Move consumer features into a subpackage

consumer/consumer.go

@@ -0,0 +1,76 @@
+package consumer
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/localhots/caller"
+	"github.com/localhots/shezmu"
+)
+
+// Subscriber is the interface that is used by daemons to subscribe to messages.
+type Subscriber interface {
+	Subscribe(consumerName, topic string) Streamer
+}
+
+// Streamer is the interface that wraps message consumers. Error handling
+// should be provided by the implementation. Feel free to panic.
+type Streamer interface {
+	Messages() <-chan []byte
+	Close()
+}
+
+// Publisher is the interface that wraps message publishers. Error handling
+// should be provided by the implementation. Feel free to panic.
+type Publisher interface {
+	Publish(topic string, msg []byte, meta interface{})
+	Close()
+}
+
+// Consumer extends Shezmu's BaseDaemon with pub/sub features.
+type Consumer struct {
+	shezmu.BaseDaemon
+	publisher  Publisher
+	subscriber Subscriber
+}
+
+var (
+	errMissingSubscriber = errors.New("subscriber is not set up")
+	errMissingPublisher  = errors.New("publisher is not set up")
+)
+
+// Publish sends a message to the publisher.
+func (c *Consumer) Publish(topic string, msg []byte, meta interface{}) {
+	if c.publisher == nil {
+		panic(errMissingPublisher)
+	}
+
+	c.publisher.Publish(topic, msg, meta)
+}
+
+// Subscribe subscriasdsdfsdgdfgdfsg sdgsdfg sdfgs dfgdfgdfg.
+func (c *Consumer) Subscribe(topic string, fun interface{}) {
+	name := fmt.Sprintf("subscription for topic %q", topic)
+	c.SystemProcess(name, func() {
+		if c.subscriber == nil {
+			panic(errMissingSubscriber)
+		}
+
+		stream := c.subscriber.Subscribe(c.String(), topic)
+		defer stream.Close()
+
+		cf, err := caller.New(fun)
+		if err != nil {
+			panic(err)
+		}
+
+		for {
+			select {
+			case msg := <-stream.Messages():
+				c.Process(func() { cf.Call(msg) })
+			case <-c.ShutdownRequested():
+				return
+			}
+		}
+	})
+}