#include "lg-renderer.h"
#include <stdint.h>
#include <stdbool.h>
#include <unistd.h>

#include <SDL_ttf.h>

#define GL_GLEXT_PROTOTYPES
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glx.h>

#include "debug.h"
#include "memcpySSE.h"
#include "utils.h"

#define VBO_BUFFERS 2

static PFNGLXGETVIDEOSYNCSGIPROC  glXGetVideoSyncSGI  = NULL;
static PFNGLXWAITVIDEOSYNCSGIPROC glXWaitVideoSyncSGI = NULL;
static PFNGLXSWAPINTERVALSGIPROC  glXSwapIntervalSGI  = NULL;

struct LGR_OpenGL
{
  LG_RendererParams params;
  bool              initialized;
  SDL_GLContext     glContext;
  bool              resizeWindow;

  LG_RendererFormat format;
  GLuint            intFormat;
  GLuint            vboFormat;
  size_t            texSize;

  uint64_t          drawStart;
  bool              hasBuffers;
  GLuint            vboID[VBO_BUFFERS];
  uint8_t         * texPixels[VBO_BUFFERS];
  int               texIndex;
  int               texList;
  int               fpsList;
  LG_RendererRect   destRect;

  bool              hasTextures;
  GLuint            vboTex[VBO_BUFFERS + 1]; // extra texture for FPS

  uint              gpuFrameCount;
  bool              fpsTexture;
  uint64_t          lastFrameTime;
  uint64_t          renderTime;
  uint64_t          frameCount;
  SDL_Rect          fpsRect;
};

void lgr_opengl_on_resize(void * opaque, const int width, const int height, const LG_RendererRect destRect);

bool lgr_opengl_check_error(const char * name)
{
  GLenum error = glGetError();
  if (error == GL_NO_ERROR)
    return false;

  const GLubyte * errStr = gluErrorString(error);
  DEBUG_ERROR("%s = %d (%s)", name, error, errStr);
  return true;
}

const char * lgr_opengl_get_name()
{
  return "OpenGL";
}

bool lgr_opengl_initialize(void ** opaque, const LG_RendererParams params, const LG_RendererFormat format)
{
  // create our local storage
  *opaque = malloc(sizeof(struct LGR_OpenGL));
  if (!*opaque)
  {
    DEBUG_INFO("Failed to allocate %lu bytes", sizeof(struct LGR_OpenGL));
    return false;
  }
  memset(*opaque, 0, sizeof(struct LGR_OpenGL));
  struct LGR_OpenGL * this = (struct LGR_OpenGL *)*opaque;
  memcpy(&this->params, &params, sizeof(LG_RendererParams));

  this->glContext = SDL_GL_CreateContext(params.window);
  if (!this->glContext)
  {
    DEBUG_ERROR("Failed to create the OpenGL context");
    return false;
  }

  if (SDL_GL_MakeCurrent(params.window, this->glContext) != 0)
  {
    DEBUG_ERROR("Failed to make the GL context current");
    return false;
  }

  if (!glXGetVideoSyncSGI)
  {
    glXGetVideoSyncSGI  = (PFNGLXGETVIDEOSYNCSGIPROC )glXGetProcAddress((const GLubyte *)"glXGetVideoSyncSGI" );
    glXWaitVideoSyncSGI = (PFNGLXWAITVIDEOSYNCSGIPROC)glXGetProcAddress((const GLubyte *)"glXWaitVideoSyncSGI");
    glXSwapIntervalSGI  = (PFNGLXSWAPINTERVALSGIPROC )glXGetProcAddress((const GLubyte *)"glXSwapIntervalSGI" );

    if (!glXGetVideoSyncSGI || !glXWaitVideoSyncSGI || !glXSwapIntervalSGI)
    {
      glXGetVideoSyncSGI = NULL;
      DEBUG_ERROR("Failed to get proc addresses");
      return false;
    }
  }

  SDL_GL_SetSwapInterval(params.vsync ? 1 : 0);

