public partial class MovementController : Node
{
	[ExportGroup("Movement")]
	[Export] public float Acceleration  { get; set; } =  4.0f;
	[Export] public float MaxSpeed      { get; set; } =  2.1f;
	[Export] public float FrictionFloor { get; set; } = 12.0f;
	[Export] public float FrictionAir   { get; set; } =  2.0f;
	[Export] public float Gravity       { get; set; } = 12.0f;

	[ExportGroup("Jumping")]
	[Export] public float JumpVelocity   { get; set; } = 4.0f;
	[Export] public float JumpEarlyTime  { get; set; } = 0.0f; // Time (in seconds) after pressing the jump button a jump may occur late.
	[Export] public float JumpCoyoteTime { get; set; } = 0.0f; // Time (in seconds) after leaving a jumpable surface when a jump may still occur.

	public float RealMoveSpeed { get; private set; }
	public bool IsSprinting { get; private set; }

	public float TimeSinceJumpPressed { get; private set; } = float.PositiveInfinity;
	public float TimeSinceOnFloor     { get; private set; } = float.PositiveInfinity;

	CharacterBody3D _player;
	CameraController _cameraController;
	public override void _Ready()
	{
		_player = GetParent<CharacterBody3D>();
		_cameraController = _player.GetNode<CameraController>("CameraController");
	}

	public override void _UnhandledInput(InputEvent @event)
	{
		// TODO: Sprinting.
		// TODO: Jumping.
	}

	public override void _PhysicsProcess(double delta)
	{
		// Get the (normalized) movement vector from the current input.
		var input = Input.GetVector("move_strafe_left", "move_strafe_right", "move_forward", "move_back");

		var velocity    = _player.Velocity;
		var horVelocity = velocity with { Y = 0 };

		// TODO: Gravity.
		// velocity.Y -= Gravity * (float)delta;

		var basis  = _player.Basis.Rotated(Vector3.Up, _cameraController.CurrentYaw);
		var target = basis * new Vector3(input.X, 0, input.Y) * MaxSpeed;
		var isMoving = target.Dot(horVelocity) > 0.0f;

		var isOnFloor = true; // _player.IsOnFloor();
		var accel = isMoving  ? Acceleration
			      : isOnFloor ? FrictionFloor
			                  : FrictionAir;

		if (IsSprinting) {
			target *= 5;
			accel  *= 5;
		}

		horVelocity = horVelocity.Lerp(target, accel * (float)delta);
		velocity.X = horVelocity.X;
		velocity.Z = horVelocity.Z;

		if (isOnFloor) TimeSinceOnFloor = 0.0f;
		else           TimeSinceOnFloor += (float)delta;

		if ((TimeSinceJumpPressed <= JumpEarlyTime) && (TimeSinceOnFloor <= JumpCoyoteTime)) {
			TimeSinceJumpPressed = TimeSinceOnFloor = float.PositiveInfinity;
			velocity.Y = JumpVelocity;
		}

		_player.Velocity = velocity;
		_player.MoveAndSlide();

		RealMoveSpeed = (_player.Velocity with { Y = 0 }).Length();
	}
}