event.go

@@ -73,6 +73,14 @@ type Event struct {
 	Timestamp time.Time              `json:"timestamp"`
 }
 
+// Common event types for Aether infrastructure
+const (
+	// EventTypeEventStored is an internal event published when an event is successfully persisted.
+	// This event allows observability components (metrics, projections, audit systems) to react
+	// to persisted events without coupling to application code.
+	EventTypeEventStored = "EventStored"
+)
+
 // Common metadata keys for distributed tracing and auditing
 const (
 	// MetadataKeyCorrelationID identifies related events across services

store/jetstream.go

@@ -9,6 +9,7 @@ import (
 
 	"git.flowmade.one/flowmade-one/aether"
 	"github.com/nats-io/nats.go"
+	"github.com/google/uuid"
 )
 
 // Default configuration values for JetStream event store
@@ -64,6 +65,8 @@ type JetStreamEventStore struct {
 	config     JetStreamConfig
 	mu         sync.Mutex       // Protects version checks during SaveEvent
 	versions   map[string]int64 // actorID -> latest version cache
+	broadcaster aether.EventBroadcaster // Optional broadcaster for EventStored events
+	namespace   string              // Optional namespace for event publishing
 }
 
 
@@ -130,6 +133,8 @@ func NewJetStreamEventStoreWithConfig(natsConn *nats.Conn, streamName string, co
 		streamName: effectiveStreamName,
 		config:     config,
 		versions:   make(map[string]int64),
+		broadcaster: nil,
+		namespace:   "",
 	}, nil
 }
 
@@ -143,6 +148,58 @@ func (jes *JetStreamEventStore) GetStreamName() string {
 	return jes.streamName
 }
 
+// NewJetStreamEventStoreWithBroadcaster creates a new JetStream-based event store with broadcaster support.
+// The broadcaster receives EventStored events when events are successfully saved.
+func NewJetStreamEventStoreWithBroadcaster(natsConn *nats.Conn, streamName string, broadcaster aether.EventBroadcaster, namespace string) (*JetStreamEventStore, error) {
+	config := DefaultJetStreamConfig()
+	if namespace != "" {
+		config.Namespace = namespace
+	}
+
+	js, err := natsConn.JetStream()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get JetStream context: %w", err)
+	}
+
+	// Apply defaults for zero values
+	if config.StreamRetention == 0 {
+		config.StreamRetention = DefaultStreamRetention
+	}
+	if config.ReplicaCount == 0 {
+		config.ReplicaCount = DefaultReplicaCount
+	}
+
+	// Apply namespace prefix to stream name if provided
+	effectiveStreamName := streamName
+	if config.Namespace != "" {
+		effectiveStreamName = fmt.Sprintf("%s_%s", sanitizeSubject(config.Namespace), streamName)
+	}
+
+	// Create or update the stream
+	stream := &nats.StreamConfig{
+		Name:      effectiveStreamName,
+		Subjects:  []string{fmt.Sprintf("%s.events.>", effectiveStreamName), fmt.Sprintf("%s.snapshots.>", effectiveStreamName)},
+		Storage:   nats.FileStorage,
+		Retention: nats.LimitsPolicy,
+		MaxAge:    config.StreamRetention,
+		Replicas:  config.ReplicaCount,
+	}
+
+	_, err = js.AddStream(stream)
+	if err != nil && !strings.Contains(err.Error(), "already exists") {
+		return nil, fmt.Errorf("failed to create stream: %w", err)
+	}
+
+	return &JetStreamEventStore{
+		js:          js,
+		streamName:  effectiveStreamName,
+		config:      config,
+		versions:    make(map[string]int64),
+		broadcaster: broadcaster,
+		namespace:   namespace,
+	}, nil
+}
+
 // SaveEvent persists an event to JetStream.
 // Returns VersionConflictError if the event's version is not strictly greater
 // than the current latest version for the actor.
@@ -203,9 +260,34 @@ func (jes *JetStreamEventStore) SaveEvent(event *aether.Event) error {
 	// Update version cache after successful publish
 	jes.versions[event.ActorID] = event.Version
 
+	// Publish EventStored event after successful save (if broadcaster is configured)
+	if jes.broadcaster != nil {
+		jes.publishEventStored(event)
+	}
+
 	return nil
 }
 
+// publishEventStored publishes an EventStored event to the broadcaster.
+// This is called after a successful SaveEvent to notify subscribers.
+func (jes *JetStreamEventStore) publishEventStored(originalEvent *aether.Event) {
+	eventStored := &aether.Event{
+		ID:        uuid.New().String(),
+		EventType: aether.EventTypeEventStored,
+		ActorID:   originalEvent.ActorID, // EventStored is about the original actor
+		Version:   originalEvent.Version, // Preserve the version of the stored event
+		Data: map[string]interface{}{
+			"eventId":   originalEvent.ID,
+			"actorId":   originalEvent.ActorID,
+			"version":   originalEvent.Version,
+			"timestamp": originalEvent.Timestamp.Unix(),
+		},
+		Timestamp: time.Now(),
+	}
+
+	jes.broadcaster.Publish(jes.namespace, eventStored)
+}
+
 // GetEvents retrieves all events for an actor since a version.
 // Note: This method silently skips malformed events for backward compatibility.
 // Use GetEventsWithErrors to receive information about malformed events.

