FIX: Use a dedicated prompt for thread titles (#464)

lib/ai_helper/chat_thread_titler.rb

@@ -8,26 +8,38 @@ module DiscourseAi
       end
 
       def suggested_title
-        return nil if thread_content.blank?
-
-        prompt = CompletionPrompt.enabled_by_name("generate_titles")
-        raise Discourse::InvalidParameters.new(:mode) if !prompt
-
-        response =
-          DiscourseAi::AiHelper::Assistant.new.generate_and_send_prompt(
-            prompt,
-            thread_content,
-            thread.original_message_user,
-          )
-        response.dig(:suggestions)&.first
+        @thread.then { thread_content(_1) }.then { call_llm(_1) }.then { cleanup(_1) }
       end
 
-      private
+      def call_llm(thread_content)
+        return nil if thread_content.blank?
 
-      attr_reader :thread
+        chat = "<input>\n#{thread_content}\n</input>"
 
-      def thread_content
-        # Replace me by a proper API call
+        prompt =
+          DiscourseAi::Completions::Prompt.new(
+            <<~TEXT.strip,
+            I want you to act as a title generator for chat between users. I will provide you with the chat transcription,
+            and you will generate a single attention-grabbing title. Please keep the title concise and under 15 words
+            and ensure that the meaning is maintained. The title will utilize the same language type of the chat.
+            I want you to only reply the suggested title and nothing else, do not write explanations.
+            You will find the chat between <input></input> XML tags.
+          TEXT
+            messages: [{ type: :user, content: chat, id: "User" }],
+          )
+
+        DiscourseAi::Completions::Llm.proxy(SiteSetting.ai_helper_model).generate(
+          prompt,
+          user: Discourse.system_user,
+        )
+      end
+
+      def cleanup(title)
+        title.split("\n").first.then { _1.match?(/^("|')(.*)("|')$/) ? title[1..-2] : _1 }
+      end
+
+      def thread_content(thread)
+        # TODO: Replace me by a proper API call
         thread
           .chat_messages
           .joins(:user)
@@ -35,6 +47,8 @@ module DiscourseAi
           .map { |username, message| "#{username}: #{message}" }
           .join("\n")
       end
+
+      attr_reader :thread
     end
   end
 end

spec/lib/modules/ai_helper/chat_thread_titler_spec.rb

@@ -6,17 +6,51 @@ RSpec.describe DiscourseAi::AiHelper::ChatThreadTitler do
   before { SiteSetting.ai_helper_model = "fake:fake" }
 
   fab!(:thread) { Fabricate(:chat_thread) }
+  fab!(:chat_message) { Fabricate(:chat_message, thread: thread) }
   fab!(:user) { Fabricate(:user) }
 
-  describe "#suggested_title" do
-    it "suggest the first option from the generate_titles prompt" do
-      titles =
-        "<item>The solitary horse</item><item>The horse etched in gold</item><item>A horse's infinite journey</item><item>A horse lost in time</item><item>A horse's last ride</item>"
+  describe "#cleanup" do
+    it "picks the first when there are multiple" do
+      titles = "The solitary horse\nThe horse etched in gold"
       expected_title = "The solitary horse"
-      result =
-        DiscourseAi::Completions::Llm.with_prepared_responses([titles]) { titler.suggested_title }
+
+      result = titler.cleanup(titles)
+
+      expect(result).to eq(expected_title)
+    end
+
+    it "cleans up double quotes enclosing the whole title" do
+      titles = '"The solitary horse"'
+      expected_title = "The solitary horse"
+
+      result = titler.cleanup(titles)
+
+      expect(result).to eq(expected_title)
+    end
+
+    it "cleans up single quotes enclosing the whole title" do
+      titles = "'The solitary horse'"
+      expected_title = "The solitary horse"
+
+      result = titler.cleanup(titles)
+
+      expect(result).to eq(expected_title)
+    end
+
+    it "leaves quotes in the middle of title" do
+      titles = "The 'solitary' horse"
+      expected_title = "The 'solitary' horse"
+
+      result = titler.cleanup(titles)
 
       expect(result).to eq(expected_title)
     end
   end
+
+  describe "#thread_content" do
+    it "returns the chat message and user" do
+      expect(titler.thread_content(thread)).to include(chat_message.message)
+      expect(titler.thread_content(thread)).to include(chat_message.user.username)
+    end
+  end
 end