module ActiveRecord
  class DestroyRestrictedAssociationError < ActiveRecordError
    def initialize(model, by)
      super("#{model.class.name} #{model.id} destroy restricted by #{by}")
    end
  end
 
  module Associations
    def self.included(base) # :nodoc:
      base.extend ClassMethods
    end
 
    module ClassMethods
 
      alias :old_configure_dependency_for_has_many :configure_dependency_for_has_many
      alias :old_configure_dependency_for_has_one  :configure_dependency_for_has_one
 
      def verify_restrict(reflection)
        case reflection.options[:dependent]
          when :restrict
            module_eval %Q{  
              before_destroy do |record|  
                unless record.#{reflection.name}.blank?  
                  raise DestroyRestrictedAssociationError.new(record, #{reflection.name.inspect})  
                end  
              end  
            }
          else
            raise ArgumentError, "The :dependent option expects either
:destroy, :delete_all, :nullify or :restrict
(#{reflection.options[:dependent].inspect})"
        end
      end
 
      def configure_dependency_for_has_many(reflection)
        old_configure_dependency_for_has_many(reflection)
      rescue ArgumentError
        verify_restrict(reflection)
      end
 
      def configure_dependency_for_has_one(reflection)
        old_configure_dependency_for_has_one(reflection)
      rescue ArgumentError
        verify_restrict(reflection)
      end
    end
  end
end