store/memory.go

@@ -2,8 +2,10 @@ package store
 
 import (
 	"sync"
+	"time"
 
 	"git.flowmade.one/flowmade-one/aether"
+	"github.com/google/uuid"
 )
 
 // InMemoryEventStore provides a simple in-memory event store for testing
@@ -11,6 +13,8 @@ type InMemoryEventStore struct {
 	mu           sync.RWMutex
 	events       map[string][]*aether.Event         // actorID -> events
 	snapshots    map[string][]*aether.ActorSnapshot // actorID -> snapshots (sorted by version)
+	broadcaster  aether.EventBroadcaster            // optional broadcaster for EventStored events
+	namespace    string                             // optional namespace for event publishing
 }
 
 // NewInMemoryEventStore creates a new in-memory event store
@@ -21,9 +25,21 @@ func NewInMemoryEventStore() *InMemoryEventStore {
 	}
 }
 
+// NewInMemoryEventStoreWithBroadcaster creates a new in-memory event store with an event broadcaster
+// The broadcaster receives EventStored events when events are successfully saved.
+func NewInMemoryEventStoreWithBroadcaster(broadcaster aether.EventBroadcaster, namespace string) *InMemoryEventStore {
+	return &InMemoryEventStore{
+		events:      make(map[string][]*aether.Event),
+		snapshots:   make(map[string][]*aether.ActorSnapshot),
+		broadcaster: broadcaster,
+		namespace:   namespace,
+	}
+}
+
 // SaveEvent saves an event to the in-memory store.
 // Returns VersionConflictError if the event's version is not strictly greater
 // than the current latest version for the actor.
+// If a broadcaster is configured, publishes an EventStored event on success.
 func (es *InMemoryEventStore) SaveEvent(event *aether.Event) error {
 	es.mu.Lock()
 	defer es.mu.Unlock()
@@ -51,9 +67,35 @@ func (es *InMemoryEventStore) SaveEvent(event *aether.Event) error {
 		es.events[event.ActorID] = make([]*aether.Event, 0)
 	}
 	es.events[event.ActorID] = append(es.events[event.ActorID], event)
+
+	// Publish EventStored event after successful save (if broadcaster is configured)
+	if es.broadcaster != nil {
+		es.publishEventStored(event)
+	}
+
 	return nil
 }
 
+// publishEventStored publishes an EventStored event to the broadcaster.
+// This is called after a successful SaveEvent to notify subscribers.
+func (es *InMemoryEventStore) publishEventStored(originalEvent *aether.Event) {
+	eventStored := &aether.Event{
+		ID:        uuid.New().String(),
+		EventType: aether.EventTypeEventStored,
+		ActorID:   originalEvent.ActorID, // EventStored is about the original actor
+		Version:   originalEvent.Version, // Preserve the version of the stored event
+		Data: map[string]interface{}{
+			"eventId":   originalEvent.ID,
+			"actorId":   originalEvent.ActorID,
+			"version":   originalEvent.Version,
+			"timestamp": originalEvent.Timestamp.Unix(),
+		},
+		Timestamp: time.Now(),
+	}
+
+	es.broadcaster.Publish(es.namespace, eventStored)
+}
+
 // GetEvents retrieves events for an actor from a specific version
 func (es *InMemoryEventStore) GetEvents(actorID string, fromVersion int64) ([]*aether.Event, error) {
 	es.mu.RLock()

