Revamp post filtering system (#18058)

* Add model for custom filter keywords

* Use CustomFilterKeyword internally

Does not change the API

* Fix /filters/edit and /filters/new

* Add migration tests

* Remove whole_word column from custom_filters (covered by custom_filter_keywords)

* Redesign /filters

Instead of a list, present a card that displays more information and handles
multiple keywords per filter.

* Redesign /filters/new and /filters/edit to add and remove keywords

This adds a new gem dependency: cocoon, as well as a npm dependency:
cocoon-js-vanilla. Those are used to easily populate and remove form fields
from the user interface when manipulating multiple keyword filters at once.

* Add /api/v2/filters to edit filter with multiple keywords

Entities:
- `Filter`: `id`, `title`, `filter_action` (either `hide` or `warn`), `context`
  `keywords`
- `FilterKeyword`: `id`, `keyword`, `whole_word`

API endpoits:
- `GET /api/v2/filters` to list filters (including keywords)
- `POST /api/v2/filters` to create a new filter
  `keywords_attributes` can also be passed to create keywords in one request
- `GET /api/v2/filters/:id` to read a particular filter
- `PUT /api/v2/filters/:id` to update a new filter
  `keywords_attributes` can also be passed to edit, delete or add keywords in
   one request
- `DELETE /api/v2/filters/:id` to delete a particular filter
- `GET /api/v2/filters/:id/keywords` to list keywords for a filter
- `POST /api/v2/filters/:filter_id/keywords/:id` to add a new keyword to a
   filter
- `GET /api/v2/filter_keywords/:id` to read a particular keyword
- `PUT /api/v2/filter_keywords/:id` to edit a particular keyword
- `DELETE /api/v2/filter_keywords/:id` to delete a particular keyword

* Change from `irreversible` boolean to `action` enum

* Remove irrelevent `irreversible_must_be_within_context` check

* Fix /filters/new and /filters/edit with update for filter_action

* Fix Rubocop/Codeclimate complaining about task names

* Refactor FeedManager#phrase_filtered?

This moves regexp building and filter caching to the `CustomFilter` class.

This does not change the functional behavior yet, but this changes how the
cache is built, doing per-custom_filter regexps so that filters can be matched
independently, while still offering caching.

* Perform server-side filtering and output result in REST API

* Fix numerous filters_changed events being sent when editing multiple keywords at once

* Add some tests

* Use the new API in the WebUI

- use client-side logic for filters we have fetched rules for.
  This is so that filter changes can be retroactively applied without
  reloading the UI.
- use server-side logic for filters we haven't fetched rules for yet
  (e.g. network error, or initial timeline loading)

* Minor optimizations and refactoring

* Perform server-side filtering on the streaming server

* Change the wording of filter action labels

* Fix issues pointed out by linter

* Change design of “Show anyway” link in accordence to review comments

* Drop “irreversible” filtering behavior

* Move /api/v2/filter_keywords to /api/v1/filters/keywords

* Rename `filter_results` attribute to `filtered`

* Rename REST::LegacyFilterSerializer to REST::V1::FilterSerializer

* Fix systemChannelId value in streaming server

* Simplify code by removing client-side filtering code

The simplifcation comes at a cost though: filters aren't retroactively
applied anymore.

3 files changed, 111 insertions, 23 deletions

diff --git a/app/models/concerns/account_interactions.rb b/app/models/concerns/account_interactions.rb
index ad1665dc4..a7401362f 100644
--- a/app/models/concerns/account_interactions.rb
+++ b/app/models/concerns/account_interactions.rb
@@ -247,6 +247,19 @@ module AccountInteractions
     account_pins.where(target_account: account).exists?
   end
 
+  def status_matches_filters(status)
+    active_filters = CustomFilter.cached_filters_for(id)
+
+    filter_matches = active_filters.filter_map do |filter, rules|
+      next if rules[:keywords].blank?
+
+      match = rules[:keywords].match(status.proper.searchable_text)
+      FilterResultPresenter.new(filter: filter, keyword_matches: [match.to_s]) unless match.nil?
+    end
+
+    filter_matches
+  end
+
   def followers_for_local_distribution
     followers.local
              .joins(:user)
diff --git a/app/models/custom_filter.rb b/app/models/custom_filter.rb
index 8e3476794..e98ed7df9 100644
--- a/app/models/custom_filter.rb
+++ b/app/models/custom_filter.rb
@@ -3,18 +3,22 @@
 #
 # Table name: custom_filters
 #
-#  id           :bigint(8)        not null, primary key
-#  account_id   :bigint(8)
-#  expires_at   :datetime
-#  phrase       :text             default(""), not null
-#  context      :string           default([]), not null, is an Array
-#  whole_word   :boolean          default(TRUE), not null
-#  irreversible :boolean          default(FALSE), not null
-#  created_at   :datetime         not null
-#  updated_at   :datetime         not null
+#  id         :bigint           not null, primary key
+#  account_id :bigint
+#  expires_at :datetime
+#  phrase     :text             default(""), not null
+#  context    :string           default([]), not null, is an Array
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#  action     :integer          default(0), not null
 #
 
 class CustomFilter < ApplicationRecord
+  self.ignored_columns = %w(whole_word irreversible)
+
+  alias_attribute :title, :phrase
+  alias_attribute :filter_action, :action
+
   VALID_CONTEXTS = %w(
     home
     notifications
@@ -26,16 +30,20 @@ class CustomFilter < ApplicationRecord
   include Expireable
   include Redisable
 
