public partial class CameraController : SpringArm3D
{
	[Export] public float MovementSmoothing { get; set; } = 8.0f;

	[Export] public Vector2 MouseSensitivity { get; set; } = new(0.2f, 0.2f); // Degrees per pixel.

	[Export] public float PitchMinimum { get; set; } = 30;
	[Export] public float PitchMaximum { get; set; } = 65;
	[Export] public float PitchSmoothing { get; set; } = 12.0f;

	// FIXME: Fix the "snappyness" when moving slowly.
	// FIXME: Fix spring arm clipping through terrain and similar.
	// TODO: Gradually return to maximum spring length.
	// TODO: Turn player transparent as the camera moves closer.

	public static bool IsMouseCaptured
		=> Input.MouseMode == Input.MouseModeEnum.Captured;

	Vector3 _offset;
	Node3D _player;
	public override void _Ready()
	{
		_offset = Position;
		_player = this.GetParentOrThrow<Node3D>();
		Transform = _player.GlobalTransform.Translated(_offset);
	}

	public override void _Input(InputEvent ev)
	{
		if (IsMouseCaptured && ev.IsActionPressed("ui_cancel")) {
			// When escape is pressed, release the mouse.
			Input.MouseMode = Input.MouseModeEnum.Visible;
			GetViewport().SetInputAsHandled();
		}
	}

	public override void _UnhandledInput(InputEvent ev)
	{
		switch (ev) {
			case InputEventMouseButton { ButtonIndex: MouseButton.Left, Pressed: true } when !IsMouseCaptured:
				// When left mouse button is pressed, capture the mouse.
				Input.MouseMode = Input.MouseModeEnum.Captured;
				GetViewport().SetInputAsHandled();
				break;
			case InputEventMouseMotion motion when IsMouseCaptured:
				ApplyRotation(-motion.Relative * MouseSensitivity);
				break;
		}
	}

	void ApplyRotation(Vector2 delta)
	{
		var (pitch, yaw, _) = RotationDegrees;
		pitch += delta.Y;
		yaw   += delta.X;
		RotationDegrees = new(pitch, yaw, 0);
	}

	public override void _Process(double delta)
	{
		Position = Position.Damp(_offset + _player.GlobalPosition, MovementSmoothing, delta);

		var pitch = RotationDegrees.X;
		var (min, max) = (-PitchMaximum, -PitchMinimum);
		if (pitch < min) pitch = pitch.Damp(min, PitchSmoothing, delta);
		if (pitch > max) pitch = pitch.Damp(max, PitchSmoothing, delta);
		RotationDegrees = RotationDegrees with { X = pitch };
	}
}