Add notifications of severed relationships (#27511)

app/models/account_relationship_severance_event.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+#
+# == Schema Information
+#
+# Table name: account_relationship_severance_events
+#
+#  id                              :bigint(8)        not null, primary key
+#  account_id                      :bigint(8)        not null
+#  relationship_severance_event_id :bigint(8)        not null
+#  created_at                      :datetime         not null
+#  updated_at                      :datetime         not null
+#
+class AccountRelationshipSeveranceEvent < ApplicationRecord
+  belongs_to :account
+  belongs_to :relationship_severance_event
+
+  delegate :severed_relationships, :type, :target_name, :purged, to: :relationship_severance_event, prefix: false
+
+  before_create :set_relationships_count!
+
+  private
+
+  def set_relationships_count!
+    self.relationships_count = severed_relationships.where(local_account: account).count
+  end
+end

app/models/concerns/account/interactions.rb

@@ -83,6 +83,11 @@ module Account::Interactions
     has_many :following, -> { order('follows.id desc') }, through: :active_relationships,  source: :target_account
     has_many :followers, -> { order('follows.id desc') }, through: :passive_relationships, source: :account
 
+    with_options class_name: 'SeveredRelationship', dependent: :destroy do
+      has_many :severed_relationships, foreign_key: 'local_account_id', inverse_of: :local_account
+      has_many :remote_severed_relationships, foreign_key: 'remote_account_id', inverse_of: :remote_account
+    end
+
     # Account notes
     has_many :account_notes, dependent: :destroy
 

app/models/concerns/account/merging.rb

@@ -48,6 +48,18 @@ module Account::Merging
       record.update_attribute(:account_warning_id, id)
     end
 
+    SeveredRelationship.where(local_account_id: other_account.id).reorder(nil).find_each do |record|
+      record.update_attribute(:local_account_id, id)
+    rescue ActiveRecord::RecordNotUnique
+      next
+    end
+
+    SeveredRelationship.where(remote_account_id: other_account.id).reorder(nil).find_each do |record|
+      record.update_attribute(:remote_account_id, id)
+    rescue ActiveRecord::RecordNotUnique
+      next
+    end
+
     # Some follow relationships have moved, so the cache is stale
     Rails.cache.delete_matched("followers_hash:#{id}:*")
     Rails.cache.delete_matched("relationships:#{id}:*")

app/models/notification.rb

@@ -54,6 +54,9 @@ class Notification < ApplicationRecord
     update: {
       filterable: false,
     }.freeze,
+    severed_relationships: {
+      filterable: false,
+    }.freeze,
     'admin.sign_up': {
       filterable: false,
     }.freeze,
@@ -86,6 +89,7 @@ class Notification < ApplicationRecord
     belongs_to :favourite, inverse_of: :notification
     belongs_to :poll, inverse_of: false
     belongs_to :report, inverse_of: false
+    belongs_to :relationship_severance_event, inverse_of: false
   end
 
   validates :type, inclusion: { in: TYPES }
@@ -182,6 +186,11 @@ class Notification < ApplicationRecord
       self.from_account_id = activity&.status&.account_id
     when 'Account'
       self.from_account_id = activity&.id
+    when 'AccountRelationshipSeveranceEvent'
+      # These do not really have an originating account, but this is mandatory
+      # in the data model, and the recipient's account will by definition
+      # always exist
+      self.from_account_id = account_id
     end
   end
 

app/models/relationship_severance_event.rb

@@ -0,0 +1,56 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: relationship_severance_events
+#
+#  id          :bigint(8)        not null, primary key
+#  type        :integer          not null
+#  target_name :string           not null
+#  purged      :boolean          default(FALSE), not null
+#  created_at  :datetime         not null
+#  updated_at  :datetime         not null
+#
+class RelationshipSeveranceEvent < ApplicationRecord
+  self.inheritance_column = nil
+
+  has_many :severed_relationships, inverse_of: :relationship_severance_event, dependent: :delete_all
+
+  enum type: {
+    domain_block: 0,
+    user_domain_block: 1,
+    account_suspension: 2,
+  }
+
+  scope :about_local_account, ->(account) { where(id: SeveredRelationship.about_local_account(account).select(:relationship_severance_event_id)) }
+
+  def import_from_active_follows!(follows)
+    import_from_follows!(follows, true)
+  end
+
+  def import_from_passive_follows!(follows)
+    import_from_follows!(follows, false)
+  end
+
+  def affected_local_accounts
+    Account.where(id: severed_relationships.select(:local_account_id))
+  end
+
+  private
+
+  def import_from_follows!(follows, active)
+    SeveredRelationship.insert_all(
+      follows.pluck(:account_id, :target_account_id, :show_reblogs, :notify, :languages).map do |account_id, target_account_id, show_reblogs, notify, languages|
+        {
+          local_account_id: active ? account_id : target_account_id,
+          remote_account_id: active ? target_account_id : account_id,
+          show_reblogs: show_reblogs,
+          notify: notify,
+          languages: languages,
+          relationship_severance_event_id: id,
+          direction: active ? :active : :passive,
+        }
+      end
+    )
+  end
+end

app/models/severed_relationship.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: severed_relationships
+#
+#  id                              :bigint(8)        not null, primary key
+#  relationship_severance_event_id :bigint(8)        not null
+#  local_account_id                :bigint(8)        not null
+#  remote_account_id               :bigint(8)        not null
+#  direction                       :integer          not null
+#  show_reblogs                    :boolean
+#  notify                          :boolean
+#  languages                       :string           is an Array
+#  created_at                      :datetime         not null
+#  updated_at                      :datetime         not null
+#
+class SeveredRelationship < ApplicationRecord
+  belongs_to :relationship_severance_event
+  belongs_to :local_account, class_name: 'Account'
+  belongs_to :remote_account, class_name: 'Account'
+
+  enum direction: {
+    passive: 0, # analogous to `local_account.passive_relationships`
+    active: 1, # analogous to `local_account.active_relationships`
+  }
+
+  scope :about_local_account, ->(account) { where(local_account: account) }
+
+  scope :active, -> { where(direction: :active) }
+  scope :passive, -> { where(direction: :passive) }
+
+  def account
+    active? ? local_account : remote_account
+  end
+
+  def target_account
+    active? ? remote_account : local_account
+  end
+end