Fix home regeneration (#6251)

* Fix regeneration marker not being removed after completion

* Return HTTP 206 from /api/v1/timelines/home if regeneration in progress
Prioritize RegenerationWorker by putting it into default queue

* Display loading indicator and poll home timeline while it regenerates

* Add graphic to regeneration message

* Make "not found" indicator consistent with home regeneration

spec/controllers/concerns/user_tracking_concern_spec.rb

@@ -43,15 +43,39 @@ describe ApplicationController, type: :controller do
       expect_updated_sign_in_at(user)
     end
 
-    it 'regenerates feed when sign in is older than two weeks' do
-      allow(RegenerationWorker).to receive(:perform_async)
-      user.update(current_sign_in_at: 3.weeks.ago)
-      sign_in user, scope: :user
-      get :show
+    describe 'feed regeneration' do
+      before do
+        alice = Fabricate(:account)
+        bob   = Fabricate(:account)
 
-      expect_updated_sign_in_at(user)
-      expect(Redis.current.get("account:#{user.account_id}:regeneration")).to eq 'true'
-      expect(RegenerationWorker).to have_received(:perform_async)
+        user.account.follow!(alice)
+        user.account.follow!(bob)
+
+        Fabricate(:status, account: alice, text: 'hello world')
+        Fabricate(:status, account: bob, text: 'yes hello')
+        Fabricate(:status, account: user.account, text: 'test')
+
+        user.update(last_sign_in_at: 'Tue, 04 Jul 2017 14:45:56 UTC +00:00', current_sign_in_at: 'Wed, 05 Jul 2017 22:10:52 UTC +00:00')
+
+        sign_in user, scope: :user
+      end
+
+      it 'sets a regeneration marker while regenerating' do
+        allow(RegenerationWorker).to receive(:perform_async)
+        get :show
+
+        expect_updated_sign_in_at(user)
+        expect(Redis.current.get("account:#{user.account_id}:regeneration")).to eq 'true'
+        expect(RegenerationWorker).to have_received(:perform_async)
+      end
+
+      it 'regenerates feed when sign in is older than two weeks' do
+        get :show
+
+        expect_updated_sign_in_at(user)
+        expect(Redis.current.zcard(FeedManager.instance.key(:home, user.account_id))).to eq 3
+        expect(Redis.current.get("account:#{user.account_id}:regeneration")).to be_nil
+      end
     end
 
     def expect_updated_sign_in_at(user)