package pfile

import "slices"

type allocList map[[2]uint64][]uint64

func newAllocList() *allocList {
	al := allocList(map[[2]uint64][]uint64{})
	return &al
}

func (al allocList) Create(collectionID, itemID, page uint64) {
	key := al.key(collectionID, itemID)
	al[key] = []uint64{page}
}

// Push is used to add pages to the storage when loading. It will append
// pages to the appropriate list, or return false if the list isn't found.
func (al allocList) Push(collectionID, itemID, page uint64) bool {
	key := al.key(collectionID, itemID)
	if _, ok := al[key]; !ok {
		return false
	}
	al[key] = append(al[key], page)
	return true
}

func (al allocList) Store(collectionID, itemID uint64, pages []uint64) {
	key := al.key(collectionID, itemID)
	al[key] = slices.Clone(pages)
}

func (al allocList) Remove(collectionID, itemID uint64) []uint64 {
	key := al.key(collectionID, itemID)
	pages := al[key]
	delete(al, key)
	return pages
}

func (al allocList) Iterate(
	each func(collectionID, itemID uint64, pages []uint64) error,
) error {
	for key, pages := range al {
		if err := each(key[0], key[1], pages); err != nil {
			return err
		}
	}
	return nil
}

func (al allocList) Len() int {
	return len(al)
}

func (al allocList) key(collectionID, itemID uint64) [2]uint64 {
	return [2]uint64{collectionID, itemID}
}