## 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.
@tool
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

## Zoom sensitivity per mouse wheel tick.
@export var zoom_sensitivity: float = 0.1

## Minimum zoom level.
@export var zoom_min: float = 0.25

## Maximum zoom level.
@export var zoom_max: float = 3.0

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 Engine.is_editor_hint():
		queue_redraw()
		return

	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 _draw() -> void:
	if not Engine.is_editor_hint():
		return
	if not clamp_enabled:
		return

	var rect_size: Vector2 = clamp_max - clamp_min
	draw_rect(Rect2(clamp_min, rect_size), Color(1, 0.4, 0, 0.35))
	draw_rect(Rect2(clamp_min, rect_size), Color(1, 0.6, 0.2, 0.8), false, 2.0)


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 _unhandled_input(event: InputEvent) -> void:
	if Engine.is_editor_hint():
		return

	if event is InputEventMouseButton:
		var mouse_event: InputEventMouseButton = event
		if mouse_event.button_index == MOUSE_BUTTON_WHEEL_UP:
			_zoom(zoom_sensitivity, mouse_event.position)
		elif mouse_event.button_index == MOUSE_BUTTON_WHEEL_DOWN:
			_zoom(-zoom_sensitivity, mouse_event.position)


func _zoom(change: float, mouse_pos: Vector2) -> void:
	var new_zoom_value: float = clampf(zoom.x + change, zoom_min, zoom_max)
	if is_equal_approx(new_zoom_value, zoom.x):
		return

	var viewport_center: Vector2 = get_viewport_rect().size / 2.0
	var offset: Vector2 = mouse_pos - viewport_center
	var world_point: Vector2 = position + offset / zoom
	zoom = Vector2(new_zoom_value, new_zoom_value)
	position = world_point - offset / zoom


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