Require last_message_id when connecting to an agent (#13)

This pull request adds a new requirement for the `last_message_id`
parameter when connecting to an agent. It must always be explicitly set,
even if it is set to `nil`. This ensures that client code is proactively
setting the value, preventing situations where an old value is used and
later messages are not displayed.

lib/gpt_agent.ex

@@ -28,11 +28,11 @@ defmodule GptAgent do
   typedstruct do
     field :assistant_id, Types.assistant_id(), enforce: true
     field :thread_id, Types.thread_id(), enforce: true
+    field :last_message_id, Types.message_id() | nil, enforce: true
     field :running?, boolean(), default: false
     field :run_id, Types.run_id() | nil
     field :tool_calls, [ToolCallRequested.t()], default: []
     field :tool_outputs, [ToolCallOutputRecorded.t()], default: []
-    field :last_message_id, Types.message_id() | nil
     field :timeout_ms, non_neg_integer(), default: @timeout_ms
   end
 
@@ -201,6 +201,12 @@ defmodule GptAgent do
     {:noreply, %{state | assistant_id: assistant_id}}
   end
 
+  @impl true
+  def handle_cast({:set_last_message_id, last_message_id}, %__MODULE__{} = state) do
+    log("Setting last message ID to #{last_message_id}")
+    {:noreply, %{state | last_message_id: last_message_id}}
+  end
+
   @impl true
   def handle_call(:shutdown, _caller, %__MODULE__{} = state) do
     log("Shutting down")
@@ -400,6 +406,8 @@ defmodule GptAgent do
     defp log(message, level \\ :debug) when is_binary(message),
       do: Logger.log(level, "[GptAgent (#{inspect(self())})] " <> message)
 
+    defp ok(data), do: {:ok, data}
+
     @impl true
     def create_thread do
       log("Creating thread")
@@ -419,7 +427,7 @@ defmodule GptAgent do
 
     @impl true
     def connect(opts) when is_list(opts) do
-      opts = validate_and_convert_opts(opts)
+      {:ok, opts} = validate_and_convert_opts(opts)
 
       opts
       |> connect_to_new_or_existing_agent()
@@ -431,24 +439,61 @@ defmodule GptAgent do
 
       case Registry.lookup(GptAgent.Registry, opts.thread_id) do
         [{pid, :gpt_agent}] ->
-          handle_existing_agent(pid)
+          handle_existing_agent(pid, opts.last_message_id)
 
         [] ->
-          handle_no_existing_agent(opts.thread_id, opts.assistant_id, opts.timeout_ms)
+          handle_no_existing_agent(
+            opts.thread_id,
+            opts.last_message_id,
+            opts.assistant_id,
+            opts.timeout_ms
+          )
       end
     end
 
     defp validate_and_convert_opts(opts) do
       Keyword.validate!(opts, [
         :thread_id,
+        :last_message_id,
+        :assistant_id,
         subscribe: true,
-        assistant_id: nil,
-        last_message_id: nil,
         timeout_ms: nil
       ])
       |> Enum.into(%{})
+      |> ok()
+      |> validate_thread_id()
+      |> validate_last_message_id()
+      |> validate_assistant_id()
     end
 
+    defp validate_thread_id({:ok, %{thread_id: _thread_id} = opts}) do
+      ok(opts)
+    end
+
+    defp validate_thread_id({:ok, _opts}) do
+      {:error, :missing_thread_id}
+    end
+
+    defp validate_last_message_id({:ok, %{last_message_id: _last_message_id} = opts}) do
+      ok(opts)
+    end
+
+    defp validate_last_message_id({:ok, _opts}) do
+      {:error, :missing_last_message_id}
+    end
+
+    defp validate_last_message_id({:error, _} = error), do: error
+
+    defp validate_assistant_id({:ok, %{assistant_id: _assistant_id} = opts}) do
+      ok(opts)
+    end
+
+    defp validate_assistant_id({:ok, _opts}) do
+      {:error, :missing_assistant_id}
+    end
+
+    defp validate_assistant_id({:error, _} = error), do: error
+
     defp maybe_subscribe({:ok, _pid} = result, opts) do
       if opts.subscribe do
         Phoenix.PubSub.subscribe(GptAgent.PubSub, "gpt_agent:#{opts.thread_id}")
@@ -459,17 +504,20 @@ defmodule GptAgent do
 
     defp maybe_subscribe(result, _opts), do: result
 
-    defp handle_existing_agent(pid) do
+    defp handle_existing_agent(pid, last_message_id) do
       log("Found existing GPT Agent with PID #{inspect(pid)}")
+      log("Updating last message ID to #{inspect(last_message_id)}")
+      GenServer.cast(pid, {:set_last_message_id, last_message_id})
       {:ok, pid}
     end
 
-    defp handle_no_existing_agent(thread_id, assistant_id, timeout_ms) do
+    defp handle_no_existing_agent(thread_id, last_message_id, assistant_id, timeout_ms) do
       log("No existing GPT Agent found, starting new one")
 
       state =
         GptAgent.new!(
           thread_id: thread_id,
+          last_message_id: last_message_id,
           assistant_id: assistant_id,
           timeout_ms: timeout_ms || default_timeout_ms()
         )

mix.exs

@@ -4,7 +4,7 @@ defmodule GptAgent.MixProject do
   def project do
     [
       app: :gpt_agent,
-      version: "5.1.1",
+      version: "6.0.0",
       elixir: "~> 1.16",
       start_permanent: Mix.env() == :prod,
       aliases: aliases(),