FEATURE: Fast-track gist regeneration when a hot topic gets a new post

app/jobs/regular/hot_topics_gist_batch.rb

@@ -2,7 +2,7 @@
 
 module ::Jobs
   class HotTopicsGistBatch < ::Jobs::Base
-    def execute(args)
+    def execute(_args)
       return if !SiteSetting.discourse_ai_enabled
       return if !SiteSetting.ai_summarization_enabled
       return if SiteSetting.ai_summarize_max_hot_topics_gists_per_batch.zero?
@@ -15,11 +15,7 @@ def execute(args)
           summarizer = DiscourseAi::Summarization.topic_gist(topic)
           gist = summarizer.existing_summary
 
-          if gist.blank? || gist.outdated
-            summarizer.delete_cached_summaries!
-
-            summarizer.summarize(Discourse.system_user)
-          end
+          summarizer.force_summarize(Discourse.system_user) if gist.blank? || gist.outdated
         end
     end
   end

app/jobs/regular/update_hot_topic_gist.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module ::Jobs
+  class UpdateHotTopicGist < ::Jobs::Base
+    sidekiq_options retry: false
+
+    def execute(args)
+      return if !SiteSetting.discourse_ai_enabled
+      return if !SiteSetting.ai_summarization_enabled
+      return if SiteSetting.ai_summarize_max_hot_topics_gists_per_batch.zero?
+
+      topic = Topic.find_by(id: args[:topic_id])
+      return if topic.blank?
+
+      return if !TopicHotScore.where(topic: topic).exists?
+
+      summarizer = DiscourseAi::Summarization.topic_gist(topic)
+      gist = summarizer.existing_summary
+      return if gist.blank?
+      return if !gist.outdated
+
+      summarizer.force_summarize(Discourse.system_user)
+    end
+  end
+end

lib/summarization/entry_point.rb

@@ -47,6 +47,19 @@ def inject_into(plugin)
         # To make sure hot topic gists are inmediately up to date, we rely on this event
         # instead of using a scheduled job.
         plugin.on(:topic_hot_scores_updated) { Jobs.enqueue(:hot_topics_gist_batch) }
+
+        # As this event can be triggered quite often, let's be overly cautious enqueueing
+        # jobs if the feature is disabled.
+        plugin.on(:post_created) do |post|
+          if SiteSetting.discourse_ai_enabled && SiteSetting.ai_summarization_enabled &&
+               SiteSetting.ai_summarize_max_hot_topics_gists_per_batch > 0 && post.topic
+            hot_score = TopicHotScore.find_by(topic: post.topic)
+
+            if hot_score.exists? && hot_score.updated_at > 1.day.ago
+              Jobs.enqueue(:update_hot_topic_gist, topic_id: post&.topic_id)
+            end
+          end
+        end
       end
     end
   end

lib/summarization/fold_content.rb

@@ -66,6 +66,11 @@ def delete_cached_summaries!
         AiSummary.where(target: strategy.target, summary_type: strategy.type).destroy_all
       end
 
+      def force_summarize(user, &on_partial_blk)
+        delete_cached_summaries!
+        summarize(user, &on_partial_blk)
+      end
+
       private
 
       attr_reader :persist_summaries

spec/jobs/regular/update_hot_topic_gist_spec.rb

@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+RSpec.describe Jobs::UpdateHotTopicGist do
+  describe "#execute" do
+    fab!(:topic_1) { Fabricate(:topic) }
+    fab!(:post_1) { Fabricate(:post, topic: topic_1, post_number: 1) }
+    fab!(:post_2) { Fabricate(:post, topic: topic_1, post_number: 2) }
+
+    before do
+      assign_fake_provider_to(:ai_summarization_model)
+      SiteSetting.ai_summarization_enabled = true
+      SiteSetting.ai_summarize_max_hot_topics_gists_per_batch = 100
+    end
+
+    context "when the hot topic has a gist" do
+      before { TopicHotScore.create!(topic_id: topic_1.id, score: 0.1) }
+      fab!(:ai_gist) do
+        Fabricate(:topic_ai_gist, target: topic_1, original_content_sha: AiSummary.build_sha("12"))
+      end
+      let(:updated_gist) { "They updated me :(" }
+
+      context "when it's up to date" do
+        it "does nothing" do
+          DiscourseAi::Completions::Llm.with_prepared_responses([updated_gist]) do
+            subject.execute(topic_id: topic_1.id)
+          end
+
+          gist = AiSummary.gist.find_by(target: topic_1)
+          expect(AiSummary.gist.where(target: topic_1).count).to eq(1)
+          expect(gist.summarized_text).not_to eq(updated_gist)
+        end
+      end
+
+      context "when it's outdated" do
+        it "regenerates the gist using the latest data" do
+          Fabricate(:post, topic: topic_1, post_number: 3)
+
+          DiscourseAi::Completions::Llm.with_prepared_responses([updated_gist]) do
+            subject.execute(topic_id: topic_1.id)
+          end
+
+          gist = AiSummary.gist.find_by(target: topic_1)
+          expect(AiSummary.gist.where(target: topic_1).count).to eq(1)
+          expect(gist.summarized_text).to eq(updated_gist)
+          expect(gist.original_content_sha).to eq(AiSummary.build_sha("123"))
+        end
+      end
+    end
+
+    context "when the topic doesn't have a hot topic score" do
+      it "does nothing" do
+        subject.execute({})
+
+        gist = AiSummary.gist.find_by(target: topic_1)
+        expect(gist).to be_nil
+      end
+    end
+
+    context "when the topic has a hot topic score but no gist" do
+      before { TopicHotScore.create!(topic_id: topic_1.id, score: 0.1) }
+
+      it "does nothing" do
+        subject.execute({})
+
+        gist = AiSummary.gist.find_by(target: topic_1)
+        expect(gist).to be_nil
+      end
+    end
+  end
+end