EBLO

eblo.rb

class I
  attr_accessor :name

  def initialize(name)
    self.name = name
  end
end

class D < I
  attr_accessor :children

  def initialize(name, &block)
    super(name)
    self.children = []
    self.instance_eval(&block) if block
  end

  def directory(name, &block)
    self.children << ::U.directory(name, &block)
  end

  def file(name, opts = {})
    self.children << ::U.file(name, opts)
  end
end

class F < I
  attr_accessor :content

  def initialize(name, opts = {})
    super(name)
    self.content = opts[:content]
  end
end

module U
  def directory(name, &block)
    ::D.new(name, &block)
  end

  def file(name, opts = {})
    ::F.new(name, opts)
  end
end

include U

# Example:
#
# directory("foo") do
#   directory("bar")
#   directory("baz")
#   file("xyz")
#   file("xyzzy", content: "boo-hoo")