namespace UnityEngine.Rendering.Universal
{
    public class DebugCascadeShadow : MonoBehaviour
    {
        public Camera targetCamera;
        public bool showCullingSpheres = true;
        public bool showCameraFrustums = true;
        public Color[] cascadeColors = new Color[]
        {
        new Color(1, 0, 0, 0.5f),   // 红
        new Color(0, 1, 0, 0.5f),   // 绿
        new Color(0, 0.5f, 1, 0.5f), // 蓝
        new Color(1, 1, 0, 0.5f)    // 黄
        };

        public static Vector3 cascadeSplits;
        public static Vector4[] cullingSpheres= new Vector4[4];
   
        void OnDrawGizmos()
        {
            if (targetCamera == null) return;
            // 可视化Culling Spheres
            if (showCullingSpheres)
            {
                for (int i = 0; i < cullingSpheres.Length; i++)
                {
                    if (cullingSpheres[i].w <= 0) continue;

                    Gizmos.color = cascadeColors[i % cascadeColors.Length];
                    Vector3 sphereCenter = cullingSpheres[i];
                    float sphereRadius = cullingSpheres[i].w;
                    Gizmos.DrawWireSphere(sphereCenter, sphereRadius);
                }
            }
            // 可视化相机视锥体级联
            if (showCameraFrustums)
            {
                float lastSplit = targetCamera.nearClipPlane;

                for (int i = 0; i < 3; i++)
                {
                    if (cascadeSplits[i] <= 0) break;

                    Gizmos.color = cascadeColors[i % cascadeColors.Length];
                    DrawCascadeFrustum(targetCamera, lastSplit, cascadeSplits[i]);
                    lastSplit = cascadeSplits[i];
                }
            }
        }



        private void DrawCascadeFrustum(Camera cam, float startDist, float endDist)
        {
            // 计算视锥体角点
            Vector3[] nearCorners = GetFrustumCorners(cam, startDist);
            Vector3[] farCorners = GetFrustumCorners(cam, endDist);

            // 绘制视锥体线框
            Gizmos.DrawLine(nearCorners[0], farCorners[0]);
            Gizmos.DrawLine(nearCorners[1], farCorners[1]);
            Gizmos.DrawLine(nearCorners[2], farCorners[2]);
            Gizmos.DrawLine(nearCorners[3], farCorners[3]);

            // 绘制近/远平面
            DrawFrustumPlane(nearCorners);
            DrawFrustumPlane(farCorners);
        }

        private Vector3[] GetFrustumCorners(Camera cam, float distance)
        {
            Vector3[] corners = new Vector3[4];
            Transform camTransform = cam.transform;

            float halfFOV = cam.fieldOfView * 0.5f * Mathf.Deg2Rad;
            float aspect = cam.aspect;

            float height = distance * Mathf.Tan(halfFOV);
            float width = height * aspect;

            // 计算相对于相机的角点
            corners[0] = camTransform.forward * distance + camTransform.up * height - camTransform.right * width; // 左下
            corners[1] = camTransform.forward * distance + camTransform.up * height + camTransform.right * width; // 右下
            corners[2] = camTransform.forward * distance - camTransform.up * height + camTransform.right * width; // 右上
            corners[3] = camTransform.forward * distance - camTransform.up * height - camTransform.right * width; // 左上

            // 转换到世界坐标
            for (int i = 0; i < 4; i++)
            {
                corners[i] = camTransform.position + corners[i];
            }

            return corners;
        }

        private void DrawFrustumPlane(Vector3[] corners)
        {
            Gizmos.DrawLine(corners[0], corners[1]);
            Gizmos.DrawLine(corners[1], corners[2]);
            Gizmos.DrawLine(corners[2], corners[3]);
            Gizmos.DrawLine(corners[3], corners[0]);
        }
    }
}