class Micon::Core
  def register_extension name, &block
    name.must_be.a Symbol
    block.must_be.defined
    
    raise "extension :#{name} already registered!" if extensions.include? name

    extensions[name] = block
  end
  
  def extension name, target = nil, *args, &default_extension    
    name.must_be.a Symbol
    
    if block = extensions[name] || default_extension
      target ? target.instance_exec(*args, &block) : block.call(*args)
    end
  end
  
  def extensions; @extensions ||= {} end
end