FEATURE: add Unseen view (#13977)

This view is the same as Latest except it hides the topics you have fully read. Based on this plugin of @davidtaylorhq https://meta.discourse.org/t/simple-unread-list-plugin-discourse-simple-unread/70013.

spec/components/topic_query_spec.rb

@@ -62,7 +62,7 @@ describe TopicQuery do
     end
   end
 
-  context "list_topics_by" do
+  context "#list_topics_by" do
 
     it "allows users to view their own invisible topics" do
       _topic = Fabricate(:topic, user: user)
@@ -74,7 +74,7 @@ describe TopicQuery do
 
   end
 
-  context "prioritize_pinned_topics" do
+  context "#prioritize_pinned_topics" do
     it "does the pagination correctly" do
       num_topics = 15
       per_page = 3
@@ -730,7 +730,7 @@ describe TopicQuery do
 
   end
 
-  context 'list_new' do
+  context '#list_new' do
 
     context 'without a new topic' do
       it "has no new topics" do
@@ -807,7 +807,7 @@ describe TopicQuery do
 
   end
 
-  context 'list_posted' do
+  context '#list_posted' do
     let(:topics) { topic_query.list_posted.topics }
 
     it "returns blank when there are no posted topics" do
@@ -861,7 +861,58 @@ describe TopicQuery do
     end
   end
 
-  context 'list_related_for do' do
+  context '#list_unseen' do
+    it "returns an empty list when there aren't topics" do
+      expect(topic_query.list_unseen.topics).to be_blank
+    end
+
+    it "doesn't return topics that were bumped last time before user joined the forum" do
+      user.first_seen_at = 10.minutes.ago
+      create_topic_with_three_posts(bumped_at: 15.minutes.ago)
+
+      expect(topic_query.list_unseen.topics).to be_blank
+    end
+
+    it "returns only topics that contain unseen posts" do
+      user.first_seen_at = 10.minutes.ago
+      topic_with_unseen_posts = create_topic_with_three_posts(bumped_at: 5.minutes.ago)
+      read_to_post(topic_with_unseen_posts, user, 1)
+
+      fully_read_topic = create_topic_with_three_posts(bumped_at: 5.minutes.ago)
+      read_to_the_end(fully_read_topic, user)
+
+      expect(topic_query.list_unseen.topics).to eq([topic_with_unseen_posts])
+    end
+
+    it "ignores staff posts if user is not staff" do
+      user.first_seen_at = 10.minutes.ago
+      topic = create_topic_with_three_posts(bumped_at: 5.minutes.ago)
+      read_to_the_end(topic, user)
+      create_post(topic: topic, post_type: Post.types[:whisper])
+
+      expect(topic_query.list_unseen.topics).to be_blank
+    end
+
+    def create_topic_with_three_posts(bumped_at:)
+      topic = Fabricate(:topic, bumped_at: bumped_at)
+      Fabricate(:post, topic: topic)
+      Fabricate(:post, topic: topic)
+      Fabricate(:post, topic: topic)
+      topic.highest_staff_post_number = 3
+      topic.highest_post_number = 3
+      topic
+    end
+
+    def read_to_post(topic, user, post_number)
+      TopicUser.update_last_read(user, topic.id, post_number, 0, 0)
+    end
+
+    def read_to_the_end(topic, user)
+      read_to_post topic, user, topic.highest_post_number
+    end
+  end
+
+  context '#list_related_for' do
 
     let(:user) do
       Fabricate(:admin)