class_name Inventory
extends RefCounted

var total_capacity: int = -1
var resource_capacities: Dictionary = {}
var _amounts: Dictionary = {}


func _init(initial: Dictionary = {}, capacity: int = -1) -> void:
	total_capacity = capacity
	for resource_id in initial:
		set_amount(String(resource_id), int(initial[resource_id]))


func amount(resource_id: String) -> int:
	return int(_amounts.get(resource_id, 0))


func total() -> int:
	var result: int = 0
	for value in _amounts.values():
		result += int(value)
	return result


func capacity_for(resource_id: String) -> int:
	return int(resource_capacities.get(resource_id, -1))


func space_for(resource_id: String) -> int:
	var space: int = 1 << 30
	if total_capacity >= 0:
		space = maxi(total_capacity - total(), 0)
	var resource_capacity: int = capacity_for(resource_id)
	if resource_capacity >= 0:
		space = mini(space, maxi(resource_capacity - amount(resource_id), 0))
	return space


func set_amount(resource_id: String, value: int) -> int:
	_amounts.erase(resource_id)
	var accepted: int = mini(maxi(value, 0), space_for(resource_id))
	if accepted > 0:
		_amounts[resource_id] = accepted
	return amount(resource_id)


func deposit(resource_id: String, requested: int) -> int:
	var moved: int = mini(maxi(requested, 0), space_for(resource_id))
	if moved > 0:
		_amounts[resource_id] = amount(resource_id) + moved
	return moved


func withdraw(resource_id: String, requested: int) -> int:
	var moved: int = mini(maxi(requested, 0), amount(resource_id))
	if moved <= 0:
		return 0
	var remaining: int = amount(resource_id) - moved
	if remaining > 0:
		_amounts[resource_id] = remaining
	else:
		_amounts.erase(resource_id)
	return moved


func transfer_to(destination: Inventory, resource_id: String, requested: int) -> int:
	if destination == null:
		return 0
	var moved: int = mini(mini(maxi(requested, 0), amount(resource_id)), destination.space_for(resource_id))
	if moved <= 0:
		return 0
	withdraw(resource_id, moved)
	destination.deposit(resource_id, moved)
	return moved


func snapshot() -> Dictionary:
	return _amounts.duplicate()