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

#define VALID_HEX_VALUES  "0123456789abcdefABCDEF"
#define BLOCK_SIZE        5
#define BLOCK_COUNT       5
#define BIT_COUNT         BLOCK_SIZE * BLOCK_COUNT
#define MAX_DEC_VALUE     pow(2, BIT_COUNT) - 1


int is_valid_hex_value(char str[]);
void dec_to_bin_arr(long dec, int* bin_arr_buf, int bin_arr_len);
void print_bin_arr(int* bin_arr, int bin_arr_len, int block_size);


int main(int argc, char* argv[]) {

  printf("\n");

  if ( argc !=3 ||
       !is_valid_hex_value(argv[1]) ||
       !is_valid_hex_value(argv[2])) {
    printf("This application will return the sum of two hex values.\n"
           "It requires exactly two valid hex arguments.\n\n");
    exit(EXIT_FAILURE);
  }

  unsigned long long first_number = strtol(argv[1], NULL, 16);
  unsigned long long second_number = strtol(argv[2], NULL, 16);
  unsigned long long sum_number = first_number + second_number;

  if (sum_number > MAX_DEC_VALUE) {
    printf("The sum is larger than %g, the max value that can be\n"
           "represented with four blocks of 4 bits.\n\n", MAX_DEC_VALUE);
    exit(EXIT_FAILURE);
  }

  printf(" * First Input Number: %ld\n"
         " * Second Input Number: %ld\n"
         " * Result: %ld\n",
         first_number, second_number, sum_number);

  int bin_arr[BIT_COUNT] = {0};
  dec_to_bin_arr(sum_number, bin_arr, BIT_COUNT);
  printf("\n");
  print_bin_arr(bin_arr, BIT_COUNT, BLOCK_SIZE);
  printf("\n\n");

  exit(EXIT_SUCCESS);
}


int is_valid_hex_value(char str[]) {

  for (int ci = 0; ci < strlen(str); ci++) {
    int char_is_valid = 0;

    for (int vci = 0; vci < strlen(VALID_HEX_VALUES); vci++)
      if (str[ci] == VALID_HEX_VALUES[vci]) char_is_valid = 1;

    if (!char_is_valid) return 0;
  }

  return 1;
}


void dec_to_bin_arr(long dec, int* bin_arr_buf, int bin_arr_len) {
  memset(bin_arr_buf, 0, sizeof bin_arr_buf);
  for (int i = 0; dec > 0; i++) {
    bin_arr_buf[i] = dec % 2;
    dec = dec / 2;
  }
}


void print_bin_arr(int* bin_arr, int bin_arr_len, int block_size) {
  for (int i = bin_arr_len - 1; i >= 0; i--) {
    printf("%d", bin_arr[i]);
    if (i % block_size == 0) printf(" ");
  }
}