From 2bfdcb6fd16ec4f92f539706701a7bc208a29cff Mon Sep 17 00:00:00 2001
From: Nicholas Molnar <65710+neekolas@users.noreply.github.com>
Date: Tue, 26 Jul 2022 12:20:56 -0700
Subject: [PATCH] fix: handle case of unsubscribe from non-existent topic
 (#276)

---
 waku/v2/protocol/filter/filter_subscribers.go |  9 +-
 .../filter/filter_subscribers_test.go         | 91 +++++++++++++++++++
 2 files changed, 96 insertions(+), 4 deletions(-)
 create mode 100644 waku/v2/protocol/filter/filter_subscribers_test.go

diff --git a/waku/v2/protocol/filter/filter_subscribers.go b/waku/v2/protocol/filter/filter_subscribers.go
index fdfd7389..d83036e2 100644
--- a/waku/v2/protocol/filter/filter_subscribers.go
+++ b/waku/v2/protocol/filter/filter_subscribers.go
@@ -120,22 +120,23 @@ func (sub *Subscribers) RemoveContentFilters(peerID peer.ID, contentFilters []*p
 
 	var peerIdsToRemove []peer.ID
 
-	for _, subscriber := range sub.subscribers {
+	for subIndex, subscriber := range sub.subscribers {
 		if subscriber.peer != peerID {
 			continue
 		}
 
 		// make sure we delete the content filter
 		// if no more topics are left
-		for i, contentFilter := range contentFilters {
+		for _, contentFilter := range contentFilters {
 			subCfs := subscriber.filter.ContentFilters
-			for _, cf := range subCfs {
+			for i, cf := range subCfs {
 				if cf.ContentTopic == contentFilter.ContentTopic {
 					l := len(subCfs) - 1
-					subCfs[l], subCfs[i] = subCfs[i], subCfs[l]
+					subCfs[i] = subCfs[l]
 					subscriber.filter.ContentFilters = subCfs[:l]
 				}
 			}
+			sub.subscribers[subIndex] = subscriber
 		}
 
 		if len(subscriber.filter.ContentFilters) == 0 {
diff --git a/waku/v2/protocol/filter/filter_subscribers_test.go b/waku/v2/protocol/filter/filter_subscribers_test.go
new file mode 100644
index 00000000..fa924f06
--- /dev/null
+++ b/waku/v2/protocol/filter/filter_subscribers_test.go
@@ -0,0 +1,91 @@
+package filter
+
+import (
+	"testing"
+	"time"
+
+	"github.com/libp2p/go-libp2p-core/peer"
+	"github.com/libp2p/go-libp2p-core/test"
+	"github.com/status-im/go-waku/waku/v2/protocol/pb"
+	"github.com/stretchr/testify/assert"
+)
+
+const TOPIC = "/test/topic"
+
+func createPeerId(t *testing.T) peer.ID {
+	peerId, err := test.RandPeerID()
+	assert.NoError(t, err)
+	return peerId
+}
+
+func firstSubscriber(subs *Subscribers, contentTopic string) *Subscriber {
+	for sub := range subs.Items(&contentTopic) {
+		return &sub
+	}
+	return nil
+}
+
+func TestAppend(t *testing.T) {
+	subs := NewSubscribers(10 * time.Second)
+	peerId := createPeerId(t)
+	contentTopic := "topic1"
+	request := pb.FilterRequest{
+		Subscribe:      true,
+		Topic:          TOPIC,
+		ContentFilters: []*pb.FilterRequest_ContentFilter{{ContentTopic: contentTopic}},
+	}
+	subs.Append(Subscriber{peerId, "request_1", request})
+
+	sub := firstSubscriber(subs, contentTopic)
+	assert.NotNil(t, sub)
+}
+
+func TestRemove(t *testing.T) {
+	subs := NewSubscribers(10 * time.Second)
+	peerId := createPeerId(t)
+	contentTopic := "topic1"
+	request := pb.FilterRequest{
+		Subscribe:      true,
+		Topic:          TOPIC,
+		ContentFilters: []*pb.FilterRequest_ContentFilter{{ContentTopic: contentTopic}},
+	}
+	subs.Append(Subscriber{peerId, "request_1", request})
+	subs.RemoveContentFilters(peerId, request.ContentFilters)
+
+	sub := firstSubscriber(subs, contentTopic)
+	assert.Nil(t, sub)
+}
+
+func TestRemovePartial(t *testing.T) {
+	subs := NewSubscribers(10 * time.Second)
+	peerId := createPeerId(t)
+	topic1 := "topic1"
+	topic2 := "topic2"
+	request := pb.FilterRequest{
+		Subscribe:      true,
+		Topic:          TOPIC,
+		ContentFilters: []*pb.FilterRequest_ContentFilter{{ContentTopic: topic1}, {ContentTopic: topic2}},
+	}
+	subs.Append(Subscriber{peerId, "request_1", request})
+	subs.RemoveContentFilters(peerId, []*pb.FilterRequest_ContentFilter{{ContentTopic: topic1}})
+
+	sub := firstSubscriber(subs, topic2)
+	assert.NotNil(t, sub)
+	assert.Len(t, sub.filter.ContentFilters, 1)
+}
+
+func TestRemoveBogus(t *testing.T) {
+	subs := NewSubscribers(10 * time.Second)
+	peerId := createPeerId(t)
+	contentTopic := "topic1"
+	request := pb.FilterRequest{
+		Subscribe:      true,
+		Topic:          TOPIC,
+		ContentFilters: []*pb.FilterRequest_ContentFilter{{ContentTopic: contentTopic}},
+	}
+	subs.Append(Subscriber{peerId, "request_1", request})
+	subs.RemoveContentFilters(peerId, []*pb.FilterRequest_ContentFilter{{ContentTopic: "does not exist"}, {ContentTopic: contentTopic}})
+
+	sub := firstSubscriber(subs, contentTopic)
+	assert.Nil(t, sub)
+}