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

namespace UnityEngine.Experimental.Rendering.HDPipeline
{
    public class DecalSystem
    {
        public const int kInvalidIndex = -1;
        public class DecalHandle
        {
            public DecalHandle(int index, int materialID)
            {
                m_MaterialID = materialID;
                m_Index = index;
            }

            public static bool IsValid(DecalHandle handle)
            {
                if (handle == null)
                    return false;
                if (handle.m_Index == kInvalidIndex)
                    return false;
                return true;
            }
            public int m_MaterialID;    // identifies decal set
            public int m_Index;         // identifies decal within the set
        }

        static DecalSystem m_Instance;
        static public DecalSystem instance
        {
            get
            {
                if (m_Instance == null)
                    m_Instance = new DecalSystem();
                return m_Instance;
            }
        }

        private const int kDefaultDrawDistance = 1000;
        public int DrawDistance
        {
            get
            {
                HDRenderPipelineAsset hdrp = GraphicsSettings.renderPipelineAsset as HDRenderPipelineAsset;
                if (hdrp != null)
                {
                    return hdrp.renderPipelineSettings.decalSettings.drawDistance;
                }
                return kDefaultDrawDistance;
            }
        }

        public Camera CurrentCamera
        {
            get
            {
                return m_Camera;
            }
            set
            {
                m_Camera = value;
            }
        }

        private static MaterialPropertyBlock m_PropertyBlock = new MaterialPropertyBlock();

        private const int kDecalBlockSize = 128;

        // to work on Vulkan Mobile?
        // Core\CoreRP\ShaderLibrary\UnityInstancing.hlsl
        // #if defined(SHADER_API_VULKAN) && defined(SHADER_API_MOBILE)
        //      #define UNITY_INSTANCED_ARRAY_SIZE  250
        private const int kDrawIndexedBatchSize = 250;

        // cube mesh bounds for decal
        static Vector4 kMin = new Vector4(-0.5f, -1.0f, -0.5f, 1.0f);
        static Vector4 kMax = new Vector4( 0.5f,  0.0f,  0.5f, 1.0f);

        static public Mesh m_DecalMesh = null;

        // clustered draw data
        static public DecalData[] m_DecalDatas = new DecalData[kDecalBlockSize];
        static public SFiniteLightBound[] m_Bounds = new SFiniteLightBound[kDecalBlockSize];
        static public LightVolumeData[] m_LightVolumes = new LightVolumeData[kDecalBlockSize];
        static public int m_DecalDatasCount = 0;

		static public float[] m_BoundingDistances = new float[1];

        private Dictionary<int, DecalSet> m_DecalSets = new Dictionary<int, DecalSet>();

        // current camera
        private Camera m_Camera;

        static public int m_DecalsVisibleThisFrame = 0;

        private Texture2DAtlas m_Atlas = null;
        public bool m_AllocationSuccess = true;

        public Texture2DAtlas Atlas
        {
            get
            {
                if (m_Atlas == null)
                {
                    m_Atlas = new Texture2DAtlas(HDUtils.hdrpSettings.decalSettings.atlasWidth, HDUtils.hdrpSettings.decalSettings.atlasHeight, RenderTextureFormat.ARGB32);
                }
                return m_Atlas;
            }
        }

        public class TextureScaleBias : IComparable
        {
            public Texture m_Texture = null;
            public Vector4 m_ScaleBias = Vector4.zero;
            public int CompareTo(object obj)
            {
                TextureScaleBias other = obj as TextureScaleBias;
                int size = m_Texture.width * m_Texture.height;
                int otherSize = other.m_Texture.width * other.m_Texture.height;
                if(size > otherSize)
                {
                    return -1;
                }
                else if( size < otherSize)
                {
                    return 1;
                }
                else
                {
                    return 0;
                }                
            }
        }

        private List<TextureScaleBias> m_TextureList = new List<TextureScaleBias>();

        private class DecalSet
        {
            public void InitializeMaterialValues()
            {
                m_Diffuse.m_Texture = m_Material.GetTexture("_BaseColorMap");
                m_Normal.m_Texture = m_Material.GetTexture("_NormalMap");
                m_Mask.m_Texture = m_Material.GetTexture("_MaskMap");
                m_Blend = m_Material.GetFloat("_DecalBlend");
            }

