Avoids running through the entire filter when collection is Empty

app/src/main/java/com/vitorpamplona/amethyst/ui/screen/CardFeedViewModel.kt

@@ -290,6 +290,7 @@ open class CardFeedViewModel(val localFilter: FeedFilter<Note>) : ViewModel() {
 }
 
 fun <T> equalImmutableLists(list1: ImmutableList<T>, list2: ImmutableList<T>): Boolean {
+    if (list1 === list2) return true
     if (list1.size != list2.size) return false
     for (i in 0 until list1.size) {
         if (list1[i] !== list2[i]) {

app/src/main/java/com/vitorpamplona/amethyst/ui/screen/FeedState.kt

@@ -2,10 +2,11 @@ package com.vitorpamplona.amethyst.ui.screen
 
 import androidx.compose.runtime.MutableState
 import com.vitorpamplona.amethyst.model.Note
+import kotlinx.collections.immutable.ImmutableList
 
 sealed class FeedState {
     object Loading : FeedState()
-    class Loaded(val feed: MutableState<List<Note>>) : FeedState()
+    class Loaded(val feed: MutableState<ImmutableList<Note>>) : FeedState()
     object Empty : FeedState()
     class FeedError(val errorMessage: String) : FeedState()
 }

app/src/main/java/com/vitorpamplona/amethyst/ui/screen/FeedViewModel.kt

@@ -25,6 +25,8 @@ import com.vitorpamplona.amethyst.ui.dal.UserProfileConversationsFeedFilter
 import com.vitorpamplona.amethyst.ui.dal.UserProfileNewThreadFeedFilter
 import com.vitorpamplona.amethyst.ui.dal.UserProfileReportsFeedFilter
 import com.vitorpamplona.amethyst.ui.dal.VideoFeedFilter
+import kotlinx.collections.immutable.ImmutableList
+import kotlinx.collections.immutable.toImmutableList
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
@@ -55,8 +57,8 @@ abstract class FeedViewModel(val localFilter: FeedFilter<Note>) : ViewModel() {
     private val _feedContent = MutableStateFlow<FeedState>(FeedState.Loading)
     val feedContent = _feedContent.asStateFlow()
 
-    fun newListFromDataSource(): List<Note> {
-        return localFilter.loadTop()
+    fun newListFromDataSource(): ImmutableList<Note> {
+        return localFilter.loadTop().toImmutableList()
     }
 
     private fun refresh() {
@@ -71,8 +73,7 @@ abstract class FeedViewModel(val localFilter: FeedFilter<Note>) : ViewModel() {
 
         val oldNotesState = _feedContent.value
         if (oldNotesState is FeedState.Loaded) {
-            // Using size as a proxy for has changed.
-            if (notes != oldNotesState.feed.value) {
+            if (!equalImmutableLists(notes, oldNotesState.feed.value)) {
                 updateFeed(notes)
             }
         } else {
@@ -80,7 +81,7 @@ abstract class FeedViewModel(val localFilter: FeedFilter<Note>) : ViewModel() {
         }
     }
 
-    private fun updateFeed(notes: List<Note>) {
+    private fun updateFeed(notes: ImmutableList<Note>) {
         val scope = CoroutineScope(Job() + Dispatchers.Main)
         scope.launch {
             val currentState = _feedContent.value
@@ -97,10 +98,20 @@ abstract class FeedViewModel(val localFilter: FeedFilter<Note>) : ViewModel() {
 
     fun refreshFromOldState(newItems: Set<Note>) {
         val oldNotesState = _feedContent.value
-        if (localFilter is AdditiveFeedFilter && oldNotesState is FeedState.Loaded) {
-            val newList = localFilter.updateListWith(oldNotesState.feed.value, newItems.toSet())
-            if (newList !== oldNotesState.feed.value) {
-                updateFeed(newList)
+        if (localFilter is AdditiveFeedFilter) {
+            if (oldNotesState is FeedState.Loaded) {
+                val newList = localFilter.updateListWith(oldNotesState.feed.value, newItems.toSet()).toImmutableList()
+                if (!equalImmutableLists(newList, oldNotesState.feed.value)) {
+                    updateFeed(newList)
+                }
+            } else if (oldNotesState is FeedState.Empty) {
+                val newList = localFilter.updateListWith(emptyList(), newItems.toSet()).toImmutableList()
+                if (newList.isNotEmpty()) {
+                    updateFeed(newList)
+                }
+            } else {
+                // Refresh Everything
+                refreshSuspended()
             }
         } else {
             // Refresh Everything
@@ -130,7 +141,9 @@ abstract class FeedViewModel(val localFilter: FeedFilter<Note>) : ViewModel() {
     init {
         collectorJob = viewModelScope.launch(Dispatchers.IO) {
             LocalCache.live.newEventBundles.collect { newNotes ->
-                if (localFilter is AdditiveFeedFilter && _feedContent.value is FeedState.Loaded) {
+                if (localFilter is AdditiveFeedFilter &&
+                    (_feedContent.value is FeedState.Loaded || _feedContent.value is FeedState.Empty)
+                ) {
                     invalidateInsertData(newNotes)
                 } else {
                     // Refresh Everything

app/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/VideoScreen.kt

@@ -86,6 +86,7 @@ import com.vitorpamplona.amethyst.ui.screen.LoadingFeed
 import com.vitorpamplona.amethyst.ui.screen.NostrVideoFeedViewModel
 import com.vitorpamplona.amethyst.ui.screen.ScrollStateKeys
 import com.vitorpamplona.amethyst.ui.screen.rememberForeverPagerState
+import kotlinx.collections.immutable.ImmutableList
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
@@ -198,7 +199,7 @@ fun FeedView(
 @OptIn(ExperimentalFoundationApi::class)
 @Composable
 fun SlidingCarousel(
-    feed: MutableState<List<Note>>,
+    feed: MutableState<ImmutableList<Note>>,
     accountViewModel: AccountViewModel,
     nav: (String) -> Unit,
     scrollStateKey: String? = null,