/**
 * Convert a little-endian buffer into a BigInt.
 * @param buf The little-endian buffer to convert
 * @returns A BigInt with the little-endian representation of buf.
 */
export function toBigIntLE(buf: Buffer): bigint {
  const reversed = Buffer.from(buf);
  reversed.reverse();
  const hex = reversed.toString('hex');
  if (hex.length === 0) {
    return BigInt(0);
  }
  return BigInt(`0x${hex}`);
}

/**
 * Convert a big-endian buffer into a BigInt
 * @param buf The big-endian buffer to convert.
 * @returns A BigInt with the big-endian representation of buf.
 */
export function toBigIntBE(buf: Buffer): bigint {
  const hex = buf.toString('hex');
  if (hex.length === 0) {
    return BigInt(0);
  }
  return BigInt(`0x${hex}`);
}

/**
 * Convert a BigInt to a little-endian buffer.
 * @param num   The BigInt to convert.
 * @param width The number of bytes that the resulting buffer should be.
 * @returns A little-endian buffer representation of num.
 */
export function toBufferLE(num: bigint, width: number): Buffer {
  const hex = num.toString(16);
  const buffer = Buffer.from(hex.padStart(width * 2, '0').slice(0, width * 2), 'hex');
  buffer.reverse();
  return buffer;
}

/**
 * Convert a BigInt to a big-endian buffer.
 * @param num   The BigInt to convert.
 * @param width The number of bytes that the resulting buffer should be.
 * @returns A big-endian buffer representation of num.
 */
export function toBufferBE(num: bigint, width: number): Buffer {
  const hex = num.toString(16);
  return Buffer.from(hex.padStart(width * 2, '0').slice(0, width * 2), 'hex');
}