tags: eliminate Tag.category_for method.

Tag.category_for looked up a tag's category in the Redis cache. This was
only used in a few places (in related tags, and on the popular/missed
search pages). Get rid of this method so we can work towards getting rid
of caching tag categories in Redis.

app/logical/post_query_builder.rb

@@ -985,6 +985,11 @@ class PostQueryBuilder
     def is_wildcard_search?
       is_single_tag? && tags.first.wildcard
     end
+
+    def simple_tag
+      return nil if !is_simple_tag?
+      Tag.find_by_name(tags.first.name)
+    end
   end
 
   memoize :split_query, :normalized_query

app/logical/related_tag_query.rb

@@ -71,9 +71,12 @@ class RelatedTagQuery
   end
 
   def other_wiki_pages
-    if Tag.category_for(query) == Tag.categories.copyright
+    tag = post_query.simple_tag
+    return [] if tag.nil?
+
+    if tag.copyright?
       copyright_other_wiki_pages
-    elsif Tag.category_for(query) == Tag.categories.general
+    elsif tag.general?
       general_other_wiki_pages
     else
       []

app/models/tag.rb

@@ -127,18 +127,6 @@ class Tag < ApplicationRecord
         Tag.where(name: tag_name).pick(:category).to_i
       end
 
-      def category_for(tag_name, options = {})
-        return Tag.categories.general if tag_name.blank?
-
-        if options[:disable_caching]
-          select_category_for(tag_name)
-        else
-          Cache.get("tc:#{Cache.hash(tag_name)}") do
-            select_category_for(tag_name)
-          end
-        end
-      end
-
       def categories_for(tag_names, options = {})
         if options[:disable_caching]
           Array(tag_names).inject({}) do |hash, tag_name|

app/views/explore/posts/missed_searches.html.erb

@@ -15,11 +15,11 @@
         </tr>
       </thead>
       <tbody>
-        <% @missed_searches.each do |tags, count| %>
+        <% @missed_searches.each do |search, count| %>
-          <tr class="tag-type-<%= Tag.category_for(tags) %>">
+          <tr class="tag-type-<%= Tag.find_by_name(search)&.category.to_i %>">
-            <td><%= link_to tags, posts_path(:tags => tags) %></td>
+            <td><%= link_to search, posts_path(tags: search) %></td>
             <td>
-              <% unless WikiPage.titled(tags).exists? %>
+              <% unless WikiPage.titled(search).exists? %>
                 N
               <% end %>
             </td>

app/views/explore/posts/searches.html.erb

@@ -13,9 +13,9 @@
         </tr>
       </thead>
       <tbody>
-        <% @searches.each do |tags, count| %>
+        <% @searches.each do |search, count| %>
-          <tr class="tag-type-<%= Tag.category_for(tags) %>">
+          <tr class="tag-type-<%= Tag.find_by_name(search)&.category.to_i %>">
-            <td><%= link_to tags, posts_path(:tags => tags) %></td>
+            <td><%= link_to search, posts_path(tags: search) %></td>
             <td style="text-align: right;"><%= count.to_i %></td>
           </tr>
         <% end %>

test/unit/tag_test.rb

@@ -13,16 +13,6 @@ class TagTest < ActiveSupport::TestCase
   end
 
   context "A tag category fetcher" do
-    should "fetch for a single tag" do
-      FactoryBot.create(:artist_tag, :name => "test")
-      assert_equal(Tag.categories.artist, Tag.category_for("test"))
-    end
-
-    should "fetch for a single tag with strange markup" do
-      FactoryBot.create(:artist_tag, :name => "!@$%")
-      assert_equal(Tag.categories.artist, Tag.category_for("!@$%"))
-    end
-
     should "fetch for multiple tags" do
       FactoryBot.create(:artist_tag, :name => "aaa")
       FactoryBot.create(:copyright_tag, :name => "bbb")