class Place < ActiveRecord::Base
 has_many :place_promotions
  has_many :livebookings_promos, :through => :place_promotions, :source => :livebookings_promo,
                      :conditions => "place_promotions.promotion_type = 'LivebookingsPromo'"
  has_many :coupons, :through => :place_promotions, :source => :coupon,
                      :conditions => "place_promotions.promotion_type = 'Coupon'"

  def promotions
    self.livebookings_promos + self.coupons
  end
end

class PlacePromotion < ActiveRecord::Base
  belongs_to :place
  belongs_to :promotion, :polymorphic => true

  belongs_to :livebookings_promo, :class_name => 'LivebookingsPromo', :foreign_key => 'promotion_id'

  belongs_to :coupon, :class_name => 'Coupon', :foreign_key => 'promotion_id'
end

class LivebookingsPromo < ActiveRecord::Base
  has_many :place_promotions, :as => :promotion
  has_many :places, :through => :place_promotions
end

class Coupon < ActiveRecord::Base
  has_many :place_promotions, :as => :promotion
  has_many :places, :through => :place_promotions
end