#include <glbinding/gl/gl.h>
#include <SDL2/SDL.h>

#include "renderutil.hh"
#include "exceptions.hh"

using namespace gl;

namespace render {
  unsigned ilog2(unsigned in)
  {
    unsigned ret = 0u;
    while (in >>= 1) ++ret;
    return ret;
  }
  
  std::tuple<unsigned, unsigned> getGLTextureMaximums()
  {
    static int maxTexSize = -1, maxArrTexLayers = -1;

    if (maxTexSize < 0)
      glGetIntegerv(GL_MAX_TEXTURE_SIZE, &maxTexSize);
    if (maxArrTexLayers < 0)
      glGetIntegerv(GL_MAX_ARRAY_TEXTURE_LAYERS, &maxArrTexLayers);

    if ((maxTexSize < 0) || (maxArrTexLayers < 0))
      throw Exception{"GL returned negative values for max tex. dimensions"};

    return std::make_tuple<unsigned, unsigned>(maxTexSize, maxArrTexLayers);
  }

  void useProgram(GLuint program)
  {
    static GLuint curProgram = 0;

    if (curProgram != program) {
      glUseProgram(program);
      curProgram = program;
    }
  }	
  
  TextureResource create2DTexture(unsigned width, unsigned height, bool alpha, unsigned levels)
  {
    TextureResource tex;
    glGenTextures(1, &tex.get());

    glBindTexture(GL_TEXTURE_2D, tex);
    unsigned logWidth = ilog2(width), logHeight = ilog2(height);
    if (levels == 0)
      levels = std::max(logWidth,logHeight)+1u;
    if(SDL_GL_ExtensionSupported("GL_ARB_texture_storage"))
      glTexStorage2D(GL_TEXTURE_2D, levels, alpha?GL_RGBA8:GL_RGB8, width, height);
    else {
      std::printf("Warning: extension GL_ARB_texture_storage not supported!\n");
      for (unsigned i = 0u; i < levels; ++i) {
	glTexImage2D(GL_TEXTURE_2D, i, static_cast<const int>(alpha?GL_RGBA8:GL_RGB8), width, height, 0,
		     alpha?GL_RGBA8:GL_RGB8, GL_UNSIGNED_BYTE, NULL);
	width = std::max(1u, (width / 2u));
	height = std::max(1u, (height / 2u));
      }
    }
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, levels-1);
 
    return tex;
  }

  TextureResource create2DArrayTexture(unsigned width, unsigned height, unsigned count,
				       bool alpha, unsigned levels)
  {
    TextureResource tex;
    glGenTextures(1, &tex.get());

    glBindTexture(GL_TEXTURE_2D_ARRAY, tex);
    unsigned logWidth = ilog2(width), logHeight = ilog2(height);
    if (levels == 0)
      levels = std::max(logWidth,logHeight)+1u;
    if(SDL_GL_ExtensionSupported("GL_ARB_texture_storage"))
      glTexStorage3D(GL_TEXTURE_2D_ARRAY, levels, alpha?GL_RGBA8:GL_RGB8, width, height, count);
    else {
      std::printf("Warning: extension GL_ARB_texture_storage not supported!\n");
      for (unsigned i = 0u; i < levels; ++i) {
	glTexImage3D(GL_TEXTURE_2D_ARRAY, i, static_cast<const int>(alpha?GL_RGBA8:GL_RGB8),
		     width, height, count,
		     0, alpha?GL_RGBA8:GL_RGB8, GL_UNSIGNED_BYTE, NULL);
	width = std::max(1u, (width / 2u));
	height = std::max(1u, (height / 2u));
      }
    }
    glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAX_LEVEL, levels-1);
 
    return tex;
  }
}