Add account migration UI (#11846)

Fix #10736

- Change data export to be available for non-functional accounts
- Change non-functional accounts to include redirecting accounts

31 files changed, 542 insertions, 73 deletions

diff --git a/app/controllers/concerns/export_controller_concern.rb b/app/controllers/concerns/export_controller_concern.rb
index e20b71a30..bfe990c82 100644
--- a/app/controllers/concerns/export_controller_concern.rb
+++ b/app/controllers/concerns/export_controller_concern.rb
@@ -5,7 +5,10 @@ module ExportControllerConcern
 
   included do
     before_action :authenticate_user!
+    before_action :require_not_suspended!
     before_action :load_export
+
+    skip_before_action :require_functional!
   end
 
   private
@@ -27,4 +30,8 @@ module ExportControllerConcern
   def export_filename
     "#{controller_name}.csv"
   end
+
+  def require_not_suspended!
+    forbidden if current_account.suspended?
+  end
 end
diff --git a/app/controllers/settings/aliases_controller.rb b/app/controllers/settings/aliases_controller.rb
new file mode 100644
index 000000000..2b675f065
--- /dev/null
+++ b/app/controllers/settings/aliases_controller.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+class Settings::AliasesController < Settings::BaseController
+  layout 'admin'
+
+  before_action :authenticate_user!
+  before_action :set_aliases, except: :destroy
+  before_action :set_alias, only: :destroy
+
+  def index
+    @alias = current_account.aliases.build
+  end
+
+  def create
+    @alias = current_account.aliases.build(resource_params)
+
+    if @alias.save
+      redirect_to settings_aliases_path, notice: I18n.t('aliases.created_msg')
+    else
+      render :show
+    end
+  end
+
+  def destroy
+    @alias.destroy!
+    redirect_to settings_aliases_path, notice: I18n.t('aliases.deleted_msg')
+  end
+
+  private
+
+  def resource_params
+    params.require(:account_alias).permit(:acct)
+  end
+
+  def set_alias
+    @alias = current_account.aliases.find(params[:id])
+  end
+
+  def set_aliases
+    @aliases = current_account.aliases.order(id: :desc).reject(&:new_record?)
+  end
+end
diff --git a/app/controllers/settings/exports_controller.rb b/app/controllers/settings/exports_controller.rb
index 3012fbf77..0e93d07a9 100644
--- a/app/controllers/settings/exports_controller.rb
+++ b/app/controllers/settings/exports_controller.rb
@@ -6,6 +6,9 @@ class Settings::ExportsController < Settings::BaseController
   layout 'admin'
 
   before_action :authenticate_user!
+  before_action :require_not_suspended!
+
+  skip_before_action :require_functional!
 
   def show
     @export  = Export.new(current_account)
@@ -34,4 +37,8 @@ class Settings::ExportsController < Settings::BaseController
   def lock_options
     { redis: Redis.current, key: "backup:#{current_user.id}" }
   end
+
+  def require_not_suspended!
+    forbidden if current_account.suspended?
+  end
 end
diff --git a/app/controllers/settings/migrations_controller.rb b/app/controllers/settings/migrations_controller.rb
index 59eb48779..90092c692 100644
--- a/app/controllers/settings/migrations_controller.rb
+++ b/app/controllers/settings/migrations_controller.rb
@@ -4,31 +4,59 @@ class Settings::MigrationsController < Settings::BaseController
   layout 'admin'
 
   before_action :authenticate_user!
+  before_action :require_not_suspended!
+  before_action :set_migrations
+  before_action :set_cooldown
+
+  skip_before_action :require_functional!
 
   def show
-    @migration = Form::Migration.new(account: current_account.moved_to_account)
+    @migration = current_account.migrations.build
   end
 
-  def update
-    @migration = Form::Migration.new(resource_params)
+  def create
+    @migration = current_account.migrations.build(resource_params)
 
-    if @migration.valid? && migration_account_changed?
-      current_account.update!(moved_to_account: @migration.account)
+    if @migration.save_with_challenge(current_user)
+      current_account.update!(moved_to_account: @migration.target_account)
       ActivityPub::UpdateDistributionWorker.perform_async(current_account.id)
-      redirect_to settings_migration_path, notice: I18n.t('migrations.updated_msg')
+      ActivityPub::MoveDistributionWorker.perform_async(@migration.id)
+      redirect_to settings_migration_path, notice: I18n.t('migrations.moved_msg', acct: current_account.moved_to_account.acct)
     else
       render :show
     end
   end
 
+  def cancel
+    if current_account.moved_to_account_id.present?
+      current_account.update!(moved_to_account: nil)
+      ActivityPub::UpdateDistributionWorker.perform_async(current_account.id)
+    end
+
+    redirect_to settings_migration_path, notice: I18n.t('migrations.cancelled_msg')
+  end
+
+  helper_method :on_cooldown?
+
   private
 
   def resource_params
-    params.require(:migration).permit(:acct)
+    params.require(:account_migration).permit(:acct, :current_password, :current_username)
+  end
+
+  def set_migrations
+    @migrations = current_account.migrations.includes(:target_account).order(id: :desc).reject(&:new_record?)
+  end
+
+  def set_cooldown
+    @cooldown = current_account.migrations.within_cooldown.first
+  end
+
+  def on_cooldown?
+    @cooldown.present?
   end
 
