require 'metaid'

class Object
  def solidify
    self
  end
end

class Range
  def solidify
    to_a.sort_by {|x| rand}.fetch(0)
  end
end

module Prototyping
  def new
    instance = self.class.allocate
    instance.class.instance_variable_get(:@prototype_copy).each do |var|
      instance.instance_variable_set :"@#{var}", instance_variable_get(:"@#{var}")
    end
    instance.class.instance_variable_get(:@prototype_solidify).each do |var|
      instance.instance_variable_set :"@#{var}", instance_variable_get(:"@#{var}").solidify
    end
    instance
  end
  
  module Meta
    def copy *names
      @prototype_copy ||= []
      names.each do |name|
        @prototype_copy << name
      end
    end
    
    def solidify *names
      @prototype_solidify ||= []
      names.each do |name|
        @prototype_solidify << name
      end
    end
  end

  def self.append_features klass
    super
    klass.meta_eval {include Meta}
  end
end

class Person
  include Prototyping
  attr_reader :name, :age, :strength
  
  copy :name, :age
  solidify :strength
  
  def initialize name, age, strength
    @name, @age, @strength = name, age, strength
  end
end

# Create a new instance of Person to be used as a prototype
scott_prototype = Person.new("Scott", 17, 1 .. 2)
puts scott_prototype.inspect # #<Person:0x27f05b0 @strength=1..2, @age=17, @name=\"Scott\">

# Create a new instance of Person from the prototype
# Copies or "solidify"s instance variables depending on the class definition
# In this case, solidifies the range @strength
scott_instance = scott_prototype.new
puts scott_instance.inspect
# Either:
#   #<Person:0x27f0430 @strength=1, @age=17, @name=\"Scott\">
# or
#  #<Person:0x27f0430 @strength=2, @age=17, @name=\"Scott\">