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

9 files changed, 610 insertions, 0 deletions

diff --git a/spec/lib/activitypub/activity/announce_spec.rb b/spec/lib/activitypub/activity/announce_spec.rb
new file mode 100644
index 000000000..54dd52a60
--- /dev/null
+++ b/spec/lib/activitypub/activity/announce_spec.rb
@@ -0,0 +1,29 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::Activity::Announce do
+  let(:sender)    { Fabricate(:account) }
+  let(:recipient) { Fabricate(:account) }
+  let(:status)    { Fabricate(:status, account: recipient) }
+
+  let(:json) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: 'foo',
+      type: 'Announce',
+      actor: ActivityPub::TagManager.instance.uri_for(sender),
+      object: ActivityPub::TagManager.instance.uri_for(status),
+    }.with_indifferent_access
+  end
+
+  describe '#perform' do
+    subject { described_class.new(json, sender) }
+
+    before do
+      subject.perform
+    end
+
+    it 'creates a reblog by sender of status' do
+      expect(sender.reblogged?(status)).to be true
+    end
+  end
+end
diff --git a/spec/lib/activitypub/activity/block_spec.rb b/spec/lib/activitypub/activity/block_spec.rb
new file mode 100644
index 000000000..23c8cc31c
--- /dev/null
+++ b/spec/lib/activitypub/activity/block_spec.rb
@@ -0,0 +1,28 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::Activity::Block do
+  let(:sender)    { Fabricate(:account) }
+  let(:recipient) { Fabricate(:account) }
+
+  let(:json) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: 'foo',
+      type: 'Block',
+      actor: ActivityPub::TagManager.instance.uri_for(sender),
+      object: ActivityPub::TagManager.instance.uri_for(recipient),
+    }.with_indifferent_access
+  end
+
+  describe '#perform' do
+    subject { described_class.new(json, sender) }
+
+    before do
+      subject.perform
+    end
+
+    it 'creates a block from sender to recipient' do
+      expect(sender.blocking?(recipient)).to be true
+    end
+  end
+end
diff --git a/spec/lib/activitypub/activity/create_spec.rb b/spec/lib/activitypub/activity/create_spec.rb
new file mode 100644
index 000000000..fcb044ebc
--- /dev/null
+++ b/spec/lib/activitypub/activity/create_spec.rb
@@ -0,0 +1,221 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::Activity::Create do
+  let(:sender) { Fabricate(:account, followers_url: 'http://example.com/followers') }
+
+  let(:json) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: 'foo',
+      type: 'Create',
+      actor: ActivityPub::TagManager.instance.uri_for(sender),
+      object: object_json,
+    }.with_indifferent_access
+  end
+
+  subject { described_class.new(json, sender) }
+
+  before do
+    stub_request(:get, 'http://example.com/attachment.png').to_return(request_fixture('avatar.txt'))
+  end
+
+  describe '#perform' do
+    before do
+      subject.perform
+    end
+
+    context 'standalone' do
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Note',
+          content: 'Lorem ipsum',
+        }
+      end
+
+      it 'creates status' do
+        status = sender.statuses.first
+
+        expect(status).to_not be_nil
+        expect(status.text).to eq 'Lorem ipsum'
+      end
+
+      it 'missing to/cc defaults to direct privacy' do
+        status = sender.statuses.first
+
+        expect(status).to_not be_nil
+        expect(status.visibility).to eq 'direct'
+      end
+    end
+
+    context 'public' do
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Note',
+          content: 'Lorem ipsum',
+          to: 'https://www.w3.org/ns/activitystreams#Public',
+        }
+      end
+
+      it 'creates status' do
+        status = sender.statuses.first
+
+        expect(status).to_not be_nil
+        expect(status.visibility).to eq 'public'
+      end
+    end
+
+    context 'unlisted' do
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Note',
+          content: 'Lorem ipsum',
+          cc: 'https://www.w3.org/ns/activitystreams#Public',
+        }
+      end
+
+      it 'creates status' do
+        status = sender.statuses.first
+
+        expect(status).to_not be_nil
+        expect(status.visibility).to eq 'unlisted'
+      end
+    end
+
+    context 'private' do
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Note',
+          content: 'Lorem ipsum',
+          to: 'http://example.com/followers',
+        }
+      end
+
+      it 'creates status' do
+        status = sender.statuses.first
+
+        expect(status).to_not be_nil
+        expect(status.visibility).to eq 'private'
+      end
+    end
+
+    context 'direct' do
+      let(:recipient) { Fabricate(:account) }
+
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Note',
+          content: 'Lorem ipsum',
+          to: ActivityPub::TagManager.instance.uri_for(recipient),
+        }
+      end
+
+      it 'creates status' do
+        status = sender.statuses.first
+
+        expect(status).to_not be_nil
+        expect(status.visibility).to eq 'direct'
+      end
+    end
+
