#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>

struct hash {
    uint16_t hl;
    uint16_t bc;
};

struct hash hashpass(uint8_t *password)
{
    uint8_t c, b, c1;

#define swap(x) (((x & 0x0f) << 4) | ((x & 0xf0) >> 4))
    c = password[0] & 0xf;
    b = swap(password[0]) & 0x03;
    c = ((password[1] & 0xf) + swap(c)) & 0xff;
    b = ((swap(password[1]) & 0x03) + ((b << 2) & 0xff)) & 0xff;
    c1 = c;
    c = password[2] & 0xf;
    b = ((swap(password[2]) & 0x03) + ((b << 2) & 0xff)) & 0xff;
    c = ((password[3] & 0xf) + swap(c)) & 0xff;
    b = ((swap(password[3]) & 0x03) + ((b << 2) & 0xff)) & 0xff;
#undef swap

    return (struct hash){.hl = (password[4] << 8) | b, .bc = (c << 8) | c1};
}

bool validpass(struct hash password)
{
    if ((password.hl & 0xe000) != 0) return false;
    if ((password.hl & 0x0007) != 0) return false;
    return true;
}

char *passchars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789?!";

void convpass(char *password, uint8_t *out)
{
    for (int x = 0; x < 5; x++) {
        *out++ = strchr(passchars, *password++) - passchars;
    }
}

void hex_dump(const unsigned char *buf, unsigned size)
{
    for (unsigned i = 0; i < size; i += 0x10) {
        printf("   ");
        for (unsigned x = i; x < i + 0x10 && x < size; x++)  {
            printf(" %02X", buf[x]);
        }
        printf("\n");
    }
}

int main(int argc, char *argv[])
{
    if (argc > 1 && strcmp(argv[1], "valid") == 0) {
        for (char **arg = argv + 2; arg < argv + argc; arg++) {
            uint8_t pwd[5];
            convpass(*arg, pwd);
            hex_dump(pwd, sizeof(pwd));
            struct hash hash = hashpass(pwd);
            printf("0x%04x 0x%04x\n", hash.hl, hash.bc);
            if (validpass(hash)) {
                printf("%s\n", *arg);
            }
        }
        return 0;
    }

    for (uint64_t x = 0; x < 0x40000000; x++) {
        uint8_t pwd[5];
        uint64_t val = x;
        for (uint8_t *c = pwd; c < pwd + 5; c++) {
            *c = val % 64;
            val /= 64;
        }
        struct hash hash = hashpass(pwd);
        if (validpass(hash)) {
            for (uint8_t *c = pwd; c < pwd + 5; c++) {
                putchar_unlocked(passchars[*c]);
            }
            putchar_unlocked('\n');
        }
    }
}