ExNtfy.Handler behaviour (ex_ntfy v0.1.0)

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Behaviour for the handler consumption style of ExNtfy.subscribe/2.

Pass handler: {MyHandler, init_arg} and the subscription invokes your callbacks in its own process instead of sending messages to an owner:

defmodule MyHandler do
  @behaviour ExNtfy.Handler

  @impl true
  def init(arg), do: {:ok, arg}

  @impl true
  def handle_message(%ExNtfy.Message{} = message, state) do
    IO.puts("#{message.topic}: #{message.message}")
    {:ok, state}
  end

  @impl true
  def handle_lifecycle(:connected, state), do: {:ok, state}
  def handle_lifecycle(_event, state), do: {:ok, state}
end

handle_lifecycle/2 is optional; lifecycle events are dropped without it. Callbacks run inside the subscription process — an exception terminates the subscription (put it under your own supervisor to restart it).

Summary

Types

lifecycle_event()

Lifecycle notifications: connection state changes, terminal {:down, reason}, and message_clear/message_delete events with their parsed message.

Callbacks

handle_lifecycle(lifecycle_event, state)

Optional: invoked for lifecycle events (see lifecycle_event/0).

handle_message(t, state)

Invoked for every :message event.

init(arg)

Invoked once at subscription start; returns the initial handler state.

Types

lifecycle_event()

@type lifecycle_event() ::
  :connected
  | :disconnected
  | {:down, term()}
  | {:message_clear | :message_delete, ExNtfy.Message.t()}

Lifecycle notifications: connection state changes, terminal {:down, reason}, and message_clear/message_delete events with their parsed message.

Callbacks

handle_lifecycle(lifecycle_event, state)

(optional) 
@callback handle_lifecycle(lifecycle_event(), state :: term()) :: {:ok, state :: term()}

Optional: invoked for lifecycle events (see lifecycle_event/0).

handle_message(t, state)

@callback handle_message(ExNtfy.Message.t(), state :: term()) :: {:ok, state :: term()}

Invoked for every :message event.

init(arg)

@callback init(arg :: term()) :: {:ok, state :: term()}

Invoked once at subscription start; returns the initial handler state.