public partial class PickupController : Node3D
{
	public Item CurrentItem { get; private set; }
	public bool HasItemsHeld => GetChildCount() > 0;
	MeshInstance3D _placementPreview;

	[Export] public Camera3D Camera { get; set; }
	[Export] public float PickupDistance { get; set; } = 2.0f;

	Player _player;
	Node3D _world;
	public override void _Ready()
	{
		_player = GetParent<Player>();
		// TODO: Find a better way to find the world.
		_world = GetNode<Node3D>("/root/Game/Workshop");
	}

	public override void _UnhandledInput(InputEvent @event)
	{
		if (!_player.IsLocal) return;
		EnsureCurrentItemValid();
		if (CurrentItem == null) return;

		if (@event.IsActionPressed("interact_pickup")) {
			if (!HasItemsHeld) {
				// Parent item to the `PickupController`.
				var prevRot = CurrentItem.GlobalRotation;
				CurrentItem.GetParent().RemoveChild(CurrentItem);
				AddChild(CurrentItem);
				CurrentItem.Mesh.Layers &= (uint)~RenderLayer.Outline;
				CurrentItem.Position = Vector3.Zero;
				CurrentItem.GlobalRotation = prevRot;
				CurrentItem.CollisionLayer &= (uint)~PhysicsLayer.Static;
				// CurrentItem.Freeze = true;

				GetViewport().SetInputAsHandled();
			}
		} else if (@event.IsActionPressed("interact_place")) {
			if (HasItemsHeld) {
				// Parent item back to the world.
				var prevTransform = CurrentItem.GlobalTransform;
				CurrentItem.CollisionLayer |= (uint)PhysicsLayer.Static;
				// CurrentItem.Freeze = false;
				RemoveChild(CurrentItem);
				_world.AddChild(CurrentItem);
				CurrentItem.GlobalTransform = prevTransform;

				GetViewport().SetInputAsHandled();
			}
		}
	}

	public override void _PhysicsProcess(double delta)
	{
		if (!_player.IsLocal) return;
		EnsureCurrentItemValid();

		if (HasItemsHeld) {
			if ((RayToMouseCursor() is RayResult ray) && (ray.Collider is Grid)) {
				// Snao rotation to nearest axis.
				// FIXME: This needs to snap to the
				// var globalRot = CurrentItem.GlobalRotation;
				// globalRot.X = Snapped(globalRot.X, Tau / 4);
				// globalRot.Y = Snapped(globalRot.Y, Tau / 4);
				// globalRot.Z = Snapped(globalRot.Z, Tau / 4);
				// CurrentItem.GlobalRotation = globalRot;

				// Snap the position to the grid.
				var halfSize = (Vector3)CurrentItem.Size * Grid.StepSize / 2;
				var pos = ray.Position + halfSize * (ray.Normal * CurrentItem.GlobalTransform.Basis);
				pos = pos.Snapped(Grid.StepSize * Vector3.One); // FIXME: This does global snapping only
				CurrentItem.GlobalPosition = pos;
			}
		} else {
			var interactable = RayToMouseCursor()?.Collider;

			// Remove the outline from the previously looked-at item.
			if (CurrentItem != null) CurrentItem.Mesh.Layers &= (uint)~RenderLayer.Outline;
			// If the ray hits anything and the object hit is an item, set it as current.
			CurrentItem = interactable as Item;
			// Add the outline to the currently looked-at item.
			if (CurrentItem != null) CurrentItem.Mesh.Layers |= (uint)RenderLayer.Outline;
		}
	}

	void EnsureCurrentItemValid()
	{
		if (CurrentItem == null) return;
		if (!IsInstanceValid(CurrentItem)) {
			CurrentItem = null;
			_placementPreview?.QueueFree();
		}
	}

	RayResult RayToMouseCursor()
	{
		var mouse = GetViewport().GetMousePosition();
		var from  = Camera.ProjectRayOrigin(mouse);
		var to    = from + Camera.ProjectRayNormal(mouse) * PickupDistance;

		var query = PhysicsRayQueryParameters3D.Create(from, to);
		query.CollisionMask = (uint)PhysicsLayer.Interactable;
		query.CollideWithAreas = true;
		// Exclude the `CurrentItem` from collision checking if it's being held.
		query.Exclude = HasItemsHeld ? [ CurrentItem.GetRid() ] : [];

		var result = GetWorld3D().DirectSpaceState.IntersectRay(query);
		return (result.Count > 0) ? new(result) : null;
	}

	class RayResult(Dictionary dict)
	{
		public CollisionObject3D Collider { get; } = dict["collider"].As<CollisionObject3D>();
		public Vector3 Position { get; } = (Vector3)dict["position"];
		public Vector3 Normal { get; } = (Vector3)dict["normal"];
	}
}