-  def migration_account_changed?
-    current_account.moved_to_account_id != @migration.account&.id &&
-      current_account.id != @migration.account&.id
+  def require_not_suspended!
+    forbidden if current_account.suspended?
   end
 end
diff --git a/app/helpers/settings_helper.rb b/app/helpers/settings_helper.rb
index 2b3fd1263..ecc73baf5 100644
--- a/app/helpers/settings_helper.rb
+++ b/app/helpers/settings_helper.rb
@@ -87,4 +87,12 @@ module SettingsHelper
       'desktop'
     end
   end
+
+  def compact_account_link_to(account)
+    return if account.nil?
+
+    link_to ActivityPub::TagManager.instance.url_for(account), class: 'name-tag', title: account.acct do
+      safe_join([image_tag(account.avatar.url, width: 15, height: 15, alt: display_name(account), class: 'avatar'), content_tag(:span, account.acct, class: 'username')], ' ')
+    end
+  end
 end
diff --git a/app/models/account_alias.rb b/app/models/account_alias.rb
new file mode 100644
index 000000000..e9a0dd79e
--- /dev/null
+++ b/app/models/account_alias.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: account_aliases
+#
+#  id         :bigint(8)        not null, primary key
+#  account_id :bigint(8)
+#  acct       :string           default(""), not null
+#  uri        :string           default(""), not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+
+class AccountAlias < ApplicationRecord
+  belongs_to :account
+
+  validates :acct, presence: true, domain: { acct: true }
+  validates :uri, presence: true
+
+  before_validation :set_uri
+  after_create :add_to_account
+  after_destroy :remove_from_account
+
+  private
+
+  def set_uri
+    target_account = ResolveAccountService.new.call(acct)
+    self.uri       = ActivityPub::TagManager.instance.uri_for(target_account) unless target_account.nil?
+  rescue Goldfinger::Error, HTTP::Error, OpenSSL::SSL::SSLError, Mastodon::Error
+    # Validation will take care of it
+  end
+
+  def add_to_account
+    account.update(also_known_as: account.also_known_as + [uri])
+  end
+
+  def remove_from_account
+    account.update(also_known_as: account.also_known_as.reject { |x| x == uri })
+  end
+end
diff --git a/app/models/account_migration.rb b/app/models/account_migration.rb
new file mode 100644
index 000000000..15830bffb
--- /dev/null
+++ b/app/models/account_migration.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: account_migrations
+#
+#  id                :bigint(8)        not null, primary key
+#  account_id        :bigint(8)
+#  acct              :string           default(""), not null
+#  followers_count   :bigint(8)        default(0), not null
+#  target_account_id :bigint(8)
+#  created_at        :datetime         not null
+#  updated_at        :datetime         not null
+#
+
+class AccountMigration < ApplicationRecord
+  COOLDOWN_PERIOD = 30.days.freeze
+
+  belongs_to :account
+  belongs_to :target_account, class_name: 'Account'
+
+  before_validation :set_target_account
+  before_validation :set_followers_count
+
+  validates :acct, presence: true, domain: { acct: true }
+  validate :validate_migration_cooldown
+  validate :validate_target_account
+
+  scope :within_cooldown, ->(now = Time.now.utc) { where(arel_table[:created_at].gteq(now - COOLDOWN_PERIOD)) }
+
+  attr_accessor :current_password, :current_username
+
+  def save_with_challenge(current_user)
+    if current_user.encrypted_password.present?
+      errors.add(:current_password, :invalid) unless current_user.valid_password?(current_password)
+    else
+      errors.add(:current_username, :invalid) unless account.username == current_username
+    end
+
+    return false unless errors.empty?
+
+    save
+  end
+
+  def cooldown_at
+    created_at + COOLDOWN_PERIOD
+  end
+
+  private
+
+  def set_target_account
+    self.target_account = ResolveAccountService.new.call(acct)
+  rescue Goldfinger::Error, HTTP::Error, OpenSSL::SSL::SSLError, Mastodon::Error
+    # Validation will take care of it
+  end
+
+  def set_followers_count
+    self.followers_count = account.followers_count
+  end
+
+  def validate_target_account
+    if target_account.nil?
+      errors.add(:acct, I18n.t('migrations.errors.not_found'))
+    else
+      errors.add(:acct, I18n.t('migrations.errors.missing_also_known_as')) unless target_account.also_known_as.include?(ActivityPub::TagManager.instance.uri_for(account))
+      errors.add(:acct, I18n.t('migrations.errors.already_moved')) if account.moved_to_account_id.present? && account.moved_to_account_id == target_account.id
+      errors.add(:acct, I18n.t('migrations.errors.move_to_self')) if account.id == target_account.id
+    end
+  end
+
+  def validate_migration_cooldown
+    errors.add(:base, I18n.t('migrations.errors.on_cooldown')) if account.migrations.within_cooldown.exists?
+  end
+end
diff --git a/app/models/concerns/account_associations.rb b/app/models/concerns/account_associations.rb
index 1db7771c7..c9cc5c610 100644
--- a/app/models/concerns/account_associations.rb
+++ b/app/models/concerns/account_associations.rb
@@ -52,6 +52,8 @@ module AccountAssociations
 
