require "socket"

@server = TCPServer.new(5678)
@players = [@server.accept, @server.accept]
@labels = %w[X O]
@board = [[nil] * 3, [nil] * 3, [nil] * 3]
@turn = 0
@winner = nil

def write(msg)
  @players[@turn].write(msg)
end

def print_board
  position = 0
  3.times do |y|
    write("+---+---+---+\r\n")
    3.times do |row|
      3.times do |x|
        last = x == 2 ? "|\r\n" : ""
        case row
        when 0
          position = y * 3 + x + 1
          write("|#{position}  #{last}")
        when 1
          entry = @board[y][x] || " "
          write("| #{entry} #{last}")
        when 2
          write("|   #{last}")
        end
      end
    end
  end
  write("+---+---+---+\r\n")
end

def get_selection
  loop do
    write("Select a position:\r\n")
    input = @players[@turn].gets
    position = input.to_i
    if position >= 1 && position <= 9
      y = (position - 1) / 3
      x = (position - 1) % 3
      return x, y if @board[y][x].nil?
    end
  end
end

def take_turn
  print_board
  x, y = get_selection
  @board[y][x] = @labels[@turn]
  print_board
end

def check_win_row(y)
  if @board[y][0] && @board[y][0] == @board[y][1] && @board[y][0] == @board[y][2]
    return @board[y][0]
  end
end

def check_win_col(x)
  if @board[0][x] && @board[0][x] == @board[1][x] && @board[0][x] == @board[2][x]
    return @board[0][x]
  end
end

def check_end
  3.times do |i|
    if @winner = check_win_row(i)
      return
    elsif @winner = check_win_col(i)
      return
    end
  end
  if @board[0][0] && @board[0][0] == @board[1][1] && @board[0][0] == @board[2][2]
    return @winner = @board[0][0]
  end
  if @board[0][2] && @board[0][2] == @board[1][1] && @board[0][2] == @board[2][0]
    return @winner = @board[0][2]
  end
end

def print_end
  if @winner
    win_msg = "#{@winner} wins!"
  else
    win_msg = "Tie game!"
  end
  @players.each do |client|
    client.write("Game over. #{win_msg}\r\n")
  end
end

9.times do
  take_turn
  @turn ^= 1
  check_end
  break if @winner
end

print_board
print_end