loading: drop the snapshot cache, one loading card per thing (#25)

The saved-list snapshot (issue #9) painted the last session's rows instantly,
then the network refresh swapped them in and the tiles jumped as newer videos
appeared — jarring. Drop the snapshot instant-paint on Home, the video lists and
the Channels screen; images stay fast because Coil already disk-caches them.

Screens now show the loading card while the first page loads instead of stale
content: one card per Home row (not a fake full row), a single card at the end
of a growing grid, and a trailing card when a Home row loads its next page.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/java/net/jeena/jtubetv/ui/list/VideoListViewModel.kt

@@ -10,7 +10,6 @@ import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.launch
 import net.jeena.jtubetv.AppGraph
 import net.jeena.jtubetv.data.PeerTubeRepository
-import net.jeena.jtubetv.ui.list.Snapshots
 
 /** Where the list's content comes from. */
 sealed interface ListSource {
@@ -56,16 +55,6 @@ class VideoListViewModel(
     var videoTotal by androidx.compose.runtime.mutableStateOf(0L)
         private set
 
-    // Snapshot caching (issue #9): live content lists only — Search results and
-    // History rows (which carry extra watch metadata) must not persist.
-    private val shouldSkipSnapshot =
-        source is ListSource.Search || source is ListSource.History
-
-    private fun cacheKey(): String = when (val s = source) {
-        is ListSource.Channel -> "channel-" + s.handle
-        else -> s::class.java.simpleName
-    }
-
     init {
         // Probe whether the instance allows the search-index ("Vidiverse") scope.
         if (source is ListSource.Search) {
@@ -74,24 +63,10 @@ class VideoListViewModel(
                     repository.serverConfig().getOrNull()?.search?.searchIndex?.enabled == true
             }
         }
-        val context = AppGraph.appContext
+        // No snapshot instant-paint any more (issue #25): the saved-list cache
-        if (context != null && !shouldSkipSnapshot) {
+        // repainted stale rows that then jumped when the fresh page landed with
-            viewModelScope.launch(kotlinx.coroutines.Dispatchers.IO) {
+        // newer videos. Screens now show the loading card until the first page
-                val videos = Snapshots.loadVideos(context, cacheKey()) ?: return@launch
+        // arrives; images stay fast via Coil's own disk cache.
-                kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.Main) {
-                    showInstant(videos.map { VideoListItem.Video(it) })
-                }
-                // Channel page banner: restore the saved one instantly too.
-                val s = source
-                if (s is ListSource.Channel) {
-                    Snapshots.loadChannelHeader(context, s.handle)?.let { header ->
-                        kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.Main) {
-                            channelHeader = header
-                        }
-                    }
-                }
-            }
-        }
     }
 
     override fun onChunkLoaded(chunk: List<VideoListItem>) {
@@ -103,20 +78,6 @@ class VideoListViewModel(
                 }
             }
         )
-        // Persist the freshly loaded content so the next app start paints
-        // instantly (issue #9).
-        if (!shouldSkipSnapshot && chunk.all { it is VideoListItem.Video }) {
-            val context = AppGraph.appContext
-            if (context != null) {
-                viewModelScope.launch(kotlinx.coroutines.Dispatchers.IO) {
-                    Snapshots.saveVideos(
-                        context,
-                        cacheKey(),
-                        items.filterIsInstance<VideoListItem.Video>().take(50).map { it.video },
-                    )
-                }
-            }
-        }
     }
 
     override suspend fun fetch(start: Long, count: Int): Result<List<VideoListItem>> {
@@ -150,22 +111,9 @@ class VideoListViewModel(
     fun loadChannelHeader(repository: PeerTubeRepository) {
         val s = source
         if (s is ListSource.Channel) {
-            // Instant restore from the snapshot, then a fresh fetch (issue #9).
-            val context = AppGraph.appContext
-            if (context != null) {
-                Snapshots.loadChannelHeader(context, s.handle)?.let { snap ->
-                    if (channelHeader == null) channelHeader = snap
-                }
-            }
             viewModelScope.launch {
                 repository.videoChannel(s.handle).getOrNull()?.let { header ->
                     channelHeader = header
-                    val ctx = AppGraph.appContext
-                    if (ctx != null) {
-                        kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.IO) {
-                            Snapshots.saveChannelHeader(ctx, s.handle, header)
-                        }
-                    }
                 }
             }
         }

app/src/main/java/net/jeena/jtubetv/ui/screens/ChannelsScreen.kt

@@ -94,10 +94,6 @@ data class UserGroup(
 
 class ChannelsViewModel(private val store: TokenStore) : ViewModel() {
 
-    private val snapshotContext = AppGraph.appContext
-    private val snapshotKey = "channels-" + (store.baseUrl ?: "").replace(Regex("[^A-Za-z0-9._-]"), "_")
-    private val snapshotRows = snapshotContext?.let { Snapshots.loadUserGroups(it, snapshotKey) }
-
     var user by mutableStateOf<UserDto?>(null)
         private set
     var userChannels by mutableStateOf<List<VideoChannelDto>>(emptyList())
@@ -127,20 +123,9 @@ class ChannelsViewModel(private val store: TokenStore) : ViewModel() {
     /** SystemClock at the last successful fast-path pass — re-entry freshness. */
     private var lastLoadedAt = 0L
 
