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

char *s[] = {
#include "s.h"
NULL
};

int main(int argc, char **argv)
{
    int i, j, k, r, c, m = -1, t = 1;
    for (c = 0; s[c]; c++)
        ;
    int l[c];
    bzero(l, sizeof(l));
    for (i = 0; i < c; i++) {
        l[i] = strlen(s[i]);
        if (l[i] > m)
            m = l[i];
    }

    int n = 4;
    char K[n + 1];


    unsigned char key[n][256];
    for (j = 0; j < n; j++)
        for (i = 0; i < 256; i++)
            key[j][i] = i;

    srandom(time(NULL));

    for (i = 0; i < c; i++)
        for (j = 0; j < l[i]; j++)
            key[j % n][s[i][j]] = 0;

    for (k = 0; k < n; k++) {
        for (i = 0, j = 0; i < 256; i++)
            if (isprint(key[k][i]))
                key[k][j++] = key[k][i];
        if (j < 1) {
            printf("No suitable key found at step %d\n", k);
            return 2;
        }
        K[k] = key[k][random() % j];
    }
    K[k] = 0;
    printf("KEY IS %s\n", K);

    char e[m + 1], d[m + 1];
    for (i = 0; i < c; i++) {
        /* encode */
        for (j = 0; j < l[i]; j++)
            e[j] = s[i][j] ^ K[j % n];
        e[j] = 0;

        /* no extra zeroes? */
        assert(strlen(e) == l[i]);

        /* decode */
        for (j = 0; j < l[i]; j++)
            d[j] = e[j] ^ K[j % n];
        d[j] = 0;

        assert(0 == strcmp(d, s[i]));
    }

    return 0;
}