/*
 * This request is similar reverse bit in another request
 * -> check reverse_bit_tg. However that coding is for 2 cases:
 *  - Reverse FULL 32 bits
 *  - Reverse exact the number counted from first bit 1 to end (ex: 0x3A --> b'11 1010)
 *
 * In this request will reverse exactly input from user as 0x3A
 */

/* Include lib */
#include <stdio.h>
#include <assert.h>
#include <string.h>

/* Define */

/* API display with bit presentation */
void bit_display_from_input(int hex_num, int bit_cnt)
{
  int i;

  for (i = (bit_cnt - 1); i >= 0 ; i--) {
    printf("%d", (hex_num >> i) & 0x1);
  }
}

/* API reverse bit from USER input */
int reverse_hex_input(int hex_num, int bit_cnt)
{
  int i, tmp, ret = 0;

  for (i = 0; i < bit_cnt; i++) {
    tmp = (hex_num >> i) & 0x1;
    ret = (ret << 1) | tmp; 
  }

  return ret;
}

/* Main func interract with user */
int main(void)
{
  int sel, hex_num, bit_cnt, ret;
  char str[32] = { 0 };

  while (1) {
    printf("\n\nSelection: \n");
    printf("0 : input hex number to reverse\n");
    printf("1 : Exit\n");
    printf("Select: ");
    scanf("%d", &sel);

    if (sel == 0) {
      printf("Input hex (without '0x'): ");
      scanf("%x", &hex_num);

      /* TODO: Write func or get lib to convert string to number */
#if 0
      printf("Input bit cnt: ");
      scanf("%d", &bit_cnt);
#else
      sprintf(str, "%x", hex_num);
      bit_cnt = strlen(str) * 4;
#endif

      /* Reverse */
      ret = reverse_hex_input(hex_num, bit_cnt);

      /* Print hex */
      printf("0x%x => 0x%x \n", hex_num, ret);

      /* Print bin */
      bit_display_from_input(hex_num, bit_cnt);
      printf(" => ");
      bit_display_from_input(ret, bit_cnt);
     } else {
      return 0;
    }
  }

  return -1;
}