feat: backend service

backend/push/subscriber.go

@@ -0,0 +1,48 @@
+package push
+
+import (
+	"strings"
+
+	pushv1 "galaxy/backend/proto/push/v1"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+// SubscribePush is the gRPC server handler. It registers the connection
+// in the subscription registry, replays any in-buffer events newer than
+// the requested cursor, and then streams live events until the client
+// cancels, the subscription is replaced by a newer connection from the
+// same gateway client id, or the Service is shut down.
+func (s *Service) SubscribePush(req *pushv1.GatewaySubscribeRequest, stream grpc.ServerStreamingServer[pushv1.PushEvent]) error {
+	if req == nil || strings.TrimSpace(req.GetGatewayClientId()) == "" {
+		return status.Error(codes.InvalidArgument, "gateway_client_id is required")
+	}
+
+	sub, replay, err := s.register(req.GetGatewayClientId(), req.GetCursor())
+	if err != nil {
+		return err
+	}
+	defer s.unregister(sub)
+
+	for _, ev := range replay {
+		if err := stream.Send(ev); err != nil {
+			return err
+		}
+	}
+
+	ctx := stream.Context()
+	for {
+		select {
+		case <-ctx.Done():
+			return nil
+		case <-sub.done:
+			return status.Error(codes.Aborted, "push subscription replaced or service stopped")
+		case ev := <-sub.ch:
+			if err := stream.Send(ev); err != nil {
+				return err
+			}
+		}
+	}
+}