From 45bae84772bb4a660de3f612cf653a65bcce9968 Mon Sep 17 00:00:00 2001
From: emonnin-epfl <etienne.monnin@epfl.ch>
Date: Sat, 24 Feb 2024 15:52:15 +0100
Subject: [PATCH] Make []string slice 'blacklist' thread-safe

---
 .../standard_hub/hub_state/ThreadSafeSlice.go | 29 +++++++++++++++++++
 be1-go/hub/standard_hub/message_handling.go   | 11 +++----
 be1-go/hub/standard_hub/mod.go                |  4 +--
 3 files changed, 37 insertions(+), 7 deletions(-)
 create mode 100644 be1-go/hub/standard_hub/hub_state/ThreadSafeSlice.go

diff --git a/be1-go/hub/standard_hub/hub_state/ThreadSafeSlice.go b/be1-go/hub/standard_hub/hub_state/ThreadSafeSlice.go
new file mode 100644
index 0000000000..8da635cf0f
--- /dev/null
+++ b/be1-go/hub/standard_hub/hub_state/ThreadSafeSlice.go
@@ -0,0 +1,29 @@
+package hub_state
+
+import (
+	"golang.org/x/exp/slices"
+	"sync"
+)
+
+type ThreadSafeSlice[E comparable] struct {
+	sync.RWMutex
+	els []E
+}
+
+func NewThreadSafeSlice[E comparable]() ThreadSafeSlice[E] {
+	return ThreadSafeSlice[E]{
+		els: make([]E, 0),
+	}
+}
+
+func (i *ThreadSafeSlice[E]) Append(elems ...E) {
+	i.Lock()
+	defer i.Unlock()
+	i.els = append(i.els, elems...)
+}
+
+func (i *ThreadSafeSlice[E]) Contains(elem E) bool {
+	i.RLock()
+	defer i.RUnlock()
+	return slices.Contains(i.els, elem)
+}
diff --git a/be1-go/hub/standard_hub/message_handling.go b/be1-go/hub/standard_hub/message_handling.go
index cad06ebe79..36ae998012 100644
--- a/be1-go/hub/standard_hub/message_handling.go
+++ b/be1-go/hub/standard_hub/message_handling.go
@@ -4,6 +4,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"popstellar/crypto"
+	"popstellar/hub/standard_hub/hub_state"
 	jsonrpc "popstellar/message"
 	"popstellar/message/answer"
 	"popstellar/message/messagedata"
@@ -210,7 +211,7 @@ func (h *Hub) handleGetMessagesByIdAnswer(senderSocket socket.Socket, answerMsg
 		}
 	}
 	// Add contents from tempBlacklist to h.blacklist
-	h.blacklist = append(h.blacklist, tempBlacklist...)
+	h.blacklist.Append(tempBlacklist...)
 	return xerrors.Errorf("failed to process messages: %v", err)
 }
 
@@ -412,7 +413,7 @@ func (h *Hub) handleHeartbeat(socket socket.Socket,
 
 	receivedIds := heartbeat.Params
 
-	missingIds := getMissingIds(receivedIds, h.hubInbox.GetIDsTable(), h.blacklist)
+	missingIds := getMissingIds(receivedIds, h.hubInbox.GetIDsTable(), &h.blacklist)
 
 	if len(missingIds) > 0 {
 		err = h.sendGetMessagesByIdToServer(socket, missingIds)
@@ -468,11 +469,11 @@ func (h *Hub) handleGreetServer(socket socket.Socket, byteMessage []byte) error
 
 // getMissingIds compares two maps of channel Ids associated to slices of message Ids to
 // determine the missing Ids from the storedIds map with respect to the receivedIds map
-func getMissingIds(receivedIds map[string][]string, storedIds map[string][]string, blacklist []string) map[string][]string {
+func getMissingIds(receivedIds map[string][]string, storedIds map[string][]string, blacklist *hub_state.ThreadSafeSlice[string]) map[string][]string {
 	missingIds := make(map[string][]string)
 	for channelId, receivedMessageIds := range receivedIds {
 		for _, messageId := range receivedMessageIds {
-			blacklisted := slices.Contains(blacklist, messageId)
+			blacklisted := blacklist.Contains(messageId)
 			storedIdsForChannel, channelKnown := storedIds[channelId]
 			if blacklisted {
 				break
@@ -580,7 +581,7 @@ func (h *Hub) loopOverMessages(messages *map[string][]json.RawMessage, senderSoc
 				continue
 			}
 
-			if slices.Contains(h.blacklist, messageData.MessageID) {
+			if h.blacklist.Contains(messageData.MessageID) {
 				break
 			}
 
diff --git a/be1-go/hub/standard_hub/mod.go b/be1-go/hub/standard_hub/mod.go
index 1567cb7724..e4872c3bd6 100644
--- a/be1-go/hub/standard_hub/mod.go
+++ b/be1-go/hub/standard_hub/mod.go
@@ -92,7 +92,7 @@ type Hub struct {
 	// the server will not ask for them again in the heartbeat
 	// and will not process them if they are received again
 	// @TODO remove the messages from the blacklist after a certain amount of time by trying to process them again
-	blacklist []string
+	blacklist state.ThreadSafeSlice[string]
 }
 
 // NewHub returns a new Hub.
@@ -126,7 +126,7 @@ func NewHub(pubKeyOwner kyber.Point, clientServerAddress string, serverServerAdd
 		hubInbox:            *inbox.NewHubInbox(rootChannel),
 		queries:             state.NewQueries(),
 		peers:               state.NewPeers(),
-		blacklist:           make([]string, 0),
+		blacklist:           state.NewThreadSafeSlice[string](),
 	}
 
 	return &hub, nil