
	defer q.mux.RUnlock()

	if q.length == 0 {
		return nil
	}

	return q.buf[0]
}

func (q *queue) rGet() interface{} {
	q.mux.RLock()
	defer q.mux.RUnlock()

	if q.length == 0 {
		return nil
	}

	return q.buf[q.length-1]
}

func (q *queue) getLen() int {
	q.mux.RLock()
	defer q.mux.RUnlock()

	return q.length
}