9 files changed, 77 insertions, 2 deletions
diff --git a/app/lib/activitypub/activity.rb b/app/lib/activitypub/activity.rb
index 0a729011f..87318fb1c 100644
--- a/app/lib/activitypub/activity.rb
+++ b/app/lib/activitypub/activity.rb
@@ -50,6 +50,8 @@ class ActivityPub::Activity
         ActivityPub::Activity::Add
       when 'Remove'
         ActivityPub::Activity::Remove
+      when 'Move'
+        ActivityPub::Activity::Move
       end
     end
   end
diff --git a/app/lib/activitypub/activity/follow.rb b/app/lib/activitypub/activity/follow.rb
index c45832648..7ca650fdf 100644
--- a/app/lib/activitypub/activity/follow.rb
+++ b/app/lib/activitypub/activity/follow.rb
@@ -6,7 +6,7 @@ class ActivityPub::Activity::Follow < ActivityPub::Activity
 
     return if target_account.nil? || !target_account.local? || delete_arrived_first?(@json['id']) || @account.requested?(target_account)
 
-    if target_account.blocking?(@account) || target_account.domain_blocking?(@account.domain)
+    if target_account.blocking?(@account) || target_account.domain_blocking?(@account.domain) || target_account.moved?
       reject_follow_request!(target_account)
       return
     end
diff --git a/app/lib/activitypub/activity/move.rb b/app/lib/activitypub/activity/move.rb
new file mode 100644
index 000000000..d7a5f595c
--- /dev/null
+++ b/app/lib/activitypub/activity/move.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+class ActivityPub::Activity::Move < ActivityPub::Activity
+  PROCESSING_COOLDOWN = 7.days.seconds
+
+  def perform
+    return if origin_account.uri != object_uri || processed?
+
+    mark_as_processing!
+
+    target_account = ActivityPub::FetchRemoteAccountService.new.call(target_uri)
+
+    return if target_account.nil? || !target_account.also_known_as.include?(origin_account.uri)
+
+    # In case for some reason we didn't have a redirect for the profile already, set it
+    origin_account.update(moved_to_account: target_account) if origin_account.moved_to_account_id.nil?
+
+    # Initiate a re-follow for each follower
+    origin_account.followers.local.select(:id).find_in_batches do |follower_accounts|
+      UnfollowFollowWorker.push_bulk(follower_accounts.map(&:id)) do |follower_account_id|
+        [follower_account_id, origin_account.id, target_account.id]
+      end
+    end
+  end
+
+  private
+
+  def origin_account
+    @account
+  end
+
+  def target_uri
+    value_or_id(@json['target'])
+  end
+
+  def processed?
+    redis.exists("move_in_progress:#{@account.id}")
+  end
+
+  def mark_as_processing!
+    redis.setex("move_in_progress:#{@account.id}", PROCESSING_COOLDOWN, true)
+  end
+end
diff --git a/app/lib/activitypub/adapter.rb b/app/lib/activitypub/adapter.rb
index d35cae889..99f4d9305 100644
--- a/app/lib/activitypub/adapter.rb
+++ b/app/lib/activitypub/adapter.rb
@@ -10,6 +10,7 @@ class ActivityPub::Adapter < ActiveModelSerializers::Adapter::Base
         'manuallyApprovesFollowers' => 'as:manuallyApprovesFollowers',
         'sensitive'                 => 'as:sensitive',
         'movedTo'                   => { '@id' => 'as:movedTo', '@type' => '@id' },
+        'alsoKnownAs'               => { '@id' => 'as:alsoKnownAs', '@type' => '@id' },
         'Hashtag'                   => 'as:Hashtag',
         'ostatus'                   => 'http://ostatus.org#',
         'atomUri'                   => 'ostatus:atomUri',
diff --git a/app/models/account.rb b/app/models/account.rb
index 66f02b27d..f354bc29b 100644
--- a/app/models/account.rb
+++ b/app/models/account.rb
@@ -44,6 +44,7 @@
 #  fields                  :jsonb
 #  actor_type              :string
 #  discoverable            :boolean
+#  also_known_as           :string           is an Array
 #
 
 class Account < ApplicationRecord
@@ -227,6 +228,10 @@ class Account < ApplicationRecord
     end
   end
 
