feat: make projector extendable

main.go

@@ -60,7 +60,12 @@ func run(ctx context.Context) error {
 			return err
 		}
 
-		es, err := es.Open(ctx, env("EV_DATA", "mem:"), streamer.New(ctx), projecter.New(ctx))
+		es, err := es.Open(
+			ctx, 
+			env("EV_DATA", "mem:"), 
+			streamer.New(ctx), 
+			projecter.New(ctx, projecter.DefaultProjection),
+		)
 		if err != nil {
 			span.RecordError(err)
 			return err

pkg/es/driver/disk-store/disk-store.go

@@ -111,10 +111,12 @@ func (d *diskStore) Open(ctx context.Context, dsn string) (driver.Driver, error)
 	}
 	logs := &openlogs{logs: c}
 	return &diskStore{
-		path:        path,
-		openlogs:    locker.New(logs),
+		path:         path,
+		openlogs:     locker.New(logs),
 		m_disk_open:  d.m_disk_open,
 		m_disk_evict: d.m_disk_evict,
+		m_disk_read:  d.m_disk_read,
+		m_disk_write: d.m_disk_write,
 	}, nil
 }
 func (d *diskStore) EventLog(ctx context.Context, streamID string) (driver.EventLog, error) {
@@ -147,9 +149,9 @@ func (d *diskStore) EventLog(ctx context.Context, streamID string) (driver.Event
 }
 
 type eventLog struct {
-	streamID string
-	events   *locker.Locked[wal.Log]
-	diskStore *diskStore   
+	streamID  string
+	events    *locker.Locked[wal.Log]
+	diskStore *diskStore
 }
 
 var _ driver.EventLog = (*eventLog)(nil)

pkg/es/driver/projecter/projecter.go

@@ -11,11 +11,12 @@ import (
 )
 
 type projector struct {
-	up driver.Driver
+	up  driver.Driver
+	fns []func(event.Event) []event.Event
 }
 
-func New(ctx context.Context) *projector {
-	return &projector{}
+func New(ctx context.Context, fns ...func(event.Event) []event.Event) *projector {
+	return &projector{fns: fns}
 }
 func (p *projector) Apply(e *es.EventStore) {
 	p.up = e.Driver
@@ -70,27 +71,13 @@ func (w *wrapper) Append(ctx context.Context, events event.Events, version uint6
 
 			for i := range events {
 				e := events[i]
-				eventType := event.TypeOf(e)
-				m := e.EventMeta()
-				streamID := m.StreamID
-				streamPos := m.Position
 
-				e1 := event.NewPtr(streamID, streamPos)
-				event.SetStreamID("$all", e1)
-
-				e2 := event.NewPtr(streamID, streamPos)
-				event.SetStreamID("$type-"+eventType, e2)
-
-				e3 := event.NewPtr(streamID, streamPos)
-				pkg, _, _ := strings.Cut(eventType, ".")
-				event.SetStreamID("$pkg-"+pkg, e3)
-
-				pevents = append(
-					pevents,
-					e1,
-					e2,
-					e3,
-				)
+				for _, fn := range w.projector.fns {
+					pevents = append(
+						pevents,
+						fn(e)...,
+					)
+				}
 			}
 
 			for i := range pevents {
@@ -126,3 +113,22 @@ func (w *wrapper) LoadForUpdate(ctx context.Context, a event.Aggregate, fn func(
 
 	return w.up.LoadForUpdate(ctx, a, fn)
 }
+
+func DefaultProjection(e event.Event) []event.Event {
+	eventType := event.TypeOf(e)
+	m := e.EventMeta()
+	streamID := m.StreamID
+	streamPos := m.Position
+
+	e1 := event.NewPtr(streamID, streamPos)
+	event.SetStreamID("$all", e1)
+
+	e2 := event.NewPtr(streamID, streamPos)
+	event.SetStreamID("$type-"+eventType, e2)
+
+	e3 := event.NewPtr(streamID, streamPos)
+	pkg, _, _ := strings.Cut(eventType, ".")
+	event.SetStreamID("$pkg-"+pkg, e3)
+
+	return []event.Event{e1, e2, e3}
+}