Day 7

Mix.install([
  {:kino, "~> 0.8.0"}
])

Part 1

test_input = """
$ cd /
$ ls
dir a
14848514 b.txt
8504156 c.dat
dir d
$ cd a
$ ls
dir e
29116 f
2557 g
62596 h.lst
$ cd e
$ ls
584 i
$ cd ..
$ cd ..
$ cd d
$ ls
4060174 j
8033020 d.log
5626152 d.ext
7214296 k
$ cd ..
$ cd p
$ cd q
$ cd p
500001 file.txt
"""

defmodule Day7 do
  def part1(input) do
    input
    |> traverse()
    |> Enum.filter(fn {_, v} ->
      is_integer(v) and v < 100_000
    end)
    |> Keyword.values()
    |> Enum.sum()
  end

  @needed 70_000_000 - 30_000_000

  def part2(input) do
    result = input |> traverse()

    result
    |> Enum.filter(fn {_, v} ->
      is_integer(v) and v > result["/"] - @needed
    end)
    |> Keyword.values()
    |> Enum.sort()
    |> hd()
  end

  def traverse(input) do
    input
    |> String.split("\n", trim: true)
    |> Enum.reduce(%{current_dir: [], files: %{}}, fn x, state ->
      parse_command(x, state)
    end)
  end

  def parse_command("$ cd /", state) do
    Map.put(state, :current_dir, ["/"])
  end

  def parse_command("$ cd ..", state) do
    [_ | rest] = Map.get(state, :current_dir, [])
    Map.put(state, :current_dir, rest)
  end

  def parse_command("$ cd " <> dir, state) do
    [h | _] = l = Map.get(state, :current_dir, [])
    new_path = h <> "/" <> dir
    Map.put(state, :current_dir, [new_path | l])
  end

  def parse_command("$ ls" <> _, y), do: y

  def parse_command("dir " <> _, y), do: y

  def parse_command(x, y) do
    [size, _] = String.split(x)

    y.current_dir
    |> Enum.reduce(y, fn current_dir, acc ->
      Map.update(acc, current_dir, String.to_integer(size), &amp;(&amp;1 + String.to_integer(size)))
    end)
  end
end

path = "Projects/aoc/2022/day7.txt"
input = File.read!(path)

IO.inspect(Day7.part1(input))
Day7.part2(input)