Remove SearchObserver, aim is to remove all observers

rails-observers gem is mostly unmaintained and is a pain to carry forward
new implementation contains significantly less magic as a bonus

app/services/search_indexer.rb

@@ -0,0 +1,154 @@
+require_dependency 'search'
+
+class SearchIndexer
+
+  def self.disable
+    @disabled = true
+  end
+
+  def self.enable
+    @disabled = false
+  end
+
+  def self.scrub_html_for_search(html)
+    HtmlScrubber.scrub(html)
+  end
+
+  def self.update_index(table, id, raw_data)
+    raw_data = Search.prepare_data(raw_data)
+
+    table_name = "#{table}_search_data"
+    foreign_key = "#{table}_id"
+
+    # insert some extra words for I.am.a.word so "word" is tokenized
+    search_data = raw_data.gsub(/\p{L}*\.\p{L}*/) do |with_dot|
+      split = with_dot.split(".")
+      if split.length > 1
+        with_dot + (" " << split[1..-1].join(" "))
+      else
+        with_dot
+      end
+    end
+
+    # for user login and name use "simple" lowercase stemmer
+    stemmer = table == "user" ? "simple" : Search.long_locale
+
+    # Would be nice to use AR here but not sure how to execut Postgres functions
+    # when inserting data like this.
+    rows = Post.exec_sql_row_count("UPDATE #{table_name}
+                                   SET
+                                      raw_data = :raw_data,
+                                      locale = :locale,
+                                      search_data = TO_TSVECTOR('#{stemmer}', :search_data)
+                                   WHERE #{foreign_key} = :id",
+                                    raw_data: raw_data,
+                                    search_data: search_data,
+                                    id: id,
+                                    locale: SiteSetting.default_locale)
+    if rows == 0
+      Post.exec_sql("INSERT INTO #{table_name}
+                    (#{foreign_key}, search_data, locale, raw_data)
+                    VALUES (:id, TO_TSVECTOR('#{stemmer}', :search_data), :locale, :raw_data)",
+                                    raw_data: raw_data,
+                                    search_data: search_data,
+                                    id: id,
+                                    locale: SiteSetting.default_locale)
+    end
+  rescue
+    # don't allow concurrency to mess up saving a post
+  end
+
+  def self.update_topics_index(topic_id, title, cooked)
+    search_data = title.dup << " " << scrub_html_for_search(cooked)[0...Topic::MAX_SIMILAR_BODY_LENGTH]
+    update_index('topic', topic_id, search_data)
+  end
+
+  def self.update_posts_index(post_id, cooked, title, category)
+    search_data = scrub_html_for_search(cooked) << " " << title.dup.force_encoding('UTF-8')
+    search_data << " " << category if category
+    update_index('post', post_id, search_data)
+  end
+
+  def self.update_users_index(user_id, username, name)
+    search_data = username.dup << " " << (name || "")
+    update_index('user', user_id, search_data)
+  end
+
+  def self.update_categories_index(category_id, name)
+    update_index('category', category_id, name)
+  end
+
+  def self.index(obj)
+    return if @disabled
+
+    if obj.class == Post && obj.cooked_changed?
+      if obj.topic
+        category_name = obj.topic.category.name if obj.topic.category
+        SearchIndexer.update_posts_index(obj.id, obj.cooked, obj.topic.title, category_name)
+        SearchIndexer.update_topics_index(obj.topic_id, obj.topic.title, obj.cooked) if obj.is_first_post?
+      else
+        Rails.logger.warn("Orphan post skipped in search_indexer, topic_id: #{obj.topic_id} post_id: #{obj.id} raw: #{obj.raw}")
+      end
+    end
+    if obj.class == User && (obj.username_changed? || obj.name_changed?)
+      SearchIndexer.update_users_index(obj.id, obj.username_lower || '', obj.name ? obj.name.downcase : '')
+    end
+
+    if obj.class == Topic && obj.title_changed?
+      if obj.posts
+        post = obj.posts.find_by(post_number: 1)
+        if post
+          category_name = obj.category.name if obj.category
+          SearchIndexer.update_posts_index(post.id, post.cooked, obj.title, category_name)
+          SearchIndexer.update_topics_index(obj.id, obj.title, post.cooked)
+        end
+      end
+    end
+
+    if obj.class == Category && obj.name_changed?
+      SearchIndexer.update_categories_index(obj.id, obj.name)
+    end
+  end
+
+
+  class HtmlScrubber < Nokogiri::XML::SAX::Document
+    attr_reader :scrubbed
+
+    def initialize
+      @scrubbed = ""
+    end
+
+    def self.scrub(html)
+      me = new
+      parser = Nokogiri::HTML::SAX::Parser.new(me)
+      begin
+        copy = "<div>"
+        copy << html unless html.nil?
+        copy << "</div>"
+        parser.parse(html) unless html.nil?
+      end
+      me.scrubbed
+    end
+
+    def start_element(name, attributes=[])
+      attributes = Hash[*attributes.flatten]
+      if attributes["alt"]
+        scrubbed << " "
+        scrubbed << attributes["alt"]
+        scrubbed << " "
+      end
+      if attributes["title"]
+        scrubbed << " "
+        scrubbed << attributes["title"]
+        scrubbed << " "
+      end
+    end
+
+    def characters(string)
+      scrubbed << " "
+      scrubbed << string
+      scrubbed << " "
+    end
+  end
+end
+