day_04.ex

defmodule Aoc.Y2020.Day04 do
  @moduledoc """
  Solved https://adventofcode.com/2020/day/4
  """
  import Aoc.Helper.IO
  @fields ~w[byr iyr eyr hgt hcl ecl pid]
  @range %{"in" => 59..76, "cm" => 150..193, "byr" => 1920..2002, "eyr" => 2020..2030, "iyr" => 2010..2020}

  def solve_part1(data) do
    data
    |> Enum.map(fn list -> MapSet.new(Enum.map(list, fn item -> String.split(item, ":") |> Enum.at(0) end)) end)
    |> Enum.map(fn mapset -> MapSet.subset?(MapSet.new(@fields), mapset) end)
    |> Enum.count(&(&1 == true))
  end

  def solve_part2(data) do
    data
    |> Enum.map(fn list -> Enum.map(list, fn item -> String.split(item, ":") end) end)
    |> Enum.filter(fn item -> MapSet.subset?(MapSet.new(@fields), MapSet.new(item, fn [field, _value] -> field end)) end)
    |> Enum.map(fn item -> Enum.all?(item, &check_validity?/1) end)
    |> Enum.count(&(&1 == true))
  end

  defp check_validity?(["cid", _value]), do: true
  defp check_validity?(["hcl", value]), do: Regex.match?(~r/^#[a-f\d]{6}$/, value)
  defp check_validity?(["ecl", value]), do: Regex.match?(~r/^(amb|blu|brn|gry|grn|hzl|oth)$/, value)
  defp check_validity?(["pid", value]), do: Regex.match?(~r/^\d{9}$/, value)

  defp check_validity?(["byr", value]),
    do: Regex.match?(~r/^\d{4}$/, value) and String.to_integer(value) in @range["byr"]

  defp check_validity?(["eyr", value]),
    do: Regex.match?(~r/^\d{4}$/, value) and String.to_integer(value) in @range["eyr"]

  defp check_validity?(["iyr", value]),
    do: Regex.match?(~r/^\d{4}$/, value) and String.to_integer(value) in @range["iyr"]

  defp check_validity?(["hgt", value]) do
    if Regex.match?(~r/^(\d+?)(in|cm?)$/, value) do
      case Regex.run(~r/^(\d+?)(in|cm?)$/, value) |> Enum.take(-2),
        do: ([num, unit] -> String.to_integer(num) in @range[unit])
    end
  end

  def get_input() do
    get_string_input("2020", "04")
    |> String.split("\n\n")
    |> Enum.map(&String.split(&1, [" ", "\n"]))
  end

  def solved_status(), do: :solved
end