FIX: search within topic not working correctly in CJK

We were splitting the term prior to search causing everything to miss

lib/search.rb

@@ -55,20 +55,26 @@ class Search
   end
 
   def self.prepare_data(search_data, purpose = :query)
-    data = search_data.squish
-    # TODO cppjieba_rb is designed for chinese, we need something else for Japanese
-    # Korean appears to be safe cause words are already space seperated
-    # For Japanese we should investigate using kakasi
-    if ['zh_TW', 'zh_CN', 'ja'].include?(SiteSetting.default_locale) || SiteSetting.search_tokenize_chinese_japanese_korean
-      require 'cppjieba_rb' unless defined? CppjiebaRb
-      mode = (purpose == :query ? :query : :mix)
-      data = CppjiebaRb.segment(search_data, mode: mode)
-      data = CppjiebaRb.filter_stop_word(data).join(' ')
-    end
+    purpose ||= :query
 
+    data = search_data.dup
     data.force_encoding("UTF-8")
-    if SiteSetting.search_ignore_accents
-      data = strip_diacritics(data)
+    if purpose != :topic
+      # TODO cppjieba_rb is designed for chinese, we need something else for Japanese
+      # Korean appears to be safe cause words are already space seperated
+      # For Japanese we should investigate using kakasi
+      if ['zh_TW', 'zh_CN', 'ja'].include?(SiteSetting.default_locale) || SiteSetting.search_tokenize_chinese_japanese_korean
+        require 'cppjieba_rb' unless defined? CppjiebaRb
+        mode = (purpose == :query ? :query : :mix)
+        data = CppjiebaRb.segment(search_data, mode: mode)
+        data = CppjiebaRb.filter_stop_word(data).join(' ')
+      else
+        data.squish!
+      end
+
+      if SiteSetting.search_ignore_accents
+        data = strip_diacritics(data)
+      end
     end
     data
   end
@@ -155,7 +161,7 @@ class Search
     term = process_advanced_search!(term)
 
     if term.present?
-      @term = Search.prepare_data(term)
+      @term = Search.prepare_data(term, Topic === @search_context ? :topic : nil)
       @original_term = PG::Connection.escape_string(@term)
     end