sources: factor out Source::URL::Newgrounds.

Also fix it so that the image URL is set as the source for Newgrounds
posts, not the page URL. It's possible to generate the page URL from the
image URL (except for images after the first in multi-image posts).

* Page: https://www.newgrounds.com/art/view/natthelich/weaver
* Image: https://art.ngfiles.com/images/1520000/1520217_natthelich_weaver.jpg?f1606365031

app/logical/sources/strategies/newgrounds.rb

@@ -1,37 +1,19 @@
 # frozen_string_literal: true
 
-# Image Urls
-# * https://art.ngfiles.com/images/1254000/1254722_natthelich_pandora.jpg
-# * https://art.ngfiles.com/images/1033000/1033622_natthelich_fire-emblem-marth-plus-progress-pic.png?f1569487181
-# * https://art.ngfiles.com/comments/57000/iu_57615_7115981.jpg
-#
-# Page URLs
-# * https://www.newgrounds.com/art/view/puddbytes/costanza-at-bat
-# * https://www.newgrounds.com/art/view/natthelich/fire-emblem-marth-plus-progress-pic (multiple)
-#
-# Profile URLs
-# * https://natthelich.newgrounds.com/
-
+# @see Source::URL::Newgrounds
 module Sources
   module Strategies
     class Newgrounds < Base
-      IMAGE_URL   = %r{\Ahttps?://art\.ngfiles\.com/images/\d+/\d+_(?<user_name>[0-9a-z-]+)_(?<illust_title>[0-9a-z-]+)\.\w+}i
-      COMMENT_URL = %r{\Ahttps?://art\.ngfiles\.com/comments/\d+/\w+\.\w+}i
-
-      PAGE_URL    = %r{\Ahttps?://(?:www\.)?newgrounds\.com/art/view/(?<user_name>[0-9a-z-]+)/(?<illust_title>[0-9a-z-]+)(?:\?.*)?}i
-
-      PROFILE_URL = %r{\Ahttps?://(?<artist_name>(?!www)[0-9a-z-]+)\.newgrounds\.com(?:/.*)?}i
-
-      def domains
-        ["newgrounds.com", "ngfiles.com"]
+      def match?
+        parsed_url&.site_name == "Newgrounds"
       end
 
       def site_name
-        "NewGrounds"
+        "Newgrounds"
       end
 
       def image_urls
-        if url =~ COMMENT_URL || url =~ IMAGE_URL
+        if parsed_url.image_url?
           [url]
         else
           urls = []
@@ -97,16 +79,25 @@ module Sources
         DText.from_html(artist_commentary_desc)
       end
 
+      # The image url should be the post source, if we can generate the page url from the image url.
+      def canonical_url
+        if page_url.present?
+          url
+        else
+          page_url
+        end
+      end
+
       def normalize_for_source
         page_url
       end
 
       def user_name
-        urls.map { |u| url[PROFILE_URL, :artist_name] || u[IMAGE_URL, :user_name] || u[PAGE_URL, :user_name] }.compact.first
+        parsed_url.username || parsed_referer&.username
       end
 
       def illust_title
-        urls.map { |u| u[IMAGE_URL, :illust_title] || u[PAGE_URL, :illust_title] }.compact.first
+        parsed_url.work_title || parsed_referer&.work_title
       end
     end
   end