     # Account migrations
     belongs_to :moved_to_account, class_name: 'Account', optional: true
+    has_many :migrations, class_name: 'AccountMigration', dependent: :destroy, inverse_of: :account
+    has_many :aliases, class_name: 'AccountAlias', dependent: :destroy, inverse_of: :account
 
     # Hashtags
     has_and_belongs_to_many :tags
diff --git a/app/models/form/migration.rb b/app/models/form/migration.rb
deleted file mode 100644
index c2a8655e1..000000000
--- a/app/models/form/migration.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-# frozen_string_literal: true
-
-class Form::Migration
-  include ActiveModel::Validations
-
-  attr_accessor :acct, :account
-
-  def initialize(attrs = {})
-    @account = attrs[:account]
-    @acct    = attrs[:account].acct unless @account.nil?
-    @acct    = attrs[:acct].gsub(/\A@/, '').strip unless attrs[:acct].nil?
-  end
-
-  def valid?
-    return false unless super
-    set_account
-    errors.empty?
-  end
-
-  private
-
-  def set_account
-    self.account = (ResolveAccountService.new.call(acct) if account.nil? && acct.present?)
-  end
-end
diff --git a/app/models/remote_follow.rb b/app/models/remote_follow.rb
index 52dd3f67b..5ea535287 100644
--- a/app/models/remote_follow.rb
+++ b/app/models/remote_follow.rb
@@ -49,7 +49,7 @@ class RemoteFollow
   end
 
   def fetch_template!
-    return missing_resource if acct.blank?
+    return missing_resource_error if acct.blank?
 
     _, domain = acct.split('@')
 
diff --git a/app/models/user.rb b/app/models/user.rb
index b48455802..9a19a53b3 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -168,7 +168,7 @@ class User < ApplicationRecord
   end
 
   def functional?
-    confirmed? && approved? && !disabled? && !account.suspended?
+    confirmed? && approved? && !disabled? && !account.suspended? && account.moved_to_account_id.nil?
   end
 
   def unconfirmed_or_pending?
diff --git a/app/serializers/activitypub/move_serializer.rb b/app/serializers/activitypub/move_serializer.rb
new file mode 100644
index 000000000..5675875fa
--- /dev/null
+++ b/app/serializers/activitypub/move_serializer.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+class ActivityPub::MoveSerializer < ActivityPub::Serializer
+  attributes :id, :type, :target, :actor
+  attribute :virtual_object, key: :object
+
+  def id
+    [ActivityPub::TagManager.instance.uri_for(object.account), '#moves/', object.id].join
+  end
+
+  def type
+    'Move'
+  end
+
+  def target
+    ActivityPub::TagManager.instance.uri_for(object.target_account)
+  end
+
+  def virtual_object
+    ActivityPub::TagManager.instance.uri_for(object.account)
+  end
+
+  def actor
+    ActivityPub::TagManager.instance.uri_for(object.account)
+  end
+end
diff --git a/app/views/auth/registrations/_status.html.haml b/app/views/auth/registrations/_status.html.haml
index b38a83d67..47112dae0 100644
--- a/app/views/auth/registrations/_status.html.haml
+++ b/app/views/auth/registrations/_status.html.haml
@@ -1,16 +1,22 @@
 %h3= t('auth.status.account_status')
 
-- if @user.account.suspended?
-  %span.negative-hint= t('user_mailer.warning.explanation.suspend')
-- elsif @user.disabled?
-  %span.negative-hint= t('user_mailer.warning.explanation.disable')
-- elsif @user.account.silenced?
-  %span.warning-hint= t('user_mailer.warning.explanation.silence')
-- elsif !@user.confirmed?
-  %span.warning-hint= t('auth.status.confirming')
-- elsif !@user.approved?
-  %span.warning-hint= t('auth.status.pending')
-- else
-  %span.positive-hint= t('auth.status.functional')
+.simple_form
+  %p.hint
+    - if @user.account.suspended?
+      %span.negative-hint= t('user_mailer.warning.explanation.suspend')
+    - elsif @user.disabled?
+      %span.negative-hint= t('user_mailer.warning.explanation.disable')
+    - elsif @user.account.silenced?
+      %span.warning-hint= t('user_mailer.warning.explanation.silence')
+    - elsif !@user.confirmed?
+      %span.warning-hint= t('auth.status.confirming')
+      = link_to t('auth.didnt_get_confirmation'), new_user_confirmation_path
+    - elsif !@user.approved?
+      %span.warning-hint= t('auth.status.pending')
+    - elsif @user.account.moved_to_account_id.present?
+      %span.positive-hint= t('auth.status.redirecting_to', acct: @user.account.moved_to_account.acct)
+      = link_to t('migrations.cancel'), settings_migration_path
+    - else
+      %span.positive-hint= t('auth.status.functional')
 
