How to have both sides view same chat in flutter - flutter

Question

I was following this tutorial https://www.youtube.com/watch?v=wHIcJDQbBFs&t= and got it working so I can send messages and it is stored as follows
chats/targetUid/messages/message
when I send a message it works and I can see them but if I sign into the account im sending it to they cannot see it. I believe its due to the following reasons.
In the tutorial you get data from the targets messages so when I open the chat its getting it from his Uid as the target but when he opens it it uses my Uid as the target.
This is my send message code.
//create Comment
Message newMessage = Message(
profImage: myProfilePic,
username: myName,
uid: myUid,
message: message,
createdAt: DateTime.now(),
);
final refMessages = _firestore.collection('chats/$targetUid/messages');
await refMessages.add(
newMessage.toJson(),
);
The code to open the message.
return ListView.builder(
itemCount: (snapshot.data! as dynamic).docs.length,
itemBuilder: (context, index) {
return InkWell(
onTap: () {
Navigator.of(context).push(
MaterialPageRoute(
builder: (context) => ChatScreen(
uid: (snapshot.data! as dynamic).docs[index]['uid'],
),
),
);
},
child: ListTile(
leading: CircleAvatar(
backgroundImage: NetworkImage(
(snapshot.data! as dynamic).docs[index]['photoUrl'],
),
),
title: Text(
(snapshot.data! as dynamic).docs[index]['username'],
),
),
);
},
);

Answer 1

I fixed it by creating a groupchat Id and storing it in firestore that way rather than the targets Uid. this is the method im using to create the groupchat Id.
String chatroomId(String user1, String user2) {
if (user1[0].toLowerCase().codeUnits[0] >
user2.toLowerCase()[0].codeUnits[0]) {
return "$user1$user2";
} else {
return "$user2$user1";
}
}