#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>

#if 0
#define PART_1
#else
#define PART_2
#endif

#if 0
    #define FILE_PATH "example.txt"
    #define T_WIDTH  5
    #define T_HEIGHT 5
#else
    #define FILE_PATH "input.txt"
    #define T_WIDTH  100
    #define T_HEIGHT 100
#endif

#define WIDTH  256
#define HEIGHT 256

#define OFFSET_X ((WIDTH/2)  - (T_WIDTH/2))
#define OFFSET_Y ((HEIGHT/2) - (T_HEIGHT/2))


int board[WIDTH][HEIGHT];
int new_board[WIDTH][HEIGHT];
int enchance_alg[512];

void parse()
{
    FILE *fp = fopen(FILE_PATH, "r");
    if(!fp) {
        fprintf(stderr, "ERROR: Could not open file: %s\n", FILE_PATH);
        exit(EXIT_FAILURE);
    }

    char line[1024] = {0};

    fgets(line, sizeof(line), fp);
    for(int i = 0; i < 512; i++)
        if(line[i] == '.')
            enchance_alg[i] = 0;
        else
            enchance_alg[i] = 1;

    fgets(line, sizeof(line), fp);

    char ch;
    int i = 0;
    while((ch = getc(fp)) != EOF)
    {
        if(ch == '\n') continue;
        else if(ch == '.')
            board[i%T_WIDTH + OFFSET_X][i/T_WIDTH + OFFSET_Y] = 0;
        else if(ch == '#')
            board[i%T_WIDTH + OFFSET_X][i/T_WIDTH + OFFSET_Y] = 1;

        i++;
    }


    fclose(fp);
}

int generate_index(int *vals)
{
    int index = 0;
    for(int i = 0; i < 9; i++)
    {
        index |= (vals[8-i] & 1)<< i;
    }
    return index;
}

void enchance()
{
    for(int i = 0; i < HEIGHT; i++)
    {
        for(int j = 0; j < WIDTH; j++)
        {
            int vals[9];
            for(int y = -1; y <= 1; y++)
                for(int x = -1; x <= 1; x++)
                {
                    int vals_i = (y+1) * 3 + (x+1);
                    if(i+y < 0 || i+y >= HEIGHT ||
                       j+x < 0 || j+x >= WIDTH)
                        vals[vals_i] = board[j][i];
                    else
                        vals[vals_i] = board[j+x][i+y];
                }
            new_board[j][i] = enchance_alg[generate_index(vals)];
        }
    }
    memcpy(board, new_board, sizeof(board));
}

void print_board()
{
    for(int i = 0; i < HEIGHT; i++)
    {
        for(int j = 0; j < WIDTH; j++)
            if(board[j][i] == 0) putc('.', stdout);
            else                 putc('#', stdout);

        putc('\n', stdout);
    }
}

void print_alg()
{
    for(int i = 0; i < 512; i++)
    {
        if(enchance_alg[i] == 0) putc('.', stdout);
        else                     putc('#', stdout);
    }
    putc('\n', stdout);
}


int main(void)
{
    parse();

#ifdef PART_1
    for(int i = 0; i < 2; i++)
#endif
#ifdef PART_2
    for(int i = 0; i < 50; i++)
#endif
        enchance();

    int lit = 0;
    for(int i = 0; i < HEIGHT; i++)
        for(int j = 0; j < WIDTH; j++)
            if(board[j][i] == 1) lit++;

    printf("%d pixels are lit\n", lit);
    return 0;
}