            public DecalSet(Material material)
            {
                m_Material = material;
                InitializeMaterialValues();
            }

            private BoundingSphere GetDecalProjectBoundingSphere(Matrix4x4 decalToWorld)
            {
                Vector4 min = new Vector4();
                Vector4 max = new Vector4();
                min = decalToWorld * kMin;
                max = decalToWorld * kMax;
                BoundingSphere res = new BoundingSphere();
                res.position = (max + min) / 2;
                res.radius = ((Vector3) (max - min)).magnitude / 2;
                return res;
            }

            public void UpdateCachedData(Transform transform, float drawDistance, float fadeScale, DecalHandle handle) 
            {
                int index = handle.m_Index;
                m_CachedDecalToWorld[index] = transform.localToWorldMatrix;

                Matrix4x4 decalRotation = Matrix4x4.Rotate(transform.rotation);
                // z/y axis swap for normal to decal space, Unity is column major
                float y0 = decalRotation.m01;
                float y1 = decalRotation.m11;
                float y2 = decalRotation.m21;
                decalRotation.m01 = decalRotation.m02;
                decalRotation.m11 = decalRotation.m12;
                decalRotation.m21 = decalRotation.m22;
                decalRotation.m02 = y0;
                decalRotation.m12 = y1;
                decalRotation.m22 = y2;

                m_CachedNormalToWorld[index] = decalRotation;
                // draw distance can't be more than global draw distance
                m_CachedDrawDistances[index].x = drawDistance < instance.DrawDistance
                    ? drawDistance
                    : instance.DrawDistance;
                m_CachedDrawDistances[index].y = fadeScale;
                m_BoundingSpheres[index] = GetDecalProjectBoundingSphere(m_CachedDecalToWorld[index]);
            }

            public DecalHandle AddDecal(Transform transform, float drawDistance, float fadeScale, int materialID)
            {
                // increase array size if no space left
                if (m_DecalsCount == m_Handles.Length)
                {
                    DecalHandle[] newHandles = new DecalHandle[m_DecalsCount + kDecalBlockSize];
                    BoundingSphere[] newSpheres = new BoundingSphere[m_DecalsCount + kDecalBlockSize];
                    Matrix4x4[] newCachedTransforms = new Matrix4x4[m_DecalsCount + kDecalBlockSize];
                    Matrix4x4[] newCachedNormalToWorld = new Matrix4x4[m_DecalsCount + kDecalBlockSize];
                    Vector2[] newCachedDrawDistances = new Vector2[m_DecalsCount + kDecalBlockSize];
                    m_ResultIndices = new int[m_DecalsCount + kDecalBlockSize];

                    m_Handles.CopyTo(newHandles, 0);
                    m_BoundingSpheres.CopyTo(newSpheres, 0);
                    m_CachedDecalToWorld.CopyTo(newCachedTransforms, 0);
                    m_CachedNormalToWorld.CopyTo(newCachedNormalToWorld, 0);
                    m_CachedDrawDistances.CopyTo(newCachedDrawDistances, 0);

                    m_Handles = newHandles;
                    m_BoundingSpheres = newSpheres;
                    m_CachedDecalToWorld = newCachedTransforms;
                    m_CachedNormalToWorld = newCachedNormalToWorld;
                    m_CachedDrawDistances = newCachedDrawDistances;
                }

                DecalHandle decalHandle = new DecalHandle(m_DecalsCount, materialID);
                m_Handles[m_DecalsCount] = decalHandle;
                UpdateCachedData(transform, drawDistance, fadeScale, decalHandle);
                m_DecalsCount++;
                return decalHandle;
            }

            public void RemoveDecal(DecalHandle handle)
            {
                int removeAtIndex = handle.m_Index;
                // replace with last decal in the list and update index
                m_Handles[removeAtIndex] = m_Handles[m_DecalsCount - 1]; // move the last decal in list
                m_Handles[removeAtIndex].m_Index = removeAtIndex;
                m_Handles[m_DecalsCount - 1] = null;

