Refactor sources

app/logical/sources/strategies.rb

@@ -0,0 +1,29 @@
+module Sources
+  module Strategies
+    def self.all
+      return [
+        Strategies::Pixiv, 
+        Strategies::NicoSeiga, 
+        Strategies::Twitter, 
+        Strategies::DeviantArt, 
+        Strategies::Tumblr, 
+        Strategies::ArtStation, 
+        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)
+    end
+
+    def self.canonical(url, referer)
+      find(url, referer).canonical_url
+    end
+  end
+end