godot-plateformer/_shared/camera/CameraSystem.gd

'''全局的相机管理器
	
	======= 外部调用函数 =======
	
'''
extends Node

@onready var camera_2d: Camera2D = %Camera2D
@onready var camera_shake_player: CameraShakePlayer = %CameraShakePlayer

var _cached_anchors: Array[CameraAnchor] = []
var _current_anchor: CameraAnchor
var _switch_tween: Tween
var _player_remote: RemoteTransform2D
var _base_camera_pos := Vector2.ZERO

##标记位，用来检测当前帧是否存在相机切换
var _switch_scheduled := false
var _dirty := false

## 玩家关卡内静态相机
const PLAYER_CAMERA_SCENE:= preload("res://_shared/camera/PlayerStaticCamera.tscn")
const CAMERA_FOLLOWER:= preload("res://_shared/camera/camera_follower.tscn")

func _ready() -> void:
	_base_camera_pos = camera_2d.global_position

func _process(delta):
	if not camera_2d:
		return

	var shake_offset := camera_shake_player.update(delta)
	camera_2d.global_position = _base_camera_pos + shake_offset

## 外部获取玩家全局相机
func get_cached_camera() -> Camera2D:
	return camera_2d

## 注册一个相机锚点
func register_anchor(anchor: CameraAnchor) -> void:
	if anchor in _cached_anchors:
		return
	_cached_anchors.append(anchor)
	anchor.on_priority_change.connect(on_anchor_priority_changed)
	_request_evaluate()

## 当相机锚点的权重改变时，向管理器触发事件
func on_anchor_priority_changed(priority:int, anchor: CameraAnchor) -> void:
	_request_evaluate()

## 注销一个相机锚点
func unregister_anchor(anchor: CameraAnchor) -> void:
	_cached_anchors.erase(anchor)
	if _current_anchor == anchor:
		_current_anchor = null
	_request_evaluate()

func _request_evaluate() -> void:
	_dirty = true
	if _switch_scheduled:
		return
	_switch_scheduled = true
	call_deferred("_commit_camera_anchor") 

func _commit_camera_anchor() -> void:
	_switch_scheduled = false
	if not _dirty:
		return
	_dirty = false

	# 清理无效
	_cached_anchors = _cached_anchors.filter(func(a): return is_instance_valid(a))

	var winner: CameraAnchor = _pick_best_anchor()

	if winner == null:
		return

	if winner == _current_anchor:
		return

	switch_anchor(winner)

func _pick_best_anchor() -> CameraAnchor:
	var best: CameraAnchor = null
	var best_p := -INF

	for a in _cached_anchors:
		if not a.enabled:
			continue
		if a._priority > best_p:
			best_p = a._priority
			best = a

	return best

## 排序已有的锚点
func _sort_anchors() -> void:
	_cached_anchors.sort_custom(func(a, b):
		return a._priority > b._priority
	)

## 尝试自切换
func _try_auto_switch() -> void:
	for a in _cached_anchors:
		if a.enabled:
			switch_anchor(a)
			_current_anchor = a
			return

## 重置所有的Camera的_priority
func reset_all_camera_priority() -> void:
	for a in _cached_anchors:
		a._priority = 0

##应用Anchor的Limit
func _apply_anchor_limits(anchor: CameraAnchor) -> void:
	if not camera_2d:
		return
	camera_2d.limit_left = anchor.global_position.x + anchor.limit_left
	camera_2d.limit_right = anchor.global_position.x + anchor.limit_right
	camera_2d.limit_top = anchor.global_position.y + anchor.limit_top
	camera_2d.limit_bottom = anchor.global_position.y + anchor.limit_bottom

func _clear_camera_limits() -> void:
	if not camera_2d:
		return
	camera_2d.limit_left = -10000000
	camera_2d.limit_right = 10000000
	camera_2d.limit_top = -10000000
	camera_2d.limit_bottom = 10000000

## 切换相机
func switch_anchor(target_anchor: CameraAnchor) -> void:
	if target_anchor == null:
		return
	if target_anchor == _current_anchor:
		return
	if not is_instance_valid(camera_2d):
		return

	#优先清除已有的remote
	if _player_remote:
		_player_remote.queue_free()
		_player_remote = null
	
	# 中断旧 Tween
	if _switch_tween and _switch_tween.is_running():
		_switch_tween.kill()
		_switch_tween = null

	var camera := camera_2d
	var blend_time : float = max(target_anchor.blend_time, 0.001)

	_clear_camera_limits()
	
	_switch_tween = get_tree().create_tween()
	_switch_tween.set_ignore_time_scale(true)
	_switch_tween.set_trans(Tween.TRANS_CUBIC)
	_switch_tween.set_ease(Tween.EASE_OUT)

	# ===== 位置 =====
	_switch_tween.tween_property(
		self,
		"_base_camera_pos",
		target_anchor.global_position,
		blend_time
	)

	# ===== Zoom =====
	_switch_tween.parallel().tween_property(
		camera,
		"zoom",
		target_anchor.zoom,
		blend_time * 1.5
	)

	# 完成回调
	_switch_tween.finished.connect(func():
		_current_anchor = target_anchor
		_update_anchor_follow_state(target_anchor)
		_apply_anchor_limits(target_anchor)
	)

	_current_anchor = target_anchor

func _update_anchor_follow_state(anchor: CameraAnchor) -> void:
	# 先清理旧的 RemoteTransform
	if _player_remote and is_instance_valid(_player_remote):
		_player_remote.queue_free()
		_player_remote = null

	if not anchor.follow_player:
		return
	
	var p := GlobalEvent.get_player()
	
	if not p or not is_instance_valid(p):
		push_warning("CameraAnchor wants to follow player, but player is not registered.")
		return

	# 创建 RemoteTransform2D
	var rt := RemoteTransform2D.new()
	rt.name = "__CameraAnchorFollow"
	rt.remote_path = camera_2d.get_path()

	p.add_child(rt)
	_player_remote = rt