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/pixiv_sketch.rb

@@ -0,0 +1,82 @@
+# frozen_string_literal: true
+
+# @see Source::URL::PixivSketch
+module Source
+  class Extractor
+    class PixivSketch < Source::Extractor
+      def match?
+        Source::URL::PixivSketch === parsed_url
+      end
+
+      def image_urls
+        if parsed_url.image_url?
+          [parsed_url.full_image_url]
+        else
+          image_urls_from_api
+        end
+      end
+
+      def image_urls_from_api
+        api_response.dig("data", "media").to_a.pluck("photo").pluck("original").pluck("url2x")
+      end
+
+      def profile_url
+        "https://sketch.pixiv.net/@#{artist_name}" if artist_name.present?
+      end
+
+      def artist_name
+        api_response.dig("data", "user", "unique_name")
+      end
+
+      def other_names
+        [artist_name, display_name].compact
+      end
+
+      def profile_urls
+        [profile_url, pixiv_profile_url].compact
+      end
+
+      def artist_commentary_desc
+        api_response.dig("data", "text")
+      end
+
+      def tags
+        api_response.dig("data", "tags").to_a.map do |tag|
+          [tag, "https://sketch.pixiv.net/tags/#{tag}"]
+        end
+      end
+
+      def display_name
+        api_response.dig("data", "user", "name")
+      end
+
+      def pixiv_profile_url
+        "https://www.pixiv.net/users/#{pixiv_user_id}" if pixiv_user_id.present?
+      end
+
+      def pixiv_user_id
+        api_response.dig("data", "user", "pixiv_user_id")
+      end
+
+      # curl https://sketch.pixiv.net/api/items/5835314698645024323.json | jq
+      def api_response
+        return {} if api_url.blank?
+
+        response = http.cache(1.minute).get(api_url)
+        return {} if response.status == 404
+
+        response.parse
+      end
+
+      def page_url
+        parsed_url.page_url || parsed_referer&.page_url
+      end
+
+      def api_url
+        parsed_url.api_url || parsed_referer&.api_url
+      end
+
+      memoize :api_response
+    end
+  end
+end