#define PCRE2_CODE_UNIT_WIDTH 8

#include "pcre2.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char *argv[]) {
    if (argc < 2) {
        printf("usage: %s pattern\n", argv[0]);
        return 0;
    } // Print manual if no string is inserted

    pcre2_code *re;
    pcre2_match_data *match_data;
    int errorcode;
    int rc;
    int checksum = 0;
    int i, j = 0;
    int tmp;

    PCRE2_SPTR pattern = (const unsigned char*)"^((?:[0-9]{2})(?:0[1-9]|1[0-2])(?:0[1-9]|[1,2][0-9]|3[0,1]))-[1-2][0-9]{6}$";
    PCRE2_SPTR input = (const unsigned char*)argv[1];

    re = pcre2_compile(pattern, -1, 0, &errorcode, &erroffset, NULL);

    if (re == NULL) {
        PCRE2_UCHAR8 buffer[120];
        (void)pcre2_get_error_message(errorcode, buffer, 120);
        /* Handle error */
        return 0;
    }

    match_data = pcre2_match_data_create(20, NULL);
    rc = pcre2_match(re, input, -1, 0, 0, match_data, NULL);

    if (rc <= 0)
        printf("INVALID(Incorrect format)\n")
    else {
        // Generate checksum
        for (i = 0; i < 13; i++) {
            if (argv[1][i] != '-') {
                tmp = argv[1][i] - '0';             // Convert ASCII to integer
                checksum += tmp * ((j++) % 8 + 2);  // Mutiply specific numbers to each digit and sum up all the results
            }
        }
        checksum = (11 - (checksum % 11)) % 10;     // If checksum is 10, check sum is 0

        // Compare checksum with last digit of input
        if (argv[1][13] - '0' != checksum) {
            printf("INVALID(Wrong Checksum)\n");
        }
        else {
            printf("VALID\n");
        }
        /* Do whatever you need to validate the match */
    }

    pcre2_match_data_free(match_data);
    pcre2_code_free(re);
}