Count of total unread messages - flutter

Question

In my flutter & firebase app, I use cloud functions to send notifications for any new messages. The problem I face is how I show count of total unread messages in the chatroom list tile as shown in red circles in this famous chat app.
My chatroom page looks almost like this picture except for the unread message counter at the right side of each tile. What logic do I have to use?
Please give me any advice to implement showing count of unread messages at the right side of each chatroom tile.
Here is my chatroom collection in firestore.

Answer 1

You can simply add 3 more fields in the document:-
1stpersonMessageCount
2ndPersonMessageCount
MessageCount
So now what you need to do is that in your chatting screen you simply need to increment the message count of the person who is sending the message everytime he send the message:-
chatRoomReference.updateData({
"messageCount":FieldValue.increment(1),
"${currentUser}messageCount":FieldValue.increment(1),
});
and for message seen purpose you can simply update the messagecount of reciever by
chatRoomReference.updateData({
"${currentUser}messageCount":snapshot.documents.length,
});
and on the page where you want to see the count of new messages you simply subtract the value of messageCount and cureentUserMessageCount.
In both the code sections you can see that currentUser is there bt don't get confused when the sender is sending the message then currentUser's value would be the sender's name or his id and when someone is reading then his id or name. Ex- John is sending then current User will be John and when mohan is reading the message then it would be mohan. Hence you will have 3 fields i.e. JohnMessageCount, MohanMessageCount and total messages i.e. messageCount.