Add Mastodon aliases and links to Webfinger when enabled

Also requires "remotestorage" service to be enabled via attribute

app/controllers/webfinger_controller.rb

@@ -7,14 +7,15 @@ class WebfingerController < ApplicationController
     resource = params[:resource]
 
     if resource && @useraddress = resource.match(/acct:(.+)/)&.[](1)
-      @username, @org = @useraddress.split("@")
+      @username, @domain = @useraddress.split("@")
 
       unless Rails.env.development?
         # Allow different domains (e.g. localhost:3000) in development only
-        head 404 and return unless @org == Setting.primary_domain
+        head 404 and return unless @domain == Setting.primary_domain
       end
 
-      unless User.where(cn: @username.downcase, ou: Setting.primary_domain).any?
+      unless @user = User.where(ou: Setting.primary_domain)
+                         .find_by(cn: @username.downcase)
         head 404 and return
       end
 
@@ -28,12 +29,50 @@ class WebfingerController < ApplicationController
   private
 
   def webfinger
-    links = [];
+    jrd = {
+      subject: "acct:#{@user.address}",
+      aliases: [],
+      links: []
+    }
 
-    # TODO check if storage service is enabled for user, not just globally
-    links << remotestorage_link if Setting.remotestorage_enabled
+    if Setting.mastodon_enabled && @user.service_enabled?(:mastodon)
+      # https://docs.joinmastodon.org/spec/webfinger/
+      jrd[:aliases] += mastodon_aliases
+      jrd[:links] += mastodon_links
+    end
 
-    { "links" => links }
+    if Setting.remotestorage_enabled && @user.service_enabled?(:remotestorage)
+      # https://datatracker.ietf.org/doc/draft-dejong-remotestorage/
+      jrd[:links] << remotestorage_link
+    end
+
+    jrd
+  end
+
+  def mastodon_aliases
+    [
+      "#{Setting.mastodon_public_url}/@#{@user.cn}",
+      "#{Setting.mastodon_public_url}/users/#{@user.cn}"
+    ]
+  end
+
+  def mastodon_links
+    [
+      {
+        rel: "http://webfinger.net/rel/profile-page",
+        type: "text/html",
+        href: "#{Setting.mastodon_public_url}/@#{@user.cn}"
+      },
+      {
+        rel: "self",
+        type: "application/activity+json",
+        href: "#{Setting.mastodon_public_url}/users/#{@user.cn}"
+      },
+      {
+        rel: "http://ostatus.org/schema/1.0/subscribe",
+        template: "#{Setting.mastodon_public_url}/authorize_interaction?uri={uri}"
+      }
+    ]
   end
 
   def remotestorage_link
@@ -41,9 +80,9 @@ class WebfingerController < ApplicationController
     storage_url = "#{Setting.rs_storage_url}/#{@username}"
 
     {
-      "rel" => "http://tools.ietf.org/id/draft-dejong-remotestorage",
-      "href" => storage_url,
-      "properties" => {
+      rel: "http://tools.ietf.org/id/draft-dejong-remotestorage",
+      href: storage_url,
+      properties: {
         "http://remotestorage.io/spec/version" => "draft-dejong-remotestorage-13",
         "http://tools.ietf.org/html/rfc6749#section-4.2" => auth_url,
         "http://tools.ietf.org/html/rfc6750#section-2.3" => nil, # access token via a HTTP query parameter