 %hr.spacer/
diff --git a/app/views/auth/registrations/edit.html.haml b/app/views/auth/registrations/edit.html.haml
index 710ee5c68..885171c58 100644
--- a/app/views/auth/registrations/edit.html.haml
+++ b/app/views/auth/registrations/edit.html.haml
@@ -13,7 +13,7 @@
       .fields-row__column.fields-group.fields-row__column-6
         = f.input :email, wrapper: :with_label, input_html: { 'aria-label' => t('simple_form.labels.defaults.email') }, required: true, disabled: current_account.suspended?
       .fields-row__column.fields-group.fields-row__column-6
-        = f.input :current_password, wrapper: :with_label, input_html: { 'aria-label' => t('simple_form.labels.defaults.current_password'), :autocomplete => 'off' }, required: true, disabled: current_account.suspended?
+        = f.input :current_password, wrapper: :with_label, input_html: { 'aria-label' => t('simple_form.labels.defaults.current_password'), :autocomplete => 'off' }, required: true, disabled: current_account.suspended?, hint: false
 
     .fields-row
       .fields-row__column.fields-group.fields-row__column-6
diff --git a/app/views/settings/aliases/index.html.haml b/app/views/settings/aliases/index.html.haml
new file mode 100644
index 000000000..5b6986368
--- /dev/null
+++ b/app/views/settings/aliases/index.html.haml
@@ -0,0 +1,29 @@
+- content_for :page_title do
+  = t('settings.aliases')
+
+= simple_form_for @alias, url: settings_aliases_path do |f|
+  = render 'shared/error_messages', object: @alias
+
+  %p.hint= t('aliases.hint_html')
+
+  %hr.spacer/
+
+  .fields-group
+    = f.input :acct, wrapper: :with_block_label, input_html: { autocapitalize: 'none', autocorrect: 'off' }
+
+  .actions
+    = f.button :button, t('aliases.add_new'), type: :submit, class: 'button'
+
+%hr.spacer/
+
+.table-wrapper
+  %table.table.inline-table
+    %thead
+      %tr
+        %th= t('simple_form.labels.account_alias.acct')
+        %th
+    %tbody
+      - @aliases.each do |account_alias|
+        %tr
+          %td= account_alias.acct
+          %td= table_link_to 'trash', t('aliases.remove'), settings_alias_path(account_alias), data: { method: :delete }
diff --git a/app/views/settings/exports/show.html.haml b/app/views/settings/exports/show.html.haml
index b13cea976..76ff76bd9 100644
--- a/app/views/settings/exports/show.html.haml
+++ b/app/views/settings/exports/show.html.haml
@@ -37,12 +37,16 @@
         %td= number_with_delimiter @export.total_domain_blocks
         %td= table_link_to 'download', t('exports.csv'), settings_exports_domain_blocks_path(format: :csv)
 
+%hr.spacer/
+
 %p.muted-hint= t('exports.archive_takeout.hint_html')
 
 - if policy(:backup).create?
   %p= link_to t('exports.archive_takeout.request'), settings_export_path, class: 'button', method: :post
 
 - unless @backups.empty?
+  %hr.spacer/
+
   .table-wrapper
     %table.table
       %thead
diff --git a/app/views/settings/migrations/show.html.haml b/app/views/settings/migrations/show.html.haml
index c69061d50..1e5c47726 100644
--- a/app/views/settings/migrations/show.html.haml
+++ b/app/views/settings/migrations/show.html.haml
@@ -1,17 +1,85 @@
 - content_for :page_title do
   = t('settings.migrate')
 
-= simple_form_for @migration, as: :migration, url: settings_migration_path, html: { method: :put } do |f|
-  - if @migration.account
-    %p.hint= t('migrations.currently_redirecting')
+.simple_form
+  - if current_account.moved_to_account.present?
+    .fields-row
+      .fields-row__column.fields-group.fields-row__column-6
+        = render 'application/card', account: current_account.moved_to_account
+      .fields-row__column.fields-group.fields-row__column-6
+        %p.hint
+          %span.positive-hint= t('migrations.redirecting_to', acct: current_account.moved_to_account.acct)
 
-    .fields-group
-      = render partial: 'application/card', locals: { account: @migration.account }
+        %p.hint= t('migrations.cancel_explanation')
+
+        %p.hint= link_to t('migrations.cancel'), cancel_settings_migration_path, data: { method: :post }
+  - else
+    %p.hint
+      %span.positive-hint= t('migrations.not_redirecting')
+
+%hr.spacer/
+
+%h3= t 'migrations.proceed_with_move'
+
+= simple_form_for @migration, url: settings_migration_path do |f|
+  - if on_cooldown?
+    %span.warning-hint= t('migrations.on_cooldown', count: ((@cooldown.cooldown_at - Time.now.utc) / 1.day.seconds).ceil)
+  - else
+    %p.hint= t('migrations.warning.before')
+
+    %ul.hint
+      %li.warning-hint= t('migrations.warning.followers')
+      %li.warning-hint= t('migrations.warning.other_data')
+      %li.warning-hint= t('migrations.warning.backreference_required')
+      %li.warning-hint= t('migrations.warning.cooldown')
+      %li.warning-hint= t('migrations.warning.disabled_account')
+
+  %hr.spacer/
 
