// Copyright 2009-2021 Intel Corporation
// SPDX-License-Identifier: Apache-2.0

#pragma once

#include "geometry.h"
#include "buffer.h"

namespace embree
{
  /*! Grid Mesh */
  struct GridMesh : public Geometry
  {
    /*! type of this geometry */
    static const Geometry::GTypeMask geom_type = Geometry::MTY_GRID_MESH;

    /*! grid */
    struct Grid 
    {
      unsigned int startVtxID;
      unsigned int lineVtxOffset;
      unsigned short resX,resY;

      /* border flags due to 3x3 vertex pattern */
      __forceinline unsigned int get3x3FlagsX(const unsigned int x) const
      {
        return (x + 2 >= (unsigned int)resX) ? (1<<15) : 0;
      }

      /* border flags due to 3x3 vertex pattern */
      __forceinline unsigned int get3x3FlagsY(const unsigned int y) const
      {
        return (y + 2 >= (unsigned int)resY) ? (1<<15) : 0;
      }

      /*! outputs grid structure */
      __forceinline friend embree_ostream operator<<(embree_ostream cout, const Grid& t) {
        return cout << "Grid { startVtxID " << t.startVtxID << ", lineVtxOffset " << t.lineVtxOffset << ", resX " << t.resX << ", resY " << t.resY << " }";
      }
    };

  public:

    /*! grid mesh construction */
    GridMesh (Device* device); 

    /* geometry interface */
  public:
    void setMask(unsigned mask);
    void setNumTimeSteps (unsigned int numTimeSteps);
    void setVertexAttributeCount (unsigned int N);
    void setBuffer(RTCBufferType type, unsigned int slot, RTCFormat format, const Ref<Buffer>& buffer, size_t offset, size_t stride, unsigned int num);
    void* getBuffer(RTCBufferType type, unsigned int slot);
    void updateBuffer(RTCBufferType type, unsigned int slot);
    void commit();
    bool verify();
    void interpolate(const RTCInterpolateArguments* const args);

    template<int N>
    void interpolate_impl(const RTCInterpolateArguments* const args)
    {
      unsigned int primID = args->primID;
      float U = args->u;
      float V = args->v;
      
      /* clamp input u,v to [0;1] range */
      U = max(min(U,1.0f),0.0f);
      V = max(min(V,1.0f),0.0f);
      
      RTCBufferType bufferType = args->bufferType;
      unsigned int bufferSlot = args->bufferSlot;
      float* P = args->P;
      float* dPdu = args->dPdu;
      float* dPdv = args->dPdv;
      float* ddPdudu = args->ddPdudu;
      float* ddPdvdv = args->ddPdvdv;
      float* ddPdudv = args->ddPdudv;
      unsigned int valueCount = args->valueCount;
      
      /* calculate base pointer and stride */
      assert((bufferType == RTC_BUFFER_TYPE_VERTEX && bufferSlot < numTimeSteps) ||
             (bufferType == RTC_BUFFER_TYPE_VERTEX_ATTRIBUTE && bufferSlot <= vertexAttribs.size()));
      const char* src = nullptr; 
      size_t stride = 0;
      if (bufferType == RTC_BUFFER_TYPE_VERTEX_ATTRIBUTE) {
        src    = vertexAttribs[bufferSlot].getPtr();
        stride = vertexAttribs[bufferSlot].getStride();
      } else {
        src    = vertices[bufferSlot].getPtr();
        stride = vertices[bufferSlot].getStride();
      }
      
      const Grid& grid = grids[primID];
      const int grid_width  = grid.resX-1;
      const int grid_height = grid.resY-1;
      const float rcp_grid_width = rcp(float(grid_width));
      const float rcp_grid_height = rcp(float(grid_height));
      const int iu = min((int)floor(U*grid_width ),grid_width);
      const int iv = min((int)floor(V*grid_height),grid_height);
      const float u = U*grid_width-float(iu);
      const float v = V*grid_height-float(iv);
      
      for (unsigned int i=0; i<valueCount; i+=N)
      {
        const size_t ofs = i*sizeof(float);
        const unsigned int idx0 = grid.startVtxID + (iv+0)*grid.lineVtxOffset + iu;
        const unsigned int idx1 = grid.startVtxID + (iv+1)*grid.lineVtxOffset + iu;
        
