Optimize Firebase query batching and presence state updates

data/src/main/java/com/devusercode/data/firebase/FirebaseChatRepository.kt

@@ -1,5 +1,6 @@
 package com.devusercode.data.firebase
 
+import android.util.Log
 import com.devusercode.core.domain.chat.model.UserPair
 import com.devusercode.core.domain.chat.repo.ChatRepository
 import com.devusercode.core.domain.user.model.User
@@ -9,13 +10,19 @@ import com.devusercode.data.local.mapper.toEntity
 import com.google.firebase.database.DataSnapshot
 import com.google.firebase.database.FirebaseDatabase
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.async
+import kotlinx.coroutines.awaitAll
 import kotlinx.coroutines.tasks.await
 import kotlinx.coroutines.withContext
 
 class FirebaseChatRepository(
     private val db: FirebaseDatabase,
     private val conversationDao: ConversationDao,
 ) : ChatRepository {
+    companion object {
+        private const val TAG = "FirebaseChatRepository"
+    }
+
     override suspend fun listOpenConversations(currentUid: String): List<UserPair> =
         withContext(Dispatchers.IO) {
             // 1) Try cache first
@@ -36,48 +43,63 @@ class FirebaseChatRepository(
             return@withContext fresh
         }
 
-    private suspend fun fetchFromNetwork(currentUid: String): List<UserPair> {
-        val convSnap =
-            db
-                .getReference("users")
-                .child(currentUid)
-                .child("conversations")
-                .get()
-                .await()
-        val cids = convSnap.children.mapNotNull { it.key }
-        val res = mutableListOf<UserPair>()
-
-        for (cid in cids) {
-            val parts =
-                db
-                    .getReference("conversations")
-                    .child(cid)
-                    .child("participants")
-                    .get()
-                    .await()
-            val otherUid = parts.children.mapNotNull { it.key }.firstOrNull { it != currentUid } ?: continue
-            val otherSnap =
+    private suspend fun fetchFromNetwork(currentUid: String): List<UserPair> =
+        withContext(Dispatchers.IO) {
+            val convSnap =
                 db
                     .getReference("users")
-                    .child(otherUid)
-                    .get()
-                    .await()
-            val user = otherSnap.toUser(otherUid)
-            val last =
-                db
-                    .getReference("conversations")
-                    .child(cid)
-                    .child("lastMessage")
+                    .child(currentUid)
+                    .child("conversations")
                     .get()
                     .await()
-            val text = last.child("text").getValue(String::class.java)
-            val time = last.child("time").getValue(Long::class.java)
+            val cids = convSnap.children.mapNotNull { it.key }
 
-            res += UserPair(user, cid, text, time)
-        }
+            // Batch all Firebase calls concurrently instead of sequentially
+            cids.map { cid ->
+                async {
+                    runCatching {
+                        val parts =
+                            db
+                                .getReference("conversations")
+                                .child(cid)
+                                .child("participants")
+                                .get()
+                                .await()
+                        val otherUid = parts.children.mapNotNull { it.key }.firstOrNull { it != currentUid } ?: return@async null
 
-        return res
-    }
+                        // Fetch user data and last message in parallel
+                        val otherSnapDeferred =
+                            async {
+                                db
+                                    .getReference("users")
+                                    .child(otherUid)
+                                    .get()
+                                    .await()
+                            }
+                        val lastDeferred =
+                            async {
+                                db
+                                    .getReference("conversations")
+                                    .child(cid)
+                                    .child("lastMessage")
+                                    .get()
+                                    .await()
+                            }
+
+                        val otherSnap = otherSnapDeferred.await()
+                        val last = lastDeferred.await()
+
+                        val user = otherSnap.toUser(otherUid)
+                        val text = last.child("text").getValue(String::class.java)
+                        val time = last.child("time").getValue(Long::class.java)
+
+                        UserPair(user, cid, text, time)
+                    }.onFailure { e ->
+                        Log.e(TAG, "Failed to fetch conversation $cid", e)
+                    }.getOrNull()
+                }
+            }.awaitAll().filterNotNull()
+        }
 
     private fun DataSnapshot.toUser(uid: String): User {
         val name =

ui/src/main/java/com/devusercode/ui/screens/home/HomeScreen.kt

@@ -68,10 +68,17 @@ fun HomeScreen(
                 title = { Text("UpChat") },
                 actions = {
                     IconButton(onClick = { menu = true }) { Icon(Icons.Default.MoreVert, contentDescription = null) }
-                    DropdownMenu(expanded = menu, onDismissRequest = { }) {
-                        DropdownMenuItem(text = { Text("Profile") }, onClick = { onProfile() })
-                        DropdownMenuItem(text = { Text("Settings") }, onClick = { onSettings() })
+                    DropdownMenu(expanded = menu, onDismissRequest = { menu = false }) {
+                        DropdownMenuItem(text = { Text("Profile") }, onClick = {
+                            menu = false
+                            onProfile()
+                        })
+                        DropdownMenuItem(text = { Text("Settings") }, onClick = {
+                            menu = false
+                            onSettings()
+                        })
                         DropdownMenuItem(text = { Text("Logout") }, onClick = {
+                            menu = false
                             vm.doLogout {
                                 // If NavHost passed a navigator, use it; else no-op
                                 onLoggedOutNavigateToAuth?.invoke(Routes.AUTH)

ui/src/main/java/com/devusercode/ui/screens/home/HomeViewModel.kt

@@ -70,9 +70,14 @@ class HomeViewModel
                     viewModelScope.launch {
                         observePresence(id).collect { (online, lastSeen) ->
                             _state.update { st ->
+                                // Optimize: Only update the specific user at the given index
                                 val updated =
-                                    st.conversations.map { p ->
-                                        if (p.user.uid == id) p.copy(user = p.user.copy(online = online, lastSeenEpochMs = lastSeen)) else p
+                                    st.conversations.toMutableList().apply {
+                                        val targetIndex = indexOfFirst { it.user.uid == id }
+                                        if (targetIndex >= 0) {
+                                            val pair = get(targetIndex)
+                                            set(targetIndex, pair.copy(user = pair.user.copy(online = online, lastSeenEpochMs = lastSeen)))
+                                        }
                                     }
                                 st.copy(conversations = updated)
                             }