// ======================================================================== //
// Copyright 2009-2017 Intel Corporation                                    //
//                                                                          //
// Licensed under the Apache License, Version 2.0 (the "License");          //
// you may not use this file except in compliance with the License.         //
// You may obtain a copy of the License at                                  //
//                                                                          //
//     http://www.apache.org/licenses/LICENSE-2.0                           //
//                                                                          //
// Unless required by applicable law or agreed to in writing, software      //
// distributed under the License is distributed on an "AS IS" BASIS,        //
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. //
// See the License for the specific language governing permissions and      //
// limitations under the License.                                           //
// ======================================================================== //

#include "../common/tutorial/tutorial_device.h"

namespace embree {

/* configuration */
#define EDGE_LEVEL 256.0f
#define ENABLE_SMOOTH_NORMALS 0

/* scene data */
RTCDevice g_device = nullptr;
RTCScene g_scene = nullptr;

/* previous camera position */
Vec3fa old_p;

__aligned(16) float cube_vertices[8][4] =
{
  { -1.0f, -1.0f, -1.0f, 0.0f },
  {  1.0f, -1.0f, -1.0f, 0.0f },
  {  1.0f, -1.0f,  1.0f, 0.0f },
  { -1.0f, -1.0f,  1.0f, 0.0f },
  { -1.0f,  1.0f, -1.0f, 0.0f },
  {  1.0f,  1.0f, -1.0f, 0.0f },
  {  1.0f,  1.0f,  1.0f, 0.0f },
  { -1.0f,  1.0f,  1.0f, 0.0f }
};

#if 1

#define NUM_INDICES 24
#define NUM_FACES 6
#define FACE_SIZE 4

unsigned int cube_indices[24] = {
  0, 1, 5, 4,
  1, 2, 6, 5,
  2, 3, 7, 6,
  0, 4, 7, 3,
  4, 5, 6, 7,
  0, 3, 2, 1,
};

unsigned int cube_faces[6] = {
  4, 4, 4, 4, 4, 4
};

#else

#define NUM_INDICES 36
#define NUM_FACES 12
#define FACE_SIZE 3

unsigned int cube_indices[36] = {
  1, 5, 4,  0, 1, 4,
  2, 6, 5,  1, 2, 5,
  3, 7, 6,  2, 3, 6,
  4, 7, 3,  0, 4, 3,
  5, 6, 7,  4, 5, 7,
  3, 2, 1,  0, 3, 1
};

unsigned int cube_faces[12] = {
  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3
};

#endif

float displacement(const Vec3fa& P)
{
  float dN = 0.0f;
  for (float freq = 1.0f; freq<40.0f; freq*= 2) {
    float n = abs(noise(freq*P));
    dN += 1.4f*n*n/freq;
  }
  return dN;
}

float displacement_du(const Vec3fa& P, const Vec3fa& dPdu)
{
  const float du = 0.001f;
  return (displacement(P+du*dPdu)-displacement(P))/du;
}

float displacement_dv(const Vec3fa& P, const Vec3fa& dPdv)
{
  const float dv = 0.001f;
  return (displacement(P+dv*dPdv)-displacement(P))/dv;
}

void displacementFunction(void* ptr, 
                                   unsigned int geomID, 
                                   unsigned int primID,
                                   unsigned int time,
                                   const float* u,      /*!< u coordinates (source) */
                                   const float* v,      /*!< v coordinates (source) */
                                   const float* nx,     /*!< x coordinates of normal at point to displace (source) */
                                   const float* ny,     /*!< y coordinates of normal at point to displace (source) */
                                   const float* nz,     /*!< z coordinates of normal at point to displace (source) */
                                   float* px,           /*!< x coordinates of points to displace (source and target) */
                                   float* py,           /*!< y coordinates of points to displace (source and target) */
                                   float* pz,           /*!< z coordinates of points to displace (source and target) */
                                   size_t N)
{
  for (unsigned int i=0; i<N; i++) {
    const Vec3fa P = Vec3fa(px[i],py[i],pz[i]);
    const Vec3fa Ng = Vec3fa(nx[i],ny[i],nz[i]);
    const Vec3fa dP = displacement(P)*Ng;
    px[i] += dP.x; py[i] += dP.y; pz[i] += dP.z;
  }
}