        const vbool<N> valid = vint<N>((int)i)+vint<N>(step) < vint<N>(int(valueCount));
        const vfloat<N> p0 = mem<vfloat<N>>::loadu(valid,(float*)&src[(idx0+0)*stride+ofs]);
        const vfloat<N> p1 = mem<vfloat<N>>::loadu(valid,(float*)&src[(idx0+1)*stride+ofs]);
        const vfloat<N> p2 = mem<vfloat<N>>::loadu(valid,(float*)&src[(idx1+1)*stride+ofs]);
        const vfloat<N> p3 = mem<vfloat<N>>::loadu(valid,(float*)&src[(idx1+0)*stride+ofs]);
        const vbool<N> left = u+v <= 1.0f;
        const vfloat<N> Q0 = select(left,p0,p2);
        const vfloat<N> Q1 = select(left,p1,p3);
        const vfloat<N> Q2 = select(left,p3,p1);
        const vfloat<N> U  = select(left,u,vfloat<N>(1.0f)-u);
        const vfloat<N> V  = select(left,v,vfloat<N>(1.0f)-v);
        const vfloat<N> W  = 1.0f-U-V;
        
        if (P) {
          mem<vfloat<N>>::storeu(valid,P+i,madd(W,Q0,madd(U,Q1,V*Q2)));
        }
        if (dPdu) { 
          assert(dPdu); mem<vfloat<N>>::storeu(valid,dPdu+i,select(left,Q1-Q0,Q0-Q1)*rcp_grid_width);
          assert(dPdv); mem<vfloat<N>>::storeu(valid,dPdv+i,select(left,Q2-Q0,Q0-Q2)*rcp_grid_height);
        }
        if (ddPdudu) { 
          assert(ddPdudu); mem<vfloat<N>>::storeu(valid,ddPdudu+i,vfloat<N>(zero));
          assert(ddPdvdv); mem<vfloat<N>>::storeu(valid,ddPdvdv+i,vfloat<N>(zero));
          assert(ddPdudv); mem<vfloat<N>>::storeu(valid,ddPdudv+i,vfloat<N>(zero));
        }
      }
    }
    
    void addElementsToCount (GeometryCounts & counts) const;
    
    __forceinline unsigned int getNumSubGrids(const size_t gridID)
    {
      const Grid &g = grid(gridID);
      return max((unsigned int)1,((unsigned int)g.resX >> 1) * ((unsigned int)g.resY >> 1));
    }

    /*! get fast access to first vertex buffer */
    __forceinline float * getCompactVertexArray () const {
      return (float*) vertices0.getPtr();
    }

  public:

    /*! returns number of vertices */
    __forceinline size_t numVertices() const {
      return vertices[0].size();
    }
    
    /*! returns i'th grid*/
    __forceinline const Grid& grid(size_t i) const {
      return grids[i];
    }

    /*! returns i'th vertex of the first time step  */
    __forceinline const Vec3fa vertex(size_t i) const { // FIXME: check if this does a unaligned load
      return vertices0[i];
    }

    /*! returns i'th vertex of the first time step */
    __forceinline const char* vertexPtr(size_t i) const {
      return vertices0.getPtr(i);
    }

    /*! returns i'th vertex of itime'th timestep */
    __forceinline const Vec3fa vertex(size_t i, size_t itime) const {
      return vertices[itime][i];
    }

    /*! returns i'th vertex of itime'th timestep */
    __forceinline const char* vertexPtr(size_t i, size_t itime) const {
      return vertices[itime].getPtr(i);
    }

    /*! returns i'th vertex of the first timestep */
    __forceinline size_t grid_vertex_index(const Grid& g, size_t x, size_t y) const {
      assert(x < (size_t)g.resX);
      assert(y < (size_t)g.resY);
      return g.startVtxID + x + y * g.lineVtxOffset;
    }
    
    /*! returns i'th vertex of the first timestep */
    __forceinline const Vec3fa grid_vertex(const Grid& g, size_t x, size_t y) const {
      const size_t index = grid_vertex_index(g,x,y);
      return vertex(index);
    }

