table_tennis.rb

#!/usr/bin/env ruby

class Game
  def play
    setup_game
    get_players
    @server = pick_starter
    until winner
      rally
      determine_server
    end
  end

  def setup_game
    @points = Hash.new(0)
  end

  def get_players
    @players = []
    @players << prompt("Who's in this game?")
    @players << prompt("Who else?")
  end

  def prompt msg
    puts msg
    input = gets
    exit 1 if input.nil?

    input.chomp
  end

  def determine_server
    point_total = @points.values.inject(:+)
    if point_total % 5 == 0
      @server = opposite_player(@server)
      puts "Now serving: #@server"
    end
  end

  def pick_starter
    starter = @players[rand(2)]
    puts "#{starter} gets to try first."
    starter
  end

  def rally
    serve
    smack_it_back until miss?
    scorer = opposite_player(@smacker)
    @points[scorer] += 1
    puts "#@smacker biffed it. Another point for #{scorer}!"
  end

  def serve
    @smacker = @server
    while miss?
      puts "Whoa, it's a let!"
    end
  end

  def miss?
    rand(5) == 0
  end

  def opposite_player(player)
    player == @players.first ? @players.last : @players.first
  end

  def smack_it_back
    @smacker = opposite_player(@smacker)
    puts "Wow this is getting intense" if rand(8) == 0
    puts "#@smacker returns successfully!"
  end

  def winner
    potential_winner = @points.find { |player, score| score >= 21 }
    return nil unless potential_winner && @points.values.inject(:-).abs >= 2
    puts "Game over! #{potential_winner[0]} wins! Final score: #{@points.values.max}-#{@points.values.min}."
    exit 0
  end
end

Game.new.play