#include <SDL2/SDL.h>
#include <iostream>
#include <cstdlib>
#include <ctime>
#include <libnoise/noise.h>

const int width = 640;
const int height = 480;

float x = width / 2;
float y = height / 2;

double map( double x, double in_min, double in_max, double out_min, double out_max) {
  return  out_min + (( out_max - out_min) * (x - in_min) / (in_max - in_min));
}

int main(int argc, char *argv[])
{

  noise::module::Perlin myNoise;

  SDL_Window *window = nullptr;
  SDL_Renderer *renderer = nullptr;

  if(SDL_Init(SDL_INIT_VIDEO) < 0 )
    std::cout << "Video Initialization Error: " << SDL_GetError() << std::endl;
  else
  {

    window = SDL_CreateWindow("SDL Perlin Noise", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_SHOWN);
    renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);

    if (window == NULL || renderer == NULL)
      std::cout << "Window creation error: " << SDL_GetError() << std::endl;
    else
    {
      bool isRunning = true;
      SDL_Event ev;

      SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_NONE);


      double n = 0; // time step
      while(isRunning)
      {

        while(SDL_PollEvent(&ev) != 0)
        {
          if(ev.type == SDL_QUIT)
            isRunning = false;
        }

        double yoff = 0;
        double xoff = 0;


        SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0);
        SDL_RenderClear(renderer);

        for (int x = 0; x < width; x++){
          yoff = 0;
          for (int y = 0; y < height; y++){
            int bright = map(myNoise.GetValue(xoff , yoff, n), -1.0, 1.0, 0, 255);
            SDL_SetRenderDrawColor(renderer, bright, bright, bright, 255);
            SDL_RenderDrawPoint(renderer, x, y);
            yoff += 0.01;
          }
          xoff += 0.01;
        }
        n += 0.01;
        SDL_RenderPresent(renderer);
      }
    }
  }

  SDL_DestroyWindow(window);
  SDL_Quit();
  std::cout << "Good Bye.\n";

  return(0);
}