// A console conway's game of life program by Bruce Hill
// Released under the MIT license, see LICENSE for details.
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <termbox.h>
#include <unistd.h>

#define CELL(cells, x, y) cells[((y) % H)*W + ((x) % W)]

static char rules[2][9] = {{0,0,0,1,0,0,0,0,0}, {0,0,1,1,0,0,0,0,0}};
static int W, H;

static void update(const char *cells, char *future_cells)
{
    for (int y = 0; y < H; y++) {
        for (int x = 0; x < W; x++) {
            int neighbors =
                CELL(cells,x-1,y-1) + CELL(cells,x,y-1) + CELL(cells,x+1,y-1)
                + CELL(cells,x-1,y) + CELL(cells,x+1,y)
                + CELL(cells,x-1,y+1) + CELL(cells,x,y+1) + CELL(cells,x+1,y+1);
            CELL(future_cells, x, y) = rules[CELL(cells, x, y)][neighbors];
            if (CELL(future_cells, x, y) != CELL(cells, x, y)) {
                tb_change_cell(2*x, y, ' ', 0, CELL(future_cells, x, y) ? 8 : 0);
                tb_change_cell(2*x+1, y, ' ', 0, CELL(future_cells, x, y) ? 8 : 0);
            }
        }
    }
}

int main(int argc, char **argv) {
    int randomize = 1;
    for (int i = 1; i < argc; i++) {
        if (strcmp(argv[i], "--help") == 0) {
            printf("Conway's Game of Life Viewer\nUsage: conway [-Z] [-S012345678] [-B012345678]\n");
            return 0;
        } else if (strncmp(argv[i], "-B", 2) == 0) {
            memset(rules[0], 0, sizeof(rules[0]));
            for (char *p = &argv[i][2]; *p; p++) {
                if ('0' <= *p && *p <= '8')
                    rules[0][*p - '0'] = 1;
            }
        } else if (strncmp(argv[i], "-S", 2) == 0) {
            memset(rules[1], 0, sizeof(rules[1]));
            for (char *p = &argv[i][2]; *p; p++) {
                if ('0' <= *p && *p <= '8')
                    rules[1][*p - '0'] = 1;
            }
        } else if (strcmp(argv[i], "-Z") == 0) {
            randomize = 0;
        }
    }

    int ret = tb_init();
    if (ret) {
        fprintf(stderr, "tb_init() failed with error code %d\n", ret);
        return 1;
    }
    tb_select_input_mode(TB_INPUT_MOUSE);

    // Cells are 2 characters wide so they look square
    char *buffers[2];
    int flipflop = 0;
  resize:
    W = tb_width()/2, H = tb_height();
    buffers[0] = calloc(W*H, sizeof(char));
    buffers[1] = calloc(W*H, sizeof(char));
    if (randomize)
        for (int x = 0; x < W; x++)
            for (int y = 0; y < H; y++)
                CELL(buffers[flipflop], x, y) = random() % 2;

    int draw_mode = 1;
    tb_clear();
    while (1) {
        update(buffers[flipflop], buffers[!flipflop]);
        flipflop = !flipflop;
      present:
        tb_present();
        usleep(60000);
        struct tb_event ev;
        int drew = 0;
        while (tb_peek_event(&ev, 0)) {
            switch (ev.type) {
                case TB_EVENT_RESIZE:
                    free(buffers[0]);
                    free(buffers[1]);
                    goto resize;

                case TB_EVENT_KEY:
                    if (ev.key == TB_KEY_ESC && tb_peek_event(&ev, 50) == 0)
                        goto done;
                    else if (ev.ch == 'q')
                        goto done;
                    else if (ev.key == TB_KEY_SPACE)
                        draw_mode = !draw_mode;
                    break;

                case TB_EVENT_MOUSE:
                    CELL(buffers[flipflop], ev.x/2, ev.y) = draw_mode;
                    tb_change_cell(2*(ev.x/2), ev.y, ' ', 0, draw_mode ? 8 : 0);
                    tb_change_cell(2*(ev.x/2)+1, ev.y, ' ', 0, draw_mode ? 8 : 0);
                    drew = 1;
                    break;
            }
        }
        if (drew) goto present;
    }
  done:
    tb_shutdown();
    return 0;
}