diaspora/lib/diaspora/relayable.rb

#   Copyright (c) 2010-2011, Diaspora Inc.  This file is
#   licensed under the Affero General Public License version 3 or later.  See
#   the COPYRIGHT file.

module Diaspora
  module Relayable
    include Encryptable

    def self.included(model)
      model.class_eval do
        #these fields must be in the schema for a relayable model
        xml_attr :parent_guid
        xml_attr :parent_author_signature
        xml_attr :author_signature

        validates_associated :parent
        validates :author, :presence => true
        
        delegate :public?, :to => :parent
      end
    end

    # @return [Boolean] true
    def relayable?
      true
    end

    # @return [String]
    def parent_guid
      return nil unless parent.present?
      self.parent.guid
    end

    def parent_guid= new_parent_guid
      self.parent = parent_class.where(:guid => new_parent_guid).first
    end

    # @return [Array<Person>]
    def subscribers(user)
      if user.owns?(self.parent)
        self.parent.subscribers(user)
      elsif user.owns?(self)
        [self.parent.author]
      else
        []
      end
    end

    def receive(user, person=nil)
      comment_or_like = self.class.where(:guid => self.guid).first || self

      #check to make sure the signature of the comment or like comes from the person claiming to authoring said comment or like
      unless comment_or_like.parent.author == user.person || comment_or_like.verify_parent_author_signature
        Rails.logger.info("event=receive status=abort reason='object signature not valid' recipient=#{user.diaspora_handle} sender=#{self.parent.author.diaspora_handle} payload_type=#{self.class} parent_id=#{self.parent.id}")
        return
      end

      #as the owner of the post being liked or commented on, you need to add your own signature in order to pass it to the people who received your original post
      if user.owns? comment_or_like.parent
        comment_or_like.parent_author_signature = comment_or_like.sign_with_key(user.encryption_key)
        comment_or_like.save!
      end

      #dispatch object DOWNSTREAM, received it via UPSTREAM
      unless user.owns?(comment_or_like)
        comment_or_like.save!
        Postzord::Dispatcher.build(user, comment_or_like).post
      end

      comment_or_like.socket_to_user(user) if comment_or_like.respond_to? :socket_to_user

      if comment_or_like.after_receive(user, person)
        comment_or_like 
      end
    end

    # @return [Object]
    def after_receive(user, person)
      self
    end

    def initialize_signatures
      #sign relayable as model creator
      self.author_signature = self.sign_with_key(author.owner.encryption_key)

      if !self.parent.blank? && self.author.owns?(self.parent)
        #sign relayable as parent object owner
        self.parent_author_signature = sign_with_key(author.owner.encryption_key)
      end
    end

    # @return [Boolean]
    def verify_parent_author_signature
      verify_signature(self.parent_author_signature, self.parent.author)
    end

    # @return [Boolean]
    def signature_valid?
      verify_signature(self.author_signature, self.author)
    end

    # @abstract
    # @return [Class]
    def parent_class
      raise NotImplementedError.new('you must override parent_class in order to enable relayable on this model')
    end

    # @abstract
    # @return An instance of Relayable#parent_class
    def parent
      raise NotImplementedError.new('you must override parent in order to enable relayable on this model')
    end

    # @abstract
    # @param parent An instance of Relayable#parent_class
    def parent= parent
      raise NotImplementedError.new('you must override parent= in order to enable relayable on this model')
    end
  end
end