#include <sys/stat.h>

#include "gl3.h"

#define GLX_CONTEXT_MAJOR_VERSION_ARB       0x2091
#define GLX_CONTEXT_MINOR_VERSION_ARB       0x2092
typedef GLXContext (*glXCreateContextAttribsARBProc)(Display*, GLXFBConfig, GLXContext, bool, const int*);

#define ERROR(condition, msg, ...) if(condition){fprintf(stderr, msg, ##__VA_ARGS__); return false;}

bool initGL(int screen, int mask, GLInfo *glinfo)
{
  glinfo->display = XOpenDisplay(NULL);
  ERROR(!glinfo->display, "Failed to open X display\n");

  // check GLX version >= 1.3
  int glx_major, glx_minor;
  ERROR(!glXQueryVersion(glinfo->display, &glx_major, &glx_minor), "Could not query GLX version\n");
  ERROR(glx_major == 1 && glx_minor < 3 || glx_major < 1, "Invalid GLX version\n");

  // Let GLX suggest a frame buffer config with a minimum feature set
  static int visual_attribs[] = {
    GLX_X_RENDERABLE    , True,
    GLX_DRAWABLE_TYPE   , GLX_WINDOW_BIT,
    GLX_RENDER_TYPE     , GLX_RGBA_BIT,
    GLX_X_VISUAL_TYPE   , GLX_TRUE_COLOR,
    GLX_RED_SIZE        , 8,
    GLX_GREEN_SIZE      , 8,
    GLX_BLUE_SIZE       , 8,
    GLX_ALPHA_SIZE      , 8,
    GLX_DEPTH_SIZE      , 24,
    GLX_STENCIL_SIZE    , 8,
    GLX_DOUBLEBUFFER    , True,
    None
  };
  int fbcount;
  GLXFBConfig *fbclist = glXChooseFBConfig(glinfo->display, screen, visual_attribs, &fbcount);
  ERROR(!fbclist, "Failed to retrieve a framebuffer config\n");
  GLXFBConfig fbc = fbclist[0];
  XFree(fbclist);

  // Create X Window
  XVisualInfo *vi = glXGetVisualFromFBConfig(glinfo->display, fbc);
  ERROR(!vi, "Failed to get visual from framebuffer config\n");
  XSetWindowAttributes swa;
  glinfo->cmap = XCreateColormap(glinfo->display, RootWindow(glinfo->display, vi->screen), vi->visual, AllocNone);
  swa.colormap = glinfo->cmap;
  swa.background_pixmap = None;
  swa.border_pixel = 0;
  swa.event_mask = mask;
  glinfo->win = XCreateWindow(glinfo->display, RootWindow(glinfo->display, vi->screen), 0, 0, 100, 100, 0, vi->depth, InputOutput, vi->visual, CWBorderPixel|CWColormap|CWEventMask, &swa);
  ERROR(!glinfo->win, "Failed to create window.\n");
  XFree(vi);

  // Print GLX Extensions
  // const char *glxExts = glXQueryExtensionsString(glinfo->display, screen);
  // printf("%s\n", glxExts);

  // Create GLX context
  glXCreateContextAttribsARBProc glXCreateContextAttribsARB = 0;
  glXCreateContextAttribsARB = (glXCreateContextAttribsARBProc) glXGetProcAddressARB((const GLubyte *) "glXCreateContextAttribsARB");
  ERROR(!glXCreateContextAttribsARB, "GLX_ARB_create_context is not supported\n");
  int context_attribs[] = {
    GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
    GLX_CONTEXT_MINOR_VERSION_ARB, 0,
    None
  };
  glinfo->ctx = glXCreateContextAttribsARB(glinfo->display, fbc, 0, True, context_attribs);
  ERROR(!glXIsDirect(glinfo->display, glinfo->ctx), "GLX context is not direct\n");

  XMapWindow(glinfo->display, glinfo->win);
  glXMakeCurrent(glinfo->display, glinfo->win, glinfo->ctx);

