defmodule Day6 do
  @example """
  abc

  a
  b
  c

  ab
  ac

  a
  a
  a
  a

  b
  """

  def part1(example \\ false) do
    parse_input(example)
    |> Enum.map(&questions_with_any_yes/1)
    |> Enum.map(&MapSet.size/1)
    |> Enum.sum()
  end

  def part2(example \\ false) do
    parse_input(example)
    |> Enum.map(&questions_with_all_yes/1)
    |> Enum.map(&MapSet.size/1)
    |> Enum.sum()
  end

  def parse_input(example) do
    if(example, do: @example, else: File.read!("lib/day6/input.txt"))
    |> String.trim()
    |> String.split("\n\n")
  end

  def questions_with_any_yes(str) do
    str
    |> String.replace(~r/\s/, "")
    |> String.to_charlist()
    |> MapSet.new()
  end

  def questions_with_all_yes(str) do
    people =
      str
      |> String.split("\n")
      |> Enum.map(fn person ->
        person
        |> String.to_charlist()
        |> MapSet.new()
      end)

    people
    |> Enum.drop(1)
    |> Enum.reduce(List.first(people), &MapSet.intersection/2)
  end
end