board.ex

defmodule TicTacToe do
  defmodule Board do
    def create(maxX \\ 3, maxY \\ 3) do
      for x <- 0..(maxX - 1),
          y <- 0..(maxY - 1) do
        {{x, y}, nil}
      end
      |> Map.new()
      |> Map.put_new(:maxY, maxY)
      |> Map.put_new(:maxX, maxX)
    end

    def is_valid_play?(b, {x, y}) do
      Map.has_key?(b, {x, y}) and b[{x, y}] == nil
    end

    def play(b, {x, y}, val) do
      case is_valid_play?(b, {x, y}) do
        true ->
          {:ok, Map.put(b, {x, y}, val)}

        false ->
          {:error, b}
      end
    end

    def get_winner(b) do
      # TODO
      nil
    end
  end

  defmodule Game do
    def create do
      %{
        status: :playing,
        winner: nil,
        board: Board.create(),
        turn: :x
      }
    end

    def play(game, {x, y}, player) do
      IO.puts("Trying to play: #{player} @ {#{x}, #{y}}")

      cond do
        !is_game_active?(game) ->
          {:error, game, "game not active"}

        !is_players_turn?(game, player) ->
          {:error, game, "not players turn"}

        !Board.is_valid_play?(game.board, {x, y}) ->
          {:error, game, "cannot play here"}

        true ->
          {
            :ok,
            game
            |> update_board({x, y}, player)
            |> switch_turn()
          }
      end
    end

    def update_board(game, {x, y}, player) do
      Map.update!(game, :board, fn board ->
        {_, new_board} = Board.play(board, {x, y}, player)
        new_board
      end)
    end

    def switch_turn(game) do
      %{
        game
        | turn:
            if game.turn == :x do
              :y
            else
              :x
            end
      }
    end

    def is_game_active?(game) do
      game.status == :playing
    end

    def is_players_turn?(game, player) do
      game.turn === player
    end

    def is_valid_player?(x) do
      x == :x or x == :o
    end
  end

  def get_2nd(iter) do
    Enum.at(Tuple.to_list(iter), 1)
  end

  def test do
    Game.create()
    |> Game.play({0, 0}, :x)
    |> get_2nd
    |> Game.play({1, 0}, :o)
    |> get_2nd
    |> Game.play({5, 0}, :x)
  end
end