using System.Collections.Generic;
using Unity.Mathematics;
using UnityEngine;
using UnityEngine.Experimental.Rendering;

namespace X.Rendering.Feature
{
    public class HizObjectsManager : MonoBehaviour
    {
        public bool ShowDebug = false;
        Texture2D centerTex;
        Texture2D sizeTex;

        private static HizObjectsManager intstance;
        public static HizObjectsManager Instance => intstance;

        private float4[] centers;
        private float4[] extents;

        private float3x2[] aabbs;

        private List<MeshRenderer> renderers = new();
        private bool[] cullResults;
        private bool needUpdateAABB = true;

        public int culledCnt = 0;

        private void Awake()
        {
            intstance = new();
        }

        void Start()
        {
            int texSize = 64;
            centerTex = new Texture2D(texSize, texSize, TextureFormat.RGBAFloat, 0, true);
            centerTex.filterMode = FilterMode.Point;
            sizeTex = new Texture2D(texSize, texSize, TextureFormat.RGBAFloat, 0, true);
            sizeTex.filterMode = FilterMode.Point;
            Shader.SetGlobalTexture(HizShaderIds.ObjectAABBCenterId, centerTex);
            Shader.SetGlobalTexture(HizShaderIds.ObjectAABBSizeId, sizeTex);
        }

        void Update()
        {
            if (needUpdateAABB)
            {
                needUpdateAABB = false;
                UpdateAABB(centerTex, sizeTex);
            }
        }

        private void OnDestroy()
        {
            Texture.DestroyImmediate(centerTex);
            Texture.DestroyImmediate(sizeTex);
        }

        private void LateUpdate()
        {
            ApplyCull(HierarchicalZOcclusionCullFeature.GetCullResult());
        }

        public void Register(MeshRenderer renderer)
        {
            if (!renderers.Contains(renderer))
            {
                renderers.Add(renderer);
                needUpdateAABB = true;
            }
        }

        public void UnRegister(MeshRenderer renderer)
        {
            if(renderers.Remove(renderer))
            {
                needUpdateAABB = true;
            }
        }

        public void UpdateAABB(ComputeBuffer aabbBuffer)
        {
            if (aabbBuffer == null || aabbs.Length != renderers.Count)
            {
                aabbs = new float3x2[renderers.Count];
            }
            for (int i = 0; i < renderers.Count; i++)
            {
                var rdr = renderers[i];
                if (rdr != null)
                {
                    Bounds bounds = rdr.bounds;
                    aabbs[i] = new float3x2(bounds.center, bounds.size);
                }
                else
                {
                    aabbs[i] = float3x2.zero;
                }
            }

            aabbBuffer.SetData(aabbs);
        }

        public void UpdateAABB(Texture2D centerTex, Texture2D sizeTex)
        {
            if (centers == null || centers.Length != centerTex.width * centerTex.height)
            {
                centers = new float4[centerTex.width * centerTex.height];
                extents = new float4[centerTex.width * centerTex.height];
            }

            if (renderers.Count == 0)
            {
                foreach (var item in GameObject.FindObjectsOfType<MeshRenderer>())
                {
                    if (item.gameObject.isStatic)
                    {
                        Register(item);
                    }
                }
            }
            if (cullResults == null || cullResults.Length != renderers.Count)
            {
                cullResults = new bool[renderers.Count];
            }

            int nullCnt = 0;
            for (int i = 0; i < renderers.Count; i++)
            {
                var rdr = renderers[i];
                if (rdr != null)
                {
                    Bounds bounds = rdr.bounds;
                    centers[i] = new float4(bounds.center, 1);
                    extents[i] = new float4(bounds.extents, 1);
                }
                else
                {
                    nullCnt++;
                    centers[i] = float4.zero;
                    extents[i] = float4.zero;
                }
            }

            if (nullCnt == renderers.Count)
            {
                renderers.Clear();
            }

            centerTex.SetPixelData(centers, 0);
            centerTex.Apply();
            sizeTex.SetPixelData(extents, 0);
            sizeTex.Apply();
            Shader.SetGlobalTexture(HizShaderIds.ObjectAABBCenterId, centerTex);
            Shader.SetGlobalTexture(HizShaderIds.ObjectAABBSizeId, sizeTex);
        }

        private void ApplyCull(CullResult cullResult)
        {
            if (cullResult.ReadDone)
            {
                culledCnt = 0;
                for (var i = 0; i < renderers.Count; i++)
                {
                    var rdr = renderers[i];
                    if (rdr && cullResult.ResultArray.IsCreated)
                    {
                        bool needCull = cullResult.ResultArray[i] > 0.5f;
#if UNITY_EDITOR
                        if (ShowDebug && rdr.GetComponent<CullDebug>() is CullDebug cullDebug && cullDebug)
                        {
                            cullDebug.Index = i;
                            cullDebug.IsCulled = needCull;
                            cullDebug.Position = centers[i].xyz;
                            cullDebug.Size = extents[i].xyz;
                        }

#endif
                        if (needCull)
                        {
                            culledCnt++;
                        }

                        if (cullResults[i] != needCull)
                        {
                            if (needCull)
                            {
                                culledCnt++;
                                rdr.renderingLayerMask = 0;
                            }
                            else
                            {
                                rdr.renderingLayerMask = 1;
                            }
                            cullResults[i] = needCull;
                        }

                    }
                }

                //Debug.Log("frameCount: " + Time.frameCount + " Buffer index " + Time.frameCount % 3 + " : cullcount = " + culledCnt);
            }

            else
            {
                ResetRenderer();
            }
        }

        private void ResetRenderer()
        {
            for (var i = 0; i < renderers.Count; i++)
            {
                var rdr = renderers[i];
                if (rdr)
                {
                    if (cullResults[i])
                    {
                        rdr.renderingLayerMask = 1;
                        cullResults[i] = false;
                    }
                }
            }
        }

        private void OnDisable()
        {
            ResetRenderer();
        }
    }
}