1 files changed, 55 insertions, 0 deletions
diff --git a/app/services/activity_pub/accept_follow_service.rb b/app/services/activity_pub/accept_follow_service.rb
new file mode 100644
index 00000000000..0ec440fa972
--- /dev/null
+++ b/app/services/activity_pub/accept_follow_service.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module ActivityPub
+  class AcceptFollowService
+    MissingInboxURLError = Class.new(StandardError)
+
+    attr_reader :subscription, :actor
+
+    def initialize(subscription, actor)
+      @subscription = subscription
+      @actor = actor
+    end
+
+    def execute
+      return if subscription.accepted?
+      raise MissingInboxURLError unless subscription.subscriber_inbox_url.present?
+
+      upload_accept_activity
+      subscription.accepted!
+    end
+
+    private
+
+    def upload_accept_activity
+      body = Gitlab::Json::LimitedEncoder.encode(payload, limit: 1.megabyte)
+
+      begin
+        Gitlab::HTTP.post(subscription.subscriber_inbox_url, body: body, headers: headers)
+      rescue StandardError => e
+        raise ThirdPartyError, e.message
+      end
+    end
+
+    def payload
+      follow = subscription.payload.dup
+      follow.delete('@context')
+
+      {
+        '@context': 'https://www.w3.org/ns/activitystreams',
+        id: "#{actor}#follow/#{subscription.id}/accept",
+        type: 'Accept',
+        actor: actor,
+        object: follow
+      }
+    end
+
+    def headers
+      {
+        'User-Agent' => "GitLab/#{Gitlab::VERSION}",
+        'Content-Type' => 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"',
+        'Accept' => 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'
+      }
+    end
+  end
+end