this seems easier than expected

app/models/billing/page_unlock_promo_code.rb

@@ -6,16 +6,13 @@ class PageUnlockPromoCode < ApplicationRecord
     page_types.split('|') & Rails.application.config.content_types[:all].map(&:name)
   end
 
-  def already_activated_users
-    promotions.select(:user_id)
-  end
 
   def activate!(user)
     return false unless uses_remaining > 0
 
     # Make sure this user hasn't activated this promo code before
     return false unless user.present?
-    # return if users.where(id: user.id).any?
+    return false if users.pluck(:id).include?(user.id)
 
     # Activate!
     # technically two requests at the same time could still double-activate at 

app/models/user.rb

@@ -25,6 +25,7 @@ class User < ApplicationRecord
   end
   has_many :promotions
 
+
   has_many :image_uploads
 
   has_one :referral_code, dependent: :destroy
@@ -133,6 +134,7 @@ class User < ApplicationRecord
     "https://www.gravatar.com/avatar/#{email_md5}?d=identicon&s=#{size}".html_safe
   end
 
+  # TODO these (3) can probably all be scopes on the related object, no?
   def active_subscriptions
     subscriptions
       .where('start_date < ?', Time.now)
@@ -144,6 +146,10 @@ class User < ApplicationRecord
     BillingPlan.where(id: billing_plan_ids).uniq
   end
 
+  def active_promotions
+    promotions.active
+  end
+
   def initialize_stripe_customer
     if self.stripe_customer_id.nil?
       customer_data = Stripe::Customer.create(email: self.email)