/**
 * evaluate the difficulty of hex32 according to nip-13.
 * @param hex32 a string of 64 chars - 32 bytes in hex representation
 */
export const zeroLeadingBitsCount = (hex32: string) => {
  let count = 0;
  for (let i = 0; i < 64; i += 2) {
    const hexbyte = hex32.slice(i, i + 2); // grab next byte
    if (hexbyte === '00') {
      count += 8;
      continue;
    }
    // reached non-zero byte; count number of 0 bits in hexbyte
    const bits = parseInt(hexbyte, 16).toString(2).padStart(8, '0');
    for (let b = 0; b < 8; b++) {
      if (bits[b] === '1' ) {
        break; // reached non-zero bit; stop
      }
      count += 1;
    }
    break;
  }
  return count;
};