// ======================================================================== //
// 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 {

/* scene data */
RTCDevice g_device = nullptr;
RTCScene g_scene = nullptr;
Vec3fa* face_colors = nullptr;
Vec3fa* vertex_colors = nullptr;

/* adds a cube to the scene */
unsigned int addCube (RTCScene scene_i)
{
  /* create a triangulated cube with 12 triangles and 8 vertices */
  unsigned int mesh = rtcNewTriangleMesh (scene_i, RTC_GEOMETRY_STATIC, 12, 8);

  /* create face and vertex color arrays */
  face_colors = (Vec3fa*) alignedMalloc(12*sizeof(Vec3fa));
  vertex_colors = (Vec3fa*) alignedMalloc(8*sizeof(Vec3fa));

  /* set vertices and vertex colors */
  Vertex* vertices = (Vertex*) rtcMapBuffer(scene_i,mesh,RTC_VERTEX_BUFFER);
  vertex_colors[0] = Vec3fa(0,0,0); vertices[0].x = -1; vertices[0].y = -1; vertices[0].z = -1;
  vertex_colors[1] = Vec3fa(0,0,1); vertices[1].x = -1; vertices[1].y = -1; vertices[1].z = +1;
  vertex_colors[2] = Vec3fa(0,1,0); vertices[2].x = -1; vertices[2].y = +1; vertices[2].z = -1;
  vertex_colors[3] = Vec3fa(0,1,1); vertices[3].x = -1; vertices[3].y = +1; vertices[3].z = +1;
  vertex_colors[4] = Vec3fa(1,0,0); vertices[4].x = +1; vertices[4].y = -1; vertices[4].z = -1;
  vertex_colors[5] = Vec3fa(1,0,1); vertices[5].x = +1; vertices[5].y = -1; vertices[5].z = +1;
  vertex_colors[6] = Vec3fa(1,1,0); vertices[6].x = +1; vertices[6].y = +1; vertices[6].z = -1;
  vertex_colors[7] = Vec3fa(1,1,1); vertices[7].x = +1; vertices[7].y = +1; vertices[7].z = +1;
  rtcUnmapBuffer(scene_i,mesh,RTC_VERTEX_BUFFER);

  /* set triangles and face colors */
  int tri = 0;
  Triangle* triangles = (Triangle*) rtcMapBuffer(scene_i,mesh,RTC_INDEX_BUFFER);

  // left side
  face_colors[tri] = Vec3fa(1,0,0); triangles[tri].v0 = 0; triangles[tri].v1 = 2; triangles[tri].v2 = 1; tri++;
  face_colors[tri] = Vec3fa(1,0,0); triangles[tri].v0 = 1; triangles[tri].v1 = 2; triangles[tri].v2 = 3; tri++;

  // right side
  face_colors[tri] = Vec3fa(0,1,0); triangles[tri].v0 = 4; triangles[tri].v1 = 5; triangles[tri].v2 = 6; tri++;
  face_colors[tri] = Vec3fa(0,1,0); triangles[tri].v0 = 5; triangles[tri].v1 = 7; triangles[tri].v2 = 6; tri++;

  // bottom side
  face_colors[tri] = Vec3fa(0.5f);  triangles[tri].v0 = 0; triangles[tri].v1 = 1; triangles[tri].v2 = 4; tri++;
  face_colors[tri] = Vec3fa(0.5f);  triangles[tri].v0 = 1; triangles[tri].v1 = 5; triangles[tri].v2 = 4; tri++;

  // top side
  face_colors[tri] = Vec3fa(1.0f);  triangles[tri].v0 = 2; triangles[tri].v1 = 6; triangles[tri].v2 = 3; tri++;
  face_colors[tri] = Vec3fa(1.0f);  triangles[tri].v0 = 3; triangles[tri].v1 = 6; triangles[tri].v2 = 7; tri++;

  // front side
  face_colors[tri] = Vec3fa(0,0,1); triangles[tri].v0 = 0; triangles[tri].v1 = 4; triangles[tri].v2 = 2; tri++;
  face_colors[tri] = Vec3fa(0,0,1); triangles[tri].v0 = 2; triangles[tri].v1 = 4; triangles[tri].v2 = 6; tri++;

  // back side
  face_colors[tri] = Vec3fa(1,1,0); triangles[tri].v0 = 1; triangles[tri].v1 = 3; triangles[tri].v2 = 5; tri++;
  face_colors[tri] = Vec3fa(1,1,0); triangles[tri].v0 = 3; triangles[tri].v1 = 7; triangles[tri].v2 = 5; tri++;

  rtcUnmapBuffer(scene_i,mesh,RTC_INDEX_BUFFER);

  rtcSetBuffer(scene_i,mesh,RTC_USER_VERTEX_BUFFER0,vertex_colors,0,sizeof(Vec3fa));

  return mesh;
}

/* 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));

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

  /* create scene */
  g_scene = rtcDeviceNewScene(g_device, RTC_SCENE_STATIC,RTC_INTERSECT1);

  /* add cube */
  addCube(g_scene);

  /* add ground plane */
  addGroundPlane(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 = face_colors[ray.primID];
    color = color + diffuse*0.5f;
    Vec3fa lightDir = normalize(Vec3fa(-1,-1,-1));

    /* 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 = 1;
    shadow.primID = 0;
    shadow.mask = -1;
    shadow.time = 0;

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

    /* add light contribution */
    if (shadow.geomID)
      color = color + diffuse*clamp(-dot(lightDir,normalize(ray.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)
{
  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;
  alignedFree(face_colors); face_colors = nullptr;
  alignedFree(vertex_colors); vertex_colors = nullptr;
}

} // namespace embree