defmodule Gumimaze do
  def read() do
    lines = "maze.txt" |> File.read!() |> String.trim() |> String.split("\n")
    for {line, y} <- Enum.with_index(lines), {c, x} <- Enum.with_index(String.to_charlist(line)), into: %{} do
      {{x, y}, c}
    end
  end

  def solve3(maze) do
    {x, y} = elem(Enum.find(maze, fn {_, v} -> v == ?S end), 0)

    solve3_supervisor(maze, x, y)
    |> Enum.max
  end

  defp solve3_supervisor(maze,x,y) do
      _ = spawn(Gumimaze, :walk3, [self(), maze, x, y, %{}, 0])
      solve3_supervisor([])
  end

  defp solve3_supervisor(score_list) do
    receive do
      {:ok, pt} ->
        solve3_supervisor([pt | score_list])
      {:error, _ } ->
        solve3_supervisor(score_list)
      after 100 ->
        score_list
    end
  end

  def walk3(parent_id, maze, x, y, walked, pt) do
    walked = Map.put(walked, {x, y}, true)
    for {x2, y2} <- [{x + 1, y}, {x, y + 1}, {x - 1, y}, {x, y - 1}] do
      case {walked[{x2, y2}], maze[{x2, y2}]} do
        {true, _} -> send(parent_id, {:error, :walked})
        {_, ?W} -> send(parent_id, {:error, :wall})
        {_, ?\s} -> spawn(Gumimaze, :walk3, [parent_id, maze, x2, y2, walked, pt])
        {_, ?1} -> spawn(Gumimaze, :walk3, [parent_id, maze, x2, y2, walked, pt + 1])
        {_, ?G} -> send(parent_id, {:ok, pt})
      end
    end
  end


  def main() do
    Gumimaze.read() |> Gumimaze.solve3() |> IO.puts
  end
end