class ActiveRecord::Base
  def to_summary
    respond_to?(:name) ? name : "to_summary unimplemented for #{self.class}"
  end
  
  def humanized_modified_attributes
    modified_attributes.keys.inject({}) do |hash, attribute|
      hash[attribute] = humanized_attribute(attribute, :read_original_attribute)
      hash
    end
  end
  
  # Turns an attribute into a human readable form:
  #  - Converts a Date or Time into a string
  #  - Displays the result of running to_summary on a belongs_to association
  def humanized_attribute(attr_name, method = :read_attribute)
    attr_name = attr_name.to_s
    value = send(method, attr_name)
    
    return nil if value.blank?
    
    if reflection = self.class.reflect_on_belongs_to_association_by_foreign_key(attr_name)
      # if the ids match, use the cached object
      cached_association = instance_variable_get("@#{reflection.name}")
      if cached_association and cached_association.id == value
        cached_association.to_summary
      else
        begin
          klass = if reflection.options[:polymorphic]
            self[attr_name.gsub(/_id$/, "_type")].constantize
          else
            reflection.klass
          end
          
          klass.find(value).to_summary
        rescue ActiveRecord::RecordNotFound
        end
      end
    else
      value.to_s
    end
  end
  
  class << self
    def reflect_on_belongs_to_association_by_foreign_key(foreign_key)
      reflections.values.find { |reflection| reflection.macro == :belongs_to && reflection.primary_key_name == foreign_key }
    end
  end
end