LEGO!

lego.rb

class Monster
  def initialize(options)
    @name = options[:name]
    @lifepoints = options[:lifepoints]
    @drop_mechanic = options[:drop_mechanic]
    @hit_log = []
    @output_buffer = []
  end
  
  def get_hit(player, hit)
    @lifepoints -= hit
    @hit_log << [player, hit]
    die if @lifepoints <= 0
    
    @output_buffer << "#{player.name} hits #{hit}."
    game_log
  end
  
  private
  
  def die
    @output_buffer << "#{winning_player.name} gets the drop."
  end
  
  def winning_player
    @drop_mechanic.winning_player(@hit_log)
  end
  
  def game_log
    result = @output_buffer.reverse.join(' ')
    @output_buffer = []
    result
  end
end

class Player
  attr_reader :name
  
  def initialize(options)
    @name = options[:name]
    @strength = options[:strength]
  end
  
  def attack(monster)
    monster.get_hit(self, @strength)
  end
end

class TagFirst
  def self.winning_player(hits)
    hits[0][0]
  end
end

class MostDamage
  def self.winning_player(hits)
    players = hits.group_by { |h| h[0] }.map { |k,v| [k, v.inject(0) { |m,o| m += o[1] }] }.sort { |a,b| b[1] <=> a[1] }
    most_damage = players[0][1]
    potential_winners = players.select { |p| p[1] == most_damage }.map { |p| p[0] }
    return potential_winners.first if potential_winners.size == 1
    
    potential_winners.map { |p| [p, hits.find_index { |h| h[0] == p }] }.sort { |a,b| a[1] <=> b[1] }.first[0]
  end
end

weakie = Player.new(name: "Weakie", strength: 100)
strong = Player.new(name: "Strongie", strength: 200)

baddie = Monster.new(name: "Baddie", lifepoints: 1000, drop_mechanic: TagFirst)

weakie.attack baddie # => "Weakie hits 100."
strong.attack baddie # => "Strongie hits 200."
weakie.attack baddie # => "Weakie hits 100."
strong.attack baddie # => "Strongie hits 200."
weakie.attack baddie # => "Weakie hits 100."
strong.attack baddie # => "Strongie hits 200."
weakie.attack baddie # => "Weakie hits 100. Weakie gets the drop."

baddie = Monster.new(name: "Baddie", lifepoints: 1000, drop_mechanic: MostDamage)

weakie.attack baddie # => "Weakie hits 100."
strong.attack baddie # => "Strongie hits 200."
weakie.attack baddie # => "Weakie hits 100."
strong.attack baddie # => "Strongie hits 200."
weakie.attack baddie # => "Weakie hits 100."
strong.attack baddie # => "Strongie hits 200."
weakie.attack baddie # => "Weakie hits 100. Strongie gets the drop."