# 94154500 too low

defmodule Day14 do
  def run do
    robots =
      File.read!("data.txt")
      |> String.trim()
      |> String.split("\n")
      |> Enum.map(&parse_robot/1)

    width = 101
    height = 103
    steps = 100

    new_robots =
      Enum.reduce(1..steps, robots, fn idx, acc ->
        step(acc, {width, height})
      end)

    quads = [
      Enum.filter(new_robots, fn r -> r.p.x < trunc(width / 2) and r.p.y < trunc(height / 2) end),
      Enum.filter(new_robots, fn r -> r.p.x > trunc(width / 2) and r.p.y < trunc(height / 2) end),
      Enum.filter(new_robots, fn r -> r.p.x < trunc(width / 2) and r.p.y > trunc(height / 2) end),
      Enum.filter(new_robots, fn r -> r.p.x > trunc(width / 2) and r.p.y > trunc(height / 2) end)
    ]

    part1 = Enum.map(quads, &length/1) |> Enum.reduce(1, &*/2)
    dbg(part1)

    # part 2, print until i guess i see a tree
    Enum.reduce(1..100_000, robots, fn idx, acc ->
      IO.puts(idx)

      res = step(acc, {width, height})

      # ok only print if we see something interesting like an empty corner?
      if corner_block(res) do
        render(res, {width, height})
      end

      res
    end)
  end

  defp corner_block(robots) do
    Enum.all?(0..10, fn col ->
      Enum.all?(0..10, fn row ->
        rs = Enum.filter(robots, fn %{p: %{x: x, y: y}} -> x == col and y == row end)
        length(rs) == 0
      end)
    end)
  end

  defp render(robots, {width, height}) do
    Enum.each(0..(height - 1), fn row ->
      Enum.each(0..(width - 1), fn col ->
        r = Enum.filter(robots, fn %{p: %{x: x, y: y}} -> x == col and y == row end) |> length
        if r == 0, do: IO.write("."), else: IO.write(r)
      end)

      IO.write("\n")
    end)

    IO.write("\n\n\n\n\n")
    Process.sleep(300)
    IO.puts(IO.ANSI.clear())

    robots
  end

  defp step(robots, {width, height}) do
    Enum.map(robots, fn %{p: p, v: v} ->
      x = Integer.mod(p.x + v.x, width)
      y = Integer.mod(p.y + v.y, height)
      %{p: %{x: x, y: y}, v: v}
    end)
  end

  defp parse_robot(str) do
    ~r/p=(.+),(.+) v=(.+),(.+)/
    |> Regex.run(str)
    |> tl()
    |> Enum.map(&String.to_integer/1)
    |> (fn [a, b, c, d] -> %{p: %{x: a, y: b}, v: %{x: c, y: d}} end).()
  end
end

Day14.run()