Example/reference plugin: a persistent message store.

Amarula is a library — it does not keep long-term message history itself. This optional plugin shows the intended pattern for a consumer-side store:

• subscribe to the socket's {:whatsapp, :messages_upsert, ..} events and persist incoming messages,
• remember our own outgoing messages,
• expose get_message/2, which the library calls (via the :get_message config callback) to re-encrypt + resend a message on a type="retry" receipt when its built-in recent-message cache has already evicted it.

It's a GenServer backed by DETS so history survives restarts. A real consumer would likely use its own database; this is the minimal working reference.

Wiring

{:ok, store} = Amarula.Plugins.MessageStore.start_link(dir: "./amarula_store")

config =
  base_config
  |> Map.put(:get_message, Amarula.Plugins.MessageStore.get_message_fun(store))

# Make the store the socket's parent_pid so it sees the events directly,
# or forward `{:whatsapp, :messages_upsert, ..}` to it from your own process.
{:ok, socket} = Amarula.new(config) |> Amarula.connect(parent_pid: store)