// -- SPINE PROXY 1.0 | Kevin Iglesias --
// This script ensures correct animation display when mixing upper and lower body animations using Unity Avatar Masks.
// Attach this script to the 'B-spineProxy' transform, which is a sibling of the 'B-hips' bone.
// In the 'originalSpine' field, assign the 'B-spine' bone (child of 'B-hips' and parent of 'B-chest').
// By default it will automatically find the 'B-spine' and assign it to the 'originalSpine' field (OnValidate).
// When using a different character rig, manually assign the corresponding spine bone to the 'originalSpine' field and recreate
// 'Rig > B-root > B-spine' structure in your character hierarchy with empty GameObjects.

// More information: https://www.keviniglesias.com/spine-proxy.html
// Contact Support: support@keviniglesias.com

using UnityEngine;

namespace KevinIglesias
{
    public class SpineProxy : MonoBehaviour
    {
        //Assign 'B-spine' (or equivalent) here:
        [SerializeField] private Transform originalSpine;

        private Quaternion rotationOffset = Quaternion.identity;

#if UNITY_EDITOR
        //Attempting to find the original spine bone.
        void OnValidate()
        {
            if(originalSpine == null)
            {
                Transform parent = transform.parent;
                if(parent != null)
                {
                    Transform hips = parent.Find("B-hips");
                    if(hips != null)
                    {
                        Transform spine = hips.Find("B-spine");
                        if(spine != null)
                        {
                            originalSpine = spine;
                        }
                    }
                }
            }
        }  
#endif
        
        //Match correct orientation on different character rigs
        void Awake()
        {
            if(originalSpine != null)
            {//originalSpine.rotation must be the default rotation in your character T-pose when this happens:
                rotationOffset = Quaternion.Inverse(transform.rotation) * originalSpine.rotation;
            }
        }

        //Copy rotations from spine proxy bone to the original spine bone.
        void LateUpdate()
        {
            if(originalSpine == null)
            {
                return;
            }
            originalSpine.rotation = transform.rotation * rotationOffset;
        }
    }
}