Add Rule34.us support.

app/logical/source/extractor/rule34_dot_us.rb

@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+# https://rule34.us is running a modified fork of Gelbooru 0.1, so its structure is similar but not identical to that of
+# other Gelbooru-based sites.
+#
+# @see Source::Extractor::Gelbooru
+# @see Source::URL::Rule34DotUs
+# @see https://rule34.us
+module Source
+  class Extractor
+    class Rule34DotUs < Source::Extractor
+      def match?
+        Source::URL::Rule34DotUs === parsed_url
+      end
+
+      def image_urls
+        if parsed_url.full_image_url.present?
+          [parsed_url.full_image_url]
+        else
+          image_url = page&.css(".tag-list-left > a[href*='/images/']")&.attr("href")&.value
+          [image_url].compact
+        end
+      end
+
+      def page_url
+        "https://rule34.us/index.php?r=posts/view&id=#{post_id}" if post_id.present?
+      end
+
+      def tags
+        page&.css("meta[name='keywords']")&.attr("content")&.value.to_s.split(/, /).compact.map do |tag|
+          [tag.tr(" ", "_"), "https://rule34.us/index.php?r=posts/index&q=#{CGI.escape(tag)}"]
+        end
+      end
+
+      def post_id
+        parsed_url.post_id || parsed_referer&.post_id || post_id_from_page
+      end
+
+      def post_id_from_page
+        # title = "Rule34 - If it exists, there is porn of it  / sora / 6204967"
+        page&.title.to_s[/([0-9]+)\z/, 1]
+      end
+
+      def api_url
+        parsed_url.page_url || parsed_referer&.page_url
+      end
+
+      memoize def page
+        return nil if api_url.blank?
+
+        response = http.cache(1.minute).get(api_url)
+        return nil unless response.status == 200
+
+        response.parse
+      end
+    end
+  end
+end