Maintain only one conversation over a model using Mailboxer

This is the first time I use Mailboxer. I wanna know how to configure (and if it's possible) the gem to have a Itinerary model from my reality having a conversation which messages that comes from users. (i.e): The conversation is over the Itinerary and not between users directly.

I want to are allowed to perform things like that:

itinerary.conversation.mailbox.conversations.first (It will always have one conversation)

conv = user1.itineraries.first.conversation
user1.reply_to_conversation(conv, "It's okey I want to buy the trip")
user2.reply_to_conversation(conv, "Ok. In a while the invoice will be send")

Also I want to get the users notified when a new message from the other user comes to the Itinerary conversation.

Users could be clients or agents (using single table inheritance). Both models have the directive acts_as_messageable and the Conversation model related with the Itinerary has it too.

Help is really appreciated.

Solution

Finally I get this working. I've marked with acts_as_messageable the involved models, Client, Agent and Itinerary. I want only mails between users (i.e Clients and Agents) and I have to return nil into the itinerary model in order to avoid the mail sending. Model Itinerary that contains a mailboxer conversation have this methods defined inside:

  def name
    return "You should add method :name in your Messageable model"
  end

  def mailboxer_email(object)
    #Check if an email should be sent for that object
    #if true
    return nil
    #if false
    #return nil
  end

The solution to maintain and respond always over a conversation was to have logic to know if a message was written by one of the members of the conversation:

if (itinerary.mailbox.conversations.first.nil?)
  current_user.send_message(itinerary, params[:body], "Itinerary messages")
else
  current_user.reply_to_conversation(itinerary.mailbox.conversations.first, params[:body], "Itinerary messages")
          end

Present messages for the conversations finally is in that way:

 messages = itinerary.mailbox.conversations.first.messages.order(:created_at)
 present messages, :with => Conversations::MessageResponseEntity, success: true

And thats what all. Hope it could help anyone.