  GLenum result = glewInit();
  ERROR(result != GLEW_OK, "Failed to initialize GLEW: %s\n", glewGetErrorString(result));

  char name[] = "Billiards";
  XClassHint *classHint = XAllocClassHint();
  classHint->res_name = classHint->res_class = name;
  XSetClassHint(glinfo->display, glinfo->win, classHint);
  XStoreName(glinfo->display, glinfo->win, name);
  XFree(classHint);

  glinfo->wm_delete_window = XInternAtom(glinfo->display, "WM_DELETE_WINDOW", false);
  glinfo->wm_protocols = XInternAtom(glinfo->display, "WM_PROTOCOLS", false);
  XSetWMProtocols(glinfo->display, glinfo->win, &glinfo->wm_delete_window, 1);

  return true;
}

void destroyGL(GLInfo *glinfo)
{
  glXMakeCurrent(glinfo->display, None, 0);
  glXDestroyContext(glinfo->display, glinfo->ctx);
  XDestroyWindow(glinfo->display, glinfo->win);
  XFreeColormap(glinfo->display, glinfo->cmap);
  XCloseDisplay(glinfo->display);
}

bool initShaders(const char *vertexShaderPath, const char *fragmentShaderPath, GLuint *program)
{
  GLuint vertexShader, fragmentShader;
  GLint result;
  int infoLogLength;
  char *infoLog;
  FILE *file;
  struct stat filestat;
  char *vertexShaderSrc, *fragmentShaderSrc;

  // load vertex shader
  file = fopen(vertexShaderPath, "r");
  ERROR(!file, "Could not open file %s\n", vertexShaderPath);
  fstat(fileno(file), &filestat);
  ERROR(filestat.st_size > 10000000, "Unreasonably large shader file\n");
  vertexShaderSrc = (char*)malloc(filestat.st_size + 1);
  vertexShaderSrc[filestat.st_size] = 0; // just for safety
  fread(vertexShaderSrc, 1, filestat.st_size, file);
  fclose(file);

  // load framgent shader
  file = fopen(fragmentShaderPath, "r");
  ERROR(!file, "Could not open file %s\n", fragmentShaderPath);
  fstat(fileno(file), &filestat);
  ERROR(filestat.st_size > 10000000, "Unreasonably large shader file\n");
  fragmentShaderSrc = (char*)malloc(filestat.st_size + 1);
  fragmentShaderSrc[filestat.st_size] = 0; // just for safety
  fread(fragmentShaderSrc, 1, filestat.st_size, file);
  fclose(file);

  // compile vertex shader
  vertexShader = glCreateShader(GL_VERTEX_SHADER);
  glShaderSource(vertexShader, 1, &vertexShaderSrc, NULL);
  glCompileShader(vertexShader);
  glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &result);
  glGetShaderiv(vertexShader, GL_INFO_LOG_LENGTH, &infoLogLength);
  infoLog = (char*)malloc(infoLogLength+1);
  glGetShaderInfoLog(vertexShader, infoLogLength, NULL, infoLog);
  ERROR(!result, "Vertex shader compile error: %s\n", infoLog);
  free(infoLog);

  // compile fragment shader
  fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
  glShaderSource(fragmentShader, 1, &fragmentShaderSrc, NULL);
  glCompileShader(fragmentShader);
  glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &result);
  glGetShaderiv(fragmentShader, GL_INFO_LOG_LENGTH, &infoLogLength);
  infoLog = (char*)malloc(infoLogLength+1);
  glGetShaderInfoLog(fragmentShader, infoLogLength, NULL, infoLog);
  ERROR(!result, "Fragment shader compile error: %s\n", infoLog);
  free(infoLog);

  // link program
  *program = glCreateProgram();
  glAttachShader(*program, vertexShader);
  glAttachShader(*program, fragmentShader);
  glLinkProgram(*program);
  glShaderSource(fragmentShader, 1, &fragmentShaderSrc, NULL);
  glCompileShader(fragmentShader);
  glGetShaderiv(*program, GL_LINK_STATUS, &result);
  glGetShaderiv(*program, GL_INFO_LOG_LENGTH, &infoLogLength);
  infoLog = (char*)malloc(infoLogLength+1);
  glGetProgramInfoLog(*program, infoLogLength, NULL, infoLog);
  ERROR(!result, "Shader linking error: %s\n", infoLog);
  free(infoLog);

  glDetachShader(*program, vertexShader);
  glDetachShader(*program, fragmentShader);

  glDeleteShader(vertexShader);
  glDeleteShader(fragmentShader);

  free(vertexShaderSrc);
  free(fragmentShaderSrc);

  return true;
}