Add event stream module

events/event_stream.go

@@ -0,0 +1,64 @@
+package events
+
+import (
+	"context"
+	"runtime"
+
+	"github.com/9seconds/mtg/v2/mtglib"
+	"github.com/OneOfOne/xxhash"
+)
+
+type eventStream struct {
+	ctx       context.Context
+	ctxCancel context.CancelFunc
+	chans     []chan mtglib.Event
+}
+
+func (e eventStream) Send(ctx context.Context, evt mtglib.Event) {
+	chanNo := int(xxhash.ChecksumString32(evt.ConnectionID())) % len(e.chans)
+
+	select {
+	case <-ctx.Done():
+	case <-e.ctx.Done():
+	case e.chans[chanNo] <- evt:
+	}
+}
+
+func (e eventStream) Shutdown() {
+	e.ctxCancel()
+}
+
+func NewEventStream(observerFactories []ObserverFactory) mtglib.EventStream {
+	ctx, cancel := context.WithCancel(context.Background())
+	rv := eventStream{
+		ctx:       ctx,
+		ctxCancel: cancel,
+		chans:     make([]chan mtglib.Event, runtime.NumCPU()),
+	}
+
+	for i := 0; i < runtime.NumCPU(); i++ {
+		rv.chans[i] = make(chan mtglib.Event, 1)
+
+		go eventStreamProcessor(ctx, rv.chans[i], newMultiObserver(observerFactories))
+	}
+
+	return rv
+}
+
+func eventStreamProcessor(ctx context.Context, eventChan <-chan mtglib.Event, observer Observer) {
+	defer observer.Shutdown()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case evt := <-eventChan:
+			switch typedEvt := evt.(type) {
+			case mtglib.EventStart:
+				observer.EventStart(typedEvt)
+			case mtglib.EventFinish:
+				observer.EventFinish(typedEvt)
+			}
+		}
+	}
+}