/* adds a cube to the scene */
unsigned int addCube (RTCScene scene_i)
{
  /* create a triangulated cube with 6 quads and 8 vertices */
  unsigned int geomID = rtcNewSubdivisionMesh(scene_i, RTC_GEOMETRY_STATIC, NUM_FACES, NUM_INDICES, 8, 0, 0, 0);

  rtcSetBuffer(scene_i, geomID, RTC_VERTEX_BUFFER, cube_vertices, 0, sizeof(Vec3fa  ));
  rtcSetBuffer(scene_i, geomID, RTC_INDEX_BUFFER,  cube_indices , 0, sizeof(unsigned int));
  rtcSetBuffer(scene_i, geomID, RTC_FACE_BUFFER,   cube_faces,    0, sizeof(unsigned int));

  float* level = (float*) rtcMapBuffer(scene_i, geomID, RTC_LEVEL_BUFFER);
  for (size_t i=0; i<NUM_INDICES; i++) level[i] = EDGE_LEVEL;
  rtcUnmapBuffer(scene_i, geomID, RTC_LEVEL_BUFFER);

  rtcSetDisplacementFunction2(scene_i,geomID,displacementFunction,nullptr);

  return geomID;
}

/* adds a ground plane to the scene */
unsigned int addGroundPlane (RTCScene scene_i)
{
  /* create a triangulated plane with 2 triangles and 4 vertices */
  unsigned int mesh = rtcNewTriangleMesh (scene_i, RTC_GEOMETRY_STATIC, 2, 4);

  /* set vertices */
  Vertex* vertices = (Vertex*) rtcMapBuffer(scene_i,mesh,RTC_VERTEX_BUFFER);
  vertices[0].x = -10; vertices[0].y = -2; vertices[0].z = -10;
  vertices[1].x = -10; vertices[1].y = -2; vertices[1].z = +10;
  vertices[2].x = +10; vertices[2].y = -2; vertices[2].z = -10;
  vertices[3].x = +10; vertices[3].y = -2; vertices[3].z = +10;
  rtcUnmapBuffer(scene_i,mesh,RTC_VERTEX_BUFFER);

  /* set triangles */
  Triangle* triangles = (Triangle*) rtcMapBuffer(scene_i,mesh,RTC_INDEX_BUFFER);
  triangles[0].v0 = 0; triangles[0].v1 = 2; triangles[0].v2 = 1;
  triangles[1].v0 = 1; triangles[1].v1 = 2; triangles[1].v2 = 3;
  rtcUnmapBuffer(scene_i,mesh,RTC_INDEX_BUFFER);

  return mesh;
}

/* called by the C++ code for initialization */
extern "C" void device_init (char* cfg)
{
  /* create new Embree device */
  g_device = rtcNewDevice(cfg);
  error_handler(rtcDeviceGetError(g_device));

  /* configure the size of the software cache used for subdivision geometry */
  rtcDeviceSetParameter1i(g_device,RTC_SOFTWARE_CACHE_SIZE,100*1024*1024);

  /* set error handler */
  rtcDeviceSetErrorFunction(g_device,error_handler);

  /* create scene */
  g_scene = rtcDeviceNewScene(g_device,RTC_SCENE_DYNAMIC | RTC_SCENE_ROBUST,RTC_INTERSECT1 | RTC_INTERPOLATE);

  /* add ground plane */
  addGroundPlane(g_scene);

  /* add cube */
  addCube(g_scene);

  /* commit changes to scene */
  rtcCommit (g_scene);

  /* set start render mode */
  renderTile = renderTileStandard;
  key_pressed_handler = device_key_pressed_default;
}

/* task that renders a single screen tile */
Vec3fa renderPixelStandard(float x, float y, const ISPCCamera& camera)
{
  /* initialize ray */
  RTCRay ray;
  ray.org = Vec3fa(camera.xfm.p);
  ray.dir = Vec3fa(normalize(x*camera.xfm.l.vx + y*camera.xfm.l.vy + camera.xfm.l.vz));
  ray.tnear = 0.0f;
  ray.tfar = inf;
  ray.geomID = RTC_INVALID_GEOMETRY_ID;
  ray.primID = RTC_INVALID_GEOMETRY_ID;
  ray.mask = -1;
  ray.time = 0;

  /* intersect ray with scene */
  rtcIntersect(g_scene,ray);

