extends Node


enum ScaleMode {
	## Stretches to fit as close as possible while maintaining the game's aspect ratio.
	ASPECT,
	## Stretches to fit as close as possible while maintaining aspect ratio and an integer scale.
	INTEGER,
	## Stretches to cover the whole screen, warping the aspect ratio.
	STRETCH,
}


## Strategy to use for scaling from game-native resolution to the window/screen size.
@export var scale_mode: ScaleMode = ScaleMode.ASPECT:
	set(value):
		scale_mode = value
		if is_node_ready():
			_update_scale()

@export_group("Internal References")
@export var _viewport: SubViewport
@export var _viewport_container: SubViewportContainer


## The native resolution of the game.
var size: Vector2i = Vector2i(
	ProjectSettings.get_setting("display/window/size/viewport_width"),
	ProjectSettings.get_setting("display/window/size/viewport_height"),
)


func _enter_tree() -> void:
	get_tree().scene_changed.connect(_on_scene_changed)
	get_tree().root.size_changed.connect(_update_scale)
	
	_update_scale.call_deferred()
	
	var current_scene = get_tree().current_scene
	if current_scene and current_scene != self:
		current_scene.reparent.call_deferred(_viewport)


func _on_scene_changed() -> void:
	for child in _viewport.get_children():
		child.queue_free()
	get_tree().current_scene.reparent(_viewport)


func _update_scale() -> void:
	var screen_size = Vector2(get_tree().root.size)
	var size_ratio = screen_size / Vector2(size)
	
	DisplayServer.window_set_min_size(size)
	
	_viewport.size = size
	_viewport_container.pivot_offset = Vector2(size) * 0.5
	_viewport_container.position = screen_size * 0.5 - Vector2(size) * 0.5
	
	match scale_mode:
		ScaleMode.ASPECT:
			# get the minimum ratio and use for both axes
			var min_scale = minf(size_ratio.x, size_ratio.y)
			_viewport_container.scale = Vector2(min_scale, min_scale)
		ScaleMode.INTEGER:
			# get the minimum ratio and use for both axes after flooring
			var min_scale = floorf(minf(size_ratio.x, size_ratio.y))
			_viewport_container.scale = Vector2(min_scale, min_scale)
		ScaleMode.STRETCH:
			# just use the ratio as-is
			_viewport_container.scale = size_ratio