[WIP]: broker ErrorHandler option (#1296)

* broker ErrorHandler option

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* rewrite Event interface, add error

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* implement new interface

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* change ErrorHandler func to broker.Handler

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

* fix

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

broker/default.go

@@ -53,8 +53,9 @@ type subscriber struct {
 }
 
 type publication struct {
-	t string
-	m *Message
+	t   string
+	err error
+	m   *Message
 }
 
 func (p *publication) Topic() string {
@@ -70,6 +71,10 @@ func (p *publication) Ack() error {
 	return nil
 }
 
+func (p *publication) Error() error {
+	return p.err
+}
+
 func (s *subscriber) Options() SubscribeOptions {
 	return s.opts
 }
@@ -390,10 +395,26 @@ func (n *natsBroker) Subscribe(topic string, handler Handler, opts ...SubscribeO
 
 	fn := func(msg *nats.Msg) {
 		var m Message
-		if err := n.opts.Codec.Unmarshal(msg.Data, &m); err != nil {
+		pub := &publication{t: msg.Subject}
+		eh := n.opts.ErrorHandler
+		err := n.opts.Codec.Unmarshal(msg.Data, &m)
+		pub.err = err
+		pub.m = &m
+		if err != nil {
+			m.Body = msg.Data
+			log.Error(err)
+			if eh != nil {
+				eh(pub)
+			}
 			return
 		}
-		handler(&publication{m: &m, t: msg.Subject})
+		if err := handler(pub); err != nil {
+			pub.err = err
+			log.Error(err)
+			if eh != nil {
+				eh(pub)
+			}
+		}
 	}
 
 	var sub *nats.Subscription