  /* shade pixels */
  Vec3fa color = Vec3fa(0.0f);
  if (ray.geomID != RTC_INVALID_GEOMETRY_ID)
  {
    Vec3fa diffuse = ray.geomID != 0 ? Vec3fa(0.9f,0.6f,0.5f) : Vec3fa(0.8f,0.0f,0.0f);
    color = color + diffuse*0.5f;
    Vec3fa lightDir = normalize(Vec3fa(-1,-1,-1));

    Vec3fa Ng = normalize(ray.Ng);
#if ENABLE_SMOOTH_NORMALS
    Vec3fa P = ray.org + ray.tfar*ray.dir;
    if (ray.geomID > 0) {
      Vec3fa dPdu,dPdv;
      unsigned int geomID = ray.geomID; {
        rtcInterpolate(g_scene,geomID,ray.primID,ray.u,ray.v,RTC_VERTEX_BUFFER,nullptr,&dPdu.x,&dPdv.x,3);
      }
      Ng = normalize(cross(dPdv,dPdu));
      dPdu = dPdu + Ng*displacement_du(P,dPdu);
      dPdv = dPdv + Ng*displacement_dv(P,dPdv);
      Ng = normalize(cross(dPdv,dPdu));
    }
#endif

    /* initialize shadow ray */
    RTCRay shadow;
    shadow.org = ray.org + ray.tfar*ray.dir;
    shadow.dir = neg(lightDir);
    shadow.tnear = 0.001f;
    shadow.tfar = inf;
    shadow.geomID = RTC_INVALID_GEOMETRY_ID;
    shadow.primID = RTC_INVALID_GEOMETRY_ID;
    shadow.mask = -1;
    shadow.time = 0;

    /* trace shadow ray */
    rtcOccluded(g_scene,shadow);

    /* add light contribution */
    if (shadow.geomID == RTC_INVALID_GEOMETRY_ID)
      color = color + diffuse*clamp(-(dot(lightDir,Ng)),0.0f,1.0f);
  }
  return color;
}

/* renders a single screen tile */
void renderTileStandard(int taskIndex,
                        int* pixels,
                        const unsigned int width,
                        const unsigned int height,
                        const float time,
                        const ISPCCamera& camera,
                        const int numTilesX,
                        const int numTilesY)
{
  const unsigned int tileY = taskIndex / numTilesX;
  const unsigned int tileX = taskIndex - tileY * numTilesX;
  const unsigned int x0 = tileX * TILE_SIZE_X;
  const unsigned int x1 = min(x0+TILE_SIZE_X,width);
  const unsigned int y0 = tileY * TILE_SIZE_Y;
  const unsigned int y1 = min(y0+TILE_SIZE_Y,height);

  for (unsigned int y=y0; y<y1; y++) for (unsigned int x=x0; x<x1; x++)
  {
    /* calculate pixel color */
    Vec3fa color = renderPixelStandard((float)x,(float)y,camera);

    /* write color to framebuffer */
    unsigned int r = (unsigned int) (255.0f * clamp(color.x,0.0f,1.0f));
    unsigned int g = (unsigned int) (255.0f * clamp(color.y,0.0f,1.0f));
    unsigned int b = (unsigned int) (255.0f * clamp(color.z,0.0f,1.0f));
    pixels[y*width+x] = (b << 16) + (g << 8) + r;
  }
}

/* task that renders a single screen tile */
void renderTileTask (int taskIndex, int* pixels,
                         const unsigned int width,
                         const unsigned int height,
                         const float time,
                         const ISPCCamera& camera,
                         const int numTilesX,
                         const int numTilesY)
{
  renderTile(taskIndex,pixels,width,height,time,camera,numTilesX,numTilesY);
}

/* called by the C++ code to render */
extern "C" void device_render (int* pixels,
                           const unsigned int width,
                           const unsigned int height,
                           const float time,
                           const ISPCCamera& camera)
{
  /* render image */
  const int numTilesX = (width +TILE_SIZE_X-1)/TILE_SIZE_X;
  const int numTilesY = (height+TILE_SIZE_Y-1)/TILE_SIZE_Y;
  parallel_for(size_t(0),size_t(numTilesX*numTilesY),[&](const range<size_t>& range) {
    for (size_t i=range.begin(); i<range.end(); i++)
      renderTileTask((int)i,pixels,width,height,time,camera,numTilesX,numTilesY);
  }); 
}

/* called by the C++ code for cleanup */
extern "C" void device_cleanup ()
{
  rtcDeleteScene (g_scene); g_scene = nullptr;
  rtcDeleteDevice(g_device); g_device = nullptr;
}

} // namespace embree