  // check if the GPU supports GL_ARB_buffer_storage first
  // there is no advantage to this renderer if it is not present.
  const GLubyte * extensions = glGetString(GL_EXTENSIONS);
  if (!gluCheckExtension((const GLubyte *)"GL_ARB_buffer_storage", extensions))
  {
    DEBUG_INFO("The GPU doesn't support GL_ARB_buffer_storage");
    return false;
  }

  // assume 24 and 32 bit formats are RGB and RGBA
  switch(format.bpp)
  {
    case 24:
      this->intFormat = GL_RGB8;
      this->vboFormat = GL_BGR;
      break;

    case 32:
      this->intFormat = GL_RGBA8;
      this->vboFormat = GL_BGRA;
      break;

    default:
      DEBUG_INFO("%d bpp not supported", format.bpp);
      return false;
  }

  // calculate the texture size in bytes
  this->texSize = format.height * format.pitch;

  // generate lists for drawing
  this->texList = glGenLists(2);
  this->fpsList = glGenLists(1);

  // generate the pixel unpack buffers
  glGenBuffers(VBO_BUFFERS, this->vboID);
  if (lgr_opengl_check_error("glGenBuffers"))
    return false;
  this->hasBuffers = true;

  // persistant bind the buffers
  for (int i = 0; i < VBO_BUFFERS; ++i)
  {
    glBindBuffer(GL_PIXEL_UNPACK_BUFFER, this->vboID[i]);
    if (lgr_opengl_check_error("glBindBuffer"))
      return false;

    glBufferStorage(GL_PIXEL_UNPACK_BUFFER, this->texSize, 0, GL_MAP_WRITE_BIT | GL_MAP_PERSISTENT_BIT);
    if (lgr_opengl_check_error("glBufferStorage"))
      return false;

    this->texPixels[i] = glMapBufferRange(GL_PIXEL_UNPACK_BUFFER, 0, this->texSize,
        GL_MAP_WRITE_BIT | GL_MAP_PERSISTENT_BIT | GL_MAP_FLUSH_EXPLICIT_BIT);
    if (lgr_opengl_check_error("glMapBufferRange"))
      return false;

    if (!this->texPixels[i])
    {
      DEBUG_ERROR("Failed to map the buffer range");
      return false;
    }

    glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
  }

  // create the textures
  glGenTextures(VBO_BUFFERS + (params.showFPS ? 1 : 0), this->vboTex);
  if (lgr_opengl_check_error("glGenTextures"))
    return false;
  this->hasTextures = true;

  // bind the textures to the unpack buffers
  for (int i = 0; i < VBO_BUFFERS; ++i)
  {
    glBindTexture(GL_TEXTURE_2D, this->vboTex[i]);
    if (lgr_opengl_check_error("glBindTexture"))
      return false;

    glTexImage2D(
      GL_TEXTURE_2D,
      0,
      this->intFormat,
      format.width, format.height,
      0,
      this->vboFormat,
      GL_UNSIGNED_BYTE,
      (void*)0
    );

    if (lgr_opengl_check_error("glTexImage2D"))
      return false;
  }

  glEnable(GL_TEXTURE_2D);
  glEnable(GL_COLOR_MATERIAL);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
  glBlendEquation(GL_FUNC_ADD);

  this->resizeWindow = true;
  this->drawStart    = nanotime();

  // copy the format into the local storage
  memcpy(&this->format, &format, sizeof(LG_RendererFormat));
  this->initialized = true;
  return true;
}

void lgr_opengl_deinitialize(void * opaque)
{
  struct LGR_OpenGL * this = (struct LGR_OpenGL *)opaque;
  if (!this)
    return;

  if (this->hasTextures)
    glDeleteTextures(VBO_BUFFERS, this->vboTex);

  if (this->hasBuffers)
    glDeleteBuffers(VBO_BUFFERS, this->vboID);

  if (this->glContext)
    SDL_GL_DeleteContext(this->glContext);

