Attach Transform To Spline

using System;
using System.Linq;
using Unity.Mathematics;
using UnityEngine;
using UnityEngine.Splines;

namespace sc.modeling.splines.runtime.auxiliary
{
    //This component may be used to fix a Transform to either the start or end of a spline
    [ExecuteAlways]
    public class AttachTransformToSpline : MonoBehaviour
    {
        public SplineContainer splineContainer;

        public enum ConnectionPoint
        {
            Start,
            End,
            Custom
        }
        [Space]
        public ConnectionPoint point;
        public PathIndexUnit customPositionType = PathIndexUnit.Distance;
        public float customPosition;

        [Space]
        [Header("Position")]
        public Vector3 offset;

        [Space]
        [Header("Rotation")]
        public bool alignRotation = true;
        public Vector3 addedRotation;

        private void Reset()
        {
            splineContainer = gameObject.GetComponentInParent<SplineContainer>();

            Apply();
        }

        private void OnEnable()
        {
            Spline.Changed += OnSplineChanged;
        }

        private void OnDisable()
        {
            Spline.Changed -= OnSplineChanged;
        }

        private void OnSplineChanged(Spline spline, int index, SplineModification modificationType)
        {
            if (!splineContainer) return;

            //Spline belongs to the assigned container?
            var splineIndex = Array.IndexOf(splineContainer.Splines.ToArray(), spline);
            if (splineIndex < 0)
                return;

            Apply();
        }

        private void OnValidate()
        {
            Apply();
        }

        private void Apply()
        {
            if (!splineContainer) return;

            float t = 0f;

            switch (point)
            {
                case ConnectionPoint.Start: t = 0f;
                    break;
                case ConnectionPoint.End: t = 1f;
                    break;
                case ConnectionPoint.Custom: t = customPosition;
                    break;
            }

            if (point == ConnectionPoint.Custom && customPositionType == PathIndexUnit.Distance)
            {
                t = splineContainer.Spline.ConvertIndexUnit(customPosition, PathIndexUnit.Distance, PathIndexUnit.Normalized);
            }

            //Ensure a tangent can always be derived at very the start and end
            t = Mathf.Clamp(t, 0.0001f, 0.9999f);

            splineContainer.Spline.Evaluate(t, out float3 splinePoint, out float3 tangent, out float3 up);

            float3 position = splinePoint;
            float3 forward = math.normalize(tangent);
            float3 right = -math.cross(forward, up);

            //Offset
            position += right * offset.x;
            position += up * offset.y;
            position += forward * offset.z;

            //Position of point on spline in world-space
            position = splineContainer.transform.TransformPoint(position);
            this.transform.position = position;

            if (alignRotation)
            {
                Quaternion rotation = Quaternion.LookRotation(forward) * Quaternion.Euler(addedRotation);
                this.transform.rotation = rotation;
            }
        }
    }
}