#include "world.h"
#include "game.h"

float hashWorldPosition(Vector3 position, Vector3 size)
{
  return (position.z * size.y) + (position.y * size.x) + position.x;
}

void sortEntitiesUID(WorldUID entities[WORLD_ENTITY_MAX], const World* world)
{
  // Lazy selection sort.
  for (int outer = 0; outer < WORLD_ENTITY_MAX - 1; ++outer)
  {
    int minIndex = outer;

    for (int inner = outer + 1; inner < WORLD_ENTITY_MAX; ++inner)
    {
      float entityHash = hashWorldPosition(
        world->entities[entities[inner]].position, world->size);
      float minHash = hashWorldPosition(
        world->entities[entities[minIndex]].position, world->size);

      if (entityHash < minHash)
      {
        minIndex = inner;
      }
    }

    WorldUID temp = entities[outer];
    entities[outer] = entities[minIndex];
    entities[minIndex] = temp;
  }
}

// Bottom up method because bottom up better. Just if politicians agreed ):
void buildWorldBVH(World* world)
{
  Entity* entities = world->entities;
  bool grouped[WORLD_ENTITY_MAX];

  // This is a mess thats not going to work.
  for (int index = 0; index < WORLD_ENTITY_MAX; ++index)
  {
    grouped[index] = false;
  }

  int nodeCount = 0;
  
  for (int nodeIndex = 0; nodeIndex < WORLD_ENTITY_MAX; ++nodeIndex)
  {
    if (grouped[nodeIndex])
    {
      continue;
    }
    
    BVHNode leaf;
    leaf.branch1 = NULL;
    leaf.branch2 = NULL;
    leaf.entities[0] = nodeIndex;
    grouped[nodeIndex] = true;

    int leafIndex = 0;

    for (int outer = 0; outer < WORLD_ENTITY_MAX; ++outer)
    {
      if (grouped[outer])
      {
        continue;
      }
      
      int closest = outer;
      
      float closestDistance = Vector3Distance(
        entities[closest].position,
        entities[nodeIndex].position);
      
      for (int inner = 0; inner < WORLD_ENTITY_MAX; ++inner)
      {
        if (grouped[inner])
        {
          continue;
        }
        
        float distance = Vector3Distance(
          entities[inner].position,
          entities[nodeIndex].position);

        if (distance < closestDistance)
        {
          closest = inner;
          closestDistance = distance;
        }
      }

      leaf.entities[leafIndex] = closest;
      grouped[closest] = true;
      ++leafIndex;

      if (leafIndex >= BVH_MAX)
      {
        break;
      }
    }

    // Create bounding box.
    leaf.box.min = entities[leaf.entities[0]].position;
    leaf.box.max = entities[leaf.entities[0]].position;

    for (int index = 1; index < BVH_MAX; ++index)
    {
      leaf.box.min = Vector3Min(leaf.box.min,
                                entities[leaf.entities[index]].position);
      leaf.box.max = Vector3Max(leaf.box.max,
                                entities[leaf.entities[index]].position);
    }

    world->bvhTest[nodeCount] = leaf;
    ++nodeCount;

    if (nodeCount >= 250)
    {
      break;
    }
  }

  // test
  for (int index = 0; index < WORLD_ENTITY_MAX; ++index)
  {
    if (!grouped[index])
    {
      printf("%d\n", index);
    }
  }
}

World createWorld(int seed)
{
  World world;
  world.size = WORLD_SIZE;

  // Heightmap image.
  int offsetX = FT_RANDOM16(seed);
  int offsetY = FT_RANDOM16(seed);
  Image image = GenImagePerlinNoise(WORLD_IMAGE_WIDTH, WORLD_IMAGE_HEIGHT,
                                    offsetX, offsetY, WORLD_IMAGE_SCALE);

  // Heightmap.
  Mesh mesh = GenMeshHeightmap(image, world.size);
  world.heightmap = LoadModelFromMesh(mesh);
  world.texture = LoadTextureFromImage(image);
  world.heightmap.materials[0].maps[MATERIAL_MAP_DIFFUSE].texture =
    world.texture;

  UnloadImage(image);

  // Entities.
  for (int index = 0; index < WORLD_ENTITY_MAX; ++index)
  {
    FT_RANDOM16(seed);
    
    Entity entity = createEntity(seed % ENTITY_COUNT, Vector3Zero());
    entity.position.x = FT_RANDOM16(seed) % (int)world.size.x;
    entity.position.z = FT_RANDOM16(seed) % (int)world.size.z;
    entity.position.y = getWorldHeightAtLocation(world, entity.position.x,
                                                 entity.position.z) + 1.0;
    world.entities[index] = entity;
  }

  buildWorldBVH(&world);

  return world;
}

void updateWorld(World* world, Game* game)
{
  DrawModel(world->heightmap, Vector3Zero(), 1.0, WHITE);

  for (int index = 0; index < WORLD_ENTITY_MAX; ++index)
  {
    updateEntity(&world->entities[index], game);
  }

  for (int index = 0; index < 250; ++index)
  {
    Color colors[] = {RED, GREEN, BLUE, ORANGE, YELLOW, PINK};
    DrawBoundingBox(world->bvhTest[index].box, colors[index % 6]);
  }
}

void freeWorld(World world)
{
  UnloadTexture(world.texture);
  UnloadModel(world.heightmap);
}

float getWorldHeightAtLocation(World world, float x, float y)
{
  float toMapX = (float)world.texture.width / world.size.x;
  float toMapY = (float)world.texture.height / world.size.z;
  int pixelX = x * toMapX;
  int pixelY = y * toMapY;

  int verticeStart = (pixelY * (world.texture.width - 1) + pixelX) * 18;
  float* vertices = &world.heightmap.meshes[0].vertices[verticeStart];

  // Clamp x and y to prevent ray being out of bounds.
  Vector2 min = (Vector2){vertices[0], vertices[2]};
  Vector2 max = (Vector2){vertices[0], vertices[2]};

  for (int index = 0; index < 18; index += 3)
  {
    Vector2 vertex = (Vector2){vertices[index], vertices[index + 2]};
    min = Vector2Min(min, vertex);
    max = Vector2Max(max, vertex);
  }

  // Cast to triangles at pixel. Really hacky indeed.
  Ray ray = (Ray){
    .position = (Vector3){
      Clamp(x, min.x, max.x),
      FLT_MAX_EXP,
      Clamp(y, min.y, max.y)},
    .direction = (Vector3){0.0, -1.0, 0.0}
  };

  RayCollision result = GetRayCollisionTriangle(
    ray,
    (Vector3){vertices[0], vertices[1], vertices[2]},
    (Vector3){vertices[3], vertices[4], vertices[5]},
    (Vector3){vertices[6], vertices[7], vertices[8]});

  // Test other triangle.
  if (!result.hit)
  {
    result = GetRayCollisionTriangle(
      ray,
      (Vector3){vertices[9], vertices[10], vertices[11]},
      (Vector3){vertices[12], vertices[13], vertices[14]},
      (Vector3){vertices[15], vertices[16], vertices[17]});
  }

  if (result.hit)
  {
    return result.point.y;
  }
  else // Fall back.
  {
    float height = 0.0;
    
    for (int index = 1; index < 18; index += 3)
    {
      height += vertices[index];
    }
    
    return height / 6.0;
  }
}

// Abortions are good. Get more abortions.