using UnityEngine;

namespace KindRetargeting
{
    [System.Serializable]
    public class ShoulderCorrectionFunction
    {
        [Header("설정")]
        [Range(0f, 5f)]
        public float blendStrength = 2f;
        [Range(0f, 1f)]
        public float maxShoulderBlend = 0.7f;
        public bool reverseLeftRotation = false;
        public bool reverseRightRotation = false;

        [Header("높이 제한 설정")]
        public float maxHeightDifference = 0.8f;
        public float minHeightDifference = -0.1f;

        [Header("보정 커브 설정")]
        public AnimationCurve shoulderCorrectionCurve = AnimationCurve.Linear(0f, 0f, 1f, 1f);

        private float leftBlendWeight = 0f;
        private float rightBlendWeight = 0f;

        private Transform leftShoulder;
        private Transform rightShoulder;
        private Transform leftUpperArm;
        private Transform rightUpperArm;
        private Transform leftLowerArm;
        private Transform rightLowerArm;

        public void Initialize(Animator targetAnimator)
        {
            leftShoulder = targetAnimator.GetBoneTransform(HumanBodyBones.LeftShoulder);
            rightShoulder = targetAnimator.GetBoneTransform(HumanBodyBones.RightShoulder);
            leftUpperArm = targetAnimator.GetBoneTransform(HumanBodyBones.LeftUpperArm);
            rightUpperArm = targetAnimator.GetBoneTransform(HumanBodyBones.RightUpperArm);
            leftLowerArm = targetAnimator.GetBoneTransform(HumanBodyBones.LeftLowerArm);
            rightLowerArm = targetAnimator.GetBoneTransform(HumanBodyBones.RightLowerArm);
        }

        public void OnUpdate()
        {
            if (leftShoulder == null || rightShoulder == null) return;

            // 왼쪽 어깨 보정
            Vector3 leftElbowPos = leftLowerArm.position;
            float leftHeightDiff = leftElbowPos.y - leftShoulder.position.y;
            float leftRawBlend = Mathf.Clamp01(
                Mathf.InverseLerp(minHeightDifference, maxHeightDifference, leftHeightDiff) * blendStrength
            );
            leftBlendWeight = shoulderCorrectionCurve.Evaluate(leftRawBlend) * maxShoulderBlend;

            // 오른쪽 어깨 보정
            Vector3 rightElbowPos = rightLowerArm.position;
            float rightHeightDiff = rightElbowPos.y - rightShoulder.position.y;
            float rightRawBlend = Mathf.Clamp01(
                Mathf.InverseLerp(minHeightDifference, maxHeightDifference, rightHeightDiff) * blendStrength
            );
            rightBlendWeight = shoulderCorrectionCurve.Evaluate(rightRawBlend) * maxShoulderBlend;

            // 어깨와 윗팔 회전 보정 적용
            if (leftBlendWeight > 0.01f)
            {
                Quaternion currentWorldShoulderRot = leftShoulder.rotation;
                Quaternion currentWorldArmRot = leftUpperArm.rotation;

                Vector3 shoulderToArm = (leftUpperArm.position - leftShoulder.position).normalized;
                Quaternion targetRotation = Quaternion.FromToRotation(leftShoulder.forward,
                    reverseLeftRotation ? shoulderToArm : -shoulderToArm);
                Quaternion targetWorldShoulderRot = targetRotation * currentWorldShoulderRot;

                leftShoulder.rotation = Quaternion.Lerp(currentWorldShoulderRot, targetWorldShoulderRot, leftBlendWeight);
                leftUpperArm.rotation = currentWorldArmRot;
            }

            if (rightBlendWeight > 0.01f)
            {
                Quaternion currentWorldShoulderRot = rightShoulder.rotation;
                Quaternion currentWorldArmRot = rightUpperArm.rotation;

                Vector3 shoulderToArm = (rightUpperArm.position - rightShoulder.position).normalized;
                Quaternion targetRotation = Quaternion.FromToRotation(rightShoulder.forward,
                    reverseRightRotation ? -shoulderToArm : shoulderToArm);
                Quaternion targetWorldShoulderRot = targetRotation * currentWorldShoulderRot;

                rightShoulder.rotation = Quaternion.Lerp(currentWorldShoulderRot, targetWorldShoulderRot, rightBlendWeight);
                rightUpperArm.rotation = currentWorldArmRot;
            }
        }
    }
}