defmodule Day11 do
  def run do
    stones =
      File.read!("data.txt")
      |> String.trim()
      |> String.split(" ")
      |> Enum.map(&String.to_integer/1)

    total = 75

    part1 =
      Enum.reduce(stones, %{stones: 0, map: %{}}, fn stone, acc ->
        {new_stones, new_map} = processStoneCounts(stone, total, acc.map)
        %{stones: acc.stones + new_stones, map: new_map}
      end)

    dbg(part1)
  end

  defp processStoneCounts(stone, steps_left, map) do
    if steps_left == 0 do
      {1, map}
    else
      key = {steps_left, stone}

      if Map.has_key?(map, key) do
        {Map.get(map, key), map}
      else
        length = Integer.digits(stone) |> length

        new_stones2 =
          case stone do
            0 ->
              [1]

            s when rem(length, 2) == 0 ->
              Integer.digits(s)
              |> Enum.split(trunc(length / 2))
              |> Tuple.to_list()
              |> Enum.map(&Integer.undigits/1)

            s ->
              [s * 2024]
          end

        if length(new_stones2) == 2 do
          {left, map2} = processStoneCounts(hd(new_stones2), steps_left - 1, map)
          {right, map3} = processStoneCounts(Enum.at(new_stones2, 1), steps_left - 1, map2)
          {left + right, Map.put(map3, key, left + right)}
        else
          {new, map2} = processStoneCounts(hd(new_stones2), steps_left - 1, map)
          {new, Map.put(map2, key, new)}
        end
      end
    end
  end
end

Day11.run()