store/memory_test.go

@@ -1905,3 +1905,181 @@ func TestSaveEvent_MetadataPreservedAcrossMultipleEvents(t *testing.T) {
 		}
 	}
 }
+
+// === EventStored Publishing Tests ===
+
+func TestSaveEvent_WithBroadcaster_PublishesEventStored(t *testing.T) {
+	// Create a mock broadcaster to capture published events
+	broadcaster := aether.NewEventBus()
+	store := NewInMemoryEventStoreWithBroadcaster(broadcaster, "test-namespace")
+
+	// Subscribe to EventStored events
+	ch := broadcaster.Subscribe("test-namespace")
+	defer broadcaster.Unsubscribe("test-namespace", ch)
+
+	event := &aether.Event{
+		ID:        "evt-123",
+		EventType: "OrderPlaced",
+		ActorID:   "order-456",
+		Version:   1,
+		Data: map[string]interface{}{
+			"total": 100.50,
+		},
+		Timestamp: time.Now(),
+	}
+
+	// Save event
+	err := store.SaveEvent(event)
+	if err != nil {
+		t.Fatalf("SaveEvent failed: %v", err)
+	}
+
+	// Check if EventStored was published
+	select {
+	case publishedEvent := <-ch:
+		if publishedEvent == nil {
+			t.Fatal("received nil event from broadcaster")
+		}
+		if publishedEvent.EventType != aether.EventTypeEventStored {
+			t.Errorf("expected EventType %q, got %q", aether.EventTypeEventStored, publishedEvent.EventType)
+		}
+		if publishedEvent.ActorID != "order-456" {
+			t.Errorf("expected ActorID %q, got %q", "order-456", publishedEvent.ActorID)
+		}
+		if publishedEvent.Version != 1 {
+			t.Errorf("expected Version 1, got %d", publishedEvent.Version)
+		}
+		// Check data contains original event info
+		if publishedEvent.Data["eventId"] != "evt-123" {
+			t.Errorf("expected eventId %q, got %q", "evt-123", publishedEvent.Data["eventId"])
+		}
+	case <-time.After(100 * time.Millisecond):
+		t.Fatal("timeout waiting for EventStored event")
+	}
+}
+
+func TestSaveEvent_VersionConflict_NoEventStored(t *testing.T) {
+	broadcaster := aether.NewEventBus()
+	store := NewInMemoryEventStoreWithBroadcaster(broadcaster, "test-namespace")
+
+	// Subscribe to EventStored events
+	ch := broadcaster.Subscribe("test-namespace")
+	defer broadcaster.Unsubscribe("test-namespace", ch)
+
+	// Save first event
+	event1 := &aether.Event{
+		ID:        "evt-1",
+		EventType: "OrderPlaced",
+		ActorID:   "order-456",
+		Version:   1,
+		Data:      map[string]interface{}{},
+		Timestamp: time.Now(),
+	}
+
+	err := store.SaveEvent(event1)
+	if err != nil {
+		t.Fatalf("SaveEvent(event1) failed: %v", err)
+	}
+
+	// Drain the first EventStored event
+	select {
+	case <-ch:
+	case <-time.After(100 * time.Millisecond):
+		t.Fatal("timeout waiting for first EventStored event")
+	}
+
+	// Try to save event with non-increasing version (should fail)
+	event2 := &aether.Event{
+		ID:        "evt-2",
+		EventType: "OrderPlaced",
+		ActorID:   "order-456",
+		Version:   1, // Same version, should conflict
+		Data:      map[string]interface{}{},
+		Timestamp: time.Now(),
+	}
+
+	err = store.SaveEvent(event2)
+	if !errors.Is(err, aether.ErrVersionConflict) {
+		t.Fatalf("expected ErrVersionConflict, got %v", err)
+	}
+
+	// Verify no EventStored event was published
+	select {
+	case <-ch:
+		t.Fatal("expected no EventStored event, but received one")
+	case <-time.After(50 * time.Millisecond):
+		// Expected - no event published
+	}
+}
+
+func TestSaveEvent_MultipleEvents_PublishesMultipleEventStored(t *testing.T) {
+	broadcaster := aether.NewEventBus()
+	store := NewInMemoryEventStoreWithBroadcaster(broadcaster, "test-namespace")
+
+	// Subscribe to EventStored events
+	ch := broadcaster.Subscribe("test-namespace")
+	defer broadcaster.Unsubscribe("test-namespace", ch)
+
+	// Save multiple events
+	for i := int64(1); i <= 3; i++ {
+		event := &aether.Event{
+			ID:        fmt.Sprintf("evt-%d", i),
+			EventType: "OrderPlaced",
+			ActorID:   "order-456",
+			Version:   i,
+			Data:      map[string]interface{}{},
+			Timestamp: time.Now(),
+		}
+
+		err := store.SaveEvent(event)
+		if err != nil {
+			t.Fatalf("SaveEvent failed: %v", err)
+		}
+	}
+
+	// Verify we received 3 EventStored events in order
+	for i := int64(1); i <= 3; i++ {
+		select {
+		case publishedEvent := <-ch:
+			if publishedEvent == nil {
+				t.Fatal("received nil event from broadcaster")
+			}
+			if publishedEvent.Version != i {
+				t.Errorf("expected Version %d, got %d", i, publishedEvent.Version)
+			}
+		case <-time.After(100 * time.Millisecond):
+			t.Fatalf("timeout waiting for EventStored event %d", i)
+		}
+	}
+}
+
+func TestSaveEvent_WithoutBroadcaster_NoPanic(t *testing.T) {
+	// Test that SaveEvent works without a broadcaster (nil broadcaster)
+	store := NewInMemoryEventStore()
+
+	event := &aether.Event{
+		ID:        "evt-123",
+		EventType: "OrderPlaced",
+		ActorID:   "order-456",
+		Version:   1,
+		Data: map[string]interface{}{
+			"total": 100.50,
+		},
+		Timestamp: time.Now(),
+	}
+
+	// This should not panic even though broadcaster is nil
+	err := store.SaveEvent(event)
+	if err != nil {
+		t.Fatalf("SaveEvent failed: %v", err)
+	}
+
+	// Verify event was saved
+	events, err := store.GetEvents("order-456", 0)
+	if err != nil {
+		t.Fatalf("GetEvents failed: %v", err)
+	}
+	if len(events) != 1 {
+		t.Fatalf("expected 1 event, got %d", len(events))
+	}
+}