tic_tac_toe.exs

defmodule TicTacToe do
  def play do
    move(" ", " ", " ", " ", " ", " ", " ", " ", " ", "X")
  end

  def draw_grid(a1, b1, c1, a2, b2, c2, a3, b3, c3) do
    IO.puts "\n   a   b   c "
    IO.puts "1  #{a1} | #{b1} | #{c1} "
    IO.puts "  ---+---+---"
    IO.puts "2  #{a2} | #{b2} | #{c2} "
    IO.puts "  ---+---+---"
    IO.puts "3  #{a3} | #{b3} | #{c3} "
  end

  def move(a1, b1, c1, a2, b2, c2, a3, b3, c3, player) do
    draw_grid(a1, b1, c1, a2, b2, c2, a3, b3, c3)
    move = String.trim(IO.gets("\n#{player} move?  "))
    make_move(move, a1, b1, c1, a2, b2, c2, a3, b3, c3, player)
  end

  def make_move("a1", " ", b1, c1, a2, b2, c2, a3, b3, c3, player) do
    move(player, b1, c1, a2, b2, c2, a3, b3, c3, next_player(player))
  end
  def make_move("b1", a1, " ", c1, a2, b2, c2, a3, b3, c3, player) do
    move(a1, player, c1, a2, b2, c2, a3, b3, c3, next_player(player))
  end
  def make_move("c1", a1, b1, " ", a2, b2, c2, a3, b3, c3, player) do
    move(a1, b1, player, a2, b2, c2, a3, b3, c3, next_player(player))
  end
  def make_move("a2", a1, b1, c1, " ", b2, c2, a3, b3, c3, player) do
    move(a1, b1, c1, player, b2, c2, a3, b3, c3, next_player(player))
  end
  def make_move("b2", a1, b1, c1, a2, " ", c2, a3, b3, c3, player) do
    move(a1, b1, c1, a2, player, c2, a3, b3, c3, next_player(player))
  end
  def make_move("c2", a1, b1, c1, a2, b2, " ", a3, b3, c3, player) do
    move(a1, b1, c1, a2, b2, player, a3, b3, c3, next_player(player))
  end
  def make_move("a3", a1, b1, c1, a2, b2, c2, " ", b3, c3, player) do
    move(a1, b1, c1, a2, b2, c2, player, b3, c3, next_player(player))
  end
  def make_move("b3", a1, b1, c1, a2, b2, c2, a3, " ", c3, player) do
    move(a1, b1, c1, a2, b2, c2, a3, player, c3, next_player(player))
  end
  def make_move("c3", a1, b1, c1, a2, b2, c2, a3, b3, " ", player) do
    move(a1, b1, c1, a2, b2, c2, a3, b3, player, next_player(player))
  end
  def make_move(_move, a1, b1, c1, a2, b2, c2, a3, b3, c3, player) do
    IO.puts "Invalid move."
    move(a1, b1, c1, a2, b2, c2, a3, b3, c3, player)
  end

  def next_player("X"), do: "O"
  def next_player("O"), do: "X"
end

TicTacToe.play