#include <SDL2/SDL.h>
#include <SDL2/SDL_pixels.h>
#include <SDL2/SDL_rect.h>
#include <SDL2/SDL_render.h>
#include <SDL2/SDL_surface.h>
#include <SDL2/SDL_video.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define WINDOW_WIDTH 800
#define WINDOW_HEIGHT 600

#define BG_COLOR 0x060616ff

void render_clear(SDL_Surface *surface, uint32_t color);
void fill_rect(SDL_Surface *surface, uint32_t x, uint32_t y, uint32_t w,
               uint32_t h, uint32_t color);

int main(void) {
  SDL_Init(SDL_INIT_EVERYTHING);

  SDL_Window *window = SDL_CreateWindow("Starfield", SDL_WINDOWPOS_CENTERED,
                                        SDL_WINDOWPOS_CENTERED, WINDOW_WIDTH,
                                        WINDOW_HEIGHT, SDL_WINDOW_SHOWN);

  SDL_Surface *surface = SDL_GetWindowSurface(window);

  SDL_Surface *canvas = SDL_CreateRGBSurfaceWithFormat(
      0, surface->w, surface->h, 32, SDL_PIXELFORMAT_ABGR32);

  bool running = true;

  SDL_Event event = {0};

  while (running) {
    while (SDL_PollEvent(&event)) {
      switch (event.type) {
      case SDL_QUIT:
        running = false;
        break;
      }
    }

    render_clear(canvas, BG_COLOR);

    SDL_BlitSurface(canvas, NULL, surface, NULL);

    SDL_UpdateWindowSurface(window);
  }

  SDL_DestroyWindow(window);

  SDL_Quit();

  return EXIT_SUCCESS;
}

void render_clear(SDL_Surface *surface, uint32_t color) {
  uint32_t length = surface->w * surface->h;

  SDL_LockSurface(surface);

  uint32_t *pixels = (uint32_t *)(surface->pixels);

  for (uint32_t i = 0; i < length; ++i) {
    pixels[i] = color;
  }

  SDL_UnlockSurface(surface);
}

void fill_rect(SDL_Surface *surface, uint32_t x, uint32_t y, uint32_t w,
               uint32_t h, uint32_t color) {
  SDL_LockSurface(surface);

  uint32_t *pixels = (uint32_t *)(surface->pixels);

  for (uint32_t row = 0; row < h; ++row) {
    for (uint32_t col = 0; col < w; ++col) {
      uint32_t i = (y + row) * surface->w + (x + col);

      pixels[i] = color;
    }
  }

  SDL_UnlockSurface(surface);
}