Fix #24 - Thread resolving for remote statuses

This is a big one, so let me enumerate:

Accounts as well as stream entry pages now contain Link headers that
reference the Atom feed and Webfinger URL for the former and Atom entry
for the latter. So you only need to HEAD those resources to get that
information, no need to download and parse HTML <link>s.

ProcessFeedService will now queue ThreadResolveWorker for each remote
status that it cannot find otherwise. Furthermore, entries are now
processed in reverse order (from bottom to top) in case a newer entry
references a chronologically previous one.

ThreadResolveWorker uses FetchRemoteStatusService to obtain a status
and attach the child status it was queued for to it.

FetchRemoteStatusService looks up the URL, first with a HEAD, tests
if it's an Atom feed, in which case it processes it directly. Next
for Link headers to the Atom feed, in which case that is fetched
and processed. Lastly if it's HTML, it is checked for <link>s to the Atom
feed, and if such is found, that is fetched and processed. The account for
the status is derived from author/name attribute in the XML and the hostname
in the URL (domain). FollowRemoteAccountService and ProcessFeedService
are used.

This means that potentially threads are resolved recursively until a dead-end
is encountered, however it is performed asynchronously over background jobs,
so it should be ok.

2 files changed, 13 insertions, 3 deletions

diff --git a/app/controllers/accounts_controller.rb b/app/controllers/accounts_controller.rb
index 2d4c2dd9a..bfdc5b6d9 100644
--- a/app/controllers/accounts_controller.rb
+++ b/app/controllers/accounts_controller.rb
@@ -2,7 +2,7 @@ class AccountsController < ApplicationController
   layout 'public'
 
   before_action :set_account
-  before_action :set_webfinger_header
+  before_action :set_link_headers
 
   def show
     respond_to do |format|
@@ -39,8 +39,11 @@ class AccountsController < ApplicationController
     @account = Account.find_local!(params[:username])
   end
 
-  def set_webfinger_header
-    response.headers['Link'] = "<#{webfinger_account_url}>; rel=\"lrdd\"; type=\"application/xrd+xml\""
+  def set_link_headers
+    response.headers['Link'] = LinkHeader.new([
+      [webfinger_account_url, [['rel', 'lrdd'], ['type', 'application/xrd+xml']]],
+      [account_url(@account, format: 'atom'), [['rel', 'alternate'], ['type', 'application/atom+xml']]]
+    ])
   end
 
   def webfinger_account_url
diff --git a/app/controllers/stream_entries_controller.rb b/app/controllers/stream_entries_controller.rb
index c26149627..e25e7f5ed 100644
--- a/app/controllers/stream_entries_controller.rb
+++ b/app/controllers/stream_entries_controller.rb
@@ -3,6 +3,7 @@ class StreamEntriesController < ApplicationController
 
   before_action :set_account
   before_action :set_stream_entry
+  before_action :set_link_headers
 
   def show
     @type = @stream_entry.activity_type.downcase
@@ -33,6 +34,12 @@ class StreamEntriesController < ApplicationController
     @account = Account.find_local!(params[:account_username])
   end
 
+  def set_link_headers
+    response.headers['Link'] = LinkHeader.new([
+      [account_stream_entry_url(@account, @stream_entry, format: 'atom'), [['rel', 'alternate'], ['type', 'application/atom+xml']]]
+    ])
+  end
+
   def set_stream_entry
     @stream_entry = @account.stream_entries.find(params[:id])
   end