-    init {
+    // No snapshot instant-paint any more (issue #25): the Channels screen shows
-        // Snapshot restore (issue #9): paint the last session's channel rows
+    // its shimmer placeholder rows until the (fast-path, few-request) load lands,
-        // instantly, including the per-channel stats (the "minutes of loading"
+    // instead of painting a stale snapshot that reshuffled as stats streamed in.
-        // complaint) — the streaming reload below then updates them in place.
-        if (snapshotRows != null) {
-            userRows = snapshotRows
-            loading = false
-        }
-        if (snapshotContext != null) {
-            statsMap.putAll(Snapshots.loadChannelStats(snapshotContext, snapshotKey))
-            if (statsMap.isNotEmpty()) stats = statsMap.toMap()
-        }
-    }
-
 
     fun load(force: Boolean = false) {
         // Re-entry (destination switch away + back) inside the freshness window:
@@ -225,11 +210,6 @@ class ChannelsViewModel(private val store: TokenStore) : ViewModel() {
         stats = statsMap.toMap()
         rebuildRows(host)
         lastLoadedAt = android.os.SystemClock.elapsedRealtime()
-        snapshotContext?.let { ctx ->
-            viewModelScope.launch(kotlinx.coroutines.Dispatchers.IO) {
-                Snapshots.saveChannelStats(ctx, snapshotKey, statsMap.toMap())
-            }
-        }
         ImagePrefetcher.channelArt(allChannels + userChannels)
     }
 
@@ -303,12 +283,6 @@ class ChannelsViewModel(private val store: TokenStore) : ViewModel() {
                 .thenByDescending { g -> g.channels.sumOf { statsMap[it.name + "@" + it.host]?.videos ?: 0 } }
                 .thenByDescending { g -> g.channels.sumOf { it.followersCount } },
         )
-        // Persist for the next cold start (issue #9).
-        snapshotContext?.let { ctx ->
-            viewModelScope.launch(kotlinx.coroutines.Dispatchers.IO) {
-                Snapshots.saveUserGroups(ctx, snapshotKey, userRows)
-            }
-        }
         Log.w(
             "JTube",
             "order now: " + userRows.take(6).joinToString(" | ") { g ->

app/src/main/java/net/jeena/jtubetv/ui/screens/HomeRows.kt

@@ -41,7 +41,6 @@ import net.jeena.jtubetv.AppGraph
 import net.jeena.jtubetv.data.PeerTubeRepository
 import net.jeena.jtubetv.data.api.VideoDto
 import net.jeena.jtubetv.ui.list.PagedListViewModel
-import net.jeena.jtubetv.ui.list.Snapshots
 import net.jeena.jtubetv.ui.screens.list.ShimmerCard
 import net.jeena.jtubetv.ui.screens.list.VideoCard
 
@@ -58,8 +57,6 @@ data class ContinueItem(val video: VideoDto, val progress: Float?)
 
 class HomeRowsViewModel(private val repository: PeerTubeRepository) : ViewModel() {
 
-    private fun contextOrNull() = AppGraph.appContext
-
     var continueItems by mutableStateOf<List<ContinueItem>>(emptyList())
         private set
     var continueLoading by mutableStateOf(true)
@@ -76,36 +73,24 @@ class HomeRowsViewModel(private val repository: PeerTubeRepository) : ViewModel(
     private var continueInFlight = false
     var continueExhausted by mutableStateOf(false)
         private set
+    /** True while the next continue page is loading — drives a trailing loading card (#25). */
+    var continueLoadingMore by mutableStateOf(false)
+        private set
     private var subsStart = 0L
     private var subsInFlight = false
     var subsExhausted by mutableStateOf(false)
         private set
+    var subsLoadingMore by mutableStateOf(false)
+        private set
     /** Exposed for the shimmer placeholders (issue #19). */
     var subsLoading = false
         private set
 
     val recent = RecentVideosViewModel(repository)
 
