defmodule Day1 do
  def get_answer({_, total, :part1}), do: total
  def get_answer({_, totals, :part2}), do: totals |> Enum.reduce(0, fn i, acc -> i + acc end)

  def init_state(:part1 = p), do: {nil, 0, p}
  def init_state(:part2 = p), do: {nil, [0, 0, 0], p}

  def execute(line, state) do
    line
      |> to_command()
      |> apply_command(state)
  end

  defp apply_command({:add, n}, state), do: apply_add(n, state)
  defp apply_command({:reset}, state), do: apply_reset(state)

  defp to_command(s) do
    try do
      {:add, s |> String.trim() |> String.to_integer()}
    rescue
      ArgumentError -> {:reset}
    end
  end

  defp apply_add(n, {nil, total, part}), do: {n, total, part}
  defp apply_add(n, {current, total, part}), do: {n + current, total, part}

  defp take_top_three(n, list) do
    [n | list]
      |> Enum.sort(:desc)
      |> Enum.take(3)
  end

  defp apply_reset({nil, _, _} = state), do: state
  defp apply_reset(state) do
    {current, total, part} = state
    case part do
      :part1 -> {nil, max(total, current), part}
      :part2 -> {nil, take_top_three(current, total), part}
    end
  end
end