package d2astar

// A priorityQueue implements heap.Interface and holds Nodes.  The
// priorityQueue is used to track open nodes by rank.
type priorityQueue []*node

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

func (pq priorityQueue) Less(i, j int) bool {
	return pq[i].rank < pq[j].rank
}

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

func (pq *priorityQueue) Push(x interface{}) {
	n := len(*pq)
	no := x.(*node)
	no.index = n
	*pq = append(*pq, no)
}

func (pq *priorityQueue) Pop() interface{} {
	old := *pq
	n := len(old)
	no := old[n-1]
	no.index = -1
	*pq = old[0 : n-1]

	return no
}