extends Node2D

## 2026-07-06 视差定案（策划：远景夕阳要时刻在画面内）：背景是"远景天幕"，
## 仅以 0.2 倍速随世界滚动（即 80% 跟随相机）——此前 0.92/0.8 的"近景层"
## 参数方向反了，背景几乎钉在世界上，所以一直"看不出视差"。
## 锚点 1734.5 = 让夕阳（原画 x≈760，世界 x≈1656）在出生点镜头（可见中心
## 1340.8）恰好居中；相机全程 [1340.8, 2753.2] 内夕阳屏幕位置从中心缓移到
## 左 282px，始终在画面内（已验算含光晕不出屏）。两端背景覆盖也已验算：
## 极左窗 [880,1801.6]⊂[581.5,2882.5]、极右窗 [2292.4,3214]⊂[1711.5,4012.5]。
## 已知取舍：步道砖烙在原画里会明显随镜头走（角色脚下滑动感），单张烙死图
## 无解；美术把"近景步道"拆成独立 1:1 层后即可消除。勿用 Parallax2D
## （历史上因 CanvasModulate/wipe 兼容性移除过，见 decisions.md）。
const PARALLAX_SCROLL_SCALE := 0.2
const PARALLAX_ANCHOR_X := 1734.5

@onready var past_background: CanvasItem = $ArtLayer/PastBackground
@onready var future_background: CanvasItem = $ArtLayer/FutureBackground
@onready var _art_layer: Node2D = $ArtLayer

var _art_base_x := 0.0


func _ready() -> void:
	_art_base_x = _art_layer.position.x
	_set_time_phase(_current_time_phase())
	var bus := _event_bus_or_null()
	if bus != null and bus.has_signal("time_phase_changed") and not bus.is_connected("time_phase_changed", _on_time_phase_changed):
		bus.connect("time_phase_changed", _on_time_phase_changed)


func _process(_delta: float) -> void:
	var camera := get_viewport().get_camera_2d()
	if camera == null:
		# headless 测试/无相机场景：背景保持原位。
		_art_layer.position.x = _art_base_x
		return
	# get_screen_center_position 含 limit 夹取，玩家贴墙时背景不会继续滑。
	var center_x := camera.get_screen_center_position().x
	_art_layer.position.x = _art_base_x + (center_x - PARALLAX_ANCHOR_X) * (1.0 - PARALLAX_SCROLL_SCALE)


func _on_time_phase_changed(_previous: StringName, current: StringName, _reason: StringName) -> void:
	_set_time_phase(current)


func _set_time_phase(time_phase: StringName) -> void:
	var use_future := time_phase == &"future"
	if past_background != null:
		past_background.visible = not use_future
	if future_background != null:
		future_background.visible = use_future


func _current_time_phase() -> StringName:
	if not is_inside_tree():
		return &"past"
	var manager := get_tree().root.get_node_or_null("TimePhaseManager")
	if manager != null:
		return StringName(str(manager.get("current_time_phase")))
	return &"past"


func _event_bus_or_null() -> Node:
	if not is_inside_tree():
		return null
	return get_tree().root.get_node_or_null("EventBus")