    /*! returns i'th vertex of the itime'th timestep */
    __forceinline const Vec3fa grid_vertex(const Grid& g, size_t x, size_t y, size_t itime) const {
      const size_t index = grid_vertex_index(g,x,y);
      return vertex(index,itime);
    }

    /*! calculates the build bounds of the i'th primitive, if it's valid */
    __forceinline bool buildBounds(const Grid& g, size_t sx, size_t sy, BBox3fa& bbox) const
    {
      BBox3fa b(empty);
      for (size_t t=0; t<numTimeSteps; t++)
      {
        for (size_t y=sy;y<min(sy+3,(size_t)g.resY);y++)
          for (size_t x=sx;x<min(sx+3,(size_t)g.resX);x++)
          {
            const Vec3fa v = grid_vertex(g,x,y,t);
            if (unlikely(!isvalid(v))) return false;
            b.extend(v);
          }
      }

      bbox = b;
      return true;
    }

    /*! calculates the build bounds of the i'th primitive at the itime'th time segment, if it's valid */
    __forceinline bool buildBounds(const Grid& g, size_t sx, size_t sy, size_t itime, BBox3fa& bbox) const
    {
      assert(itime < numTimeSteps);
      BBox3fa b0(empty);
      for (size_t y=sy;y<min(sy+3,(size_t)g.resY);y++)
        for (size_t x=sx;x<min(sx+3,(size_t)g.resX);x++)
        {
          const Vec3fa v = grid_vertex(g,x,y,itime);
          if (unlikely(!isvalid(v))) return false;
          b0.extend(v);
        }

      /* use bounds of first time step in builder */
      bbox = b0;
      return true;
    }

    __forceinline bool valid(size_t gridID, size_t itime=0) const {
      return valid(gridID, make_range(itime, itime));
    }

    /*! check if the i'th primitive is valid between the specified time range */
    __forceinline bool valid(size_t gridID, const range<size_t>& itime_range) const
    {
      if (unlikely(gridID >= grids.size())) return false;
      const Grid &g = grid(gridID);
      if (unlikely(g.startVtxID + 0                                     >= vertices0.size())) return false;
      if (unlikely(g.startVtxID + (g.resY-1)*g.lineVtxOffset + g.resX-1 >= vertices0.size())) return false;

      for (size_t y=0;y<g.resY;y++)
        for (size_t x=0;x<g.resX;x++)
          for (size_t itime = itime_range.begin(); itime <= itime_range.end(); itime++)
            if (!isvalid(grid_vertex(g,x,y,itime))) return false;
      return true;
    }


    __forceinline BBox3fa bounds(const Grid& g, size_t sx, size_t sy, size_t itime) const
    {
      BBox3fa box(empty);
      buildBounds(g,sx,sy,itime,box);
      return box;
    }

    __forceinline LBBox3fa linearBounds(const Grid& g, size_t sx, size_t sy, size_t itime) const {
      BBox3fa bounds0, bounds1;
      buildBounds(g,sx,sy,itime+0,bounds0);
      buildBounds(g,sx,sy,itime+1,bounds1);
      return LBBox3fa(bounds0,bounds1);
    }

    /*! calculates the linear bounds of the i'th primitive for the specified time range */
    __forceinline LBBox3fa linearBounds(const Grid& g, size_t sx, size_t sy, const BBox1f& dt) const {
      return LBBox3fa([&] (size_t itime) { return bounds(g,sx,sy,itime); }, dt, time_range, fnumTimeSegments);
    }

  public:
    BufferView<Grid> grids;      //!< array of triangles
    BufferView<Vec3fa> vertices0;        //!< fast access to first vertex buffer
    vector<BufferView<Vec3fa>> vertices; //!< vertex array for each timestep
    vector<RawBufferView> vertexAttribs; //!< vertex attributes
  };

  namespace isa
  {
    struct GridMeshISA : public GridMesh
    {
      GridMeshISA (Device* device)
        : GridMesh(device) {}
    };
  }

  DECLARE_ISA_FUNCTION(GridMesh*, createGridMesh, Device*);
}