package common

import (
	"container/list"
	"sync"
)

// LockList list
type LockList struct {
	cache *list.List
	cv    *sync.Cond
	cond  bool
	size  int
}

// NewLockList new
func NewLockList(size int) *LockList {
	return &LockList{
		cache: list.New(),
		cv:    sync.NewCond(&sync.Mutex{}),
		cond:  false,
		size:  size,
	}
}

// Push push
func (l *LockList) Push(v interface{}) {
	l.cv.L.Lock()
	l.cache.PushBack(v)

	for l.cache.Len() > l.size {
		l.cache.Remove(l.cache.Front())
	}

	l.cond = true
	l.cv.Signal()
	l.cv.L.Unlock()
}

// Pop pop
func (l *LockList) Pop() []interface{} {

	var batch []interface{}

	l.cv.L.Lock()

	for !l.cond {
		l.cv.Wait()
	}

	elem := l.cache.Front()
	if elem != nil {
		batch = append(batch, elem.Value)
		l.cache.Remove(l.cache.Front())
	}

	l.cond = false
	l.cv.L.Unlock()

	return batch
}

// Drain drain all element
func (l *LockList) Drain() []interface{} {

	var batch []interface{}

	l.cv.L.Lock()

	for !l.cond {
		l.cv.Wait()
	}

	for {

		elem := l.cache.Front()
		if elem == nil {
			break
		}

		batch = append(batch, elem.Value)
		l.cache.Remove(l.cache.Front())
	}

	l.cond = false
	l.cv.L.Unlock()

	return batch
}