extends RefCounted

## STB-RESIZE-01 的真实窗口适配器（PlayableFlow.window）。
##
## macOS Retina 下 DisplayServer 的窗口尺寸是物理像素，逻辑尺寸 = 物理像素 / 屏幕缩放。
## 流程只按逻辑尺寸判定；物理像素、缩放和视口尺寸一并写进事件，Retina 的 2x 不是分辨率错误。
## 请求尺寸超出当前屏幕可用区域（含标题栏）时如实拒绝（request_logical_size 返回 false），
## 由流程记为 BLOCKED，不缩小目标冒充通过。headless / 全屏 / 最大化窗口不可调整。

var _viewport: Viewport

func _init(viewport: Viewport = null) -> void:
	_viewport = viewport

func availability() -> Dictionary:
	if DisplayServer.get_name() == "headless":
		return {"ok": false, "reason": "headless display server has no window"}
	match DisplayServer.window_get_mode():
		DisplayServer.WINDOW_MODE_FULLSCREEN, DisplayServer.WINDOW_MODE_EXCLUSIVE_FULLSCREEN:
			return {"ok": false, "reason": "window is fullscreen; logical size switching needs windowed mode"}
		DisplayServer.WINDOW_MODE_MAXIMIZED:
			return {"ok": false, "reason": "window is maximized; logical size switching needs windowed mode"}
		DisplayServer.WINDOW_MODE_MINIMIZED:
			return {"ok": false, "reason": "window is minimized"}
	if screen_scale() <= 0.0:
		return {"ok": false, "reason": "screen scale unavailable"}
	return {"ok": true, "reason": ""}

func screen_scale() -> float:
	return DisplayServer.screen_get_scale(DisplayServer.window_get_current_screen())

func physical_size() -> Vector2i:
	return DisplayServer.window_get_size()

func logical_size() -> Vector2i:
	var scale := screen_scale()
	var size := physical_size()
	if scale <= 0.0:
		return size
	return Vector2i(roundi(size.x / scale), roundi(size.y / scale))

func viewport_size() -> Vector2i:
	if _viewport == null or not is_instance_valid(_viewport):
		return Vector2i.ZERO
	return Vector2i(_viewport.get_visible_rect().size)

## Returns false (no request sent) when the size cannot fit the usable screen area.
func request_logical_size(size: Vector2i) -> bool:
	var scale := screen_scale()
	if scale <= 0.0 or size.x <= 0 or size.y <= 0:
		return false
	var target := Vector2i(roundi(size.x * scale), roundi(size.y * scale))
	var screen := DisplayServer.window_get_current_screen()
	var usable := DisplayServer.screen_get_usable_rect(screen)
	var decorations := DisplayServer.window_get_size_with_decorations() - DisplayServer.window_get_size()
	if target.x + decorations.x > usable.size.x or target.y + decorations.y > usable.size.y:
		return false
	DisplayServer.window_set_size(target)
	# Keep the whole window on the usable area so the OS does not clamp the size back.
	var position := DisplayServer.window_get_position()
	var clamped := Vector2i(clampi(position.x, usable.position.x, usable.end.x - target.x - decorations.x),
		clampi(position.y, usable.position.y, usable.end.y - target.y - decorations.y))
	if clamped != position:
		DisplayServer.window_set_position(clamped)
	return true