// Make sure you add the SDL2 library to the library list when compiling: -lSDL2

#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>

#if _WIN32
#  include <Windows.h>
#endif
#if __APPLE__
#  include <OpenGL/gl.h>
#  include <OpenGL/glu.h>
#else
#  include <GL/gl.h>
#  include <GL/glu.h>
#endif

#include <SDL2/SDL.h>

typedef struct { float x, y; } vec2f;

SDL_Window *mainWindow = 0;

// Particles
const int n = 100;
vec2f r[n];
vec2f v[n];

void init()
{
  // Initialise particle positions and velocities here
}
  
void drawAxes(float length)
{
}

  
void display()
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glLoadIdentity();

  drawAxes(1.0);

  // Draw particles here. 

  SDL_GL_SwapWindow(mainWindow);

  // Always check for GL errors at least once per frame
  int err;
  while ((err = glGetError()) != GL_NO_ERROR) {
    printf("display: %s\n",gluErrorString(err));
  }
  
}

void update()
{
  // Update positions here 
}

bool handleKeyDown(SDL_Keysym *key)
{
  // Handle key press events here
  switch (key->sym)
  {
  case SDLK_ESCAPE:
    return true;
    break;

  default:
    break;
  }

  return false;
}

bool handleEvents()
{
  SDL_Event event;

  while (SDL_PollEvent(&event))
  {
    switch (event.type)
    {
    case SDL_MOUSEMOTION:
      break;

    case SDL_MOUSEBUTTONDOWN:
      break;

    case SDL_KEYDOWN:
      return handleKeyDown(&event.key.keysym);
      break;

    case SDL_WINDOWEVENT:
      switch (event.window.event)
      {
      case SDL_WINDOWEVENT_RESIZED:
        if (event.window.windowID == SDL_GetWindowID(mainWindow))
          SDL_SetWindowSize(mainWindow, event.window.data1, event.window.data2);
        break;
      case SDL_WINDOWEVENT_CLOSE:
        return false;
        break;
      default:
        break;
      }
      break;

    default:
      break;
    }
  }

  return false;
}

void reshape (int w, int h)
{
  glViewport (0, 0, (GLsizei) w, (GLsizei) h); 
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}


int main(int argc, char **argv)
{
  if (SDL_Init(SDL_INIT_VIDEO) < 0) {
      fprintf(stderr, "Unable to init SDL: %s\n", SDL_GetError());
    return EXIT_SUCCESS;
  }

  SDL_GL_SetAttribute(SDL_GL_RED_SIZE, 8);
  SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE, 8);
  SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
  SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
  SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);

 
  mainWindow = SDL_CreateWindow("Tutorial 1", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE);
  if (!mainWindow) {
    fprintf(stderr, "Failed to create a window: %s\n", SDL_GetError());
    return EXIT_SUCCESS;
  }

  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
  SDL_GLContext mainGLContext = SDL_GL_CreateContext(mainWindow);
  if (mainGLContext == 0) {
    fprintf(stderr, "Unable to get OpenGL context: %s\n", SDL_GetError());
    return EXIT_SUCCESS;
  }

  if (SDL_GL_MakeCurrent(mainWindow, mainGLContext) != 0) {
    fprintf(stderr, "Unable to make OpenGL context current: %s\n", SDL_GetError());
    return EXIT_SUCCESS;
  }

  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);

  int w, h;
  SDL_GetWindowSize(mainWindow, &w, &h);
  reshape(w, h);

  init();

  bool done = false;
  // Main event and display loop goes here

  SDL_DestroyWindow(mainWindow);
  SDL_Quit();

  return EXIT_SUCCESS;
}