protofsm: add optional daemon event on init

In this commit, we add an optional daemon event that can be specified to
dispatch during init. This is useful for instances where before we
start, we want to make sure we have a registered spend/conf notification
before normal operation starts.

We also add new unit tests to cover this, and the prior spend/conf event
additions.

Author: Roasbeef

protofsm/state_machine.go

@@ -135,17 +135,21 @@ type StateMachine[Event any, Env Environment] struct {
 
 	stateQuery chan stateQuery[Event, Env]
 
+	initEvent fn.Option[DaemonEvent]
+
 	startOnce sync.Once
 	stopOnce  sync.Once
 
 	// TODO(roasbeef): also use that context guard here?
 }
 
 // NewStateMachine creates a new state machine given a set of daemon adapters,
-// an initial state, and an environment.
+// an initial state, an environment, and an event to process as if emitted at
+// the onset of the state machine. Such an event can be used to set up tracking
+// state such as a txid confirmation event.
 func NewStateMachine[Event any, Env Environment](adapters DaemonAdapters,
-	initialState State[Event, Env],
-	env Env) StateMachine[Event, Env] {
+	initialState State[Event, Env], env Env,
+	initEvent fn.Option[DaemonEvent]) StateMachine[Event, Env] {
 
 	return StateMachine[Event, Env]{
 		daemon:         adapters,
@@ -154,6 +158,7 @@ func NewStateMachine[Event any, Env Environment](adapters DaemonAdapters,
 		stateQuery:     make(chan stateQuery[Event, Env]),
 		quit:           make(chan struct{}),
 		env:            env,
+		initEvent:      initEvent,
 		newStateEvents: fn.NewEventDistributor[State[Event, Env]](),
 	}
 }
@@ -443,6 +448,9 @@ func (s *StateMachine[Event, Env]) applyEvents(newEvent Event) (State[Event, Env
 			currentState = transition.NextState
 
 			// Notify our subscribers of the new state transition.
+			//
+			// TODO(roasbeef): will only give us the outer state?
+			//  * let FSMs choose which state to emit?
 			s.newStateEvents.NotifySubscribers(currentState)
 
 			return nil
@@ -464,6 +472,16 @@ func (s *StateMachine[Event, Env]) driveMachine() {
 	// TODO(roasbeef): move into env? read only to start with
 	currentState := s.currentState
 
+	// Before we start, if we have an init daemon event specified, then
+	// we'll handle that now.
+	err := fn.MapOptionZ(s.initEvent, func(event DaemonEvent) error {
+		return s.executeDaemonEvent(event)
+	})
+	if err != nil {
+		log.Errorf("unable to execute init event: %w", err)
+		return
+	}
+
 	// We just started driving the state machine, so we'll notify our
 	// subscribers of this starting state.
 	s.newStateEvents.NotifySubscribers(currentState)

protofsm/state_machine_test.go

@@ -211,6 +211,52 @@ func (d *dummyAdapters) RegisterSpendNtfn(outpoint *wire.OutPoint,
 	}, err
 }
 
+// TestStateMachineOnInitDaemonEvent tests that the state machine will properly
+// execute any init-level daemon events passed into it.
+func TestStateMachineOnInitDaemonEvent(t *testing.T) {
+	// First, we'll create our state machine given the env, and our
+	// starting state.
+	env := &dummyEnv{}
+	startingState := &dummyStateStart{}
+
+	adapters := newDaemonAdapters()
+
+	// We'll make an init event that'll send to a peer, then transition us
+	// to our terminal state.
+	initEvent := &SendMsgEvent[dummyEvents]{
+		TargetPeer:    *pub1,
+		PostSendEvent: fn.Some(dummyEvents(&goToFin{})),
+	}
+
+	stateMachine := NewStateMachine[dummyEvents, *dummyEnv](
+		adapters, startingState, env, fn.Some[DaemonEvent](initEvent),
+	)
+
+	// Before we start up the state machine, we'll assert that the send
+	// message adapter is called on start up.
+	adapters.On("SendMessages", *pub1, mock.Anything).Return(nil)
+
+	stateMachine.Start()
+	defer stateMachine.Stop()
+
+	// As we're triggering internal events, we'll also subscribe to the set
+	// of new states so we can assert as we go.
+	stateSub := stateMachine.RegisterStateEvents()
+	defer stateMachine.RemoveStateSub(stateSub)
+
+	// Assert that we go from the starting state to the final state.  The
+	// state machine should now also be on the final terminal state.
+	expectedStates := []State[dummyEvents, *dummyEnv]{
+		&dummyStateStart{}, &dummyStateFin{},
+	}
+	assertStateTransitions(t, stateSub, expectedStates)
+
+	// We'll now assert that after the daemon was started, the send message
+	// adapter was called above as specified in the init event.
+	adapters.AssertExpectations(t)
+	env.AssertExpectations(t)
+}
+
 // TestStateMachineInternalEvents tests that the state machine is able to add
 // new internal events to the event queue for further processing during a state
 // transition.
@@ -222,10 +268,10 @@ func TestStateMachineInternalEvents(t *testing.T) {
 	env := &dummyEnv{}
 	startingState := &dummyStateStart{}
 
-	adapters := &dummyAdapters{}
+	adapters := newDaemonAdapters()
 
 	stateMachine := NewStateMachine[dummyEvents, *dummyEnv](
-		adapters, startingState, env,
+		adapters, startingState, env, fn.None[DaemonEvent](),
 	)
 	stateMachine.Start()
 	defer stateMachine.Stop()
@@ -269,10 +315,10 @@ func TestStateMachineDaemonEvents(t *testing.T) {
 		canSend: &boolTrigger,
 	}
 
-	adapters := &dummyAdapters{}
+	adapters := newDaemonAdapters()
 
 	stateMachine := NewStateMachine[dummyEvents, *dummyEnv](
-		adapters, startingState, env,
+		adapters, startingState, env, fn.None[DaemonEvent](),
 	)
 	stateMachine.Start()
 	defer stateMachine.Stop()