// ======================================================================== //
// Copyright 2009-2014 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.isph"

#define PARALLEL_COMMIT

/* scene data */
RTCScene g_scene = NULL;
uniform Vec3f* uniform colors = NULL;

/* render function to use */
renderPixelFunc renderPixel;

/* error reporting function */
void error_handler(const uniform RTCError code, const uniform int8* uniform str)
{
  print("Embree: ");
  switch (code) {
  case RTC_UNKNOWN_ERROR    : print("RTC_UNKNOWN_ERROR"); break;
  case RTC_INVALID_ARGUMENT : print("RTC_INVALID_ARGUMENT"); break;
  case RTC_INVALID_OPERATION: print("RTC_INVALID_OPERATION"); break;
  case RTC_OUT_OF_MEMORY    : print("RTC_OUT_OF_MEMORY"); break;
  case RTC_UNSUPPORTED_CPU  : print("RTC_UNSUPPORTED_CPU"); break;
  default                   : print("invalid error code"); break;
  }
  if (str) { 
    print(" ("); 
    while (*str) putchar(*str++); 
    print(")\n"); 
  }
  abort();
}

/* rtcCommitThread called by all ISPC worker threads to enable parallel build */
#if defined(PARALLEL_COMMIT)
task void parallelCommit(RTCScene scene) {
  rtcCommitThread (scene,threadIndex,threadCount); 
}
#endif

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

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

  /* create triangle color array */
  colors = uniform new uniform Vec3f[12];

  /* set triangles and colors */
  uniform int tri = 0;
  uniform Triangle* uniform triangles = (uniform Triangle* uniform) rtcMapBuffer(scene_i,mesh,RTC_INDEX_BUFFER);
  
  // left side
  colors[tri] = make_Vec3f(1,0,0); triangles[tri].v0 = 0; triangles[tri].v1 = 2; triangles[tri].v2 = 1; tri++;
  colors[tri] = make_Vec3f(1,0,0); triangles[tri].v0 = 1; triangles[tri].v1 = 2; triangles[tri].v2 = 3; tri++;

  // right side
  colors[tri] = make_Vec3f(0,1,0); triangles[tri].v0 = 4; triangles[tri].v1 = 5; triangles[tri].v2 = 6; tri++;
  colors[tri] = make_Vec3f(0,1,0); triangles[tri].v0 = 5; triangles[tri].v1 = 7; triangles[tri].v2 = 6; tri++;

  // bottom side
  colors[tri] = make_Vec3f(0.5f);  triangles[tri].v0 = 0; triangles[tri].v1 = 1; triangles[tri].v2 = 4; tri++;
  colors[tri] = make_Vec3f(0.5f);  triangles[tri].v0 = 1; triangles[tri].v1 = 5; triangles[tri].v2 = 4; tri++;

  // top side
  colors[tri] = make_Vec3f(1.0f);  triangles[tri].v0 = 2; triangles[tri].v1 = 6; triangles[tri].v2 = 3; tri++;
  colors[tri] = make_Vec3f(1.0f);  triangles[tri].v0 = 3; triangles[tri].v1 = 6; triangles[tri].v2 = 7; tri++;

  // front side
  colors[tri] = make_Vec3f(0,0,1); triangles[tri].v0 = 0; triangles[tri].v1 = 4; triangles[tri].v2 = 2; tri++;
  colors[tri] = make_Vec3f(0,0,1); triangles[tri].v0 = 2; triangles[tri].v1 = 4; triangles[tri].v2 = 6; tri++;

  // back side
  colors[tri] = make_Vec3f(1,1,0); triangles[tri].v0 = 1; triangles[tri].v1 = 3; triangles[tri].v2 = 5; tri++;
  colors[tri] = make_Vec3f(1,1,0); triangles[tri].v0 = 3; triangles[tri].v1 = 7; triangles[tri].v2 = 5; tri++;

  rtcUnmapBuffer(scene_i,mesh,RTC_INDEX_BUFFER);

  return mesh;
}

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

  /* set vertices */
  uniform Vertex* uniform vertices = (uniform Vertex* uniform) 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 */
  uniform Triangle* uniform triangles = (uniform Triangle* uniform) 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 */
export void device_init (uniform int8* uniform cfg)
{
  /* initialize ray tracing core */
  rtcInit(cfg);

  /* set error handler */
  rtcSetErrorFunction(error_handler);
 
