implements #2350

app/logical/downloads/file.rb

@@ -22,6 +22,20 @@ module Downloads
       @data[:get_thumbnail] = options[:get_thumbnail]
     end
 
+    def size
+      headers = {
+        "User-Agent" => "#{Danbooru.config.safe_app_name}/#{Danbooru.config.version}"
+      }
+      @source, headers, @data = before_download(@source, headers, @data)
+      url = URI.parse(@source)
+      Net::HTTP.start(url.host, url.port, :use_ssl => url.is_a?(URI::HTTPS)) do |http|
+        http.read_timeout = 3
+        http.request_head(url.request_uri, headers) do |res|
+          return res.content_length
+        end
+      end
+    end
+
     def download!
       @source, @data = http_get_streaming(@source, @data) do |response|
         self.content_type = response["Content-Type"]

app/logical/sources/site.rb

@@ -3,7 +3,7 @@
 module Sources
   class Site
     attr_reader :url, :strategy
-    delegate :get, :referer_url, :site_name, :artist_name, :profile_url, :image_url, :tags, :artist_record, :unique_id, :page_count, :file_url, :ugoira_frame_data, :to => :strategy
+    delegate :get, :get_size, :referer_url, :site_name, :artist_name, :profile_url, :image_url, :tags, :artist_record, :unique_id, :page_count, :file_url, :ugoira_frame_data, :to => :strategy
 
     def self.strategies
       [Strategies::Pixiv, Strategies::NicoSeiga, Strategies::DeviantArt, Strategies::Nijie, Strategies::Twitter]

app/logical/sources/strategies/base.rb

@@ -18,6 +18,10 @@ module Sources
         raise NotImplementedError
       end
 
+      def get_size
+        @get_size ||= Downloads::File.new(@image_url).size
+      end
+
       # Subclasses should return true only if the URL is in its final normalized form.
       #
       # Sources::Site.new("http://img.pixiv.net/img/evazion").normalized_for_artist_finder?