GenServer that manages active conversation flows per chat.

Subscribes to PubSub updates and routes them to the correct flow. Sends prompts and error messages back via the Telegram API.

Supervision Tree

Add the Engine before any bots that use flows:

children = [
  {Hotline.Poller, []},
  {Hotline.Flow.Engine, []},
  {MyBot, []}
]

Starting Flows

# From a Bot's handle_update/2:
def handle_update(%{message: %{text: "/register", chat: %{id: chat_id}}}, state) do
  Hotline.Flow.Engine.start_flow(chat_id, MyBot.Flows.Registration)
  {:noreply, state}
end

Integration with Bots

Use handles_update?/1 to skip updates being handled by an active flow:

def handle_update(update, state) do
  unless Hotline.Flow.Engine.handles_update?(update) do
    # normal handling
  end
  {:noreply, state}
end

Testing

Inject a :sender function to capture messages in tests:

test_pid = self()
sender = fn params, _opts -> send(test_pid, {:sent, params}); {:ok, %{}} end
{:ok, engine} = Engine.start_link(sender: sender, name: :test_engine)