feat: waku_relay_get_peers_in_mesh to libwaku (#3352)

library/libwaku.h

@@ -127,6 +127,11 @@ int waku_relay_get_num_peers_in_mesh(void* ctx,
                            WakuCallBack callback,
                            void* userData);
 
+int waku_relay_get_peers_in_mesh(void* ctx,
+                           const char* pubSubTopic,
+                           WakuCallBack callback,
+                           void* userData);
+
 int waku_store_query(void* ctx,
                         const char* jsonQuery,
                         const char* peerAddr,

library/libwaku.nim

@@ -471,6 +471,27 @@ proc waku_relay_get_num_peers_in_mesh(
   initializeLibrary()
   checkLibwakuParams(ctx, callback, userData)
 
+  let pst = pubSubTopic.alloc()
+  defer:
+    deallocShared(pst)
+
+  handleRequest(
+    ctx,
+    RequestType.RELAY,
+    RelayRequest.createShared(RelayMsgType.NUM_MESH_PEERS, pst),
+    callback,
+    userData,
+  )
+
+proc waku_relay_get_peers_in_mesh(
+    ctx: ptr WakuContext,
+    pubSubTopic: cstring,
+    callback: WakuCallBack,
+    userData: pointer,
+): cint {.dynlib, exportc.} =
+  initializeLibrary()
+  checkLibwakuParams(ctx, callback, userData)
+
   let pst = pubSubTopic.alloc()
   defer:
     deallocShared(pst)

library/waku_thread/inter_thread_communication/requests/protocols/relay_request.nim

@@ -18,6 +18,7 @@ type RelayMsgType* = enum
   NUM_CONNECTED_PEERS
   LIST_CONNECTED_PEERS
     ## to return the list of all connected peers to an specific pubsub topic
+  NUM_MESH_PEERS
   LIST_MESH_PEERS
     ## to return the list of only the peers that conform the mesh for a particular pubsub topic
   ADD_PROTECTED_SHARD ## Protects a shard with a public key
@@ -135,11 +136,17 @@ proc process*(
       return err($error)
     ## returns a comma-separated string of peerIDs
     return ok(connPeers.mapIt($it).join(","))
-  of LIST_MESH_PEERS:
+  of NUM_MESH_PEERS:
     let numPeersInMesh = waku.node.wakuRelay.getNumPeersInMesh($self.pubsubTopic).valueOr:
-      error "LIST_MESH_PEERS failed", error = error
+      error "NUM_MESH_PEERS failed", error = error
       return err($error)
     return ok($numPeersInMesh)
+  of LIST_MESH_PEERS:
+    let meshPeers = waku.node.wakuRelay.getPeersInMesh($self.pubsubTopic).valueOr:
+      error "LIST_MESH_PEERS failed", error = error
+      return err($error)
+    ## returns a comma-separated string of peerIDs
+    return ok(meshPeers.mapIt($it).join(","))
   of ADD_PROTECTED_SHARD:
     try:
       let relayShard =

waku/waku_relay/protocol.nim

@@ -323,21 +323,35 @@ proc addObserver*(w: WakuRelay, observer: PubSubObserver) {.gcsafe.} =
 proc getDHigh*(T: type WakuRelay): int =
   return GossipsubParameters.dHigh
 
-proc getNumPeersInMesh*(w: WakuRelay, pubsubTopic: PubsubTopic): Result[int, string] =
-  ## Returns the number of peers in a mesh defined by the passed pubsub topic.
+proc getPeersInMesh*(
+    w: WakuRelay, pubsubTopic: PubsubTopic
+): Result[seq[PeerId], string] =
+  ## Returns the list of peerIds in a mesh defined by the passed pubsub topic.
   ## The 'mesh' atribute is defined in the GossipSub ref object.
 
   if not w.mesh.hasKey(pubsubTopic):
-    debug "getNumPeersInMesh - there is no mesh peer for the given pubsub topic",
+    debug "getPeersInMesh - there is no mesh peer for the given pubsub topic",
       pubsubTopic = pubsubTopic
-    return ok(0)
+    return ok(newSeq[PeerId]())
 
   let peersRes = catch:
     w.mesh[pubsubTopic]
 
   let peers: HashSet[PubSubPeer] = peersRes.valueOr:
-    return
-      err("getNumPeersInMesh - exception accessing " & pubsubTopic & ": " & error.msg)
+    return err("getPeersInMesh - exception accessing " & pubsubTopic & ": " & error.msg)
+
+  let peerIds = toSeq(peers).mapIt(it.peerId)
+
+  return ok(peerIds)
+
+proc getNumPeersInMesh*(w: WakuRelay, pubsubTopic: PubsubTopic): Result[int, string] =
+  ## Returns the number of peers in a mesh defined by the passed pubsub topic.
+
+  let peers = w.getPeersInMesh(pubsubTopic).valueOr:
+    return err(
+      "getNumPeersInMesh - failed retrieving peers in mesh: " & pubsubTopic & ": " &
+        error
+    )
 
   return ok(peers.len)