sources: rename Sources::Strategies to Source::Extractor.

Rename Sources::Strategies to Source::Extractor. A Source::Extractor
represents a thing that extracts information from a given URL.

app/logical/source/extractor/moebooru.rb

@@ -0,0 +1,96 @@
+# frozen_string_literal: true
+
+# @see Source::URL::Moebooru
+module Source
+  class Extractor
+    class Moebooru < Source::Extractor
+      delegate :artist_name, :profile_url, :tag_name, :artist_commentary_title, :artist_commentary_desc, :dtext_artist_commentary_title, :dtext_artist_commentary_desc, to: :sub_extractor, allow_nil: true
+      delegate :site_name, :domain, to: :parsed_url
+
+      def match?
+        Source::URL::Moebooru === parsed_url
+      end
+
+      def image_urls
+        return [] if post_md5.blank? || file_ext.blank?
+        [Source::URL::Moebooru.full_image_url(site_name, post_md5, file_ext, post_id)]
+      end
+
+      def page_url
+        return nil if post_id.blank?
+        "https://#{domain}/post/show/#{post_id}"
+      end
+
+      def tags
+        api_response[:tags].to_s.split.map do |tag|
+          [tag, "https://#{domain}/post?tags=#{CGI.escape(tag)}"]
+        end
+      end
+
+      # XXX the base extractor excludes artist tags from the translated tags; we don't want that for moebooru.
+      def translated_tags
+        tags.map(&:first).flat_map(&method(:translate_tag)).uniq.sort
+      end
+
+      # Moebooru returns an empty array when doing an md5:<hash> search for a
+      # deleted post. Because of this, api_response may be empty in some cases.
+      def api_response
+        if post_id_from_url.present?
+          params = { tags: "id:#{post_id_from_url}" }
+        elsif post_md5_from_url.present?
+          params = { tags: "md5:#{post_md5_from_url}" }
+        else
+          return {}
+        end
+
+        response = http.cache(1.minute).get("https://#{domain}/post.json", params: params)
+        post = response.parse.first&.with_indifferent_access
+        post || {}
+      end
+      memoize :api_response
+
+      concerning :HelperMethods do
+        def sub_extractor
+          @sub_extractor ||= Source::Extractor.find(api_response[:source], default: nil)
+        end
+
+        def file_ext
+          if parsed_url.original_file_ext.present?
+            parsed_url.original_file_ext
+
+          # file_ext is not present in konachan's api (only on yande.re)
+          elsif api_response[:file_ext].present?
+            api_response[:file_ext]
+
+          # file_url is not present in yande.re's api on deleted posts
+          elsif api_response[:file_url].present?
+            api_response[:file_url][/\.(jpg|jpeg|png|gif)\z/i, 1]
+
+          # the api_response wasn't available because it's a deleted post.
+          elsif post_md5.present?
+            %w[jpg png gif].find { |ext| http_exists?("https://#{domain}/image/#{post_md5}.#{ext}") }
+
+          else
+            nil
+          end
+        end
+
+        def post_id_from_url
+          parsed_url.work_id || parsed_referer&.work_id
+        end
+
+        def post_md5_from_url
+          parsed_url.md5 || parsed_referer&.md5
+        end
+
+        def post_id
+          post_id_from_url || api_response[:id]
+        end
+
+        def post_md5
+          post_md5_from_url || api_response[:md5]
+        end
+      end
+    end
+  end
+end