-    init {
+    // No snapshot instant-paint any more (issue #25): Home shows one loading card
-        // Snapshot restore (issue #9): Home paints from the last session's rows
+    // per row until the network pages land, instead of painting a stale snapshot
-        // immediately; the loads below freshen them from the network.
+    // that then jumped as newer videos arrived.
-        val context = contextOrNull()
-        if (context != null) {
-            viewModelScope.launch(kotlinx.coroutines.Dispatchers.IO) {
-                val savedContinue = Snapshots.loadContinue(context, "home-continue")
-                val savedSubs = Snapshots.loadVideos(context, "home-subs")
-                kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.Main) {
-                    if (continueItems.isEmpty() && savedContinue != null) {
-                        continueItems = savedContinue
-                        continueLoading = false
-                    }
-                    if (subItems.isEmpty() && savedSubs != null) {
-                        subItems = savedSubs
-                    }
-                }
-            }
-        }
-    }
 
     private fun fetchSubs() {
         viewModelScope.launch {
@@ -116,12 +101,6 @@ class HomeRowsViewModel(private val repository: PeerTubeRepository) : ViewModel(
             subItems = subs
             subsLoading = false
             net.jeena.jtubetv.ui.list.ImagePrefetcher.videoThumbnails(subs)
-            // Snapshot for the next cold start (issue #9).
-            contextOrNull()?.let { ctx ->
-                kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.IO) {
-                    Snapshots.saveVideos(ctx, "home-subs", subs)
-                }
-            }
         }
     }
 
@@ -177,6 +156,7 @@ class HomeRowsViewModel(private val repository: PeerTubeRepository) : ViewModel(
     fun continueMore() {
         if (continueInFlight || continueExhausted || continueItems.isEmpty()) return
         continueInFlight = true
+        continueLoadingMore = true
         viewModelScope.launch {
             val page = fetchContinuePage()
             if (page.isNotEmpty()) {
@@ -184,6 +164,7 @@ class HomeRowsViewModel(private val repository: PeerTubeRepository) : ViewModel(
                 net.jeena.jtubetv.ui.list.ImagePrefetcher.videoThumbnails(page.map { it.video })
             }
             continueInFlight = false
+            continueLoadingMore = false
         }
     }
 
@@ -191,6 +172,7 @@ class HomeRowsViewModel(private val repository: PeerTubeRepository) : ViewModel(
     fun subsMore() {
         if (subsInFlight || subsExhausted || subItems.isEmpty()) return
         subsInFlight = true
+        subsLoadingMore = true
         viewModelScope.launch {
             val page = repository.subscriptionVideos(subsStart, SUB_PAGE).getOrNull()?.data ?: emptyList()
             subsStart += page.size
@@ -200,6 +182,7 @@ class HomeRowsViewModel(private val repository: PeerTubeRepository) : ViewModel(
                 net.jeena.jtubetv.ui.list.ImagePrefetcher.videoThumbnails(page)
             }
             subsInFlight = false
+            subsLoadingMore = false
         }
     }
 
@@ -211,12 +194,6 @@ class HomeRowsViewModel(private val repository: PeerTubeRepository) : ViewModel(
             continueItems = items
             continueLoading = false
             net.jeena.jtubetv.ui.list.ImagePrefetcher.videoThumbnails(items.map { it.video })
-            // Snapshot for the next cold start (issue #9).
-            contextOrNull()?.let { ctx ->
-                kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.IO) {
-                    Snapshots.saveContinue(ctx, "home-continue", items)
-                }
-            }
         }
     }
 
@@ -236,28 +213,8 @@ class HomeRowsViewModel(private val repository: PeerTubeRepository) : ViewModel(
 /** Paged "New videos" row content. */
 class RecentVideosViewModel(private val repository: PeerTubeRepository) : PagedListViewModel<VideoDto>() {
 
-    // Instant restore from the last session (issue #9); showInstant() refreshes
-    // the first page in the background.
-    init {
-        val context = AppGraph.appContext
-        if (context != null) {
-            viewModelScope.launch(kotlinx.coroutines.Dispatchers.IO) {
-                Snapshots.loadVideos(context, "RecentVideos")?.let { snapshot ->
-                    kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.Main) {
-                        showInstant(snapshot)
-                    }
-                }
-            }
-        }
-    }
-
     override fun onChunkLoaded(chunk: List<VideoDto>) {
         net.jeena.jtubetv.ui.list.ImagePrefetcher.videoThumbnails(chunk)
-        AppGraph.appContext?.let { ctx ->
-            viewModelScope.launch(kotlinx.coroutines.Dispatchers.IO) {
-                Snapshots.saveVideos(ctx, "RecentVideos", items.take(50))
-            }
-        }
     }
 
