moebooru: delegate to substrategy based on post source (#3911).

If the yande.re or konachan.com post has a source from a supported site,
for example Pixiv or Twitter, then delegate the artist and commentary
lookup to that substrategy.

Only do this for sources from recognized sites, not the null strategy.

app/logical/sources/strategies.rb

@@ -12,15 +12,12 @@ module Sources
         Strategies::Nijie, 
         Strategies::Pawoo,
         Strategies::Moebooru,
-
-        Strategies::Null # MUST BE LAST!
       ]
     end
 
-    def self.find(url, referer=nil)
-      all
-        .detect { |strategy| strategy.match?(url, referer) }
-        .new(url, referer)
+    def self.find(url, referer=nil, default: Strategies::Null)
+      strategy = all.detect { |strategy| strategy.match?(url, referer) } || default
+      strategy&.new(url, referer)
     end
 
     def self.canonical(url, referer)

app/logical/sources/strategies/moebooru.rb

@@ -36,6 +36,8 @@ module Sources
       URL_SLUG = %r!/(?:yande\.re%20|Konachan\.com%20-%20)(?<id>\d+).*!i
       IMAGE_URL = %r!#{BASE_URL}/(?<type>image|jpeg|sample)/(?<md5>\h{32})#{URL_SLUG}?\.(?<ext>jpg|jpeg|png|gif)\z!i
 
+      delegate :artist_name, :profile_url, :unique_id, :artist_commentary_title, :artist_commentary_desc, :dtext_artist_commentary_title, :dtext_artist_commentary_desc, to: :sub_strategy, allow_nil: true
+
       def self.match?(*urls)
         urls.compact.any? { |x| x.match?(BASE_URL) }
       end
@@ -73,14 +75,6 @@ module Sources
         image_url
       end
 
-      def profile_url
-        nil
-      end
-
-      def artist_name
-        nil
-      end
-
       def tags
         api_response[:tags].to_s.split.map do |tag|
           [tag.tr("_", " "), "https://#{site_name}/post?tags=#{CGI.escape(tag)}"]
@@ -109,6 +103,10 @@ module Sources
       memoize :api_response
 
       concerning :HelperMethods do
+        def sub_strategy
+          @sub_strategy ||= Sources::Strategies.find(api_response[:source], default: nil)
+        end
+
         def file_host
           case site_name
           when "yande.re" then "files.yande.re"

app/logical/sources/strategies/null.rb

@@ -1,10 +1,6 @@
 module Sources
   module Strategies
     class Null < Base
-      def self.match?(*urls)
-        true
-      end
-
       def image_urls
         [url]
       end