Add support for using any of the current related tag types

Regardless of category or query. This meant that the category value
had to be passed in as either null or the value itself for both types
of functions. It also fixes an issue where the category wasn't settable
on the pattern matching type.

app/controllers/related_tags_controller.rb

@@ -4,9 +4,10 @@ class RelatedTagsController < ApplicationController
   def show
     query = params[:query] || search_params[:query]
     category = params[:category] || search_params[:category]
+    type = params[:type] || search_params[:type]
     limit = params[:limit]
 
-    @query = RelatedTagQuery.new(query: query, category: category, user: CurrentUser.user, limit: limit)
+    @query = RelatedTagQuery.new(query: query, category: category, type: type, user: CurrentUser.user, limit: limit)
     respond_with(@query)
   end
 end

app/logical/related_tag_query.rb

@@ -2,12 +2,13 @@ class RelatedTagQuery
   include ActiveModel::Serializers::JSON
   include ActiveModel::Serializers::Xml
 
-  attr_reader :query, :category, :user, :limit
+  attr_reader :query, :category, :type, :user, :limit
 
-  def initialize(query: nil, category: nil, user: nil, limit: nil)
+  def initialize(query: nil, category: nil, type: nil, user: nil, limit: nil)
     @user = user
     @query = TagAlias.to_aliased(query.to_s.downcase.strip).join(" ")
     @category = category
+    @type = type
     @limit = (limit =~ /^\d+/ ? limit.to_i : 25)
   end
 
@@ -16,25 +17,39 @@ class RelatedTagQuery
   end
 
   def tags
-    if query =~ /\*/
-      pattern_matching_tags
+    if type == "frequent"
+      frequent_tags
+    elsif type == "similar"
+      similar_tags
+    elsif type == "like"
+      pattern_matching_tags("*#{query}*")
+    elsif query =~ /\*/
+      pattern_matching_tags(query)
     elsif category.present?
-      RelatedTagCalculator.frequent_tags_for_search(query, category: Tag.categories.value_for(category)).take(limit)
+      frequent_tags
     elsif query.present?
-      RelatedTagCalculator.similar_tags_for_search(query).take(limit)
+      similar_tags
     else
       Tag.none
     end
   end
 
   def tags_overlap
-    if query =~ /\*/
+    if type == "like" || query =~ /\*/
       {}
     else
       tags.map { |v| [v.name, v.overlap_count] }.to_h
     end
   end
 
+  def frequent_tags
+    @frequent_tags ||= RelatedTagCalculator.frequent_tags_for_search(query, category: category_of).take(limit)
+  end
+
+  def similar_tags
+    @similar_tags ||= RelatedTagCalculator.similar_tags_for_search(query, category: category_of).take(limit)
+  end
+
   # Returns the top 20 most frequently added tags within the last 20 edits made by the user in the last hour.
   def recent_tags(since: 1.hour.ago, max_edits: 20, max_tags: 20)
     return [] unless user.present? && PostVersion.enabled?
@@ -99,8 +114,15 @@ class RelatedTagQuery
     Tag.categories_for(list_of_tag_names).to_a
   end
 
-  def pattern_matching_tags
-    Tag.nonempty.name_matches(query).order("post_count desc, name asc").limit(limit)
+  def category_of
+    (category.present? ? Tag.categories.value_for(category) : nil)
+  end
+
+  def pattern_matching_tags(tag_query)
+    tags = Tag.nonempty.name_matches(tag_query)
+    tags = tags.where(category: Tag.categories.value_for(category)) if category.present?
+    tags = tags.order("post_count desc, name asc").limit(limit)
+    tags
   end
 
   def wiki_page