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/tumblr.rb

@@ -0,0 +1,145 @@
+# frozen_string_literal: true
+
+# @see Source::URL::Tumblr
+class Source::Extractor
+  class Tumblr < Source::Extractor
+    def self.enabled?
+      Danbooru.config.tumblr_consumer_key.present?
+    end
+
+    def match?
+      Source::URL::Tumblr === parsed_url
+    end
+
+    def image_urls
+      return [find_largest(parsed_url)].compact if parsed_url.asset_url?
+
+      assets = []
+
+      case post[:type]
+      when "photo"
+        assets += post[:photos].map do |photo|
+          sizes = [photo[:original_size]] + photo[:alt_sizes]
+          biggest = sizes.max_by { |x| x[:width] * x[:height] }
+          biggest[:url]
+        end
+
+      when "video"
+        assets += [post[:video_url]]
+      end
+
+      assets += inline_images
+      assets.map { |url| find_largest(url) }
+    end
+
+    def page_url
+      parsed_url.page_url || parsed_referer&.page_url || post_url_from_image_html&.page_url
+    end
+
+    def profile_url
+      parsed_url.profile_url || parsed_referer&.profile_url || post_url_from_image_html&.profile_url
+    end
+
+    def artist_commentary_title
+      case post[:type]
+      when "text", "link"
+        post[:title]
+
+      when "answer"
+        "#{post[:asking_name]} asked: #{post[:question]}"
+
+      else
+        nil
+      end
+    end
+
+    def artist_commentary_desc
+      case post[:type]
+      when "text"
+        post[:body]
+
+      when "link"
+        post[:description]
+
+      when "photo", "video"
+        post[:caption]
+
+      when "answer"
+        post[:answer]
+
+      else
+        nil
+      end
+    end
+
+    def tags
+      post[:tags].to_a.map do |tag|
+        [tag, "https://tumblr.com/tagged/#{CGI.escape(tag)}"]
+      end.uniq
+    end
+
+    def normalize_tag(tag)
+      tag = tag.tr("-", "_")
+      super(tag)
+    end
+
+    def dtext_artist_commentary_desc
+      DText.from_html(artist_commentary_desc).strip
+    end
+
+    def find_largest(image_url)
+      parsed_image = Source::URL.parse(image_url)
+      if parsed_image.full_image_url.present?
+        image_url_html(parsed_image.full_image_url)&.at("img[src*='/#{parsed_image.directory}/']")&.[](:src)
+      elsif parsed_image.variants.present?
+        # Look for the biggest available version on media.tumblr.com. A bigger
+        # version may or may not exist.
+        parsed_image.variants.find { |variant| http_exists?(variant) }
+      else
+        parsed_image.original_url
+      end
+    end
+
+    def post_url_from_image_html
+      extracted = image_url_html(parsed_url)&.at("[href*='/post/']")&.[](:href)
+      Source::URL.parse(extracted)
+    end
+
+    def image_url_html(image_url)
+      resp = http.cache(1.minute).headers(accept: "text/html").get(image_url)
+      return nil if resp.code != 200
+      resp.parse
+    end
+
+    def inline_images
+      html = Nokogiri::HTML5.fragment(artist_commentary_desc)
+      html.css("img").map { |node| node["src"] }
+    end
+
+    def artist_name
+      parsed_url.blog_name || parsed_referer&.blog_name || post_url_from_image_html&.blog_name
+    end
+
+    def work_id
+      parsed_url.work_id || parsed_referer&.work_id || post_url_from_image_html&.work_id
+    end
+
+    def api_response
+      return {} unless self.class.enabled?
+      return {} unless artist_name.present? && work_id.present?
+
+      response = http.cache(1.minute).get(
+        "https://api.tumblr.com/v2/blog/#{artist_name}/posts",
+        params: { id: work_id, api_key: Danbooru.config.tumblr_consumer_key }
+      )
+
+      return {} if response.code != 200
+      response.parse.with_indifferent_access
+    end
+    memoize :api_response
+
+    def post
+      api_response.dig(:response, :posts)&.first || {}
+    end
+  end
+end