sources: add 4chan.org upload support.

Add upload support for 4chan.org. You can upload either individual posts or entire threads at a time.

app/logical/source/extractor/four_chan.rb

@@ -0,0 +1,133 @@
+# frozen_string_literal: true
+
+# Source extractor for 4chan.org.
+#
+# TODO:
+#
+# * If given only an image URL, scrape the board catalog to find which thread it belongs to.
+# * If the thread is expired, scrape data from archive sites.
+# * If the image or video is a soundpost, remux the file to include the sound (https://github.com/rcc11/4chan-sounds-player#creating-sound-images)
+#
+# @see https://github.com/4chan/4chan-API
+# @see https://github.com/4chan/4chan-API/blob/master/pages/Threads.md
+module Source
+  class Extractor
+    class FourChan < Source::Extractor
+      def match?
+        Source::URL::FourChan === parsed_url
+      end
+
+      def image_urls
+        if parsed_url.full_image_url.present?
+          [parsed_url.full_image_url]
+        # If this is a post URL, or an image URL for which we can find the post
+        elsif post.present? && post["tim"].present? && post["ext"].present?
+          ["https://i.4cdn.org/#{board}/#{post["tim"]}#{post["ext"]}"]
+        # If this is a thread URL
+        elsif thread_id.present? && post_id_from_url.nil?
+          api_response.map do |post|
+            "https://i.4cdn.org/#{board}/#{post["tim"]}#{post["ext"]}" if post["tim"].present? && post["ext"].present?
+          end.compact
+        # If this is a thumbnail image URL and we can't get the full image URL from the API
+        elsif parsed_url.image_url?
+          [url.to_s]
+        else
+          []
+        end
+      end
+
+      def page_url
+        if board.present? && thread_id.present? && post_id.present?
+          "https://#{domain}/#{board}/thread/#{thread_id}#p#{post_id}"
+        elsif board.present? && thread_id.present?
+          "https://#{domain}/#{board}/thread/#{thread_id}"
+        end
+      end
+
+      def artist_commentary_title
+        if post.present?
+          "#{post["name"]}#{post["trip"]} #{post["now"]} No.#{post["no"]}"
+        end
+      end
+
+      def artist_commentary_desc
+        commentary = String.new
+
+        if post["filename"].present?
+          commentary << "<a href=\"https://i.4cdn.org/#{board}/#{post["tim"]}#{post["ext"]}\">#{post["filename"]}#{post["ext"]}</a> (#{post["fsize"].to_fs(:human_size)}, #{post["w"]}x#{post["h"]})\n"
+        end
+
+        if post["com"].present?
+          commentary << post["com"]
+        end
+
+        commentary.presence
+      end
+
+      def dtext_artist_commentary_desc
+        DText.from_html(artist_commentary_desc) do |element|
+          if element.name == "a" && element["class"] == "quotelink"
+            # `<a href="#p1234" class="quotelink">&gt;&gt;1234</a>`
+            if element["href"].starts_with?("#")
+              element["href"] = "https://#{domain}/#{board}/thread/#{thread_id}#{element["href"]}"
+            # `<a href="/vt/thread/1234#p5678" class="quotelink">&gt;&gt;5678</a>`
+            elsif element["href"].starts_with?("/")
+              element["href"] = "https://#{domain}#{element["href"]}"
+            end
+          end
+        end
+      end
+
+      def domain
+        if parsed_url.domain in "4chan.org" | "4channel.org"
+          "boards.#{parsed_url.domain}"
+        elsif parsed_referer&.domain in "4chan.org" | "4channel.org"
+          "boards.#{parsed_referer.domain}"
+        end
+      end
+
+      def board
+        parsed_url.board || parsed_referer&.board
+      end
+
+      def thread_id
+        parsed_url.thread_id || parsed_referer&.thread_id
+      end
+
+      def image_id
+        parsed_url.image_id || parsed_referer&.image_id
+      end
+
+      def post_id
+        post_id_from_url || post_id_from_api
+      end
+
+      def post_id_from_url
+        parsed_url.post_id || parsed_referer&.post_id
+      end
+
+      def post_id_from_api
+        post["no"]
+      end
+
+      memoize def post
+        api_response.find do |post|
+          (image_id.present? && post["tim"] == image_id) || post["no"] == post_id_from_url
+        end.to_h
+      end
+
+      memoize def api_response
+        return [] unless api_url.present?
+
+        response = http.cache(1.minute).get(api_url)
+        return [] unless response.status == 200
+
+        response.parse["posts"]
+      end
+
+      def api_url
+        "https://a.4cdn.org/#{board}/thread/#{thread_id}.json" if board.present? && thread_id.present?
+      end
+    end
+  end
+end