Refactor normalize_for_artist_finder!

Refactors things such that Sources::Site has a normalize_for_artist_finder!
method that delegates to the strategy for the appropriate site. This way
any site that needs to normalize URLs for the artist finder can do so.

app/controllers/artists_controller.rb

@@ -118,7 +118,7 @@ class ArtistsController < ApplicationController
   end
 
   def finder
-    url = Sources::Strategies::Pixiv.new(url).normalize_for_artist_finder!(params[:url])
+    url = Sources::Site.new(params[:url]).normalize_for_artist_finder!
 
     @artists = Artist.url_matches(url).order("id desc").limit(20)
     respond_with(@artists) do |format|

app/logical/sources/site.rb

@@ -20,6 +20,14 @@ module Sources
       end
     end
 
+    def normalize_for_artist_finder!
+      if available?
+        return strategy.normalize_for_artist_finder!
+      else
+        return url
+      end
+    end
+
     def translated_tags
       untranslated_tags = tags
       untranslated_tags = untranslated_tags.map(&:first)

app/logical/sources/strategies/base.rb

@@ -18,6 +18,10 @@ module Sources
         raise NotImplementedError
       end
 
+      def normalize_for_artist_finder!
+        url
+      end
+
       def site_name
         raise NotImplementedError
       end

app/logical/sources/strategies/pixiv.rb

@@ -25,13 +25,12 @@ module Sources
         @pixiv_moniker
       end
 
-      def normalize_for_artist_finder!(url)
+      def normalize_for_artist_finder!
-        illust_id = illust_id_from_url(url)
-
         # http://i2.pixiv.net/img04/img/syounen_no_uta/46170939_m.jpg
         if url =~ %r!/img/([^/]+)/\d+(?:_\w+)?\.(?:jpg|jpeg|png|gif)!i
           username = $1
         else
+          illust_id = illust_id_from_url(url)
           get_metadata_from_spapi!(illust_id) do |metadata|
             username = metadata[24]
           end