   = render 'shared/error_messages', object: @migration
 
-  .fields-group
-    = f.input :acct, placeholder: t('migrations.acct')
+  .fields-row
+    .fields-row__column.fields-group.fields-row__column-6
+      = f.input :acct, wrapper: :with_block_label, input_html: { autocapitalize: 'none', autocorrect: 'off' }, disabled: on_cooldown?
+
+    .fields-row__column.fields-group.fields-row__column-6
+      - if current_user.encrypted_password.present?
+        = f.input :current_password, wrapper: :with_block_label, input_html: { :autocomplete => 'off' }, required: true, disabled: on_cooldown?
+      - else
+        = f.input :current_username, wrapper: :with_block_label, input_html: { :autocomplete => 'off' }, required: true, disabled: on_cooldown?
 
   .actions
-    = f.button :button, t('migrations.proceed'), type: :submit, class: 'negative'
+    = f.button :button, t('migrations.proceed_with_move'), type: :submit, class: 'button button--destructive', disabled: on_cooldown?
+
+- unless @migrations.empty?
+  %hr.spacer/
+
+  %h3= t 'migrations.past_migrations'
+
+  %hr.spacer/
+
+  .table-wrapper
+    %table.table.inline-table
+      %thead
+        %tr
+          %th= t('migrations.acct')
+          %th= t('migrations.followers_count')
+          %th
+      %tbody
+        - @migrations.each do |migration|
+          %tr
+            %td
+              - if migration.target_account.present?
+                = compact_account_link_to migration.target_account
+              - else
+                = migration.acct
+
+            %td= number_with_delimiter migration.followers_count
+
+            %td
+              %time.time-ago{ datetime: migration.created_at.iso8601, title: l(migration.created_at) }= l(migration.created_at)
+
+%hr.spacer/
+
+%h3= t 'migrations.incoming_migrations'
+%p.muted-hint= t('migrations.incoming_migrations_html', path: settings_aliases_path)
diff --git a/app/views/settings/profiles/show.html.haml b/app/views/settings/profiles/show.html.haml
index f042011d6..6929f54f3 100644
--- a/app/views/settings/profiles/show.html.haml
+++ b/app/views/settings/profiles/show.html.haml
@@ -60,6 +60,11 @@
 %h6= t('auth.migrate_account')
 %p.muted-hint= t('auth.migrate_account_html', path: settings_migration_path)
 
+%hr.spacer/
+
+%h6= t 'migrations.incoming_migrations'
+%p.muted-hint= t('migrations.incoming_migrations_html', path: settings_aliases_path)
+
 - if open_deletion?
   %hr.spacer/
 
