package datastructures

import "container/heap"

type HeapItem struct {
	Value    any
	Priority int
	index    int
}

type MinHeap []*HeapItem

func (m MinHeap) Len() int           { return len(m) }
func (m MinHeap) Less(i, j int) bool { return m[i].Priority < m[j].Priority }
func (m MinHeap) Swap(i, j int) {
	m[i], m[j] = m[j], m[i]
	m[i].index = i
	m[j].index = j
}

func (m *MinHeap) Push(x any) {
	*m = append(*m, x.(*HeapItem))
}

func (m *MinHeap) Pop() any {
	old := *m
	n := len(old)
	item := old[n-1]
	item.index = 0
	old[n-1] = nil
	*m = old[0 : n-1]
	return item
}

func (m *MinHeap) Update(item *HeapItem, priority int) {
	item.Priority = priority
	heap.Fix(m, item.index)
}