Invite module

account.rb

class Account < ActiveRecord::Base
  include SimpleTree
  include Invitation
end

invitation.rb

require 'securerandom'

module Invitation
  extend ActiveSupport::Concern
  
  included do
    before_create :generate_invitation_token
    
    define_model_callbacks :invite, :only => [:after, :before]
    
    scope :inviter, lambda { |token| where(:invitation_token => token) }
  end
    
  module ClassMethods
    # Generate a token checking if one does not already exist in the database.
    def invitation_token
      generate_token(:invitation_token)
    end
    
    # Generate a token by looping and ensuring does not already exist.
    def generate_token(column, limit=8)
      loop do
        token = ::SecureRandom.base64(16).tr('+/=lIO0', 'pqrsxyz').slice(0, limit)
        break token unless where({ column => token }).exists?
      end
    end

    def find_invite!(token)
      invitor = inviter(token).first
      raise ActiveRecord::RecordNotFound, "Invitor by #{token} not found" if invitor.nil?
      invitor
    end
  end
  
  # Join account by set parent record
  def invite(account)
    if account && account.parent.nil? && account != self && !account.children.where(:id => id).exists?
      run_callbacks :invite do
        account.parent_id = self.id
        account.save(:validate => false)
      end
    end
    
    !account.nil? && account.parent == self
  end
  
  protected
    
    # Generates a new random token for invitation, and stores the time
    # this token is being generated
    def generate_invitation_token
      self.invitation_token = self.class.invitation_token
    end
end

invitations_controller.rb

class InvitationsController < ApplicationController
  before_filter :find_invitor
  
  def show
    if account_signed_in?
      @invitor.invite(current_account)
      redirect_to account_dashboard_path
    else
      cookies[:invite] = @invitor.invitation_token
      redirect_to root_path
    end
  end
  
  protected
  
    def find_invitor
      @invitor = Writer.find_invite!(params[:id])
    end
end

sessions_controller.rb

class SessionsController < ActionController::Metal
  def create
    ...
    redirect_to account_callback_path(resource)
  end
  
  protected
  
  def account_callback_path(resource)
    ...

    if inviter = find_inviter
      "/invitations/#{inviter.invitation_token}"
    else
      ...
    end
  end
  
  def find_inviter
    token = request.cookie_jar[:invite] || params['invite'] || request.env['omniauth.params']['invite']
    token.blank? ? nil : Account.find_invite(token)
  end
end

simple_tree.rb

module SimpleTree
  extend ActiveSupport::Concern
  
  included do
    belongs_to :parent, 
      :class_name => self.base_class.to_s, 
      :foreign_key => :parent_id,
      :inverse_of => :children,
      :counter_cache => :children_count
      
    has_many :children, 
      :class_name => self.base_class.to_s, 
      :foreign_key => :parent_id,
      :inverse_of => :parent
    
    scope :roots, lambda { where(:parent_id => nil) }
    scope :with_children, lambda { where("#{quoted_table_name}.children_count > 0") }
  end
  
  def has_children?
    !children_count.zero?
  end
  
  def root?
    parent_id.nil?
  end
end