defmodule AOC.Day2 do
  def parse_line(line) do
    [min, max, char, password] = String.split(line, [" ", "-", ":"], trim: true)
    password = String.to_charlist(password)
    [char] = String.to_charlist(char)
    min = String.to_integer(min)
    max = String.to_integer(max)
    [password, char, min, max]
  end

  def validate_password1(password, char, min, max) do
    count = Enum.count(password, &(&1 == char))
    count in min..max
  end

  def part1 do
    AOC.Util.input_lines(2, 1)
    |> Enum.map(&parse_line/1)
    |> Enum.map(&apply(__MODULE__, :validate_password1, &1))
    |> Enum.count(&Function.identity/1)
  end

  def validate_password2(password, char, pos1, pos2) do
    m1 = Enum.at(password, pos1 - 1) == char
    m2 = Enum.at(password, pos2 - 1) == char

    (m1 or m2) and not (m1 and m2)
  end

  def part2 do
    AOC.Util.input_lines(2, 1)
    |> Enum.map(&parse_line/1)
    |> Enum.map(&apply(__MODULE__, :validate_password2, &1))
    |> Enum.count(&Function.identity/1)
  end
end