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#include <cstdio>
#include <cstdlib>
#include <SDL.h>
#define GLM_FORCE_RADIANS 1
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>


#include "glad/glad.h"

static const int SCREEN_FULLSCREEN = 1;
static const int SCREEN_WIDTH  = 960;
static const int SCREEN_HEIGHT = 540;
static SDL_Window *window = NULL;
static SDL_GLContext maincontext;

static void sdl_die(const char * message) {
  fprintf(stderr, "%s: %s\n", message, SDL_GetError());
  exit(2);
}

void init_screen(const char * caption) {
  // Initialize SDL
  if (SDL_Init(SDL_INIT_VIDEO) < 0)
  sdl_die("Couldn't initialize SDL");
  atexit (SDL_Quit);
  SDL_GL_LoadLibrary(NULL); // Default OpenGL is fine.

  // Request an OpenGL 4.5 context (should be core)
  SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5);
  // Also request a depth buffer
  SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
  SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

  // Create the window
  if (SCREEN_FULLSCREEN) {
    window = SDL_CreateWindow(
      caption,
      SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
      0, 0, SDL_WINDOW_FULLSCREEN_DESKTOP | SDL_WINDOW_OPENGL
    );
  } else {
    window = SDL_CreateWindow(
      caption,
      SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
      SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_OPENGL
    );
  }
  if (window == NULL) sdl_die("Couldn't set video mode");

  maincontext = SDL_GL_CreateContext(window);
  if (maincontext == NULL)
    sdl_die("Failed to create OpenGL context");

  // Check OpenGL properties
  printf("OpenGL loaded\n");
  gladLoadGLLoader(SDL_GL_GetProcAddress);
  printf("Vendor:   %s\n", glGetString(GL_VENDOR));
  printf("Renderer: %s\n", glGetString(GL_RENDERER));
  printf("Version:  %s\n", glGetString(GL_VERSION));

  // Use v-sync
  SDL_GL_SetSwapInterval(1);

  // Disable depth test and face culling.
  glDisable(GL_DEPTH_TEST);
  glDisable(GL_CULL_FACE);

  int w,h;
  SDL_GetWindowSize(window, &w, &h);
  glViewport(0, 0, w, h);
  glClearColor(0.0f, 0.5f, 1.0f, 0.0f);
}

#undef main
int main() {
  init_screen("OpenGL 4.5");
  SDL_Event event;

  bool quit = false;
  while (!quit) {
    SDL_GL_SwapWindow(window);
    while (SDL_PollEvent(&event)) {
      if (event.type == SDL_QUIT) {
        quit = true;
      }
    }
  }
}