package main

import (
	"time"
)

// From https://golang.org/pkg/container/heap/

type Song struct {
	time  time.Time
	song  string
	week  int
	sync  bool
	index int
}

type SongPriorityQueue []*Song

func (pq SongPriorityQueue) Len() int {
	return len(pq)
}

func (pq SongPriorityQueue) Less(i, j int) bool {
	return pq[i].time.Before(pq[j].time)

}
func (pq SongPriorityQueue) Swap(i, j int) {
	pq[i], pq[j] = pq[j], pq[i]
	pq[i].index = i
	pq[j].index = j
}

func (pq *SongPriorityQueue) Push(x interface{}) {
	n := len(*pq)
	item := x.(*Song)
	item.index = n
	*pq = append(*pq, item)
}

func (pq *SongPriorityQueue) Pop() interface{} {
	old := *pq
	n := len(old)
	item := old[n-1]
	item.index = -1 // for safety
	*pq = old[0 : n-1]
	return item
}