Conversation Flow // Mongoid

gistfile1.rb

class Conversation 
  include Mongoid::Document
  include Mongoid::Timestamps

  has_and_belongs_to_many :participants, :class_name => 'User', inverse_of: :conversations
  embeds_many :messages, :class_name => 'Message'
end

gistfile2.rb

class Message 
  include Mongoid::Document
  include Mongoid::Timestamps

  embedded_in :conversation
  belongs_to :user

  field :seen, :type => Mongoid::Boolean, :default => false
  field :body
end

gistfile3.rb

class User 
  include Mongoid::Document
  include Mongoid::Timestamps

  has_and_belongs_to_many :conversations, class_name: 'Conversation', inverse_of: :participants

end