package main

import (
	"container/heap"
	"sync"
	"time"
)

var (
	queue     = make(Queue, 0, 32)
	queueLock sync.Mutex
)

type Future struct {
	ts    time.Time
	index int
	work  func()
}

type Queue []*Future

func (q Queue) Len() int { return len(q) }

func (q Queue) Less(i, j int) bool {
	return q[i].ts.Before(q[j].ts)
}

func (q Queue) Swap(i, j int) {
	q[i], q[j] = q[j], q[i]
	q[i].index = j
	q[j].index = i
}

func (q *Queue) Push(v interface{}) {
	n := len(*q)
	future := v.(*Future)
	future.index = n
	*q = append(*q, future)
}

func (q *Queue) Pop() interface{} {
	old := *q
	n := len(old)
	future := old[n-1]
	future.index = -1
	*q = old[0 : n-1]
	return future
}

func At(ts time.Time, work func()) {
	heap.Push(&queue, &Future{ts: ts, work: work})
}

func After(delay time.Duration, work func()) {
	heap.Push(&queue, &Future{ts: time.Now().Add(delay), work: work})
}

func RunQueue() {
	defer log_info("Queue runner done.")
	heap.Init(&queue)
	ticker := time.Tick(10 * time.Millisecond)
	for {
		select {
		case <-ticker:
			if queue.Len() == 0 {
				break
			}
			future, ok := heap.Pop(&queue).(*Future)
			if !ok {
				log_error("there's shit on the work heap")
				break
			}
			if future.ts.Before(time.Now()) {
				future.work()
			} else {
				heap.Push(&queue, future)
			}
		}
	}
}

func ResetQueue() {
	queueLock.Lock()
	defer queueLock.Unlock()

	log_info("Reseting worker queue.")
	queue = make(Queue, 0, 32)
	heap.Init(&queue)
}