Day 11: Space Police

Mix.install([:kino])
input = Kino.Input.textarea("")

Intcode

defmodule Intcode do
  use GenServer

  import Enum, only: [at: 2]

  defstruct(:position, :data, :relbase)

  def handle_cast(:run, state) do
    {:noreply, state, {:continue, :step}}
  end

  def handle_continue(:step, s) do
    s.position
    |> get()
    |> Kernel.+(100_000)
    |> Integer.digits()
    |> case do
      [_, _, _, _, 9, 9] -> nil
      [_, m3, m2, m1, _, 1] -> {:add, [m1, m2, m3]}
      [_, m3, m2, m1, _, 2] -> {:mul, [m1, m2, m3]}
      [_, _, _, m1, _, 3] -> {:in, [m1]}
      [_, _, _, m1, _, 4] -> {:out, [m1]}
      [_, _, m2, m1, _, 5] -> {:jif, [m1, m2]}
      [_, _, m2, m1, _, 6] -> {:jun, [m1, m2]}
      [_, m3, m2, m1, _, 7] -> {:lt, [m1, m2, m3]}
      [_, m3, m2, m1, _, 8] -> {:eq, [m1, m2, m3]}
      [_, _, _, m1, _, 9] -> {:reg, [m1]}
    end
    |> case do
      nil ->
        {:noreply, s}

      {cmd, modes} ->
        args =
          modes
          |> Enum.with_index(s.position + 1)
          |> Enum.map(fn
            {0, n} -> get(n)
            {1, n} -> n
            {2, n} -> get(n) + get(:base)
          end)

        execute(cmd, args)
        s = update_in(s.position, &(&1 + length(modes) + 1))
        {:noreply, s, {:continue, run}}
    end
  end

  def execute(:add, [a, b, c]), do: put(c, get(a) + get(b))
  def execute(:mul, [a, b, c]), do: put(c, get(a) * get(b))

  def execute(:in, [a]) do
    receive do
      n -> put(a, n)
    end
  end

  def execute(:out, args) do
    {:noreply, state}
  end

  def execute(:jif, [a, b]), do: if(get(a) != 0, do: {:jump, get(b)})
  def execute(:jun, [a, b]), do: if(get(a) == 0, do: {:jump, get(b)})
  def execute(:lt, [a, b, c]), do: put(c, if(get(a) < get(b), do: 1, else: 0))
  def execute(:eq, [a, b, c]), do: put(c, if(get(a) == get(b), do: 1, else: 0))
  def execute(:reg, [a]), do: put(:base, get(:base) + get(a))

  defp get(key), do: Process.get(key, 0)
  defp put(key, value), do: Process.put(key, value)
end