#include "md5.h"
#include <string.h>
#include <stdio.h>

unsigned int lsrf(); /* Get a random number */

static void checksum_hash(const unsigned char* input, unsigned char hashstring[33])
{
    md5_state_t state;
    md5_byte_t result[16];
    unsigned int checksum = 0;
    const unsigned char *temp;

    for(temp = input; *temp != '\0'; temp++)
        checksum += *temp;

    checksum %= 9;
    checksum++;

    md5_init(&state);
    md5_append(&state, input, strlen(input));

    do
    {
        md5_finish(&state, result);
        sprintf(hashstring,
            "%.2X%.2X%.2X%.2X%.2X%.2X%.2X%.2X%.2X%.2X%.2X%.2X%.2X%.2X%.2X%.2X",
            result[0], result[1], result[2], result[3], result[4], result[5],
            result[6], result[7], result[8], result[9], result[10], result[11],
            result[12], result[13], result[14], result[15]);

        md5_init(&state);
        md5_append(&state, hashstring, 32);
        checksum--;
    }while(checksum != 0);
}

/*
int main(int argc, char* argv[])
{
    char string[33];

    checksum_hash("1234", string);
    printf(string);
    return 0;
}
*/

void generate(const unsigned char* name, unsigned char* code)
{
    static const char product_hash[4] = "A190";
    static const char available_chars[32] = "ABCDEFGHJKLMNPQRSTUVWXY123456789";
    static const unsigned int divisors[] = {9, 2, 6};

    unsigned char name_hash[33];
    unsigned int i, j, sum;

    for(i = 0; i < 3; i++)
    {
        for(sum = j = 0; j < 4; j++)
        {
            *code = available_chars[lsrf() % 32];
            sum += *code;
            code++;
        }

        do
        {
            *code = available_chars[lsrf() % 32];
        } while(((sum + *code) % 256) % divisors[i] != 0);

        code++;
        *code = '-';
        code++;
    }

    checksum_hash(name, name_hash);

    for(i = 0; i < 4; i++)
    {
        *code = available_chars[(name_hash[i] + product_hash[i]) % 32];
        code++;
    }
}