## Scrolls the camera when the mouse cursor reaches the screen edge.
## Attach to a Camera2D node. Requires an OrthographicCamera2D or ViewportContainer
## to determine screen bounds at runtime.
extends Camera2D

## Speed at which the camera scrolls (pixels per second).
@export var scroll_speed: float = 400.0

## Distance from the edge (in pixels) that triggers scrolling.
@export var edge_margin: float = 40.0

## Whether to clamp the camera position to a specific region.
@export var clamp_enabled: bool = false

## Minimum bounds when clamping (in world space).
@export var clamp_min: Vector2 = Vector2.ZERO

## Maximum bounds when clamping (in world space).
@export var clamp_max: Vector2 = Vector2.ZERO

var _screen_rect: Rect2


func _ready() -> void:
	_update_screen_rect()
	var viewport: Viewport = get_viewport()
	if viewport != null:
		viewport.size_changed.connect(_update_screen_rect)


func _process(delta: float) -> void:
	if is_zero_approx(scroll_speed):
		return

	var mouse_pos: Vector2 = get_viewport().get_mouse_position()
	var scroll_dir: Vector2 = _get_scroll_direction(mouse_pos)

	if scroll_dir != Vector2.ZERO:
		position += scroll_dir * scroll_speed * delta

	if clamp_enabled:
		_clamp_position()


func _get_scroll_direction(mouse_pos: Vector2) -> Vector2:
	var direction: Vector2 = Vector2.ZERO

	if mouse_pos.x < _screen_rect.position.x + edge_margin:
		direction.x -= 1.0
	elif mouse_pos.x > _screen_rect.position.x + _screen_rect.size.x - edge_margin:
		direction.x += 1.0

	if mouse_pos.y < _screen_rect.position.y + edge_margin:
		direction.y -= 1.0
	elif mouse_pos.y > _screen_rect.position.y + _screen_rect.size.y - edge_margin:
		direction.y += 1.0

	return direction.normalized()


func _clamp_position() -> void:
	position.x = clampf(position.x, clamp_min.x, clamp_max.x)
	position.y = clampf(position.y, clamp_min.y, clamp_max.y)


func _update_screen_rect() -> void:
	var viewport: Viewport = get_viewport()
	if viewport != null:
		_screen_rect = viewport.get_visible_rect()