add way to query subscribed topics

floodsub.go

@@ -33,6 +33,9 @@ type PubSub struct {
 	// addSub is a control channel for us to add and remove subscriptions
 	addSub chan *addSub
 
+	//
+	getTopics chan *topicReq
+
 	// a notification channel for incoming streams from other peers
 	newPeers chan inet.Stream
 
@@ -75,6 +78,7 @@ func NewFloodSub(ctx context.Context, h host.Host) *PubSub {
 		newPeers:     make(chan inet.Stream),
 		peerDead:     make(chan peer.ID),
 		addSub:       make(chan *addSub),
+		getTopics:    make(chan *topicReq),
 		myTopics:     make(map[string]chan *Message),
 		topics:       make(map[string]map[peer.ID]struct{}),
 		peers:        make(map[peer.ID]chan *RPC),
@@ -112,6 +116,12 @@ func (p *PubSub) processLoop(ctx context.Context) {
 			for _, t := range p.topics {
 				delete(t, pid)
 			}
+		case treq := <-p.getTopics:
+			var out []string
+			for t := range p.myTopics {
+				out = append(out, t)
+			}
+			treq.resp <- out
 		case sub := <-p.addSub:
 			p.handleSubscriptionChange(sub)
 		case rpc := <-p.incoming:
@@ -270,12 +280,22 @@ type addSub struct {
 	resp  chan chan *Message
 }
 
-func (p *PubSub) Subscribe(topic string) (<-chan *Message, error) {
+func (p *PubSub) Subscribe(ctx context.Context, topic string) (<-chan *Message, error) {
 	return p.SubscribeComplicated(&pb.TopicDescriptor{
 		Name: proto.String(topic),
 	})
 }
 
+type topicReq struct {
+	resp chan []string
+}
+
+func (p *PubSub) GetTopics() []string {
+	out := make(chan []string, 1)
+	p.getTopics <- &topicReq{resp: out}
+	return <-out
+}
+
 func (p *PubSub) SubscribeComplicated(td *pb.TopicDescriptor) (<-chan *Message, error) {
 	if td.GetAuth().GetMode() != pb.TopicDescriptor_AuthOpts_NONE {
 		return nil, fmt.Errorf("Auth method not yet supported")

floodsub_test.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"fmt"
 	"math/rand"
+	"sort"
 	"testing"
 	"time"
 
@@ -360,3 +361,58 @@ func TestTreeTopology(t *testing.T) {
 
 	checkMessageRouting(t, "fizzbuzz", []*PubSub{psubs[9], psubs[3]}, chs)
 }
+
+func assertHasTopics(t *testing.T, ps *PubSub, exptopics ...string) {
+	topics := ps.GetTopics()
+	sort.Strings(topics)
+	sort.Strings(exptopics)
+
+	if len(topics) != len(exptopics) {
+		t.Fatalf("expected to have %v, but got %v", exptopics, topics)
+	}
+
+	for i, v := range exptopics {
+		if topics[i] != v {
+			t.Fatalf("expected %s but have %s", v, topics[i])
+		}
+	}
+}
+
+func TestSubReporting(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	host := getNetHosts(t, ctx, 1)[0]
+	psub := NewFloodSub(ctx, host)
+
+	_, err := psub.Subscribe(ctx, "foo")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = psub.Subscribe(ctx, "bar")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assertHasTopics(t, psub, "foo", "bar")
+
+	_, err = psub.Subscribe(ctx, "baz")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assertHasTopics(t, psub, "foo", "bar", "baz")
+
+	psub.Unsub("bar")
+	assertHasTopics(t, psub, "foo", "baz")
+	psub.Unsub("foo")
+	assertHasTopics(t, psub, "baz")
+
+	_, err = psub.Subscribe(ctx, "fish")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	assertHasTopics(t, psub, "baz", "fish")
+}