class ConventionalExtensions::Loader

def extension_path_for(extension)
  @directory_name + "#{extension}.rb"
end

def extension_paths
  Dir.glob extension_path_for("*")
end

def initialize(klass, path)
  @klass, @name = klass, klass.name
  @directory_name = File.join path.match(/(?=\/extensions|\.rb)/).pre_match, "extensions/"
end

def load(*extensions)
  paths = extensions.empty? ? extension_paths : extensions.map { extension_path_for _1 }
  paths.each { load_one _1 }
end

def load_one(extension)
  contents = File.read extension
  case
  when contents.match?(/\s*class #{@name}/)
    require extension
  when !$LOADED_FEATURES.include?(extension)
    $LOADED_FEATURES << extension
    @klass.class_eval contents, extension, 0
  end
end