3 files changed, 34 insertions, 0 deletions
diff --git a/app/models/account.rb b/app/models/account.rb
index 5acc8d621..59d338f5a 100644
--- a/app/models/account.rb
+++ b/app/models/account.rb
@@ -352,6 +352,12 @@ class Account < ApplicationRecord
     shared_inbox_url.presence || inbox_url
   end
 
+  def synchronization_uri_prefix
+    return 'local' if local?
+
+    @synchronization_uri_prefix ||= uri[/http(s?):\/\/[^\/]+\//]
+  end
+
   class Field < ActiveModelSerializers::Model
     attributes :name, :value, :verified_at, :account, :errors
 
diff --git a/app/models/concerns/account_interactions.rb b/app/models/concerns/account_interactions.rb
index 6a0ad5aa9..e2c4b8acf 100644
--- a/app/models/concerns/account_interactions.rb
+++ b/app/models/concerns/account_interactions.rb
@@ -243,6 +243,26 @@ module AccountInteractions
          .where('users.current_sign_in_at > ?', User::ACTIVE_DURATION.ago)
   end
 
+  def remote_followers_hash(url_prefix)
+    Rails.cache.fetch("followers_hash:#{id}:#{url_prefix}") do
+      digest = "\x00" * 32
+      followers.where(Account.arel_table[:uri].matches(url_prefix + '%', false, true)).pluck_each(:uri) do |uri|
+        Xorcist.xor!(digest, Digest::SHA256.digest(uri))
+      end
+      digest.unpack('H*')[0]
+    end
+  end
+
+  def local_followers_hash
+    Rails.cache.fetch("followers_hash:#{id}:local") do
+      digest = "\x00" * 32
+      followers.where(domain: nil).pluck_each(:username) do |username|
+        Xorcist.xor!(digest, Digest::SHA256.digest(ActivityPub::TagManager.instance.uri_for_username(username)))
+      end
+      digest.unpack('H*')[0]
+    end
+  end
+
   private
 
   def remove_potential_friendship(other_account, mutual = false)
diff --git a/app/models/follow.rb b/app/models/follow.rb
index 0b4ddbf3f..55a9da792 100644
--- a/app/models/follow.rb
+++ b/app/models/follow.rb
@@ -41,8 +41,10 @@ class Follow < ApplicationRecord
 
   before_validation :set_uri, only: :create
   after_create :increment_cache_counters
+  after_create :invalidate_hash_cache
   after_destroy :remove_endorsements
   after_destroy :decrement_cache_counters
+  after_destroy :invalidate_hash_cache
 
   private
 
@@ -63,4 +65,10 @@ class Follow < ApplicationRecord
     account&.decrement_count!(:following_count)
     target_account&.decrement_count!(:followers_count)
   end
+
+  def invalidate_hash_cache
+    return if account.local? && target_account.local?
+
+    Rails.cache.delete("followers_hash:#{target_account_id}:#{account.synchronization_uri_prefix}")
+  end
 end