@tool
extends Node
class_name CameraPointer

const _CONSTANTS := preload("res://addons/reedcamera/_data/CameraSystemConst.gd")

var _camera: Camera2D
var _editor_valid := false
var _runtime_registered := false
var _warned := false

var _final_offset := Vector2.ZERO
var _base_position: Vector2

func _enter_tree() -> void:
	if Engine.is_editor_hint():
		call_deferred("_editor_verify")

func _exit_tree() -> void:
	if Engine.is_editor_hint():
		return

	_request_unregister()

func _process(delta: float) -> void:
	if Engine.is_editor_hint():
		return
	
	if not _camera:
		return
	
	_update_base_position()
	_update_camera_offset()
	_apply_camera_transform()

func _update_base_position():
	for child in get_children():
		if child.has_method("get_base_position"):
			_base_position = child.get_base_position()
			return

	# fallback
	_base_position = _camera.global_position

func _update_camera_offset():
	var offset := Vector2.ZERO

	for child in get_children():
		if child.has_method("get_camera_offset"):
			offset += child.get_camera_offset()

	_final_offset = offset

func _apply_camera_transform():
	_camera.global_position = _base_position
	_camera.offset = _final_offset


func _notification(what: int) -> void:
	if not Engine.is_editor_hint():
		return
	
	match what:
		NOTIFICATION_PARENTED, NOTIFICATION_UNPARENTED:
			#print("重設parent")
			call_deferred("_editor_verify")

## 編輯器層面的通過性驗證
func _editor_verify() -> void:
	_camera = _find_camera()
	_editor_valid = _camera != null
	#print(_editor_valid)

	if not _editor_valid:
		_emit_config_warning()
	else:
		_warned = false

func _ready() -> void:
	if Engine.is_editor_hint():
		return

	_camera = _find_camera()
	if not _camera:
		return

	_request_register()

func _find_camera() -> Camera2D:
	var p := get_parent()
	return p as Camera2D if p is Camera2D else null

func _request_register() -> void:
	var sys := Engine.get_singleton(_CONSTANTS.CAMERA_SYSTEM_NAME)
	if not sys:
		return

	_runtime_registered = sys.request_register_pointer(self)

func _request_unregister() -> void:
	if not _runtime_registered:
		return

	var sys := Engine.get_singleton(_CONSTANTS.CAMERA_SYSTEM_NAME)
	if sys:
		sys.request_unregister_pointer(self)

	_runtime_registered = false

func _emit_config_warning() -> void:
	if not Engine.is_editor_hint():
		return

	if _warned:
		return

	push_warning(
		"[CameraPointer] Invalid configuration: parent node must be Camera2D. "
		+ "Current parent: %s" % (get_parent() if get_parent() else "null")
	)

	_warned = true

func get_camera() -> Camera2D:
	return _camera