+    context 'as a reply' do
+      let(:original_status) { Fabricate(:status) }
+
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Note',
+          content: 'Lorem ipsum',
+          inReplyTo: ActivityPub::TagManager.instance.uri_for(original_status),
+        }
+      end
+
+      it 'creates status' do
+        status = sender.statuses.first
+
+        expect(status).to_not be_nil
+        expect(status.thread).to eq original_status
+        expect(status.reply?).to be true
+        expect(status.in_reply_to_account).to eq original_status.account
+        expect(status.conversation).to eq original_status.conversation
+      end
+    end
+
+    context 'with mentions' do
+      let(:recipient) { Fabricate(:account) }
+
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Note',
+          content: 'Lorem ipsum',
+          tag: [
+            {
+              type: 'Mention',
+              href: ActivityPub::TagManager.instance.uri_for(recipient),
+            },
+          ],
+        }
+      end
+
+      it 'creates status' do
+        status = sender.statuses.first
+
+        expect(status).to_not be_nil
+        expect(status.mentions.map(&:account)).to include(recipient)
+      end
+    end
+
+    context 'with media attachments' do
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Note',
+          content: 'Lorem ipsum',
+          attachment: [
+            {
+              type: 'Document',
+              mime_type: 'image/png',
+              url: 'http://example.com/attachment.png',
+            },
+          ],
+        }
+      end
+
+      it 'creates status' do
+        status = sender.statuses.first
+
+        expect(status).to_not be_nil
+        expect(status.media_attachments.map(&:remote_url)).to include('http://example.com/attachment.png')
+      end
+    end
+
+    context 'with hashtags' do
+      let(:object_json) do
+        {
+          id: 'bar',
+          type: 'Note',
+          content: 'Lorem ipsum',
+          tag: [
+            {
+              type: 'Hashtag',
+              href: 'http://example.com/blah',
+              name: '#test',
+            },
+          ],
+        }
+      end
+
+      it 'creates status' do
+        status = sender.statuses.first
+
+        expect(status).to_not be_nil
+        expect(status.tags.map(&:name)).to include('test')
+      end
+    end
+  end
+end
diff --git a/spec/lib/activitypub/activity/delete_spec.rb b/spec/lib/activitypub/activity/delete_spec.rb
new file mode 100644
index 000000000..398669b48
--- /dev/null
+++ b/spec/lib/activitypub/activity/delete_spec.rb
@@ -0,0 +1,28 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::Activity::Delete do
+  let(:sender)    { Fabricate(:account) }
+  let(:status)    { Fabricate(:status, account: sender, uri: 'foobar') }
+
+  let(:json) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: 'foo',
+      type: 'Delete',
+      actor: ActivityPub::TagManager.instance.uri_for(sender),
+      object: ActivityPub::TagManager.instance.uri_for(status),
+    }.with_indifferent_access
+  end
+
+  describe '#perform' do
+    subject { described_class.new(json, sender) }
+
+    before do
+      subject.perform
+    end
+
+    it 'deletes sender\'s status' do
+      expect(Status.find_by(id: status.id)).to be_nil
+    end
+  end
+end
diff --git a/spec/lib/activitypub/activity/follow_spec.rb b/spec/lib/activitypub/activity/follow_spec.rb
new file mode 100644
index 000000000..7c0e447f3
--- /dev/null
+++ b/spec/lib/activitypub/activity/follow_spec.rb
@@ -0,0 +1,28 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::Activity::Follow do
+  let(:sender)    { Fabricate(:account) }
+  let(:recipient) { Fabricate(:account) }
+
+  let(:json) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: 'foo',
+      type: 'Follow',
+      actor: ActivityPub::TagManager.instance.uri_for(sender),
+      object: ActivityPub::TagManager.instance.uri_for(recipient),
+    }.with_indifferent_access
+  end
+
+  describe '#perform' do
+    subject { described_class.new(json, sender) }
+
+    before do
+      subject.perform
+    end
+
+    it 'creates a follow from sender to recipient' do
+      expect(sender.following?(recipient)).to be true
+    end
+  end
+end
diff --git a/spec/lib/activitypub/activity/like_spec.rb b/spec/lib/activitypub/activity/like_spec.rb
new file mode 100644
index 000000000..b69615a9d
--- /dev/null
+++ b/spec/lib/activitypub/activity/like_spec.rb
@@ -0,0 +1,29 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::Activity::Like do
+  let(:sender)    { Fabricate(:account) }
+  let(:recipient) { Fabricate(:account) }
+  let(:status)    { Fabricate(:status, account: recipient) }
+
+  let(:json) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: 'foo',
+      type: 'Like',
+      actor: ActivityPub::TagManager.instance.uri_for(sender),
+      object: ActivityPub::TagManager.instance.uri_for(status),
+    }.with_indifferent_access
+  end
+
+  describe '#perform' do
+    subject { described_class.new(json, sender) }
