#include <stdlib.h>
#include <time.h>
#include "SDL2/SDL.h"

#define HEIGHT 80
#define WIDTH 130
#define SPF 1000 / 30

void wrap(int *a, int w) {
	if (*a < 0) *a = w - 1;
	else if (*a > w - 1) *a = 0;
}

int place(int x, int y) {
	wrap(&x, WIDTH);
	wrap(&y, HEIGHT);
	return x + y * WIDTH;
}

int neighbors(char *cells, int x, int y) {
	int count = 0;
	for (int i = -1; i <= 1; i++)
		for (int j = -1; j <= 1; j++) {
			if (i == 0 && j == 0) continue;
			if (cells[place(i + x, j + y)] & 2) count++;
		}
	return count;
}

int resize(SDL_Renderer *r) {
	int w, h;
	SDL_GetRendererOutputSize(r, &w, &h);
	return w / WIDTH < h / HEIGHT ? w / WIDTH : h / HEIGHT;
}

char inside(int n, char *v) {
	char result = 0;
	if (n >= 0 && n <= 8)
		for (int i = 0; i < strlen(v); i++) {
			result |= (n == v[i] - 48);
		}
	return result;
}

void init(char *cells, char random) {
	for (int x = 0; x < WIDTH; x++) {
		for (int y = 0; y < HEIGHT; y++) {
			if (random) cells[place(x, y)] ^= 3 * (rand() % 2);
			else cells[place(x, y)] = 0;
		}
	}
}

int main(int argc, char **argv) {
	if (argc != 3) exit(1);
	srand(time(0));
	SDL_Init(SDL_INIT_VIDEO);
	SDL_Window *w = SDL_CreateWindow(argv[0], 0, 0, 800, 600, SDL_WINDOW_RESIZABLE);
	SDL_Renderer *r = SDL_CreateRenderer(w, -1, SDL_RENDERER_ACCELERATED);
	int cellsize = resize(r);
	int oldtime = 0;
	int newtime = 0;
	char paused = 0;
	char grid = 1;
	int symtime = 0;
	int rendertime = 0;
	char cells[WIDTH * HEIGHT];
	init(cells, 1);
	SDL_Event e = {0};
  int exit = 0;
	while (!exit) {
		SDL_Delay(SPF);
		while (SDL_PollEvent(&e)) {
			if (e.window.event == SDL_WINDOWEVENT_RESIZED)
				cellsize = resize(r);
			if (e.key.state == SDL_PRESSED) {
				if (e.key.keysym.sym == SDLK_BACKSPACE)
					init(cells, 0);
				if (e.key.keysym.sym == SDLK_RETURN)
					init(cells, 1);
				if (e.key.keysym.sym == SDLK_SPACE)
					paused ^= 1;
				if (e.key.keysym.sym == SDLK_PERIOD) {
					paused = 1;
					symtime = SPF + 1;
				}
				if (e.key.keysym.sym == SDLK_g) {
					grid ^= 1;
				}
        if (e.key.keysym.sym == SDLK_q) {
          exit = 1;
        }
			}
			int mx, my;
			int mstate = SDL_GetMouseState(&mx, &my);
			if (mstate & SDL_BUTTON(SDL_BUTTON_RIGHT)) {
				cells[place(mx / cellsize, my / cellsize)] = 0;
				paused = 1;
			} else if (mstate & SDL_BUTTON(SDL_BUTTON_LEFT)) {
				cells[place(mx / cellsize, my / cellsize)] = 3;
				paused = 1;
			}
		};
		oldtime = newtime;
		newtime = SDL_GetTicks();
		if (!paused) symtime += newtime - oldtime;
		if (symtime > SPF) {
			symtime = 0;
			for (int x = 0; x < WIDTH; x++)
				for (int y = 0; y < HEIGHT; y++) {
					int n = neighbors(cells, x, y);
					if (inside(n, argv[1]) && ~cells[place(x, y)] & 2)
						cells[place(x, y)] |= 1; // Birth
					if (!inside(n, argv[2]) && cells[place(x, y)] & 2)
						cells[place(x, y)] &= 2; // Death
				}
			for (int i = 0; i < WIDTH * HEIGHT; i++)
			       	cells[i] = cells[i] & 1 ? 3 : 0;
		}
		rendertime += newtime - oldtime;
		if (rendertime > SPF) {
			rendertime = 0;
			SDL_SetRenderDrawColor(r, 160, 160, 160, 255);
			SDL_RenderClear(r);
			for (int x = 0; x < WIDTH; x++)
				for (int y = 0; y < HEIGHT; y++) {
					SDL_Rect rect = { x * cellsize, y * cellsize, cellsize, cellsize };
					if (grid && cellsize > 1) {
						rect.x += 1;
						rect.y += 1;
						rect.w -= 1;
						rect.h -= 1;
					}
					if (cells[place(x, y)]) SDL_SetRenderDrawColor(r, 0, 0, 0, 255);
					else SDL_SetRenderDrawColor(r, 255, 255, 255, 255);
					SDL_RenderFillRect(r, &rect);
				}
			SDL_RenderPresent(r);
		}
	}
	SDL_DestroyRenderer(r);
	SDL_DestroyWindow(w);
	SDL_Quit();
	return 0;
}