extends SceneTree

## 节奏点从两侧向中心的移动必须由音乐时钟连续驱动：
## 进度 = RhythmManager 当前拍内进度，不允许 beat_flash 期间瞬移到中心。

var failures: Array[String] = []


func _init() -> void:
	_run.call_deferred()


func _run() -> void:
	root.size = Vector2i(1152, 648)
	var rhythm := root.get_node_or_null("RhythmManager")
	_expect(rhythm != null, "RhythmManager autoload should exist")
	if rhythm == null:
		_finish()
		return

	var scene: PackedScene = load("res://scenes/ui/rhythm_track.tscn")
	_expect(scene != null, "rhythm_track.tscn should load")
	if scene == null:
		_finish()
		return
	var track := scene.instantiate() as Control
	root.add_child(track)
	await process_frame

	var beat_time := float(rhythm.get("beat_time"))
	var left_mover := track.get_node("LeftMover") as Control
	var right_mover := track.get_node("RightMover") as Control
	var left_start := track.get("left_mover_start") as Vector2
	var right_start := track.get("right_mover_start") as Vector2
	var center := track.get("track_center") as Vector2

	# 把音乐时钟冻结在拍内 37% 处，节奏点必须停在 37% 的插值位置。
	rhythm.call("pause_clock")
	rhythm.set("_paused_song_position", beat_time * 0.37)
	# beat_flash 拉满：旧实现会在此瞬移到中心，新实现必须继续跟随时钟。
	track.set("beat_flash", 1.0)
	track.call("_update_movers")
	_expect_mover_at(left_mover, left_start.lerp(center, 0.37), "left mover follows the musical clock at 37%")
	_expect_mover_at(right_mover, right_start.lerp(center, 0.37), "right mover follows the musical clock at 37%")

	# 时钟推进到 82%：节奏点连续前进，不回跳。
	rhythm.set("_paused_song_position", beat_time * 0.82)
	track.call("_update_movers")
	_expect_mover_at(left_mover, left_start.lerp(center, 0.82), "left mover keeps gliding at 82%")
	_expect_mover_at(right_mover, right_start.lerp(center, 0.82), "right mover keeps gliding at 82%")

	# 拍点整数时刻（进度 0）：节奏点回到两侧起点，开始下一拍收束。
	rhythm.set("_paused_song_position", beat_time * 1.0)
	track.call("_update_movers")
	_expect_mover_at(left_mover, left_start, "left mover restarts from the edge on the beat")
	_expect_mover_at(right_mover, right_start, "right mover restarts from the edge on the beat")

	rhythm.call("resume_clock")
	track.free()
	_finish()


func _expect_mover_at(mover: Control, expected_center: Vector2, label: String) -> void:
	var actual := Vector2(
		(mover.offset_left + mover.offset_right) * 0.5,
		(mover.offset_top + mover.offset_bottom) * 0.5
	)
	if actual.distance_to(expected_center) > 0.75:
		failures.append("%s: expected %s, got %s" % [label, expected_center, actual])


func _expect(condition: bool, label: String) -> void:
	if not condition:
		failures.append(label)


func _finish() -> void:
	if failures.is_empty():
		print("PASS rhythm mover smoothness")
		quit(0)
	else:
		for failure: String in failures:
			push_error(failure)
		quit(1)