                // update cached data
                m_BoundingSpheres[removeAtIndex] = m_BoundingSpheres[m_DecalsCount - 1];
                m_CachedDecalToWorld[removeAtIndex] = m_CachedDecalToWorld[m_DecalsCount - 1];
                m_CachedNormalToWorld[removeAtIndex] = m_CachedNormalToWorld[m_DecalsCount - 1];
                m_CachedDrawDistances[removeAtIndex] = m_CachedDrawDistances[m_DecalsCount - 1];
                m_DecalsCount--;
                handle.m_Index = kInvalidIndex;
            }

            public void BeginCull()
            {
                if (m_CullingGroup != null)
                {
                    Debug.LogError("Begin/EndCull() called out of sequence for decal projectors.");
                }

                // let the culling group code do some of the heavy lifting for global draw distance
                m_BoundingDistances[0] = DecalSystem.instance.DrawDistance;
                m_NumResults = 0;
                m_CullingGroup = new CullingGroup();
                m_CullingGroup.targetCamera = instance.CurrentCamera;
                m_CullingGroup.SetDistanceReferencePoint( m_CullingGroup.targetCamera.transform.position);
                m_CullingGroup.SetBoundingDistances(m_BoundingDistances);
                m_CullingGroup.SetBoundingSpheres(m_BoundingSpheres);
                m_CullingGroup.SetBoundingSphereCount(m_DecalsCount);
            }

            public int QueryCullResults()
            {
                m_NumResults = m_CullingGroup.QueryIndices(true, m_ResultIndices, 0);
                return m_NumResults;
            }

            private void GetDecalVolumeDataAndBound(Matrix4x4 decalToWorld, Matrix4x4 worldToView)
            {
                var influenceX = decalToWorld.GetColumn(0) * 0.5f;
                var influenceY = decalToWorld.GetColumn(1) * 0.5f;
                var influenceZ = decalToWorld.GetColumn(2) * 0.5f;
                var pos = decalToWorld.GetColumn(3) - influenceY; // decal cube mesh pivot is at 0,0,0, with bottom face at -1 on the y plane

                Vector3 influenceExtents = new Vector3();
                influenceExtents.x = influenceX.magnitude;
                influenceExtents.y = influenceY.magnitude;
                influenceExtents.z = influenceZ.magnitude;

                // transform to camera space (becomes a left hand coordinate frame in Unity since Determinant(worldToView)<0)
                var influenceRightVS = worldToView.MultiplyVector(influenceX / influenceExtents.x);
                var influenceUpVS = worldToView.MultiplyVector(influenceY / influenceExtents.y);
                var influenceForwardVS = worldToView.MultiplyVector(influenceZ / influenceExtents.z);
                var influencePositionVS = worldToView.MultiplyPoint(pos); // place the mesh pivot in the center

                m_Bounds[m_DecalDatasCount].center = influencePositionVS;
                m_Bounds[m_DecalDatasCount].boxAxisX = influenceRightVS * influenceExtents.x;
                m_Bounds[m_DecalDatasCount].boxAxisY = influenceUpVS * influenceExtents.y;
                m_Bounds[m_DecalDatasCount].boxAxisZ = influenceForwardVS * influenceExtents.z;
                m_Bounds[m_DecalDatasCount].scaleXY.Set(1.0f, 1.0f);
                m_Bounds[m_DecalDatasCount].radius = influenceExtents.magnitude;

                // The culling system culls pixels that are further
                //   than a threshold to the box influence extents.
                // So we use an arbitrary threshold here (k_BoxCullingExtentOffset)
                m_LightVolumes[m_DecalDatasCount].lightCategory = (uint)LightCategory.Decal;
                m_LightVolumes[m_DecalDatasCount].lightVolume = (uint)LightVolumeType.Box;
                m_LightVolumes[m_DecalDatasCount].featureFlags = (uint)LightFeatureFlags.Env;
                m_LightVolumes[m_DecalDatasCount].lightPos = influencePositionVS;
                m_LightVolumes[m_DecalDatasCount].lightAxisX = influenceRightVS;
                m_LightVolumes[m_DecalDatasCount].lightAxisY = influenceUpVS;
                m_LightVolumes[m_DecalDatasCount].lightAxisZ = influenceForwardVS;
                m_LightVolumes[m_DecalDatasCount].boxInnerDist = influenceExtents - LightLoop.k_BoxCullingExtentThreshold;
                m_LightVolumes[m_DecalDatasCount].boxInvRange.Set(1.0f / LightLoop.k_BoxCullingExtentThreshold.x, 1.0f /LightLoop. k_BoxCullingExtentThreshold.y, 1.0f / LightLoop.k_BoxCullingExtentThreshold.z);
            }