  free(this);
}

bool lgr_opengl_is_compatible(void * opaque, const LG_RendererFormat format)
{
  const struct LGR_OpenGL * this = (struct LGR_OpenGL *)opaque;
  if (!this || !this->initialized)
    return false;

  return (memcmp(&this->format, &format, sizeof(LG_RendererFormat)) == 0);
}

void lgr_opengl_on_resize(void * opaque, const int width, const int height, const LG_RendererRect destRect)
{
  struct LGR_OpenGL * this = (struct LGR_OpenGL *)opaque;
  if (!this || !this->initialized)
    return;

  this->params.width  = width;
  this->params.height = height;
  memcpy(&this->destRect, &destRect, sizeof(LG_RendererRect));

  this->resizeWindow  = true;
}

bool lgr_opengl_render(void * opaque, const uint8_t * data, bool resample)
{
  struct LGR_OpenGL * this = (struct LGR_OpenGL *)opaque;
  if (!this || !this->initialized)
    return false;

  if (SDL_GL_MakeCurrent(this->params.window, this->glContext) != 0)
  {
    DEBUG_ERROR("Failed to make the GL context current");
    return false;
  }

  if (this->resizeWindow)
  {
    // setup the projection matrix
    glViewport(0, 0, this->params.width, this->params.height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0, this->params.width, this->params.height, 0);
    glMatrixMode(GL_MODELVIEW);

    // update the display lists
    for(int i = 0; i < VBO_BUFFERS; ++i)
    {
      glNewList(this->texList + i, GL_COMPILE);
        glBindTexture(GL_TEXTURE_2D, this->vboTex[i]);
        glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
        glBegin(GL_TRIANGLE_STRIP);
          glTexCoord2f(0.0f, 0.0f); glVertex2i(this->destRect.x                   , this->destRect.y                   );
          glTexCoord2f(1.0f, 0.0f); glVertex2i(this->destRect.x + this->destRect.w, this->destRect.y                   );
          glTexCoord2f(0.0f, 1.0f); glVertex2i(this->destRect.x                   , this->destRect.y + this->destRect.h);
          glTexCoord2f(1.0f, 1.0f); glVertex2i(this->destRect.x + this->destRect.w, this->destRect.y + this->destRect.h);
        glEnd();
      glEndList();
    }

    this->resizeWindow  = false;
  }

  glClear(GL_COLOR_BUFFER_BIT);
  if (this->params.showFPS && this->renderTime > 1e9)
  {
    char str[128];
    const float avgFPS = 1000.0f / (((float)this->renderTime / this->frameCount) / 1e6f);
    snprintf(str, sizeof(str), "FPS: %8.4f", avgFPS);
    SDL_Color color = {0xff, 0xff, 0xff};
    SDL_Surface *textSurface = NULL;
    if (!(textSurface = TTF_RenderText_Blended(this->params.font, str, color)))
    {
      DEBUG_ERROR("Failed to render text");
      return false;
    }

    glBindTexture(GL_TEXTURE_2D       , this->vboTex[VBO_BUFFERS]);
    glPixelStorei(GL_UNPACK_ALIGNMENT , 4                        );
    glPixelStorei(GL_UNPACK_ROW_LENGTH, textSurface->w           );
    glTexImage2D(
      GL_TEXTURE_2D,
      0,
      textSurface->format->BytesPerPixel,
      textSurface->w,
      textSurface->h,
      0,
      GL_BGRA,
      GL_UNSIGNED_BYTE,
      textSurface->pixels
    );

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

    glBindTexture(GL_TEXTURE_2D, 0);

    this->fpsRect.x = 5;
    this->fpsRect.y = 5;
    this->fpsRect.w = textSurface->w;
    this->fpsRect.h = textSurface->h;

