@tool
class_name SceneManager
extends Node

@export var MainNodes: Array[Node]
@export var GameView: Node
@export var TransitionNode: Node

func _enter_tree() -> void:
	check()

func _ready() -> void:
	if !Engine.is_editor_hint():
		add_to_group("SceneManager")
	get_tree().node_removed.connect(check)

# =========================
# 对外 API
# =========================
static func change(scene_path: String) -> void:
	var mgr := get_instance()
	if mgr:
		mgr._change(scene_path)
	else:
		push_error("SceneManager not found in scene tree")

# =========================
# 内部逻辑
# =========================
func _change(scene_path: String) -> void:
	if GameView == null:
		push_error("SceneManager: GameView is null")
		return
	
	# 清空旧场景
	for child in GameView.get_children():
		child.queue_free()
	
	# 加载新场景
	var packed: PackedScene = load(scene_path)
	if packed == null:
		push_error("Failed to load scene: %s" % scene_path)
		return
	
	var instance := packed.instantiate()
	GameView.add_child(instance)
	
	print_debug("SceneManager: Changed scene to ", scene_path)

# =========================
# 结构检查 / 自修复
# =========================
func check(node: Node = null) -> void:
	if TransitionNode == node:
		TransitionNode = null

	var tr := find_child("Transition")
	if tr != null:
		if TransitionNode == null:
			TransitionNode = tr
	else:
		if TransitionNode == null:
			var transition := Control.new()
			transition.name = "Transition"
			add_child.call_deferred(transition)
			transition.set_owner.call_deferred(self)
			TransitionNode = transition

# =========================
# 工具
# =========================
static func get_instance() -> SceneManager:
	var tree := Engine.get_main_loop() as SceneTree
	return tree.get_first_node_in_group("SceneManager") as SceneManager