added dispatcher.go

dispatcher/dispatcher.go

@@ -0,0 +1,39 @@
+package dispatcher
+
+import "errors"
+
+type Dispatcher struct {
+	listeners map[int16]chan string
+	counter   int16
+}
+
+func New() Dispatcher {
+	return Dispatcher{
+		listeners: map[int16]chan string{},
+		counter:   0,
+	}
+}
+
+func (d *Dispatcher) Publish(message string) {
+	for _, ch := range d.listeners {
+		ch <- message
+	}
+}
+
+func (d *Dispatcher) Subscribe() (id int16, receiver <-chan string) {
+	key := d.counter
+	d.counter++
+	rec := make(chan string)
+	d.listeners[key] = rec
+	return key, rec
+}
+
+func (d *Dispatcher) Unsubscribe(id int16) error {
+	receiver, ok := d.listeners[id]
+	if !ok {
+		return errors.New("no subscription with id")
+	}
+	delete(d.listeners, id)
+	close(receiver)
+	return nil
+}