const { Glib, Maps, Sets, Vector, twodee } = require('../../lib');

const parse = (input) => {
  const pairs = Glib.fromLines(input).map((i) => i.split(')')).array;
  const parents = pairs.glib.map((pair) => pair.safeReverse()).toMap();
  const children = pairs.glib.toMapSet();

  const points = new Map(
    pairs.glib
      .flatMap((i) => i)
      .unique()
      .map((point) => [
        point,
        {
          children: children.get(point),
          parent: parents.get(point),
        },
      ]),
  );

  return points;
};

const count = (map, source = 'COM', depth = 0n) => {
  return (
    (map.get(source).children || []).glib
      .map((name) => count(map, name, depth + 1n))
      .sum() + depth
  );
};

const distance = (source, destination, info) => {
  let current = source;
  let distance = 0n;
  while (current !== destination && current !== 'COM') {
    distance++;
    current = info.get(current).parent;
  }
  if (current !== destination) {
    throw new Error('no link (toward COM)');
  }
  return distance;
};

const allParents = (source, input) =>
  new Glib(
    (function*() {
      let current = source;
      while (current !== 'COM') {
        current = input.get(current).parent;
        yield current;
      }
    })(),
  );

module.exports = {
  '1': (input) => count(parse(input), 'COM'),
  2: (input) => {
    input = parse(input);
    return (
      Sets.and(allParents('YOU', input).set, allParents('SAN', input).set)
        .glib.map(
          (midpoint) =>
            distance('YOU', midpoint, input) + distance('SAN', midpoint, input),
        )
        .min() - 2n
    );
  },
};