module EnumerableExtensions
  refine Array do
    def second
      self[1]
    end

    def middle
      self[size / 2]
    end
  end
end

using EnumerableExtensions

class Singleton
  private_class_method :new

  @instance = nil

  def self.instance
    @instance ||= new
  end
end

module_function

def log(level, message)
  warn "[#{level.upcase}] #{message}"
end

require "ostruct"
require "set"
require "delegate"

Point = Struct.new(:x, :y, keyword_init: true)
p = Point.new(x: 10, y: 20)

class Stack
  include Enumerable

  def initialize
    @items = []
  end

  def push(item)
    @items.push(item)
  end

  def pop
    @items.pop
  end

  def each(&block)
    @items.each(&block)
  end
end

s = Stack.new
s.push(1)
s.push(2)
s.each { |i| puts i }

$global_count = 0
DEFAULT_TIMEOUT = 30

puts "Global: #{$global_count}, Timeout: #{DEFAULT_TIMEOUT}"