defmodule Aoc2023.Day4 do
  use Aoc2023

  defp numbers(values) do
    values |> String.split() |> Enum.map(&String.to_integer/1) |> MapSet.new()
  end

  def parse(input) do
    input
    |> lines
    |> Enum.map(
      &Regex.run(~r/Card\s+(?<id>\d+): (?<winning>(\s*\d+)+) \| (?<values>(\s*\d+)+)/, &1,
        capture: ["id", "winning", "values"]
      )
    )
    |> Enum.map(fn [id, winning, values] ->
      {String.to_integer(id),
       MapSet.intersection(numbers(winning), numbers(values)) |> MapSet.size()}
    end)
  end

  def part1(input) do
    for {_, count} <- input,
        count > 0 do
      2 ** (count - 1)
    end
    |> Enum.sum()
  end

  def part2(input) do
    for {id, count} <- input,
        id_ <- (id + 1)..(id + count)//1,
        reduce: input |> Enum.map(elem(0) &&& const(1)) |> Enum.into(%{}) do
      acc -> Map.update!(acc, id_, &(&1 + Map.get(acc, id)))
    end
    |> Enum.map(pipe(elem(1)))
    |> Enum.sum()
  end
end