Add CURRENTLY_TYPING Message

ServerMessage.ts

@@ -3,6 +3,7 @@ export enum MessageType {
   TEXT = 1,
   ID_RESPONSE = 3,
   TYPING = 4,
+  CURRENTLY_TYPING = 5,
 }
 
 export type ServerMessage = {
@@ -91,7 +92,33 @@ export function isIdResponseMessage(obj: unknown): obj is IdResponseMessage {
 
 export type TypingMessage = ServerMessage & {
   type: MessageType.TYPING;
-}
+};
 export function isTypingMessage(obj: unknown): obj is TypingMessage {
   return isServerMessage(obj, MessageType.TYPING);
 }
+
+export type CurrentlyTypingMessage = ServerMessage & {
+  type: MessageType.CURRENTLY_TYPING;
+  currently: string[];
+};
+export function isCurrentlyTypingMessage(
+  obj: unknown
+): obj is CurrentlyTypingMessage {
+  if (!isServerMessage(obj, MessageType.CURRENTLY_TYPING)) {
+    return false;
+  }
+  if (
+    !Object.hasOwnProperty.call(obj, "currently") ||
+    typeof obj !== "object" ||
+    !(
+      (obj as ServerMessage & { currently: unknown }).currently instanceof Array
+    ) ||
+    Array.prototype.some.call(
+      (obj as ServerMessage & { currently: unknown[] }).currently,
+      (element) => typeof element !== "string"
+    )
+  ) {
+    return false;
+  }
+  return true;
+}