feat(behaviours): add grabable (#19)

plugin/src/objects/behaviours/Grabable.cs

@@ -0,0 +1,83 @@
+using System.Linq;
+using PiUtils.Util;
+using UnityEngine;
+
+namespace PiUtils.Objects.Behaviours;
+public class Grabable : MonoBehaviour
+{
+	private static readonly PluginLogger Logger = PluginLogger.GetLogger<Grabable>();
+
+	public bool IsGrabbed { get; private set; } = false;
+	public bool IsHovered { get; private set; } = false;
+
+	public float grabDistance = 0.2f;
+
+	public bool snapToHand = false;
+	public Option<Vector3> grabOffset = Option<Vector3>.None();
+	public Option<Quaternion> grabRotation = Option<Quaternion>.None();
+
+	public Transform originalParent { get; private set; }
+
+	public Grabable() { }
+
+	public Grabable(float? grabDistance, bool snapToHand, Option<Vector3> grabOffset, Option<Quaternion> grabRotation)
+	{
+		this.grabDistance = grabDistance ?? this.grabDistance;
+		this.snapToHand = snapToHand;
+		this.grabOffset = grabOffset;
+		this.grabRotation = grabRotation;
+	}
+
+	public bool TryGrab(Transform grabbingTransform)
+	{
+		if (IsGrabbed)
+		{
+			Logger.LogDebug("Object already grabbed: " + gameObject.name);
+			return false;
+		}
+
+		var distance = Vector3.Distance(transform.position, grabbingTransform.position);
+		if (grabDistance >= 0 && distance >= grabDistance)
+		{
+			Logger.LogDebug($"Object too far to grab: {gameObject.name} ({distance} > {grabDistance})");
+			return false;
+		}
+
+		Grab(grabbingTransform);
+		return IsGrabbed;
+	}
+
+	public void Grab(Transform grabbingTransform)
+	{
+		if (IsGrabbed)
+		{
+			return;
+		}
+
+		Logger.LogDebug("Grabbing object: " + gameObject.name);
+
+		IsGrabbed = true;
+		originalParent = transform.parent;
+
+		if (snapToHand)
+		{
+			transform.position = grabbingTransform.position + grabOffset.FirstOrDefault();
+			transform.rotation = grabbingTransform.rotation * grabRotation.FirstOrDefault();
+		}
+
+		transform.SetParent(grabbingTransform, true);
+	}
+
+	public void Release()
+	{
+		if (!IsGrabbed)
+		{
+			return;
+		}
+
+		IsGrabbed = false;
+		transform.SetParent(originalParent, true);
+
+		originalParent = null;
+	}
+}

plugin/src/util/Option.cs

@@ -11,6 +11,16 @@ private Option(T[] data)
 		this.data = data;
 	}
 
+	public static Option<T> New(T value)
+	{
+		if (value == null)
+		{
+			return None();
+		}
+
+		return Some(value);
+	}
+
 	public static Option<T> Some(T value)
 	{
 		return new Option<T>([value]);
@@ -21,6 +31,11 @@ public static Option<T> None()
 		return new Option<T>([]);
 	}
 
+	public bool IsSome()
+	{
+		return data.Length > 0;
+	}
+
 	public IEnumerator<T> GetEnumerator()
 	{
 		return ((IEnumerable<T>)data).GetEnumerator();