+
+    before do
+      subject.perform
+    end
+
+    it 'creates a favourite from sender to status' do
+      expect(sender.favourited?(status)).to be true
+    end
+  end
+end
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
diff --git a/spec/lib/activitypub/activity/update_spec.rb b/spec/lib/activitypub/activity/update_spec.rb
new file mode 100644
index 000000000..0bd6d00d9
--- /dev/null
+++ b/spec/lib/activitypub/activity/update_spec.rb
@@ -0,0 +1,41 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::Activity::Update do
+  let!(:sender) { Fabricate(:account) }
+  
+  before do
+    sender.update!(uri: ActivityPub::TagManager.instance.uri_for(sender))
+  end
+
+  let(:modified_sender) do 
+    sender.dup.tap do |modified_sender|
+      modified_sender.display_name = 'Totally modified now'
+    end
+  end
+
+  let(:actor_json) do
+    ActiveModelSerializers::SerializableResource.new(modified_sender, serializer: ActivityPub::ActorSerializer, key_transform: :camel_lower).as_json
+  end
+
+  let(:json) do
+    {
+      '@context': 'https://www.w3.org/ns/activitystreams',
+      id: 'foo',
+      type: 'Update',
+      actor: ActivityPub::TagManager.instance.uri_for(sender),
+      object: actor_json,
+    }.with_indifferent_access
+  end
+
+  describe '#perform' do
+    subject { described_class.new(json, sender) }
+
+    before do
+      subject.perform
+    end
+
+    it 'updates profile' do
+      expect(sender.reload.display_name).to eq 'Totally modified now'
+    end
+  end
+end
diff --git a/spec/lib/activitypub/tag_manager_spec.rb b/spec/lib/activitypub/tag_manager_spec.rb
new file mode 100644
index 000000000..8f7662e24
--- /dev/null
+++ b/spec/lib/activitypub/tag_manager_spec.rb
@@ -0,0 +1,99 @@
+require 'rails_helper'
+
+RSpec.describe ActivityPub::TagManager do
+  include RoutingHelper
+
+  subject { described_class.instance }
+
+  describe '#url_for' do
+    it 'returns a string' do
+      account = Fabricate(:account)
+      expect(subject.url_for(account)).to be_a String
+    end
+  end
+
+  describe '#uri_for' do
+    it 'returns a string' do
+      account = Fabricate(:account)
+      expect(subject.uri_for(account)).to be_a String
+    end
+  end
+
+  describe '#to' do
+    it 'returns public collection for public status' do
+      status = Fabricate(:status, visibility: :public)
+      expect(subject.to(status)).to eq ['https://www.w3.org/ns/activitystreams#Public']
+    end
+
+    it 'returns followers collection for unlisted status' do
+      status = Fabricate(:status, visibility: :unlisted)
+      expect(subject.to(status)).to eq [account_followers_url(status.account)]
+    end
+
+    it 'returns followers collection for private status' do
+      status = Fabricate(:status, visibility: :private)
+      expect(subject.to(status)).to eq [account_followers_url(status.account)]
+    end
+
+    it 'returns URIs of mentions for direct status' do
+      status    = Fabricate(:status, visibility: :direct)
+      mentioned = Fabricate(:account)
+      status.mentions.create(account: mentioned)
+      expect(subject.to(status)).to eq [subject.uri_for(mentioned)]
+    end
+  end
+
+  describe '#cc' do
+    it 'returns followers collection for public status' do
+      status = Fabricate(:status, visibility: :public)
+      expect(subject.cc(status)).to eq [account_followers_url(status.account)]
+    end
+
+    it 'returns public collection for unlisted status' do
+      status = Fabricate(:status, visibility: :unlisted)
+      expect(subject.cc(status)).to eq ['https://www.w3.org/ns/activitystreams#Public']
+    end
+
+    it 'returns empty array for private status' do
+      status = Fabricate(:status, visibility: :private)
+      expect(subject.cc(status)).to eq []
+    end
+
+    it 'returns empty array for direct status' do
+      status = Fabricate(:status, visibility: :direct)
+      expect(subject.cc(status)).to eq []
+    end
+
+    it 'returns URIs of mentions for non-direct status' do
+      status    = Fabricate(:status, visibility: :public)
+      mentioned = Fabricate(:account)
+      status.mentions.create(account: mentioned)
+      expect(subject.cc(status)).to include(subject.uri_for(mentioned))
+    end
+  end
+
+  describe '#local_uri?' do
+    it 'returns false for non-local URI' do
+      expect(subject.local_uri?('http://example.com/123')).to be false
+    end
+
+    it 'returns true for local URIs' do
+      account = Fabricate(:account)
+      expect(subject.local_uri?(subject.uri_for(account))).to be true
+    end
+  end
+
+  describe '#uri_to_local_id' do
+    it 'returns the local ID' do
+      account = Fabricate(:account)
+      expect(subject.uri_to_local_id(subject.uri_for(account), :username)).to eq account.username
+    end
+  end
+
+  describe '#uri_to_resource' do
+    it 'returns the local resource' do
+      account = Fabricate(:account)
+      expect(subject.uri_to_resource(subject.uri_for(account), Account)).to eq account
+    end
+  end
+end