Day 01

Section

defmodule Day01 do
  def part1(input_file_path) do
    input_file_path
    |> prepare()
    |> Enum.max()
  end

  def part2(input_file_path) do
    input_file_path
    |> prepare()
    |> top3()
    |> Enum.sum()
  end

  defp prepare(input_file_path) do
    input_file_path
    |> File.stream!()
    |> Stream.map(&String.trim/1)
    |> Stream.chunk_by(&(&1 == ""))
    |> Stream.reject(&(&1 == [""]))
    |> Stream.map(&sum_chunk/1)
  end

  defp sum_chunk(chunk) do
    chunk
    |> Stream.map(&String.to_integer/1)
    |> Enum.sum()
  end

  defp top3(enumerable) do
    Enum.reduce(enumerable, [0, 0, 0], fn
      n, [t1, t2, _t3] when n > t1 -> [n, t1, t2]
      n, [t1, t2, _t3] when n > t2 -> [t1, n, t2]
      n, [t1, t2, t3] when n > t3 -> [t1, t2, n]
      _, tops -> tops
    end)
  end
end

input_file_path = "#{__DIR__}/day01.txt"

Day01.part1(input_file_path)

Day01.part2(input_file_path)