votes: make private favorites and upvotes a Gold-only option.

Make private favorites and upvotes a Gold-only account option.

Existing Members with private favorites enabled are allowed to keep it
enabled, as long as they don't disable it. If they disable it, then they
can't re-enable it again without upgrading to Gold first.

This is a Gold-only option to prevent uploaders from creating multiple
accounts to upvote their own posts. If private upvotes were allowed for
Members, then it would be too easy to use fake accounts and private
upvotes to upvote your own posts.

app/logical/concerns/has_bit_flags.rb

@@ -6,6 +6,7 @@ module HasBitFlags
   def has_bit_flags(attributes, field: :bit_flags)
     attributes.each.with_index do |attribute, i|
       bit_flag = 1 << i
+      field_was = "#{field}_was"
 
       define_method(attribute) do
         send(field) & bit_flag > 0
@@ -15,6 +16,14 @@ module HasBitFlags
         send(field) & bit_flag > 0
       end
 
+      define_method("#{attribute}_was") do
+        send(field_was) & bit_flag > 0
+      end
+
+      define_method("#{attribute}_was?") do
+        send(field_was) & bit_flag > 0
+      end
+
       define_method("#{attribute}=") do |val|
         if val.to_s =~ /[t1y]/
           send("#{field}=", send(field) | bit_flag)

app/models/user.rb

@@ -103,6 +103,7 @@ class User < ApplicationRecord
   validates :per_page, inclusion: { in: (1..PostSets::Post::MAX_PER_PAGE) }
   validates :password, confirmation: true
   validates :comment_threshold, inclusion: { in: (-100..5) }
+  validate  :validate_enable_private_favorites, on: :update
   before_validation :normalize_blacklisted_tags
   before_create :promote_to_owner_if_first_user
   has_many :artist_versions, foreign_key: :updater_id
@@ -192,6 +193,14 @@ class User < ApplicationRecord
     end
   end
 
+  concerning :ValidationMethods do
+    def validate_enable_private_favorites
+      if enable_private_favorites_was == false && enable_private_favorites == true && !Pundit.policy!(self, self).can_enable_private_favorites?
+        errors.add(:base, "Can't enable privacy mode without a Gold account")
+      end
+    end
+  end
+
   concerning :AuthenticationMethods do
     def password=(new_password)
       @password = new_password

app/policies/user_policy.rb

@@ -31,6 +31,10 @@ class UserPolicy < ApplicationPolicy
     user.is_admin? || record.id == user.id || !record.enable_private_favorites?
   end
 
+  def can_enable_private_favorites?
+    user.is_gold?
+  end
+
   def permitted_attributes_for_create
     [:name, :password, :password_confirmation, { email_address_attributes: [:address] }]
   end

app/views/users/edit.html.erb

@@ -63,7 +63,13 @@
         <%= f.input :hide_deleted_posts, :as => :select, :label => "Deleted post filter", :hint => "Remove deleted posts from search results", :include_blank => false, :collection => [["Yes", "true"], ["No", "false"]] %>
         <%= f.input :show_deleted_children, :as => :select, :label => "Show deleted children", :hint => "Show thumbnail borders on parent posts even if the children are deleted", :include_blank => false, :collection => [["Yes", "true"], ["No", "false"]] %>
         <%= f.input :disable_categorized_saved_searches, :hint => "Don't show dialog box when creating a new saved search", :as => :select, :collection => [["No", "false"], ["Yes", "true"]], :include_blank => false %>
-        <%= f.input :enable_private_favorites, :label => "Private favorites and votes", :as => :select, :hint => "Make your favorites and upvotes private", :collection => [["No", "false"], ["Yes", "true"]], :include_blank => false %>
+        <% if policy(@user).can_enable_private_favorites? %>
+          <%= f.input :enable_private_favorites, label: "Private favorites and votes", as: :select, hint: "Make your favorites and upvotes private", collection: { "No" => false, "Yes" => true }, include_blank: false %>
+        <% elsif @user.enable_private_favorites? %>
+          <%= f.input :enable_private_favorites, label: "Private favorites and votes", as: :select, hint: "Make your favorites and upvotes private. (Warning: if you disable this, you can't re-enable it without ".html_safe + link_to("upgrading to a Gold account", new_user_upgrade_path) + " first. (".html_safe + link_to_wiki("learn more", "help:privacy_mode") + ")".html_safe, collection: { "No" => false, "Yes" => true }, include_blank: false %>
+        <% else %>
+          <%= f.input :enable_private_favorites, label: "Private favorites and votes", as: :select, hint: link_to("Upgrade to Danbooru Gold to enable private favorites and upvotes", new_user_upgrade_path), collection: { "No" => false, "Yes" => true }, include_blank: false %>
+        <% end %>
         <%= f.input :disable_tagged_filenames, :as => :select, :hint => "Don't include tags in image filenames", :collection => [["No", "false"], ["Yes", "true"]], :include_blank => false %>
         <%= f.input :disable_mobile_gestures, :as => :select, :hint => "Disable swipe left / swipe right gestures on mobile", :collection => [["No", "false"], ["Yes", "true"]], :include_blank => false %>
         <%= f.input :disable_post_tooltips, :as => :select, :hint => "Disable advanced tooltips when hovering over thumbnails", :collection => [["No", "false"], ["Yes", "true"]], :include_blank => false %>

test/functional/users_controller_test.rb

@@ -420,6 +420,34 @@ class UsersControllerTest < ActionDispatch::IntegrationTest
         assert_equal("xyz", @user.favorite_tags)
       end
 
+      context "for a Member-level user" do
+        should "allow disabling the private favorites option" do
+          @user = create(:user, enable_private_favorites: true)
+          put_auth user_path(@user), @user, params: { user: { enable_private_favorites: false }}
+
+          assert_redirected_to edit_user_path(@user)
+          assert_equal(false, @user.reload.enable_private_favorites)
+        end
+
+        should "not allow enabling the private favorites option" do
+          @user = create(:user, enable_private_favorites: false)
+          put_auth user_path(@user), @user, params: { user: { enable_private_favorites: true }}
+
+          assert_redirected_to edit_user_path(@user)
+          assert_equal(false, @user.reload.enable_private_favorites)
+        end
+      end
+
+      context "for a Gold-level user" do
+        should "allow enabling the private favorites option" do
+          @user = create(:gold_user, enable_private_favorites: false)
+          put_auth user_path(@user), @user, params: { user: { enable_private_favorites: true }}
+
+          assert_redirected_to edit_user_path(@user)
+          assert_equal(true, @user.reload.enable_private_favorites)
+        end
+      end
+
       context "changing the level" do
         should "not work" do
           @owner = create(:owner_user)