class Utility {
  /**
   * This method calculates the CRC-8-AUTOSAR checksum of the given
   * array of bytes.
   *
   * This code is based on the code examples from the following page:
   * http://www.sunshine2k.de/articles/coding/crc/understanding_crc.html
   *
   * The specifics of the algorithm is coming from the AUTOSAR CRC specification:
   * https://www.autosar.org/fileadmin/user_upload/standards/classic/21-11/AUTOSAR_SWS_CRCLibrary.pdf
   *
   * > Utility.crc8([0x0, 0x0, 0x0, 0x0]).toString(16)
   * "12"
   * > Utility.crc8([0xF2, 0x01, 0x83]).toString(16)
   * "c2"
   * > Utility.crc8([0x0F, 0xAA, 0x00, 0x55]).toString(16)
   * "c6"
   * > Utility.crc8([0x00, 0xff, 0x55, 0x11]).toString(16)
   * "77"
   * > Utility.crc8([0x33, 0x22, 0x55, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff]).toString(16)
   * "11"
   * > Utility.crc8([0x92, 0x6b, 0x55]).toString(16)
   * "33"
   * > Utility.crc8([0xff, 0xff, 0xff, 0xff]).toString(16)
   * "6c"
   *
   * @param {Number[]} bytes
   * @return {Number}
   */
  static crc8Autosar(bytes) {
    const polynomial = 0x2f;
    const xorOut = 0xff;
    let crc = 0xff;

    for (const byte of bytes) {
      crc ^= byte;

      for (let i = 0; i < 8; i++) {
        if ((crc & 0x80) != 0) {
          crc = ((crc << 1) ^ polynomial) & 0xff;
        } else {
          crc <<= 1;
        }
      }
    }

    return crc ^ xorOut;
  }

  /**
   * Take a bit array and encode the contents using manchester encoding.
   *
   * @param {Number[]} bitArray
   * @return {Number[]}
   */
  static manchesterEncode(bitArray) {
    const encodedBits = [];

    for (const bit of bitArray) {
      encodedBits.push(bit ^ 1);
      encodedBits.push(bit ^ 0);
    }

    return encodedBits;
  }

  /**
   * Set the information message on the page to the given string.
   * @param {String} text
   */
  static setMessage(text) {
    const message = document.getElementById("message");
    message.textContent = text;
  }
}