Refactor DefaultPrompt into Chats.Prompt with build/2

lib/music_library/chats/artist_chat.ex

@@ -6,7 +6,7 @@ defmodule MusicLibrary.Chats.ArtistChat do
   @behaviour MusicLibrary.Chats.StreamProvider
 
   alias MusicLibrary.Artists.ArtistInfo
-  alias MusicLibrary.Chats.DefaultPrompt
+  alias MusicLibrary.Chats.Prompt
 
   @impl true
   @spec stream_response([map()], {map(), ArtistInfo.t()}, (String.t() -> any())) ::
@@ -20,16 +20,13 @@ defmodule MusicLibrary.Chats.ArtistChat do
   defp build_instructions(artist, artist_info) do
     context = build_context(artist, artist_info)
 
-    """
-    #{DefaultPrompt.identity()}
+    Prompt.build("""
     Answer questions about the artist the user is currently viewing. \
-    Use the provided artist information as your primary reference, \
+    Use the provided artist information as your primary reference.
 
-    #{DefaultPrompt.approach()}
-
-    Album information:
-    #{context}
-    """
+    Artist information:
+    #{context}\
+    """)
   end
 
   defp build_context(artist, artist_info) do

lib/music_library/chats/default_prompt.ex

@@ -1,23 +0,0 @@
-defmodule MusicLibrary.Chats.DefaultPrompt do
-  @moduledoc false
-
-  def identity do
-    """
-    You are a knowledgeable music assistant.
-    """
-  end
-
-  def approach do
-    """
-    Use web search to find additional up-to-date \
-    information when helpful. Be concise and accurate. When unsure, say so. \
-    Include links when they add genuine value, and at least one per response \
-    (but not one per paragraph).
-
-    Vary your response style and structure. Don't repeat information already \
-    discussed in the conversation. Refer back to earlier points naturally \
-    instead of restating them. DO NOT INCLUDE A SUMMARY AT THE END OF YOUR MESSAGE. \
-    DO NOT PROVIDE SUGGESTIONS OR ASK QUESTIONS AS A MEAN TO CONTINUE THE CONVERSATION.
-    """
-  end
-end

lib/music_library/chats/prompt.ex

@@ -0,0 +1,45 @@
+defmodule MusicLibrary.Chats.Prompt do
+  @moduledoc """
+  Builds complete chat prompts by interpolating identity, content, and approach.
+  """
+
+  @doc """
+  Builds a complete prompt from the given `text` and options.
+
+  Options:
+    * `:identity` - the identity preamble (defaults to a music assistant identity)
+    * `:approach` - the approach guidance (defaults to standard response guidelines)
+  """
+  @spec build(String.t(), keyword()) :: String.t()
+  def build(text, opts \\ []) do
+    identity = Keyword.get(opts, :identity, default_identity())
+    approach = Keyword.get(opts, :approach, default_approach())
+
+    """
+    #{identity}
+    #{text}
+
+    #{approach}\
+    """
+  end
+
+  defp default_identity do
+    """
+    You are a knowledgeable music assistant.\
+    """
+  end
+
+  defp default_approach do
+    """
+    Use web search to find additional up-to-date \
+    information when helpful. Be concise and accurate. When unsure, say so. \
+    Include links when they add genuine value, and at least one per response \
+    (but not one per paragraph).
+
+    Vary your response style and structure. Don't repeat information already \
+    discussed in the conversation. Refer back to earlier points naturally \
+    instead of restating them. DO NOT INCLUDE A SUMMARY AT THE END OF YOUR MESSAGE. \
+    DO NOT PROVIDE SUGGESTIONS OR ASK QUESTIONS AS A MEAN TO CONTINUE THE CONVERSATION.\
+    """
+  end
+end

lib/music_library/chats/record_chat.ex

@@ -5,7 +5,7 @@ defmodule MusicLibrary.Chats.RecordChat do
 
   @behaviour MusicLibrary.Chats.StreamProvider
 
-  alias MusicLibrary.Chats.DefaultPrompt
+  alias MusicLibrary.Chats.Prompt
   alias MusicLibrary.Records.Record
 
   @impl true
@@ -25,16 +25,13 @@ defmodule MusicLibrary.Chats.RecordChat do
         text -> text
       end
 
-    """
-    #{DefaultPrompt.identity()}
+    Prompt.build("""
     Answer questions about the album the user is currently viewing. \
-    Use the provided album information as your primary reference, \
-
-    #{DefaultPrompt.approach()}
+    Use the provided album information as your primary reference.
 
     Album information:
-    #{context}
-    """
+    #{context}\
+    """)
   end
 
   defp basic_context(%Record{} = record) do