+  def also_known_as
+    self[:also_known_as] || []
+  end
+
   def fields
     (self[:fields] || []).map { |f| Field.new(self, f) }
   end
diff --git a/app/serializers/activitypub/actor_serializer.rb b/app/serializers/activitypub/actor_serializer.rb
index 72c30dc73..6746c1782 100644
--- a/app/serializers/activitypub/actor_serializer.rb
+++ b/app/serializers/activitypub/actor_serializer.rb
@@ -14,6 +14,7 @@ class ActivityPub::ActorSerializer < ActiveModel::Serializer
   has_many :virtual_attachments, key: :attachment
 
   attribute :moved_to, if: :moved?
+  attribute :also_known_as, if: :also_known_as?
 
   class EndpointsSerializer < ActiveModel::Serializer
     include RoutingHelper
@@ -116,6 +117,10 @@ class ActivityPub::ActorSerializer < ActiveModel::Serializer
     ActivityPub::TagManager.instance.uri_for(object.moved_to_account)
   end
 
+  def also_known_as?
+    !object.also_known_as.empty?
+  end
+
   class CustomEmojiSerializer < ActivityPub::EmojiSerializer
   end
 
diff --git a/app/services/activitypub/process_account_service.rb b/app/services/activitypub/process_account_service.rb
index 5c865dae2..d6480028f 100644
--- a/app/services/activitypub/process_account_service.rb
+++ b/app/services/activitypub/process_account_service.rb
@@ -75,6 +75,7 @@ class ActivityPub::ProcessAccountService < BaseService
     @account.note                    = @json['summary'] || ''
     @account.locked                  = @json['manuallyApprovesFollowers'] || false
     @account.fields                  = property_values || {}
+    @account.also_known_as           = as_array(@json['alsoKnownAs'] || []).map { |item| value_or_id(item) }
     @account.actor_type              = actor_type
   end
 
diff --git a/app/services/follow_service.rb b/app/services/follow_service.rb
index 0020bc9fe..862926260 100644
--- a/app/services/follow_service.rb
+++ b/app/services/follow_service.rb
@@ -12,7 +12,7 @@ class FollowService < BaseService
     target_account = ResolveAccountService.new.call(target_account, skip_webfinger: true)
 
     raise ActiveRecord::RecordNotFound if target_account.nil? || target_account.id == source_account.id || target_account.suspended?
-    raise Mastodon::NotPermittedError  if target_account.blocking?(source_account) || source_account.blocking?(target_account)
+    raise Mastodon::NotPermittedError  if target_account.blocking?(source_account) || source_account.blocking?(target_account) || target_account.moved?
 
     if source_account.following?(target_account)
       # We're already following this account, but we'll call follow! again to
diff --git a/app/workers/unfollow_follow_worker.rb b/app/workers/unfollow_follow_worker.rb
new file mode 100644
index 000000000..a2133bb8c
--- /dev/null
+++ b/app/workers/unfollow_follow_worker.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+class UnfollowFollowWorker
+  include Sidekiq::Worker
+
+  sidekiq_options queue: 'pull'
+
+  def perform(follower_account_id, old_target_account_id, new_target_account_id)
+    follower_account   = Account.find(follower_account_id)
+    old_target_account = Account.find(old_target_account_id)
+    new_target_account = Account.find(new_target_account_id)
+
+    UnfollowService.new.call(follower_account, old_target_account)
+    FollowService.new.call(follower_account, new_target_account)
+  rescue ActiveRecord::RecordNotFound
+    true
+  end
+end