## SpellContextPool — SpellContext 对象池（Autoload: SpellContextPool）
## 权威来源：implementation_plan.md §2.1、S1 验收 P-S1-04
extends Node

const POOL_SIZE: int = 32  # P-S1-04: pool size 不超过 32

var _pool:   Array = []   # Array[SpellContext]
var _in_use: PackedByteArray = PackedByteArray()
var _slots:  Array = []   # Array[SpellContext] 固定槽位

func _ready() -> void:
	_slots.resize(POOL_SIZE)
	_in_use.resize(POOL_SIZE)
	for i in POOL_SIZE:
		_slots[i]   = SpellContext.new()
		_in_use[i]  = 0
		_pool.append(i)  # 空闲 ID 表

## 取出一个 SpellContext。若 has_persistent_memory=true 则保留 registers
func acquire(caster_id: int, has_persistent_memory: bool = false) -> SpellContext:
	if _pool.is_empty():
		push_warning("SpellContextPool: 池已耗尽，动态创建 SpellContext（建议上调 POOL_SIZE=%d）" % POOL_SIZE)
		var ctx_dyn := SpellContext.new()
		ctx_dyn.caster_id = caster_id
		if not has_persistent_memory:
			ctx_dyn.clear_registers()
		return ctx_dyn
	var slot_id: int = _pool[_pool.size() - 1]
	_pool.resize(_pool.size() - 1)
	var ctx: SpellContext = _slots[slot_id]
	_in_use[slot_id] = int(1)
	ctx.reset()
	ctx.caster_id = caster_id
	if not has_persistent_memory:
		ctx.clear_registers()
	return ctx

func release(ctx: SpellContext) -> void:
	for i in _slots.size():
		if _slots[i] == ctx:
			if _in_use[i] != 0:
				_in_use[i] = 0
				_pool.append(i)
			return
	# 动态分配的（池已耗尽时）直接丢弃

func get_available_count() -> int:
	return _pool.size()

func reset() -> void:
	_pool.clear()
	for i in _slots.size():
		_in_use[i] = 0
		_pool.append(i)