Day 10

Mix.install([:kino])

Input

input = Kino.Input.textarea("")

Pre-work

defmodule VS do
  def tick({cycle, x, signal, screen}) do
    new_signal = signal + if(rem(cycle + 1, 40) == 20, do: (cycle + 1) * x, else: 0)
    {cycle + 1, x, new_signal, nxt_scrn(screen, cycle, x)}
  end

  def addx({c, x, sig, scrn}, v), do: {c, x + String.to_integer(v), sig, scrn}

  defp nxt_scrn(screen, cycle, x) do
    screen <>
      if(rem(cycle, 40) in [x - 1, x, x + 1], do: "#", else: ".") <>
      if(rem(cycle + 1, 40) == 0, do: "\n", else: "")
  end
end

{_, _, signal, screen} =
  input
  |> Kino.Input.read()
  |> String.split("\n")
  |> Enum.reduce({0, 1, 0, ""}, fn
    "noop", acc -> VS.tick(acc)
    "addx " <> v, acc -> acc |> VS.tick() |> VS.tick() |> VS.addx(v)
  end)

Part 1

signal

Part 2

IO.puts(screen)