+  enum action: [:warn, :hide], _suffix: :action
+
   belongs_to :account
+  has_many :keywords, class_name: 'CustomFilterKeyword', foreign_key: :custom_filter_id, inverse_of: :custom_filter, dependent: :destroy
+  accepts_nested_attributes_for :keywords, reject_if: :all_blank, allow_destroy: true
 
-  validates :phrase, :context, presence: true
+  validates :title, :context, presence: true
   validate :context_must_be_valid
-  validate :irreversible_must_be_within_context
-
-  scope :active_irreversible, -> { where(irreversible: true).where(Arel.sql('expires_at IS NULL OR expires_at > NOW()')) }
 
   before_validation :clean_up_contexts
-  after_commit :remove_cache
+
+  before_save :prepare_cache_invalidation!
+  before_destroy :prepare_cache_invalidation!
+  after_commit :invalidate_cache!
 
   def expires_in
     return @expires_in if defined?(@expires_in)
@@ -44,22 +52,55 @@ class CustomFilter < ApplicationRecord
     [30.minutes, 1.hour, 6.hours, 12.hours, 1.day, 1.week].find { |expires_in| expires_in.from_now >= expires_at }
   end
 
-  private
+  def irreversible=(value)
+    self.action = value ? :hide : :warn
+  end
 
-  def clean_up_contexts
-    self.context = Array(context).map(&:strip).filter_map(&:presence)
+  def irreversible?
+    hide_action?
+  end
+
+  def self.cached_filters_for(account_id)
+    active_filters = Rails.cache.fetch("filters:v3:#{account_id}") do
+      scope = CustomFilterKeyword.includes(:custom_filter).where(custom_filter: { account_id: account_id }).where(Arel.sql('expires_at IS NULL OR expires_at > NOW()'))
+      scope.to_a.group_by(&:custom_filter).map do |filter, keywords|
+        keywords.map! do |keyword|
+          if keyword.whole_word
+            sb = /\A[[:word:]]/.match?(keyword.keyword) ? '\b' : ''
+            eb = /[[:word:]]\z/.match?(keyword.keyword) ? '\b' : ''
+
+            /(?mix:#{sb}#{Regexp.escape(keyword.keyword)}#{eb})/
+          else
+            /#{Regexp.escape(keyword.keyword)}/i
+          end
+        end
+        [filter, { keywords: Regexp.union(keywords) }]
+      end
+    end.to_a
+
+    active_filters.select { |custom_filter, _| !custom_filter.expired? }
+  end
+
+  def prepare_cache_invalidation!
+    @should_invalidate_cache = true
   end
 
-  def remove_cache
-    Rails.cache.delete("filters:#{account_id}")
+  def invalidate_cache!
+    return unless @should_invalidate_cache
+    @should_invalidate_cache = false
+
+    Rails.cache.delete("filters:v3:#{account_id}")
     redis.publish("timeline:#{account_id}", Oj.dump(event: :filters_changed))
+    redis.publish("timeline:system:#{account_id}", Oj.dump(event: :filters_changed))
   end
 
-  def context_must_be_valid
-    errors.add(:context, I18n.t('filters.errors.invalid_context')) if context.empty? || context.any? { |c| !VALID_CONTEXTS.include?(c) }
+  private
+
+  def clean_up_contexts
+    self.context = Array(context).map(&:strip).filter_map(&:presence)
   end
 
-  def irreversible_must_be_within_context
-    errors.add(:irreversible, I18n.t('filters.errors.invalid_irreversible')) if irreversible? && !context.include?('home') && !context.include?('notifications')
+  def context_must_be_valid
+    errors.add(:context, I18n.t('filters.errors.invalid_context')) if context.empty? || context.any? { |c| !VALID_CONTEXTS.include?(c) }
   end
 end
diff --git a/app/models/custom_filter_keyword.rb b/app/models/custom_filter_keyword.rb
new file mode 100644
index 000000000..bf5c55746
--- /dev/null
+++ b/app/models/custom_filter_keyword.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+# == Schema Information
+#
+# Table name: custom_filter_keywords
+#
+#  id               :bigint           not null, primary key
+#  custom_filter_id :bigint           not null
+#  keyword          :text             default(""), not null
+#  whole_word       :boolean          default(TRUE), not null
+#  created_at       :datetime         not null
+#  updated_at       :datetime         not null
+#
+
+class CustomFilterKeyword < ApplicationRecord
+  belongs_to :custom_filter
+
+  validates :keyword, presence: true
+
+  alias_attribute :phrase, :keyword
+
+  before_save :prepare_cache_invalidation!
+  before_destroy :prepare_cache_invalidation!
+  after_commit :invalidate_cache!
+
+  private
+
+  def prepare_cache_invalidation!
+    custom_filter.prepare_cache_invalidation!
+  end
+
+  def invalidate_cache!
+    custom_filter.invalidate_cache!
+  end
+end