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/lofter.rb

@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+# @see Source::URL::Lofter
+module Source
+  class Extractor
+    class Lofter < Source::Extractor
+      def match?
+        Source::URL::Lofter === parsed_url
+      end
+
+      def image_urls
+        if parsed_url.image_url?
+          [parsed_url.full_image_url]
+        else
+          images = page&.search(".imgclasstag img")
+          images.to_a.pluck("src").map { |url| Source::URL.parse(url).full_image_url }
+        end
+      end
+
+      def profile_url
+        return nil if artist_name.blank?
+        "https://#{artist_name}.lofter.com"
+      end
+
+      def page_url
+        return nil if illust_id.blank? || profile_url.blank?
+
+        "#{profile_url}/post/#{illust_id}"
+      end
+
+      def page
+        return nil if page_url.blank?
+
+        response = http.cache(1.minute).get(page_url)
+        response.parse if response.status == 200
+      end
+
+      def tags
+        return [] if artist_name.blank?
+        page&.search("[href*='#{artist_name}.lofter.com/tag/']").to_a.map do |tag|
+          href = tag.attr("href")
+          [Source::URL.parse(href).unescaped_tag, href]
+        end
+      end
+
+      def artist_commentary_desc
+        page&.search(".ct .text, .content .text, .posts .photo .text").to_a.compact.first&.to_html
+      end
+
+      def illust_id
+        parsed_url.work_id || parsed_referer&.work_id
+      end
+
+      def artist_name
+        parsed_url.username || parsed_referer&.username
+      end
+
+      memoize :page
+    end
+  end
+end