package gg

// The structure to store objects
// with O(1) add, remove and search operations.
type Objects struct {
	// The place to store all the objects.
	store []Object

	// Find index by Object.
	searchMap map[Object] int

	// Available nil values in the store.
	freeIndexes []int
}

func NewObjects() *Objects {
	ret := &Objects{}
	ret.searchMap = map[Object] int {}
	return ret
}

func (objects *Objects) has(object Object) bool {
	_, ok := objects.searchMap[object]
	return ok
}

func (objects *Objects) add(object Object) bool {
	if objects.has(object) {
		return false
	}
	if len(objects.freeIndexes) > 0 {
		freeIndex := objects.freeIndexes[0]
		objects.freeIndexes = objects.freeIndexes[1:]

		objects.store[freeIndex] = object
		objects.searchMap[object] = freeIndex
	} else {
		objects.store = append(objects.store, object)
		objects.searchMap[object] = len(objects.store)-1
	}
	return true
}

func (objects *Objects) remove(object Object) bool {
	objectIndex, ok := objects.searchMap[object]
	if !ok {
		return false
	}

	objects.store[objectIndex] = nil
	objects.freeIndexes = append(
		objects.freeIndexes,
		objectIndex,
	)

	return true
}