     override suspend fun fetch(start: Long, count: Int): Result<List<VideoDto>> =
@@ -315,9 +272,10 @@ fun HomeRowsScreen(
         }
         item {
             if (viewModel.continueLoading && viewModel.continueItems.isEmpty()) {
-                // Dummy cards with the faint shimmer while the row loads (#19);
+                // One placeholder card per row while it loads (#25): a single card
+                // reads as "this row is coming", not a fake full row of content.
                 // "Watch something first" only when there is genuinely no history.
-                ShimmerRow()
+                ShimmerRow(size = 1)
             } else if (viewModel.continueItems.isEmpty()) {
                 Box(Modifier.fillParentMaxWidth(0f).padding(start = 16.dp)) {
                     Text(
@@ -339,6 +297,7 @@ fun HomeRowsScreen(
                     autoFocusOnLoad = true,
                     autoFocusAllowed = { !userNavigated },
                     refocusPulse = drawerPulse,
+                    trailingLoading = viewModel.continueLoadingMore,
                 ) { index, video ->
                     // Grow the row on demand (issue #18), same hook as the recent row.
                     if (index >= viewModel.continueItems.size - PagedListViewModel.LOOKAHEAD) {
@@ -358,7 +317,7 @@ fun HomeRowsScreen(
         item {
             if (recentItems.isEmpty()) {
                 LaunchedEffect("kick-recent") { viewModel.recent.loadMore() }
-                ShimmerRow()
+                ShimmerRow(size = 1)
             } else {
                 FocusScrollRow(
                     videos = recentItems,
@@ -368,6 +327,7 @@ fun HomeRowsScreen(
                     clickedIndex = recentRestore,
                     restoreToken = restoreToken,
                     refocusPulse = drawerPulse,
+                    trailingLoading = viewModel.recent.loadingMore,
                 ) { index, video ->
                     if (index >= recentItems.size - PagedListViewModel.LOOKAHEAD) {
                         LaunchedEffect(index) { viewModel.recent.loadMore() }
@@ -386,7 +346,7 @@ fun HomeRowsScreen(
             }
             item {
                 if (viewModel.subItems.isEmpty() && viewModel.subsLoading) {
-                    ShimmerRow()
+                    ShimmerRow(size = 1)
                 } else {
                 FocusScrollRow(
                     videos = viewModel.subItems,
@@ -396,6 +356,7 @@ fun HomeRowsScreen(
                     clickedIndex = subRestore,
                     restoreToken = restoreToken,
                     refocusPulse = drawerPulse,
+                    trailingLoading = viewModel.subsLoadingMore,
                 ) { index, video ->
                     if (index >= viewModel.subItems.size - PagedListViewModel.LOOKAHEAD) {
                         LaunchedEffect(index) { viewModel.subsMore() }
@@ -444,6 +405,9 @@ fun FocusScrollRow(
     // NOTE: stays before [afterItem] — the trailing lambda binds to the last
     // declared parameter.
     refocusPulse: Int = 0,
+    // A trailing loading card at the row's end while the next page loads (#25),
+    // so it's clear more is coming when scrolling right.
+    trailingLoading: Boolean = false,
     afterItem: @Composable (index: Int, video: VideoDto) -> Unit = { _, _ -> },
 ) {
     val rowState = rememberLazyListState()
@@ -518,5 +482,14 @@ fun FocusScrollRow(
             )
             afterItem(index, video)
         }
+        if (trailingLoading) {
+            item(key = "trailing-loading") {
+                ShimmerCard(
+                    modifier = Modifier
+                        .padding(horizontal = 4.dp)
+                        .width(rowCardWidth()),
+                )
+            }
+        }
     }
 }

app/src/main/java/net/jeena/jtubetv/ui/screens/list/VideoListScreen.kt

@@ -239,22 +239,19 @@ fun VideoListScreen(
             }
         }
         if (viewModel.loadingMore) {
-            // Growing the list: placeholder row (issue #19) instead of the
+            // Growing the list: a single loading card at the end (#25) so it's
-            // permanent spinner chip that used to sit under every list.
+            // clear more is coming, without faking a whole row of content.
-            item(key = "load-more-placeholders") {
+            item(key = "load-more-placeholder") {
-                androidx.compose.foundation.layout.Row {
-                    repeat(cardsPerRow) {
                 ShimmerCard(
                     modifier = Modifier
                         .padding(6.dp)
-                                .width(rowCardWidth()),
+                        .width(rowCardWidth() - 12.dp),
                 )
             }
         }
     }
     }
 }
-}
 
 @Composable
 private fun SearchHeader(viewModel: VideoListViewModel, onOpenDrawer: () -> Unit = {}) {