I am using firestore for my chat application

I have 2 tabs, first one is for to display all registered users and another second tab to display all users I've chatted with.

i have created 2 collections in firestore

1. users : to store all registered users
2. chatrooms : to store all messages of particular user

i have combined 2 users id to identify sender and receiver and stored it in messages.

Code:

1. //get all registered users
const querySanp = await firestore()
  .collection('users')
  .where('uid', '!=', user.uid)
  .get();
const allusers = querySanp.docs.map(docSnap => docSnap.data());
setUsers(allusers);

2. //get all registered users
 const docid = uid > user.uid ? user.uid + '-' + uid : uid + '-' + user.uid;

const messageRef = firestore()
  .collection('chatrooms')
  .doc(docid)
  .collection('messages')
  .orderBy('createdAt', 'desc');

const unSubscribe = messageRef.onSnapshot(querySnap => {
  const allmsg = querySnap.docs.map(docSanp => {
    const data = docSanp.data();
    if (data.createdAt) {
      return {
        ...docSanp.data(),
        createdAt: docSanp.data().createdAt.toDate(),
      };
    } else {
      return {
        ...docSanp.data(),
        createdAt: new Date(),
      };
    }
  });
  setMessages(allmsg);
});

How to get users i have chat with ?