defmodule AOC.Day6 do
  use AOC.Day, day: 6

  def parse_input(lines), do: lines |> hd() |> String.to_charlist()

  def part1(input) do
    find_marker(input, 0, 4)
  end

  def part2(input) do
    find_marker(input, 0, 14)
  end

  def find_marker(signal, index, length) do
    distinct =
      signal
      |> Enum.take(length)
      |> MapSet.new()
      |> Enum.count()

    if distinct == length do
      index + length
    else
      signal
      |> tl()
      |> find_marker(index + 1, length)
    end
  end
end