public partial class CameraController : Camera3D
{
	[ExportCategory("Follow")]
	[Export] public float FollowDistance  { get; set; } = 1.2f;
	[Export] public float FollowYOffset   { get; set; } = 1.0f;
	[Export] public float FollowSmoothing { get; set; } = 12.0f;

	[ExportCategory("Rotation")]
	[Export] public Vector2 MouseSensitivity { get; set; } = new(0.2f, 0.2f); // Degrees per pixel.
	[Export] public float PitchMinimum   { get; set; } = 20;
	[Export] public float PitchMaximum   { get; set; } = 65;
	[Export] public float PitchSmoothing { get; set; } = 12.0f;

	// 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;

	Node3D _player;
	Vector3 _smoothPlayerPos;
	public override void _Ready()
	{
		_player = this.GetParentOrThrow<Node3D>();
		_smoothPlayerPos = _player.GlobalPosition;
		Transform = _player.GlobalTransform.Translated(new(0.0f, FollowYOffset, 0.0f));
	}

	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 _PhysicsProcess(double delta)
	{
		_smoothPlayerPos = _smoothPlayerPos.Damp(_player.GlobalPosition, FollowSmoothing, delta);

		var target = _smoothPlayerPos
		           + Basis.Z    * FollowDistance
		           + Vector3.Up * FollowYOffset;

		Position   = OffsetRayIntersection(_smoothPlayerPos, target, 0.2f);
	}

	Vector3 OffsetRayIntersection(Vector3 from, Vector3 to, float margin)
	{
		const PhysicsLayer CollisionMask = PhysicsLayer.Terrain
		                                 | PhysicsLayer.Objects;
		var query = PhysicsRayQueryParameters3D.Create(from, to, (uint)CollisionMask);
		var result = GetWorld3D().DirectSpaceState.IntersectRay(query);
		if (result.Count > 0) {
			var hit = (Vector3)result["position"];
			var safeDistance = Max(0, from.DistanceTo(hit) - margin);
			return from + (to - from).Normalized() * safeDistance;
		} else {
			// No intersection occured,
			return to;
		}
	}

	public override void _Process(double 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 };
	}
}