Accept remote quotes of local quotes according to set policy (#35629)

app/lib/activitypub/activity/quote_request.rb

@@ -9,12 +9,31 @@ class ActivityPub::Activity::QuoteRequest < ActivityPub::Activity
     quoted_status = status_from_uri(object_uri)
     return if quoted_status.nil? || !quoted_status.account.local? || !quoted_status.distributable?
 
-    # For now, we don't support being quoted by external servers
-    reject_quote_request!(quoted_status)
+    if Mastodon::Feature.outgoing_quotes_enabled? && StatusPolicy.new(@account, quoted_status).quote?
+      accept_quote_request!(quoted_status)
+    else
+      reject_quote_request!(quoted_status)
+    end
   end
 
   private
 
+  def accept_quote_request!(quoted_status)
+    status = status_from_uri(@json['instrument'])
+    # TODO: import inlined quote post if possible
+    status ||= ActivityPub::FetchRemoteStatusService.new.call(@json['instrument'], on_behalf_of: @account.followers.local.first, request_id: @options[:request_id])
+    # TODO: raise if status is nil
+
+    # Sanity check
+    return unless status.quote.quoted_status == quoted_status
+
+    status.quote.update!(activity_uri: @json['id'])
+    status.quote.accept!
+
+    json = Oj.dump(serialize_payload(status.quote, ActivityPub::AcceptQuoteRequestSerializer))
+    ActivityPub::DeliveryWorker.perform_async(json, quoted_status.account_id, @account.inbox_url)
+  end
+
   def reject_quote_request!(quoted_status)
     quote = Quote.new(
       quoted_status: quoted_status,

app/serializers/activitypub/accept_quote_request_serializer.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+class ActivityPub::AcceptQuoteRequestSerializer < ActivityPub::Serializer
+  attributes :id, :type, :actor, :result
+
+  has_one :object, serializer: ActivityPub::QuoteRequestSerializer
+
+  def id
+    [ActivityPub::TagManager.instance.uri_for(object.quoted_account), '#accepts/quote_requests/', object.id].join
+  end
+
+  def type
+    'Accept'
+  end
+
+  def actor
+    ActivityPub::TagManager.instance.uri_for(object.quoted_account)
+  end
+
+  def result
+    ActivityPub::TagManager.instance.approval_uri_for(object)
+  end
+end

app/serializers/activitypub/quote_request_serializer.rb

@@ -23,6 +23,7 @@ class ActivityPub::QuoteRequestSerializer < ActivityPub::Serializer
   end
 
   def instrument
+    # TODO: inline object?
     ActivityPub::TagManager.instance.uri_for(object.status)
   end
 end

spec/lib/activitypub/activity/quote_request_spec.rb

@@ -2,7 +2,7 @@
 
 require 'rails_helper'
 
-RSpec.describe ActivityPub::Activity::QuoteRequest do
+RSpec.describe ActivityPub::Activity::QuoteRequest, feature: :outgoing_quotes do
   let(:sender)    { Fabricate(:account, domain: 'example.com') }
   let(:recipient) { Fabricate(:account) }
   let(:quoted_post) { Fabricate(:status, account: recipient) }
@@ -47,5 +47,44 @@ RSpec.describe ActivityPub::Activity::QuoteRequest do
           end, recipient.id, sender.inbox_url)
       end
     end
+
+    context 'when trying to quote a quotable local status' do
+      let(:status_json) do
+        {
+          '@context': [
+            'https://www.w3.org/ns/activitystreams',
+            {
+              '@id': 'https://w3id.org/fep/044f#quote',
+              '@type': '@id',
+            },
+            {
+              '@id': 'https://w3id.org/fep/044f#quoteAuthorization',
+              '@type': '@id',
+            },
+          ],
+          id: 'https://example.com/unknown-status',
+          type: 'Note',
+          summary: 'Show more',
+          content: 'Hello universe',
+          quote: ActivityPub::TagManager.instance.uri_for(quoted_post),
+          attributedTo: ActivityPub::TagManager.instance.uri_for(sender),
+        }.deep_stringify_keys
+      end
+
+      before do
+        stub_request(:get, 'https://example.com/unknown-status').to_return(status: 200, body: Oj.dump(status_json), headers: { 'Content-Type': 'application/activity+json' })
+        quoted_post.update(quote_approval_policy: Status::QUOTE_APPROVAL_POLICY_FLAGS[:public] << 16)
+      end
+
+      it 'accepts the quote and sends an Accept activity' do
+        expect { subject.perform }
+          .to change { quoted_post.reload.quotes.accepted.count }.by(1)
+          .and enqueue_sidekiq_job(ActivityPub::DeliveryWorker)
+          .with(satisfying do |body|
+            outgoing_json = Oj.load(body)
+            outgoing_json['type'] == 'Accept' && %w(type id actor object instrument).all? { |key| json[key] == outgoing_json['object'][key] }
+          end, recipient.id, sender.inbox_url)
+      end
+    end
   end
 end

spec/serializers/activitypub/accept_quote_request_serializer_spec.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe ActivityPub::AcceptQuoteRequestSerializer do
+  subject { serialized_record_json(record, described_class, adapter: ActivityPub::Adapter) }
+
+  describe 'serializing an object' do
+    let(:record) { Fabricate(:quote, state: :accepted) }
+
+    it 'returns expected attributes' do
+      expect(subject.deep_symbolize_keys)
+        .to include(
+          actor: eq(ActivityPub::TagManager.instance.uri_for(record.quoted_account)),
+          id: match("#accepts/quote_requests/#{record.id}"),
+          object: include(
+            type: 'QuoteRequest',
+            instrument: ActivityPub::TagManager.instance.uri_for(record.status),
+            object: ActivityPub::TagManager.instance.uri_for(record.quoted_status)
+          ),
+          type: 'Accept'
+        )
+    end
+  end
+end