module UndoableHelper

  def self.included (base)
    base.extend(UndoableMethods)
  end
  
  module UndoableMethods
    def undoable_methods
      # extend ClassMethods
      include InstanceMethods
    end
  end
  
  module InstanceMethods
    def change(description, undo_redirect, redo_redirect, &block)
      undo_manager.change(description, undo_redirect, redo_redirect, &block)
    end
    def undo_description
      undo_manager.undo_description
    end

    def redo_description
      undo_manager.redo_description
    end
    
    def undo_redo_links
      links = []
      links << "Undo #{link_to(undo_description, undo_path)}" if undo_description
      links << "Redo #{link_to(redo_description, redo_path)}" if redo_description
      links.join(" - ")
    end
    
    def undo
      redirect_to(undo_manager.undo)
    end

    def redo
      redirect_to(undo_manager.redo)
    end

    protected
    def undo_manager
      session['undo_manager'] ||= UndoManager.create
      UndoManager.current = session['undo_manager']
    end
  end
  
  # module ClassMethods
  # end

end