            private void AssignCurrentBatches(ref Matrix4x4[] decalToWorldBatch, ref Matrix4x4[] normalToWorldBatch, int batchCount)
            {
                if (m_DecalToWorld.Count == batchCount)
                {
                    decalToWorldBatch = new Matrix4x4[kDrawIndexedBatchSize];
                    m_DecalToWorld.Add(decalToWorldBatch);
                    normalToWorldBatch = new Matrix4x4[kDrawIndexedBatchSize];
                    m_NormalToWorld.Add(normalToWorldBatch);
                }
                else
                {
                    decalToWorldBatch = m_DecalToWorld[batchCount];
                    normalToWorldBatch = m_NormalToWorld[batchCount];
                }
            }

            public void CreateDrawData()
            {
                if (m_NumResults == 0)
                    return;

                int instanceCount = 0;
                int batchCount = 0;
                Matrix4x4[] decalToWorldBatch = null;
                Matrix4x4[] normalToWorldBatch = null;

                AssignCurrentBatches(ref decalToWorldBatch, ref normalToWorldBatch, batchCount);

                Vector3 cameraPos = instance.CurrentCamera.transform.position;
                Matrix4x4 worldToView = LightLoop.WorldToCamera(instance.CurrentCamera);
                for (int resultIndex = 0; resultIndex < m_NumResults; resultIndex++)
                {
                    int decalIndex = m_ResultIndices[resultIndex];
                    // do additional culling based on individual decal draw distances
                    float distanceToDecal = (cameraPos - m_BoundingSpheres[decalIndex].position).magnitude;
                    float cullDistance = m_CachedDrawDistances[decalIndex].x + m_BoundingSpheres[decalIndex].radius;
                    if (distanceToDecal < cullDistance)
                    {
                        // d-buffer data
                        decalToWorldBatch[instanceCount] = m_CachedDecalToWorld[decalIndex];
                        normalToWorldBatch[instanceCount] = m_CachedNormalToWorld[decalIndex];
                        float fadeFactor = Mathf.Clamp((cullDistance - distanceToDecal) / (cullDistance * (1.0f - m_CachedDrawDistances[decalIndex].y)), 0.0f, 1.0f);
                        normalToWorldBatch[instanceCount].m03 = fadeFactor * m_Blend;   // vector3 rotation matrix so bottom row and last column can be used for other data to save space

                        // clustered forward data
                        m_DecalDatas[m_DecalDatasCount].worldToDecal = decalToWorldBatch[instanceCount].inverse;
                        m_DecalDatas[m_DecalDatasCount].normalToWorld = normalToWorldBatch[instanceCount];
                        m_DecalDatas[m_DecalDatasCount].diffuseScaleBias = m_Diffuse.m_ScaleBias;
                        m_DecalDatas[m_DecalDatasCount].normalScaleBias = m_Normal.m_ScaleBias;
                        m_DecalDatas[m_DecalDatasCount].maskScaleBias = m_Mask.m_ScaleBias;
                        GetDecalVolumeDataAndBound(decalToWorldBatch[instanceCount], worldToView);
                        m_DecalDatasCount++;

