1 files changed, 60 insertions, 24 deletions

diff --git a/app/services/fetch_atom_service.rb b/app/services/fetch_atom_service.rb
index 3ac441e3e..9c5777b5d 100644
--- a/app/services/fetch_atom_service.rb
+++ b/app/services/fetch_atom_service.rb
@@ -1,21 +1,17 @@
 # frozen_string_literal: true
 
 class FetchAtomService < BaseService
+  include JsonLdHelper
+
   def call(url)
     return if url.blank?
 
-    response = Request.new(:head, url).perform
-
-    Rails.logger.debug "Remote status HEAD request returned code #{response.code}"
+    result = process(url)
 
-    response = Request.new(:get, url).perform if response.code == 405
+    # retry without ActivityPub
+    result ||= process(url) if @unsupported_activity
 
-    Rails.logger.debug "Remote status GET request returned code #{response.code}"
-
-    return nil if response.code != 200
-    return [url, fetch(url)] if response.mime_type == 'application/atom+xml'
-    return process_headers(url, response) if response['Link'].present?
-    process_html(fetch(url))
+    result
   rescue OpenSSL::SSL::SSLError => e
     Rails.logger.debug "SSL error: #{e}"
     nil
@@ -26,27 +22,67 @@ class FetchAtomService < BaseService
 
   private
 
-  def process_html(body)
-    Rails.logger.debug 'Processing HTML'
+  def process(url, terminal = false)
+    @url = url
+    perform_request
+    process_response(terminal)
+  end
+
+  def perform_request
+    accept = 'text/html'
+    accept = 'application/activity+json, application/ld+json, application/atom+xml, ' + accept unless @unsupported_activity
+
+    @response = Request.new(:get, @url)
+                       .add_headers('Accept' => accept)
+                       .perform
+  end
 
-    page = Nokogiri::HTML(body)
-    alternate_link = page.xpath('//link[@rel="alternate"]').find { |link| link['type'] == 'application/atom+xml' }
+  def process_response(terminal = false)
+    return nil if @response.code != 200
 
-    return nil if alternate_link.nil?
-    [alternate_link['href'], fetch(alternate_link['href'])]
+    if @response.mime_type == 'application/atom+xml'
+      [@url, @response.to_s, :ostatus]
+    elsif ['application/activity+json', 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'].include?(@response.mime_type)
+      if supported_activity?(@response.to_s)
+        [@url, @response.to_s, :activitypub]
+      else
+        @unsupported_activity = true
+        nil
+      end
+    elsif @response['Link'] && !terminal
+      process_headers
+    elsif @response.mime_type == 'text/html' && !terminal
+      process_html
+    end
   end
 
-  def process_headers(url, response)
-    Rails.logger.debug 'Processing link header'
+  def process_html
+    page = Nokogiri::HTML(@response.to_s)
+
+    json_link = page.xpath('//link[@rel="alternate"]').find { |link| ['application/activity+json', 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'].include?(link['type']) }
+    atom_link = page.xpath('//link[@rel="alternate"]').find { |link| link['type'] == 'application/atom+xml' }
+
+    result ||= process(json_link['href'], terminal: true) unless json_link.nil? || @unsupported_activity
+    result ||= process(atom_link['href'], terminal: true) unless atom_link.nil?
+
+    result
+  end
+
+  def process_headers
+    link_header = LinkHeader.parse(@response['Link'].is_a?(Array) ? @response['Link'].first : @response['Link'])
+
+    json_link = link_header.find_link(%w(rel alternate), %w(type application/activity+json)) || link_header.find_link(%w(rel alternate), ['type', 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'])
+    atom_link = link_header.find_link(%w(rel alternate), %w(type application/atom+xml))
 
-    link_header    = LinkHeader.parse(response['Link'].is_a?(Array) ? response['Link'].first : response['Link'])
-    alternate_link = link_header.find_link(%w(rel alternate), %w(type application/atom+xml))
+    result ||= process(json_link.href, terminal: true) unless json_link.nil? || @unsupported_activity
+    result ||= process(atom_link.href, terminal: true) unless atom_link.nil?
 
-    return process_html(fetch(url)) if alternate_link.nil?
-    [alternate_link.href, fetch(alternate_link.href)]
+    result
   end
 
-  def fetch(url)
-    Request.new(:get, url).perform.to_s
+  def supported_activity?(body)
+    json = body_to_json(body)
+    return false unless supported_context?(json)
+    json['type'] == 'Person' ? json['inbox'].present? : true
   end
 end