Add ActivityPub inbox (#4216)

* Add ActivityPub inbox

* Handle ActivityPub deletes

* Handle ActivityPub creates

* Handle ActivityPub announces

* Stubs for handling all activities that need to be handled

* Add ActivityPub actor resolving

* Handle conversation URI passing in ActivityPub

* Handle content language in ActivityPub

* Send accept header when fetching actor, handle JSON parse errors

* Test for ActivityPub::FetchRemoteAccountService

* Handle public key and icon/image when embedded/as array/as resolvable URI

* Implement ActivityPub::FetchRemoteStatusService

* Add stubs for more interactions

* Undo activities implemented

* Handle out of order activities

* Hook up ActivityPub to ResolveRemoteAccountService, handle
Update Account activities

* Add fragment IDs to all transient activity serializers

* Add tests and fixes

* Add stubs for missing tests

* Add more tests

* Add more tests

1 files changed, 107 insertions, 0 deletions

diff --git a/spec/lib/activitypub/activity/undo_spec.rb b/spec/lib/activitypub/activity/undo_spec.rb
new file mode 100644
index 000000000..4629a033f
--- /dev/null
+++ b/spec/lib/activitypub/activity/undo_spec.rb
@@ -0,0 +1,107 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::Activity::Undo do
+  let(:sender) { Fabricate(:account) }
+
+  let(:json) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: 'foo',
+      type: 'Undo',
+      actor: ActivityPub::TagManager.instance.uri_for(sender),
+      object: object_json,
+    }.with_indifferent_access
+  end
+
+  subject { described_class.new(json, sender) }
+
+  describe '#perform' do
+    context 'with Announce' do
+      let(:status) { Fabricate(:status) }
+
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Announce',
+          actor: ActivityPub::TagManager.instance.uri_for(sender),
+          object: ActivityPub::TagManager.instance.uri_for(status),
+        }
+      end
+
+      before do
+        Fabricate(:status, reblog: status, account: sender, uri: 'bar')
+      end
+
+      it 'deletes the reblog' do
+        subject.perform
+        expect(sender.reblogged?(status)).to be false
+      end
+    end
+
+    context 'with Block' do
+      let(:recipient) { Fabricate(:account) }
+
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Block',
+          actor: ActivityPub::TagManager.instance.uri_for(sender),
+          object: ActivityPub::TagManager.instance.uri_for(recipient),
+        }
+      end
+
+      before do
+        sender.block!(recipient)
+      end
+
+      it 'deletes block from sender to recipient' do
+        subject.perform
+        expect(sender.blocking?(recipient)).to be false
+      end
+    end
+
+    context 'with Follow' do
+      let(:recipient) { Fabricate(:account) }
+
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Follow',
+          actor: ActivityPub::TagManager.instance.uri_for(sender),
+          object: ActivityPub::TagManager.instance.uri_for(recipient),
+        }
+      end
+
+      before do
+        sender.follow!(recipient)
+      end
+
+      it 'deletes follow from sender to recipient' do
+        subject.perform
+        expect(sender.following?(recipient)).to be false
+      end
+    end
+
+    context 'with Like' do
+      let(:status) { Fabricate(:status) }
+
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Like',
+          actor: ActivityPub::TagManager.instance.uri_for(sender),
+          object: ActivityPub::TagManager.instance.uri_for(status),
+        }
+      end
+
+      before do
+        Fabricate(:favourite, account: sender, status: status)
+      end
+
+      it 'deletes favourite from sender to status' do
+        subject.perform
+        expect(sender.favourited?(status)).to be false
+      end
+    end
+  end
+end