const { Glib, BNMath: Math, fn } = require('../../lib');

const solve2 = fn.memo((number, inputs) => {
  let paths = 0n;
  const end = Math.max(number - 3n, 0n);
  for (let next = number - 1n; next >= end; next--) {
    if (inputs.has(next)) {
      paths += solve2(next, inputs);
    } else if (next === 0n) {
      paths += 1n;
    }
  }
  return paths;
});

module.exports = {
  '1': (input) => {
    let previous = 0n;
    const differences = new Map([[3n, 1n]]);
    input = Glib.fromLines(input)
      .toInts()
      .array.safeSort((a, b) => (a - b > 0 ? 1 : -1))
      .glib.forEach((joltage) => {
        const difference = joltage - previous;
        if (difference > 3n) {
          throw new Error('invalid');
        }
        differences.set(difference, (differences.get(difference) || 0n) + 1n);
        previous = joltage;
      });
    return (differences.get(1n) || 0n) * (differences.get(3n) || 0n);
  },
  '2': (input) => {
    const target =
      Glib.fromLines(input)
        .toInts()
        .max() + 3n;

    return solve2(target, Glib.fromLines(input).toInts().set);
  },
};