  /* create scene */
  g_scene = rtcNewScene(RTC_SCENE_STATIC,RTC_INTERSECT_UNIFORM | RTC_INTERSECT_VARYING);

  /* add cube */
  addCube(g_scene);

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

  /* commit changes to scene */

#if !defined(PARALLEL_COMMIT)
  rtcCommit (g_scene);
#else
  launch[ getNumHWThreads() ] parallelCommit(g_scene); sync;
#endif

  /* set start render mode */
  renderPixel = renderPixelStandard;
}

/* task that renders a single screen tile */
Vec3f renderPixelStandard(float x, float y, const uniform Vec3f& vx, const uniform Vec3f& vy, const uniform Vec3f& vz, const uniform Vec3f& p)
{
  /* initialize ray */
  RTCRay ray;
  ray.org = p;
  ray.dir = normalize(x*vx + y*vy + 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 */
  Vec3f color = make_Vec3f(0.0f);
  if (ray.geomID != RTC_INVALID_GEOMETRY_ID) 
  {
    Vec3f diffuse = colors[ray.primID];
    color = color + diffuse*0.5f; // FIXME: +=
    Vec3f lightDir = normalize(make_Vec3f(-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); // FIXME: +=
  }
  return color;
}

unsigned int rand_lcg(unsigned int &rng_state)
{
    // LCG values from Numerical Recipes
    rng_state = 1664525 * rng_state + 1013904223;
    return rng_state;
}
 
unsigned int rand_xorshift(unsigned int &rng_state)
{
    // Xorshift algorithm from George Marsaglia's paper
    rng_state ^= (rng_state << 13);
    rng_state ^= (rng_state >> 17);
    rng_state ^= (rng_state << 5);
    return rng_state;
}

unsigned int wang_hash(unsigned int &seed)
{
    seed = (seed ^ 61) ^ (seed >> 16);
    seed *= 9;
    seed = seed ^ (seed >> 4);
    seed *= 0x27d4eb2d;
    seed = seed ^ (seed >> 15);
    return seed;
}

/* task that renders a single screen tile */
task void renderTile(uniform int* uniform pixels,
                     const uniform int width,
                     const uniform int height, 
                     const uniform float time,
                     const uniform Vec3f& vx, 
                     const uniform Vec3f& vy, 
                     const uniform Vec3f& vz, 
                     const uniform Vec3f& p,
                     const uniform int numTilesX, 
                     const uniform int numTilesY)
{
  const uniform int tileY = taskIndex / numTilesX;
  const uniform int tileX = taskIndex - tileY * numTilesX;
  const uniform int x0 = tileX * TILE_SIZE_X;
  const uniform int x1 = min(x0+TILE_SIZE_X,width);
  const uniform int y0 = tileY * TILE_SIZE_Y;
  const uniform int y1 = min(y0+TILE_SIZE_Y,height);

  //unsigned int seed = tileY*numTilesX+tileX+programIndex;

  //seed = wang_hash( seed );
   
  foreach (y = y0 ... y1, x = x0 ... x1)
  {
   unsigned int seed = y * width + x + programIndex;
   rand_xorshift(seed);
   rand_xorshift(seed);

    /* calculate pixel color */
    Vec3f color = renderPixel(x,y,vx,vy,vz,p);
    //float f = ((float)rand_xorshift(seed)) * (1.0f / 4294967296.0f);
    //float f = ((float)wang_hash(seed)) * (1.0f / 4294967296.0f);
    //Vec3f color = make_Vec3f(f);

    /* 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;
  }
}

/* called by the C++ code to render */
export void device_render (uniform int* uniform pixels,
                    const uniform int width,
                    const uniform int height,
                    const uniform float time,
                    const uniform Vec3f& vx, 
                    const uniform Vec3f& vy, 
                    const uniform Vec3f& vz, 
                    const uniform Vec3f& p)
{
  const uniform int numTilesX = (width +TILE_SIZE_X-1)/TILE_SIZE_X;
  const uniform int numTilesY = (height+TILE_SIZE_Y-1)/TILE_SIZE_Y;
  launch[numTilesX*numTilesY] renderTile(pixels,width,height,time,vx,vy,vz,p,numTilesX,numTilesY); sync;
  rtcDebug();
}

/* called by the C++ code for cleanup */
export void device_cleanup ()
{
  rtcDeleteScene (g_scene);
  delete[] colors;
  rtcExit();
}