    SDL_FreeSurface(textSurface);

    this->renderTime = 0;
    this->frameCount = 0;
    this->fpsTexture = true;

    glNewList(this->fpsList, GL_COMPILE);
      glEnable(GL_BLEND);
      glDisable(GL_TEXTURE_2D);
      glColor4f(0.0f, 0.0f, 1.0f, 0.5f);
      glBegin(GL_TRIANGLE_STRIP);
        glVertex2i(this->fpsRect.x                  , this->fpsRect.y                  );
        glVertex2i(this->fpsRect.x + this->fpsRect.w, this->fpsRect.y                  );
        glVertex2i(this->fpsRect.x                  , this->fpsRect.y + this->fpsRect.h);
        glVertex2i(this->fpsRect.x + this->fpsRect.w, this->fpsRect.y + this->fpsRect.h);
      glEnd();
      glEnable(GL_TEXTURE_2D);

      glBindTexture(GL_TEXTURE_2D, this->vboTex[VBO_BUFFERS]);
      glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
      glBegin(GL_TRIANGLE_STRIP);
        glTexCoord2f(0.0f , 0.0f); glVertex2i(this->fpsRect.x                  , this->fpsRect.y                  );
        glTexCoord2f(1.0f , 0.0f); glVertex2i(this->fpsRect.x + this->fpsRect.w, this->fpsRect.y                  );
        glTexCoord2f(0.0f , 1.0f); glVertex2i(this->fpsRect.x                  , this->fpsRect.y + this->fpsRect.h);
        glTexCoord2f(1.0f,  1.0f); glVertex2i(this->fpsRect.x + this->fpsRect.w, this->fpsRect.y + this->fpsRect.h);
      glEnd();
      glDisable(GL_BLEND);
    glEndList();
  }

  // copy the buffer to the texture
  memcpySSE(this->texPixels[this->texIndex], data, this->texSize);

  glBindBuffer(GL_PIXEL_UNPACK_BUFFER, this->vboID[this->texIndex]);
  glFlushMappedBufferRange(GL_PIXEL_UNPACK_BUFFER, 0, this->texSize);

  // bind the texture and update it
  glBindTexture(GL_TEXTURE_2D         , this->vboTex[this->texIndex]);
  glPixelStorei(GL_UNPACK_ALIGNMENT   , 4                           );
  glPixelStorei(GL_UNPACK_ROW_LENGTH  , this->format.width          );

  // update the texture
  glTexSubImage2D(
    GL_TEXTURE_2D,
    0,
    0, 0,
    this->format.width ,
    this->format.height,
    this->vboFormat,
    GL_UNSIGNED_BYTE,
    (void*)0
  );

  const bool mipmap = resample && (
    (this->format.width  > this->destRect.w) ||
    (this->format.height > this->destRect.h));

  // unbind the buffer
  glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);

  // configure the texture
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
  glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
  if (mipmap)
  {
    glGenerateMipmap(GL_TEXTURE_2D);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
  }
  else
  {
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
  }

  // draw the screen
  glCallList(this->texList + this->texIndex);

  if (this->fpsTexture)
    glCallList(this->fpsList);

  ++this->frameCount;
  SDL_GL_SwapWindow(this->params.window);
  glFlush();

  // wait until the frame has been presented, this is to avoid the video card
  // buffering frames, we would rather skip a frame then fall behind the guest
  uint count;
  glXGetVideoSyncSGI(&count);
  if (this->gpuFrameCount == count)
  {
    uint remainder;
    glXWaitVideoSyncSGI(count, 1, &remainder);
    this->gpuFrameCount = count + 1;
  }
  else
    this->gpuFrameCount = count;

  const uint64_t t    = nanotime();
  this->renderTime   += t - this->lastFrameTime;
  this->lastFrameTime = t;

  if (++this->texIndex == VBO_BUFFERS)
    this->texIndex = 0;

  return true;
}

const LG_Renderer LGR_OpenGL =
{
  .get_name      = lgr_opengl_get_name,
  .initialize    = lgr_opengl_initialize,
  .deinitialize  = lgr_opengl_deinitialize,
  .is_compatible = lgr_opengl_is_compatible,
  .on_resize     = lgr_opengl_on_resize,
  .render        = lgr_opengl_render
};