Doubly Polymorphic Join Models, for fun and profit

double_polymorphism.rb

class Delivery < ActiveRecord::Base
  belongs_to :deliverable, :polymorphic => true
  belongs_to :receivable, :polymorphic => true
  has_many :delivery_impressions
  has_many :users, :through => :delivery_impressions

  belongs_to :sender, :class_name => 'User', :foreign_key => :sender_id
end

class DeliveryImpression < ActiveRecord::Base
  belongs_to :delivery
  belongs_to :user

  has_one :deliverable, :through => :delivery

end

class User < ActiveRecord::Base

  has_many :delivery_impressions
  has_many :deliveries, :through => :delivery_impressions

  has_many :direct_deliveries, :as => :receivable, :class_name => 'Delivery'
  has_many :direct_messages, :through => :direct_deliveries, :as => :deliverable, :source => :deliverable, :source_type => 'Message'

  has_many :sent_deliveries, :class_name => 'Delivery', :foreign_key => :sender_id
  has_many :ideas, :through => :sent_deliveries, :source => :deliverable, :source_type => 'Idea'
  has_many :sent_messages, :through => :sent_deliveries, :source => :deliverable, :source_type => 'Message'
  has_many :sent_notifications, :through => :sent_deliveries, :source => :deliverable, :source_type => 'Notification'


  def unread_messages
    delivery_impressions.where(:read => false).count
  end
end

class Project < ActiveRecord::Base
  has_friendly_id :title, :use_slug => true

  has_many :deliveries, :as => :receivable
  has_many :ideas, :through => :deliveries, :as => :deliverable, :source => :deliverable, :source_type => 'Idea'
  has_many :messages, :through => :deliveries, :as => :deliverable, :source => :deliverable, :source_type => 'Message'
  has_many :notifications, :through => :deliveries, :as => :deliverable, :source => :deliverable, :source_type => 'Notification'

  has_one :sender, :through => :delivery, :class_name => 'User'
end

class Idea < ActiveRecord::Base

  has_one :delivery, :as => :deliverable
  has_one :project, :through => :delivery, :as => :receivable, :source => :receivable, :source_type => 'Project'

  has_one :sender, :through => :delivery, :class_name => 'User'

  has_many :receipts, :class_name => 'Delivery', :as => :receivable
  has_many :replies, :through => :receipts, :as => :deliverable, :source => :deliverable, :source_type => 'Reply'

  def unread_replies(user)
    DeliveryImpression.joins(:delivery).where('deliverable_type = ? AND receivable_type = ? AND receivable_id = ? AND `delivery_impressions`.read = ? AND user_id = ?', 'Reply', 'Idea', id, false, user).count
  end


end

class Message < ActiveRecord::Base
  has_one :delivery, :as => :deliverable
  has_one :project, :through => :delivery, :as => :receivable, :source => :receivable, :source_type => 'Project'

  has_many :direct_users, :through => :delivery, :as => :receivable, :source => :receivable, :source_type => 'User'

  has_many :receipts, :class_name => 'Delivery', :as => :receivable
  has_many :replies, :through => :receipts, :as => :deliverable, :source => :deliverable, :source_type => 'Reply'

  has_one :sender, :through => :delivery, :class_name => 'User'
end

class Reply < ActiveRecord::Base
  has_one :delivery, :as => :deliverable
  has_one :idea, :through => :delivery, :as => :receivable, :source => :receivable, :source_type => 'Idea'
  has_one :message, :through => :delivery, :as => :receivable, :source => :receivable, :source_type => 'Message'
  
end

class Notification < ActiveRecord::Base
  has_one :delivery, :as => :deliverable
  has_one :project, :through => :delivery, :as => :receivable, :source => :receivable, :source_type => 'Project'
  has_one :sender, :through => :delivery, :class_name => 'User'
end