resurrect broker event (#26)

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

broker/broker.go

@@ -14,7 +14,15 @@ type Broker interface {
 }
 
 // Handler is used to process messages via a subscription of a topic.
-type Handler func(*Message) error
+type Handler func(Event) error
+
+// Event is given to a subscription handler for processing
+type Event interface {
+	Topic() string
+	Message() *Message
+	Ack() error
+	Error() error
+}
 
 // Message is used to transfer data
 type Message struct {

broker/options.go

@@ -9,8 +9,6 @@ import (
 )
 
 type Options struct {
-	AutoAck bool
-
 	Addrs  []string
 	Secure bool
 	Codec  codec.Marshaler
@@ -26,6 +24,12 @@ type Options struct {
 	Context context.Context
 }
 
+func NewOptions() Options {
+	return Options{
+		Context: context.Background(),
+	}
+}
+
 type PublishOptions struct {
 	// Other options for implementations of the interface
 	// can be stored in a context
@@ -63,7 +67,10 @@ func PublishContext(ctx context.Context) PublishOption {
 type SubscribeOption func(*SubscribeOptions)
 
 func NewSubscribeOptions(opts ...SubscribeOption) SubscribeOptions {
-	opt := SubscribeOptions{}
+	opt := SubscribeOptions{
+		AutoAck: true,
+		Context: context.Background(),
+	}
 
 	for _, o := range opts {
 		o(&opt)
@@ -87,6 +94,14 @@ func Codec(c codec.Marshaler) Option {
 	}
 }
 
+// SubscribeAutoAck will disable auto acking of messages
+// after they have been handled.
+func SubscribeAutoAck(b bool) SubscribeOption {
+	return func(o *SubscribeOptions) {
+		o.AutoAck = b
+	}
+}
+
 // ErrorHandler will catch all broker errors that cant be handled
 // in normal way, for example Codec errors
 func ErrorHandler(h Handler) Option {