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

4 files changed, 115 insertions, 0 deletions

diff --git a/spec/services/activitypub/fetch_remote_account_service_spec.rb b/spec/services/activitypub/fetch_remote_account_service_spec.rb
new file mode 100644
index 000000000..786d7f7f2
--- /dev/null
+++ b/spec/services/activitypub/fetch_remote_account_service_spec.rb
@@ -0,0 +1,96 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::FetchRemoteAccountService do
+  subject { ActivityPub::FetchRemoteAccountService.new }
+
+  let!(:actor) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: 'https://example.com/alice',
+      type: 'Person',
+      preferredUsername: 'alice',
+      name: 'Alice',
+      summary: 'Foo bar',
+    }
+  end
+
+  describe '#call' do
+    let(:account) { subject.call('https://example.com/alice') }
+
+    shared_examples 'sets profile data' do
+      it 'returns an account' do
+        expect(account).to be_an Account
+      end
+
+      it 'sets display name' do
+        expect(account.display_name).to eq 'Alice'
+      end
+
+      it 'sets note' do
+        expect(account.note).to eq 'Foo bar'
+      end
+
+      it 'sets URL' do
+        expect(account.url).to eq 'https://example.com/alice'
+      end
+    end
+
+    context 'when URI and WebFinger share the same host' do
+      let!(:webfinger) { { subject: 'acct:alice@example.com', links: [{ rel: 'self', href: 'https://example.com/alice' }] } }
+
+      before do
+        stub_request(:get, 'https://example.com/alice').to_return(body: Oj.dump(actor))
+        stub_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com').to_return(body: Oj.dump(webfinger), headers: { 'Content-Type': 'application/jrd+json' })
+      end
+
+      it 'fetches resource' do
+        account
+        expect(a_request(:get, 'https://example.com/alice')).to have_been_made.once
+      end
+
+      it 'looks up webfinger' do
+        account
+        expect(a_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com')).to have_been_made.once
+      end
+
+      it 'sets username and domain from webfinger' do
+        expect(account.username).to eq 'alice'
+        expect(account.domain).to eq 'example.com'
+      end
+
+      include_examples 'sets profile data'
+    end
+
+    context 'when WebFinger presents different domain than URI' do
+      let!(:webfinger) { { subject: 'acct:alice@iscool.af', links: [{ rel: 'self', href: 'https://example.com/alice' }] } }
+
+      before do
+        stub_request(:get, 'https://example.com/alice').to_return(body: Oj.dump(actor))
+        stub_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com').to_return(body: Oj.dump(webfinger), headers: { 'Content-Type': 'application/jrd+json' })
+        stub_request(:get, 'https://iscool.af/.well-known/webfinger?resource=acct:alice@iscool.af').to_return(body: Oj.dump(webfinger), headers: { 'Content-Type': 'application/jrd+json' })
+      end
+
+      it 'fetches resource' do
+        account
+        expect(a_request(:get, 'https://example.com/alice')).to have_been_made.once
+      end
+
+      it 'looks up webfinger' do
+        account
+        expect(a_request(:get, 'https://example.com/.well-known/webfinger?resource=acct:alice@example.com')).to have_been_made.once
+      end
+
+      it 'looks up "redirected" webfinger' do
+        account
+        expect(a_request(:get, 'https://iscool.af/.well-known/webfinger?resource=acct:alice@iscool.af')).to have_been_made.once
+      end
+
+      it 'sets username and domain from final webfinger' do
+        expect(account.username).to eq 'alice'
+        expect(account.domain).to eq 'iscool.af'
+      end
+
+      include_examples 'sets profile data'
+    end
+  end
+end
diff --git a/spec/services/activitypub/fetch_remote_status_service_spec.rb b/spec/services/activitypub/fetch_remote_status_service_spec.rb
new file mode 100644
index 000000000..47a33b6cb
--- /dev/null
+++ b/spec/services/activitypub/fetch_remote_status_service_spec.rb
@@ -0,0 +1,5 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::FetchRemoteStatusService do
+  pending
+end
diff --git a/spec/services/activitypub/process_account_service_spec.rb b/spec/services/activitypub/process_account_service_spec.rb
new file mode 100644
index 000000000..84a74c231
--- /dev/null
+++ b/spec/services/activitypub/process_account_service_spec.rb
@@ -0,0 +1,5 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::ProcessAccountService do
+  pending
+end
diff --git a/spec/services/activitypub/process_collection_service_spec.rb b/spec/services/activitypub/process_collection_service_spec.rb
new file mode 100644
index 000000000..6486483f6
--- /dev/null
+++ b/spec/services/activitypub/process_collection_service_spec.rb
@@ -0,0 +1,9 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::ProcessCollectionService do
+  subject { ActivityPub::ProcessCollectionService.new }
+
+  describe '#call' do
+    pending
+  end
+end