diff --git a/app/workers/activitypub/move_distribution_worker.rb b/app/workers/activitypub/move_distribution_worker.rb
new file mode 100644
index 000000000..396d5258f
--- /dev/null
+++ b/app/workers/activitypub/move_distribution_worker.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+class ActivityPub::MoveDistributionWorker
+  include Sidekiq::Worker
+  include Payloadable
+
+  sidekiq_options queue: 'push'
+
+  def perform(migration_id)
+    @migration = AccountMigration.find(migration_id)
+
+    ActivityPub::DeliveryWorker.push_bulk(inboxes) do |inbox_url|
+      [signed_payload, @account.id, inbox_url]
+    end
+
+    ActivityPub::DeliveryWorker.push_bulk(Relay.enabled.pluck(:inbox_url)) do |inbox_url|
+      [signed_payload, @account.id, inbox_url]
+    end
+  rescue ActiveRecord::RecordNotFound
+    true
+  end
+
+  private
+
+  def inboxes
+    @inboxes ||= @migration.account.followers.inboxes
+  end
+
+  def signed_payload
+    @signed_payload ||= Oj.dump(serialize_payload(@migration, ActivityPub::MoveSerializer, signer: @account))
+  end
+end
diff --git a/config/locales/en.yml b/config/locales/en.yml
index dabb679e7..c29c7f871 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -554,6 +554,12 @@ en:
     new_trending_tag:
       body: 'The hashtag #%{name} is trending today, but has not been previously reviewed. It will not be displayed publicly unless you allow it to, or just save the form as it is to never hear about it again.'
       subject: New hashtag up for review on %{instance} (#%{name})
+  aliases:
+    add_new: Create alias
+    created_msg: Successfully created a new alias. You can now initiate the move from the old account.
+    deleted_msg: Successfully remove the alias. Moving from that account to this one will no longer be possible.
+    hint_html: If you want to move from another account to this one, here you can create an alias, which is required before you can proceed with moving followers from the old account to this one. This action by itself is <strong>harmless and reversible</strong>. <strong>The account migration is initiated from the old account</strong>.
+    remove: Unlink alias
   appearance:
     advanced_web_interface: Advanced web interface
     advanced_web_interface_hint: 'If you want to make use of your entire screen width, the advanced web interface allows you to configure many different columns to see as much information at the same time as you want: Home, notifications, federated timeline, any number of lists and hashtags.'
@@ -613,6 +619,7 @@ en:
       confirming: Waiting for e-mail confirmation to be completed.
       functional: Your account is fully operational.
       pending: Your application is pending review by our staff. This may take some time. You will receive an e-mail if your application is approved.
+      redirecting_to: Your account is inactive because it is currently redirecting to %{acct}.
     trouble_logging_in: Trouble logging in?
   authorize_follow:
     already_following: You are already following this account
@@ -801,10 +808,32 @@ en:
       images_and_video: Cannot attach a video to a status that already contains images
       too_many: Cannot attach more than 4 files
   migrations:
-    acct: username@domain of the new account
-    currently_redirecting: 'Your profile is set to redirect to:'
-    proceed: Save
-    updated_msg: Your account migration setting successfully updated!
+    acct: Moved to
+    cancel: Cancel redirect
+    cancel_explanation: Cancelling the redirect will re-activate your current account, but will not bring back followers that have been moved to that account.
+    cancelled_msg: Successfully cancelled the redirect.
+    errors:
+      already_moved: is the same account you have already moved to
+      missing_also_known_as: is not back-referencing this account
+      move_to_self: cannot be current account
+      not_found: could not be found
+      on_cooldown: You are on cooldown
+    followers_count: Followers at time of move
+    incoming_migrations: Moving from a different account
+    incoming_migrations_html: To move from another account to this one, first you need to <a href="%{path}">create an account alias</a>.
+    moved_msg: Your account is now redirecting to %{acct} and your followers are being moved over.
+    not_redirecting: Your account is not redirecting to any other account currently.
+    on_cooldown: You have recently migrated your account. This function will become available again in %{count} days.
+    past_migrations: Past migrations
+    proceed_with_move: Move followers
+    redirecting_to: Your account is redirecting to %{acct}.
+    warning:
+      backreference_required: The new account must first be configured to back-reference this one
+      before: 'Before proceeding, please read these notes carefully:'
+      cooldown: After moving there is a cooldown period during which you will not be able to move again
+      disabled_account: Your current account will not be fully usable afterwards. However, you will have access to data export as well as re-activation.
+      followers: This action will move all followers from the current account to the new account
+      other_data: No other data will be moved automatically
   moderation:
     title: Moderation
   notification_mailer:
@@ -950,6 +979,7 @@ en:
   settings:
     account: Account
     account_settings: Account settings
+    aliases: Account aliases
     appearance: Appearance
     authorized_apps: Authorized apps
     back: Back to Mastodon
diff --git a/config/locales/simple_form.en.yml b/config/locales/simple_form.en.yml
index c9ffcfc13..3d909e999 100644
--- a/config/locales/simple_form.en.yml
+++ b/config/locales/simple_form.en.yml
@@ -2,6 +2,10 @@
 en:
   simple_form:
     hints:
+      account_alias:
+        acct: Specify the username@domain of the account you want to move from
+      account_migration:
+        acct: Specify the username@domain of the account you want to move to
       account_warning_preset:
         text: You can use toot syntax, such as URLs, hashtags and mentions
       admin_account_action:
@@ -15,6 +19,8 @@ en:
         avatar: PNG, GIF or JPG. At most %{size}. Will be downscaled to %{dimensions}px
         bot: This account mainly performs automated actions and might not be monitored
         context: One or multiple contexts where the filter should apply
+        current_password: For security purposes please enter the password of the current account
+        current_username: To confirm, please enter the username of the current account
         digest: Only sent after a long period of inactivity and only if you have received any personal messages in your absence
         discoverable: The profile directory is another way by which your account can reach a wider audience
         email: You will be sent a confirmation e-mail
@@ -60,6 +66,10 @@ en:
         fields:
           name: Label
           value: Content
+      account_alias:
+        acct: Handle of the old account
+      account_migration:
+        acct: Handle of the new account
       account_warning_preset:
         text: Preset text
       admin_account_action:
diff --git a/config/navigation.rb b/config/navigation.rb
index 38668bbf7..32c299143 100644
--- a/config/navigation.rb
+++ b/config/navigation.rb
@@ -5,7 +5,7 @@ SimpleNavigation::Configuration.run do |navigation|
     n.item :web, safe_join([fa_icon('chevron-left fw'), t('settings.back')]), root_url
 
