FEATURE: new search order for read topics (#33353)

Introduces order:read and r to search through recently read topics

Also applies to filter route

lib/search.rb

@@ -864,6 +864,17 @@ class Search
       else
         posts = posts.order("posts.like_count DESC")
       end
+    elsif @order == :read && @guardian.user
+      posts =
+        posts.joins(
+          "JOIN topic_users tu ON tu.topic_id = posts.topic_id AND tu.user_id = #{@guardian.user.id.to_i}",
+        ).where("tu.last_visited_at IS NOT NULL")
+
+      if aggregate_search
+        posts = posts.order("MAX(tu.last_visited_at) DESC")
+      else
+        posts = posts.reorder("tu.last_visited_at DESC")
+      end
     elsif allow_relevance_search
       posts = sort_by_relevance(posts, type_filter: type_filter, aggregate_search: aggregate_search)
     end
@@ -938,6 +949,9 @@ class Search
         if word == "l"
           @order = :latest
           nil
+        elsif word == "r"
+          @order = :read if @guardian.user
+          nil
         elsif word =~ /\Aorder:\w+\z/i
           @order = word.downcase.gsub("order:", "").to_sym
           nil

lib/topics_filter.rb

@@ -545,6 +545,19 @@ class TopicsFilter
     "views" => {
       column: "topics.views",
     },
+    "read" => {
+      column: "tu.last_visited_at",
+      scope: -> do
+        if @guardian.user
+          @scope.joins(
+            "JOIN topic_users tu ON tu.topic_id = topics.id AND tu.user_id = #{@guardian.user.id.to_i}",
+          ).where("tu.last_visited_at IS NOT NULL")
+        else
+          # make sure this works for anon
+          @scope.joins("LEFT JOIN topic_users tu ON 1 = 0")
+        end
+      end,
+    },
   }
   private_constant :ORDER_BY_MAPPINGS
 

spec/lib/search_spec.rb

@@ -3135,4 +3135,35 @@ RSpec.describe Search do
       expect(results.posts).to contain_exactly(regular_post)
     end
   end
+
+  it "orders posts by the timestamp of the user's last visit to each topic" do
+    user = Fabricate(:user)
+
+    post2 = nil
+    freeze_time 2.hours.ago do
+      post2 = Fabricate(:post, raw: "Read order term")
+      TopicUser.update_last_read(user, post2.topic.id, post2.post_number, 1, 0)
+    end
+
+    post1 = nil
+    freeze_time 1.hour.ago do
+      post1 = Fabricate(:post, raw: "Read order term")
+      TopicUser.update_last_read(user, post1.topic.id, post1.post_number, 1, 0)
+    end
+
+    _unread_post = Fabricate(:post, raw: "Read order term")
+
+    result = Search.execute("Read order term order:read", guardian: Guardian.new(user))
+    expect(result.posts.map(&:id)).to eq([post1.id, post2.id])
+
+    result = Search.execute("Read order term r", guardian: Guardian.new(user))
+
+    # also allow for the r shortcul like we have l
+    expect(result.posts.map(&:id)).to eq([post1.id, post2.id])
+
+    result = Search.execute("Read order term r", guardian: Guardian.new)
+
+    # no op on anon - all included
+    expect(result.posts.map(&:id).length).to eq(3)
+  end
 end

spec/lib/topics_filter_spec.rb

@@ -1530,6 +1530,59 @@ RSpec.describe TopicsFilter do
         include_examples "ordering topics filters", "title", "topic's title"
       end
 
+      describe "when ordering by user's last visit to topics" do
+        fab!(:user)
+        fab!(:topic)
+        fab!(:topic2) { Fabricate(:topic) }
+        fab!(:topic3) { Fabricate(:topic) }
+
+        before do
+          freeze_time 3.hours.ago do
+            TopicUser.update_last_read(user, topic3.id, 1, 1, 0)
+          end
+
+          freeze_time 2.hours.ago do
+            TopicUser.update_last_read(user, topic.id, 1, 1, 0)
+          end
+
+          freeze_time 1.hour.ago do
+            TopicUser.update_last_read(user, topic2.id, 1, 1, 0)
+          end
+        end
+
+        describe "when query string is `order:read`" do
+          it "should return topics ordered by last visited date in descending order for logged in users" do
+            expect(
+              TopicsFilter
+                .new(guardian: Guardian.new(user))
+                .filter_from_query_string("order:read")
+                .pluck(:id),
+            ).to eq([topic2.id, topic.id, topic3.id])
+          end
+
+          it "should not apply any special ordering for anonymous users" do
+            topics =
+              TopicsFilter
+                .new(guardian: Guardian.new)
+                .filter_from_query_string("order:read")
+                .where(id: [topic.id, topic2.id, topic3.id])
+
+            expect(topics.pluck(:id)).to contain_exactly(topic.id, topic2.id, topic3.id)
+          end
+        end
+
+        describe "when query string is `order:read-asc`" do
+          it "should return topics ordered by last visited date in ascending order for logged in users" do
+            expect(
+              TopicsFilter
+                .new(guardian: Guardian.new(user))
+                .filter_from_query_string("order:read-asc")
+                .pluck(:id),
+            ).to eq([topic3.id, topic.id, topic2.id])
+          end
+        end
+      end
+
       describe "composing multiple order filters" do
         fab!(:topic) { Fabricate(:topic, created_at: Time.zone.local(2023, 1, 1), views: 2) }
         fab!(:topic2) { Fabricate(:topic, created_at: Time.zone.local(2024, 1, 1), views: 2) }