[misc] Separate shared code dependencies (#4288)

* Separate shared code dependencies

* Fix import

* Test respective shared code

* Update openapi ref

* Fix test

* Fix test path

shared/relay/messages/peer_state.go

@@ -0,0 +1,92 @@
+package messages
+
+import (
+	"fmt"
+)
+
+func MarshalSubPeerStateMsg(ids []PeerID) ([][]byte, error) {
+	return marshalPeerIDs(ids, byte(MsgTypeSubscribePeerState))
+}
+
+func UnmarshalSubPeerStateMsg(buf []byte) ([]PeerID, error) {
+	return unmarshalPeerIDs(buf)
+}
+
+func MarshalUnsubPeerStateMsg(ids []PeerID) ([][]byte, error) {
+	return marshalPeerIDs(ids, byte(MsgTypeUnsubscribePeerState))
+}
+
+func UnmarshalUnsubPeerStateMsg(buf []byte) ([]PeerID, error) {
+	return unmarshalPeerIDs(buf)
+}
+
+func MarshalPeersOnline(ids []PeerID) ([][]byte, error) {
+	return marshalPeerIDs(ids, byte(MsgTypePeersOnline))
+}
+
+func UnmarshalPeersOnlineMsg(buf []byte) ([]PeerID, error) {
+	return unmarshalPeerIDs(buf)
+}
+
+func MarshalPeersWentOffline(ids []PeerID) ([][]byte, error) {
+	return marshalPeerIDs(ids, byte(MsgTypePeersWentOffline))
+}
+
+func UnMarshalPeersWentOffline(buf []byte) ([]PeerID, error) {
+	return unmarshalPeerIDs(buf)
+}
+
+// marshalPeerIDs is a generic function to marshal peer IDs with a specific message type
+func marshalPeerIDs(ids []PeerID, msgType byte) ([][]byte, error) {
+	if len(ids) == 0 {
+		return nil, fmt.Errorf("no list of peer ids provided")
+	}
+
+	const maxPeersPerMessage = (MaxMessageSize - sizeOfProtoHeader) / peerIDSize
+	var messages [][]byte
+
+	for i := 0; i < len(ids); i += maxPeersPerMessage {
+		end := i + maxPeersPerMessage
+		if end > len(ids) {
+			end = len(ids)
+		}
+		chunk := ids[i:end]
+
+		totalSize := sizeOfProtoHeader + len(chunk)*peerIDSize
+		buf := make([]byte, totalSize)
+		buf[0] = byte(CurrentProtocolVersion)
+		buf[1] = msgType
+
+		offset := sizeOfProtoHeader
+		for _, id := range chunk {
+			copy(buf[offset:], id[:])
+			offset += peerIDSize
+		}
+
+		messages = append(messages, buf)
+	}
+
+	return messages, nil
+}
+
+// unmarshalPeerIDs is a generic function to unmarshal peer IDs from a buffer
+func unmarshalPeerIDs(buf []byte) ([]PeerID, error) {
+	if len(buf) < sizeOfProtoHeader {
+		return nil, fmt.Errorf("invalid message format")
+	}
+
+	if (len(buf)-sizeOfProtoHeader)%peerIDSize != 0 {
+		return nil, fmt.Errorf("invalid peer list size: %d", len(buf)-sizeOfProtoHeader)
+	}
+
+	numIDs := (len(buf) - sizeOfProtoHeader) / peerIDSize
+
+	ids := make([]PeerID, numIDs)
+	offset := sizeOfProtoHeader
+	for i := 0; i < numIDs; i++ {
+		copy(ids[i][:], buf[offset:offset+peerIDSize])
+		offset += peerIDSize
+	}
+
+	return ids, nil
+}