     n.item :profile, safe_join([fa_icon('user fw'), t('settings.profile')]), settings_profile_url, if: -> { current_user.functional? } do |s|
-      s.item :profile, safe_join([fa_icon('pencil fw'), t('settings.appearance')]), settings_profile_url, highlights_on: %r{/settings/profile|/settings/migration}
+      s.item :profile, safe_join([fa_icon('pencil fw'), t('settings.appearance')]), settings_profile_url
       s.item :featured_tags, safe_join([fa_icon('hashtag fw'), t('settings.featured_tags')]), settings_featured_tags_url
       s.item :identity_proofs, safe_join([fa_icon('key fw'), t('settings.identity_proofs')]), settings_identity_proofs_path, highlights_on: %r{/settings/identity_proofs*}, if: proc { current_account.identity_proofs.exists? }
     end
@@ -20,13 +20,13 @@ SimpleNavigation::Configuration.run do |navigation|
     n.item :filters, safe_join([fa_icon('filter fw'), t('filters.index.title')]), filters_path, highlights_on: %r{/filters}, if: -> { current_user.functional? }
 
     n.item :security, safe_join([fa_icon('lock fw'), t('settings.account')]), edit_user_registration_url do |s|
-      s.item :password, safe_join([fa_icon('lock fw'), t('settings.account_settings')]), edit_user_registration_url, highlights_on: %r{/auth/edit|/settings/delete}
+      s.item :password, safe_join([fa_icon('lock fw'), t('settings.account_settings')]), edit_user_registration_url, highlights_on: %r{/auth/edit|/settings/delete|/settings/migration|/settings/aliases}
       s.item :two_factor_authentication, safe_join([fa_icon('mobile fw'), t('settings.two_factor_authentication')]), settings_two_factor_authentication_url, highlights_on: %r{/settings/two_factor_authentication}
       s.item :authorized_apps, safe_join([fa_icon('list fw'), t('settings.authorized_apps')]), oauth_authorized_applications_url
     end
 
-    n.item :data, safe_join([fa_icon('cloud-download fw'), t('settings.import_and_export')]), settings_export_url, if: -> { current_user.functional? } do |s|
-      s.item :import, safe_join([fa_icon('cloud-upload fw'), t('settings.import')]), settings_import_url
+    n.item :data, safe_join([fa_icon('cloud-download fw'), t('settings.import_and_export')]), settings_export_url do |s|
+      s.item :import, safe_join([fa_icon('cloud-upload fw'), t('settings.import')]), settings_import_url, if: -> { current_user.functional? }
       s.item :export, safe_join([fa_icon('cloud-download fw'), t('settings.export')]), settings_export_url
     end
 
diff --git a/config/routes.rb b/config/routes.rb
index dcfa079a0..37e0cbdee 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -134,8 +134,14 @@ Rails.application.routes.draw do
     end
 
     resource :delete, only: [:show, :destroy]
-    resource :migration, only: [:show, :update]
 
+    resource :migration, only: [:show, :create] do
+      collection do
+        post :cancel
+      end
+    end
+
+    resources :aliases, only: [:index, :create, :destroy]
     resources :sessions, only: [:destroy]
     resources :featured_tags, only: [:index, :create, :destroy]
   end
diff --git a/db/migrate/20190914202517_create_account_migrations.rb b/db/migrate/20190914202517_create_account_migrations.rb
new file mode 100644
index 000000000..cb9d71c09
--- /dev/null
+++ b/db/migrate/20190914202517_create_account_migrations.rb
@@ -0,0 +1,12 @@
+class CreateAccountMigrations < ActiveRecord::Migration[5.2]
+  def change
+    create_table :account_migrations do |t|
+      t.belongs_to :account, foreign_key: { on_delete: :cascade }
+      t.string :acct, null: false, default: ''
+      t.bigint :followers_count, null: false, default: 0
+      t.belongs_to :target_account, foreign_key: { to_table: :accounts, on_delete: :nullify }
+
+      t.timestamps
+    end
+  end
+end
diff --git a/db/migrate/20190915194355_create_account_aliases.rb b/db/migrate/20190915194355_create_account_aliases.rb
new file mode 100644
index 000000000..32ce031d9
--- /dev/null
+++ b/db/migrate/20190915194355_create_account_aliases.rb
@@ -0,0 +1,11 @@
+class CreateAccountAliases < ActiveRecord::Migration[5.2]
+  def change
+    create_table :account_aliases do |t|
+      t.belongs_to :account, foreign_key: { on_delete: :cascade }
+      t.string :acct, null: false, default: ''
+      t.string :uri, null: false, default: ''
+
+      t.timestamps
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 749f79dee..fabeb16f3 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -15,6 +15,15 @@ ActiveRecord::Schema.define(version: 2019_09_17_213523) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
+  create_table "account_aliases", force: :cascade do |t|
+    t.bigint "account_id"
+    t.string "acct", default: "", null: false
+    t.string "uri", default: "", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["account_id"], name: "index_account_aliases_on_account_id"
+  end
+
   create_table "account_conversations", force: :cascade do |t|
     t.bigint "account_id"
     t.bigint "conversation_id"
@@ -49,6 +58,17 @@ ActiveRecord::Schema.define(version: 2019_09_17_213523) do
     t.index ["account_id"], name: "index_account_identity_proofs_on_account_id"
   end
 