                        instanceCount++;
                        if (instanceCount == kDrawIndexedBatchSize)
                        {
                            instanceCount = 0;
                            batchCount++;
                            AssignCurrentBatches(ref decalToWorldBatch, ref normalToWorldBatch, batchCount);
                        }
                    }
                }
            }

            public void EndCull()
            {
                if (m_CullingGroup == null)
                {
                    Debug.LogError("Begin/EndCull() called out of sequence for decal projectors.");
                }
                else
                {
                    m_CullingGroup.Dispose();
                    m_CullingGroup = null;
                }
            }

            public void AddToTextureList(ref List<TextureScaleBias> textureList)
            {
                if(m_Diffuse.m_Texture != null)
                {
                    textureList.Add(m_Diffuse);
                }
                if (m_Normal.m_Texture != null)
                {
                    textureList.Add(m_Normal);
                }
                if (m_Mask.m_Texture != null)
                {
                    textureList.Add(m_Mask);
                }
            }

           
           

            public void RenderIntoDBuffer(CommandBuffer cmd)
            {
                if(m_NumResults == 0)
                    return;
                int batchIndex = 0;
                int totalToDraw = m_NumResults;
                for (; batchIndex < m_NumResults / kDrawIndexedBatchSize; batchIndex++)
                {
                    m_PropertyBlock.SetMatrixArray(HDShaderIDs._NormalToWorldID, m_NormalToWorld[batchIndex]);
                    cmd.DrawMeshInstanced(m_DecalMesh, 0, KeyMaterial, 0, m_DecalToWorld[batchIndex], kDrawIndexedBatchSize, m_PropertyBlock);
                    totalToDraw -= kDrawIndexedBatchSize;
                }

                if(totalToDraw > 0)
                {
                    m_PropertyBlock.SetMatrixArray(HDShaderIDs._NormalToWorldID, m_NormalToWorld[batchIndex]);
                    cmd.DrawMeshInstanced(m_DecalMesh, 0, KeyMaterial, 0, m_DecalToWorld[batchIndex], totalToDraw, m_PropertyBlock);
                }
            }

            public Material KeyMaterial
            {
                get
                {
                    return this.m_Material;
                }
            }

            public int Count
            {
                get
                {
                    return this.m_DecalsCount;
                }
            }

            private List<Matrix4x4[]> m_DecalToWorld = new List<Matrix4x4[]>();
            private List<Matrix4x4[]> m_NormalToWorld = new List<Matrix4x4[]>();

            private CullingGroup m_CullingGroup = null;
            private BoundingSphere[] m_BoundingSpheres = new BoundingSphere[kDecalBlockSize];
            private DecalHandle[] m_Handles = new DecalHandle[kDecalBlockSize];
            private int[] m_ResultIndices = new int[kDecalBlockSize];
            private int m_NumResults = 0;
            private int m_DecalsCount = 0;
            private Matrix4x4[] m_CachedDecalToWorld = new Matrix4x4[kDecalBlockSize];
            private Matrix4x4[] m_CachedNormalToWorld = new Matrix4x4[kDecalBlockSize];
			private Vector2[] m_CachedDrawDistances = new Vector2[kDecalBlockSize]; // x - draw distance, y - fade scale
            private Material m_Material;
            private float m_Blend = 0;

            TextureScaleBias m_Diffuse = new TextureScaleBias();
            TextureScaleBias m_Normal = new TextureScaleBias();
            TextureScaleBias m_Mask = new TextureScaleBias();
        }

        public DecalHandle AddDecal(Transform transform, float drawDistance, float fadeScale, Material material)
        {			
            DecalSet decalSet = null;
            int key = material.GetInstanceID();
            if (!m_DecalSets.TryGetValue(key, out decalSet))
            {
                decalSet = new DecalSet(material);
                m_DecalSets.Add(key, decalSet);
            }
            return decalSet.AddDecal(transform, drawDistance, fadeScale, key);
        }

        public void RemoveDecal(DecalHandle handle)
        {
            if (!DecalHandle.IsValid(handle))
                return;

            DecalSet decalSet = null;
            int key = handle.m_MaterialID;
            if (m_DecalSets.TryGetValue(key, out decalSet))
            {
                decalSet.RemoveDecal(handle);
                if (decalSet.Count == 0)
                {
                    m_DecalSets.Remove(key);
                }
            }
        }

        public void UpdateCachedData(Transform transform, float drawDistance, float fadeScale, DecalHandle handle)
        {
            if(!DecalHandle.IsValid(handle))
                return;

