const { Glib } = require('../../lib');

const START = 0b0;
const END = 0b1111111111;

const decode = (bp) => {
  if (!bp.match(/^[bf]+[lr]+$/i, '')) {
    throw new Error('invalid input');
  }
  const binary = bp.replace(/[br]/gi, '1').replace(/[fl]/gi, '0');
  return BigInt('0b' + binary);
};

const encode = (seatId, columnCharacters, length) => {
  const binary = seatId.toString(2).padStart(length, '0');
  return (
    binary
      .slice(0, -columnCharacters)
      .replace(/1/g, 'B')
      .replace(/0/g, 'F') +
    binary
      .slice(-columnCharacters)
      .replace(/1/g, 'R')
      .replace(/0/g, 'L')
  );
};

module.exports = {
  '1': (input) =>
    Glib.fromLines(input)
      .map(decode)
      .reduce((max, current) => (max > current ? max : current), -Infinity),
  '2': (input) => {
    const foundSid = new Map(
      Glib.fromLines(input).map((bp) => [decode(bp), bp]),
    );
    return Glib.fromSequence(START, END)
      .filter(
        (sid) =>
          !foundSid.has(sid) &&
          foundSid.has(sid - 1n) &&
          foundSid.has(sid + 1n),
      )
      .join();
  },
};