module RGen::Util::MethodDelegation

# File lib/rgen/util/method_delegation.rb, line 9
def registerDelegate(delegate, object, method)
  method = method.to_sym
  createDelegateStore(object)
  if object._methodDelegates[method]
    object._methodDelegates[method] << delegate
  else
    object._methodDelegates[method] = [delegate]
    createDelegatingMethod(object, method)
  end
end

# File lib/rgen/util/method_delegation.rb, line 20
def unregisterDelegate(delegate, object, method)
  method = method.to_sym
  return unless object.respond_to?(:_methodDelegates)
  return unless object._methodDelegates[method]
  object._methodDelegates[method].delete(delegate)
  if object._methodDelegates[method].empty?
    object._methodDelegates[method] = nil
    removeDelegatingMethod(object, method)
    removeDelegateStore(object)
  end
end

# File lib/rgen/util/method_delegation.rb, line 104
def aliasMethodName(method)
  "#{method}_delegate_original"
end

# File lib/rgen/util/method_delegation.rb, line 34
def createDelegateStore(object)
  return if object.respond_to?(:_methodDelegates)
  class << object
    def _methodDelegates
      @_methodDelegates ||= {}
    end
  end
end

# File lib/rgen/util/method_delegation.rb, line 50
  def createDelegatingMethod(object, method)
    if hasMethod(object, method)
      object.instance_eval <<-END
        class << self
          alias #{aliasMethodName(method)} #{method}
        end
      END
    end
    
    # define the delegating method
    object.instance_eval <<-END
      class << self
        def #{method}(*args, &block)
          @_methodDelegates[:#{method}].each do |d|
            catch(:continue) do
              return d.#{method}_delegated(self, *args, &block)
            end
          end
          # if aliased method does not exist, we want an exception
          #{aliasMethodName(method)}(*args, &block)
        end
      end
    END
  end

# File lib/rgen/util/method_delegation.rb, line 94
def hasMethod(object, method)
  # in Ruby 1.9, #methods returns symbols
  if object.methods.first.is_a?(Symbol)
    method = method.to_sym
  else
    method = method.to_s
  end
  object.methods.include?(method)
end

# File lib/rgen/util/method_delegation.rb, line 43
def removeDelegateStore(object)
  return unless object.respond_to?(:_methodDelegates)
  class << object
    remove_method(:_methodDelegates)
  end
end

# File lib/rgen/util/method_delegation.rb, line 75
  def removeDelegatingMethod(object, method)
    if hasMethod(object, aliasMethodName(method))
      # there is an aliased original, restore it
      object.instance_eval <<-END
        class << self
          alias #{method} #{aliasMethodName(method)}
          remove_method(:#{aliasMethodName(method)})
        end
      END
    else
      # just delete the delegating method
      object.instance_eval <<-END
        class << self
          remove_method(:#{method})
        end
      END
    end
  end