Tag change notices

This adds a small notice at the bottom of post searches if a single tag search is the target of any tag change request.

app/logical/alias_and_implication_importer.rb

@@ -100,6 +100,30 @@ class AliasAndImplicationImporter
     end
   end
 
+  def affected_tags
+    tokens = self.class.tokenize(text)
+    tokens.inject([]) do |all, token|
+      case token[0]
+      when :create_alias, :remove_alias, :create_implication, :remove_implication
+        all << token[1]
+        all << token[2]
+        all
+
+      when :mass_update
+        all += Tag.scan_tags(token[1])
+        all += Tag.scan_tags(token[2])
+        all
+
+      when :change_category
+        all << token[1]
+        all
+
+      else
+        all
+      end
+    end
+  end
+
 private
 
   def parse(tokens, approver)

app/logical/tag_change_notice_service.rb

@@ -0,0 +1,18 @@
+module TagChangeNoticeService
+  extend self
+
+  def redis_client
+    ::Redis.new(url: Danbooru.config.redis_url)
+  end
+
+  def get_forum_topic_id(tag)
+    redis_client.get("tcn:#{tag}")
+  end
+
+  def update_cache(affected_tags, forum_topic_id)
+    rc = redis_client
+    affected_tags.each do |tag|
+      rc.setex("tcn:#{tag}", 1.week, forum_topic_id)
+    end
+  end
+end