            DecalSet decalSet = null;
            int key = handle.m_MaterialID;
            if (m_DecalSets.TryGetValue(key, out decalSet))
            {
                decalSet.UpdateCachedData(transform, drawDistance, fadeScale, handle);
            }
        }

        public void BeginCull()
        {
            foreach (var pair in m_DecalSets)
            {
                pair.Value.BeginCull();
            }
        }

		private int QueryCullResults()
		{
		    int totalVisibleDecals = 0;
            foreach (var pair in m_DecalSets)
            {
                totalVisibleDecals += pair.Value.QueryCullResults();
            }
		    return totalVisibleDecals;
		}

        public void EndCull()
        {
            m_DecalsVisibleThisFrame = QueryCullResults();
            foreach (var pair in m_DecalSets)
            {
                pair.Value.EndCull();
            }
        }
       
        public void RenderIntoDBuffer(CommandBuffer cmd)
        {
            if (m_DecalMesh == null)
                m_DecalMesh = CoreUtils.CreateCubeMesh(kMin, kMax);

            foreach (var pair in m_DecalSets)
            {
                pair.Value.RenderIntoDBuffer(cmd);
            }
        }

        public void SetAtlas(CommandBuffer cmd)
        {
            cmd.SetGlobalTexture(HDShaderIDs._DecalAtlas2DID, Atlas.AtlasTexture);
        }

        public void AddTexture(CommandBuffer cmd, TextureScaleBias textureScaleBias) 
        {
            if (textureScaleBias.m_Texture != null)
            {
                if (!Atlas.AddTexture(cmd, ref textureScaleBias.m_ScaleBias,textureScaleBias.m_Texture))
                {
                    m_AllocationSuccess = false;
                }
            }
            else
            {
                textureScaleBias.m_ScaleBias = Vector4.zero;
            }
        }

        // updates textures, texture atlas indices and blend value
        public void UpdateCachedMaterialData()
        {
            //instance.m_AllocationSuccess = true;
            m_TextureList.Clear();
            foreach (var pair in m_DecalSets)
            {
                pair.Value.InitializeMaterialValues();
                pair.Value.AddToTextureList(ref m_TextureList);
            }
        }

        public void UpdateTextureAtlas(CommandBuffer cmd)
        { 
            m_AllocationSuccess = true;
            foreach (TextureScaleBias textureScaleBias in m_TextureList)
            {
                AddTexture(cmd, textureScaleBias);
            }

            if (!m_AllocationSuccess) // texture failed to find space in the atlas
            {
                m_TextureList.Sort();   // sort the texture list largest to smallest for better packing
                Atlas.ResetAllocator(); // clear all allocations 
                // try again                
                m_AllocationSuccess = true;
                foreach (TextureScaleBias textureScaleBias in m_TextureList)
                {
                    AddTexture(cmd, textureScaleBias);
                }

                if(!m_AllocationSuccess) // still failed to allocate, decal atlas size needs to increase
                {
                    Debug.LogWarning("Decal texture atlas out of space, decals on transparent geometry might not render correctly, atlas size can be changed in HDRenderPipelineAsset");
                }
            }
        }

        public void CreateDrawData()
        {
            m_DecalDatasCount = 0;
            // reallocate if needed
            if (m_DecalsVisibleThisFrame > m_DecalDatas.Length)
            {
                int newDecalDatasSize = ((m_DecalsVisibleThisFrame + kDecalBlockSize - 1) / kDecalBlockSize) * kDecalBlockSize;
                m_DecalDatas = new DecalData[newDecalDatasSize];
                m_Bounds = new  SFiniteLightBound[newDecalDatasSize];
                m_LightVolumes = new LightVolumeData[newDecalDatasSize];
            }
            foreach (var pair in m_DecalSets)
            {
                pair.Value.CreateDrawData();
            }
        }

        public void Cleanup()
        {
            if (m_Atlas != null)
                m_Atlas.Release();
            CoreUtils.Destroy(m_DecalMesh);
            // set to null so that they get recreated
            m_DecalMesh = null;
            m_Atlas = null;
        }
    }
}