+  create_table "account_migrations", force: :cascade do |t|
+    t.bigint "account_id"
+    t.string "acct", default: "", null: false
+    t.bigint "followers_count", default: 0, null: false
+    t.bigint "target_account_id"
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["account_id"], name: "index_account_migrations_on_account_id"
+    t.index ["target_account_id"], name: "index_account_migrations_on_target_account_id"
+  end
+
   create_table "account_moderation_notes", force: :cascade do |t|
     t.text "content", null: false
     t.bigint "account_id", null: false
@@ -768,10 +788,13 @@ ActiveRecord::Schema.define(version: 2019_09_17_213523) do
     t.index ["user_id"], name: "index_web_settings_on_user_id", unique: true
   end
 
+  add_foreign_key "account_aliases", "accounts", on_delete: :cascade
   add_foreign_key "account_conversations", "accounts", on_delete: :cascade
   add_foreign_key "account_conversations", "conversations", on_delete: :cascade
   add_foreign_key "account_domain_blocks", "accounts", name: "fk_206c6029bd", on_delete: :cascade
   add_foreign_key "account_identity_proofs", "accounts", on_delete: :cascade
+  add_foreign_key "account_migrations", "accounts", column: "target_account_id", on_delete: :nullify
+  add_foreign_key "account_migrations", "accounts", on_delete: :cascade
   add_foreign_key "account_moderation_notes", "accounts"
   add_foreign_key "account_moderation_notes", "accounts", column: "target_account_id"
   add_foreign_key "account_pins", "accounts", column: "target_account_id", on_delete: :cascade
diff --git a/spec/controllers/settings/migrations_controller_spec.rb b/spec/controllers/settings/migrations_controller_spec.rb
index 4d814a45e..36e4ba86e 100644
--- a/spec/controllers/settings/migrations_controller_spec.rb
+++ b/spec/controllers/settings/migrations_controller_spec.rb
@@ -21,6 +21,7 @@ describe Settings::MigrationsController do
 
       let(:user) { Fabricate(:user, account: account) }
       let(:account) { Fabricate(:account, moved_to_account: moved_to_account) }
+
       before { sign_in user, scope: :user }
 
       context 'when user does not have moved to account' do
@@ -32,7 +33,7 @@ describe Settings::MigrationsController do
         end
       end
 
-      context 'when user does not have moved to account' do
+      context 'when user has a moved to account' do
         let(:moved_to_account) { Fabricate(:account) }
 
         it 'renders show page' do
@@ -43,21 +44,22 @@ describe Settings::MigrationsController do
     end
   end
 
-  describe 'PUT #update' do
+  describe 'POST #create' do
     context 'when user is not sign in' do
-      subject { put :update }
+      subject { post :create }
 
       it_behaves_like 'authenticate user'
     end
 
     context 'when user is sign in' do
-      subject { put :update, params: { migration: { acct: acct } } }
+      subject { post :create, params: { account_migration: { acct: acct, current_password: '12345678' } } }
+
+      let(:user) { Fabricate(:user, password: '12345678') }
 
-      let(:user) { Fabricate(:user) }
       before { sign_in user, scope: :user }
 
       context 'when migration account is changed' do
-        let(:acct) { Fabricate(:account) }
+        let(:acct) { Fabricate(:account, also_known_as: [ActivityPub::TagManager.instance.uri_for(user.account)]) }
 
         it 'updates moved to account' do
           is_expected.to redirect_to settings_migration_path
diff --git a/spec/fabricators/account_alias_fabricator.rb b/spec/fabricators/account_alias_fabricator.rb
new file mode 100644
index 000000000..94dde9bb8
--- /dev/null
+++ b/spec/fabricators/account_alias_fabricator.rb
@@ -0,0 +1,5 @@
+Fabricator(:account_alias) do
+  account
+  acct 'test@example.com'
+  uri 'https://example.com/users/test'
+end
diff --git a/spec/fabricators/account_migration_fabricator.rb b/spec/fabricators/account_migration_fabricator.rb
new file mode 100644
index 000000000..3b3fc2077
--- /dev/null
+++ b/spec/fabricators/account_migration_fabricator.rb
@@ -0,0 +1,6 @@
+Fabricator(:account_migration) do
+  account
+  target_account
+  followers_count 1234
+  acct 'test@example.com'
+end
diff --git a/spec/models/account_alias_spec.rb b/spec/models/account_alias_spec.rb
new file mode 100644
index 000000000..27ec215aa
--- /dev/null
+++ b/spec/models/account_alias_spec.rb
@@ -0,0 +1,5 @@
+require 'rails_helper'
+
+RSpec.describe AccountAlias, type: :model do
+
+end
diff --git a/spec/models/account_migration_spec.rb b/spec/models/account_migration_spec.rb
new file mode 100644
index 000000000..8461b4b28
--- /dev/null
+++ b/spec/models/account_migration_spec.rb
@@ -0,0 +1,5 @@
+require 'rails_helper'
+
+RSpec.describe AccountMigration, type: :model do
+
+end