perf(home): reduce redundant requests on home refresh

Drop a duplicate getLibraries call from loadLatestLibraryContent by
reusing the libraries already loaded earlier in the same refresh.

Add a 30s debounce to HomeRefreshCoordinator.onResumed so rapid
resume/tab-switch events coalesce into a single refresh; pull-to-refresh
bypasses the gate via onRefresh.

Rate-limit SyncPlaybackPositionsHomeRefreshSideEffect to once every
6h with a 25-item cap and a rotating window cursor, so users with many
downloads no longer fire one getItemInfo call per item on every resume.

core/src/main/java/hu/bbara/purefin/core/feature/browse/home/refresh/HomeRefreshCoordinator.kt

@@ -1,27 +1,56 @@
 package hu.bbara.purefin.core.feature.browse.home.refresh
 
+import android.os.SystemClock
 import hu.bbara.purefin.core.data.HomeRepository
 import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
+import timber.log.Timber
 import javax.inject.Inject
+import javax.inject.Singleton
+import kotlin.concurrent.atomics.AtomicLong
+import kotlin.concurrent.atomics.ExperimentalAtomicApi
 
+// Singleton so the debounce window is shared across all ViewModel instances.
+// A new coordinator per ViewModel would reset the timer on configuration
+// changes and defeat the purpose of coalescing rapid resume/tab-switch
+// events.
+@Singleton
 class HomeRefreshCoordinator @Inject constructor(
     private val homeRepository: HomeRepository,
     private val sideEffects: Set<@JvmSuppressWildcards HomeRefreshSideEffect>,
 ) {
     private val sideEffectsMutex = Mutex()
 
+    // AtomicLong matches the rate-limit pattern used by the playback-position
+    // side effect and is safe to read/write from any coroutine dispatcher.
+    @OptIn(ExperimentalAtomicApi::class)
+    private val lastRefreshAtMs = AtomicLong(0L)
+
+    @OptIn(ExperimentalAtomicApi::class)
     suspend fun onResumed() {
+        val now = SystemClock.elapsedRealtime()
+        if (now - lastRefreshAtMs.load() < RESUME_DEBOUNCE_MS) {
+            Timber.tag(TAG).d("Skipping onResumed refresh (debounced)")
+            return
+        }
         refreshHomeData()
         runSideEffects()
+        // Updated unconditionally on completion. refreshHomeData() catches
+        // non-cancellation exceptions internally, so a failed refresh still
+        // counts as "we just touched the server" and the next onResumed
+        // within RESUME_DEBOUNCE_MS will be skipped. Pull-to-refresh always
+        // bypasses this gate via onRefresh.
+        lastRefreshAtMs.store(SystemClock.elapsedRealtime())
     }
 
+    @OptIn(ExperimentalAtomicApi::class)
     suspend fun onRefresh(setRefreshing: (Boolean) -> Unit) {
         refreshHomeData(setRefreshing)
         runSideEffects()
+        lastRefreshAtMs.store(SystemClock.elapsedRealtime())
     }
 
     private suspend fun refreshHomeData(
@@ -54,4 +83,11 @@ class HomeRefreshCoordinator @Inject constructor(
             }
         }
     }
+
+    private companion object {
+        const val TAG = "HomeRefreshCoordinator"
+        // Coalesce rapid resume/tab-switch events into a single refresh.
+        // Pull-to-refresh bypasses this gate via onRefresh.
+        const val RESUME_DEBOUNCE_MS = 30_000L
+    }
 }

data/src/main/java/hu/bbara/purefin/data/catalog/InMemoryAppContentRepository.kt

@@ -303,27 +303,24 @@ class InMemoryAppContentRepository @Inject constructor(
     }
 
     private suspend fun loadLatestLibraryContent() {
-        val librariesItem = runCatching { jellyfinApiClient.getLibraries() }
-            .getOrElse { error ->
-                handleRefreshFailure(error, "Unable to load latest library content")
-            }
-        val filteredLibraries = librariesItem.filter {
-            it.collectionType == CollectionType.MOVIES || it.collectionType == CollectionType.TVSHOWS
-        }
+        // Reuse the libraries already loaded by loadLibraries() so we don't refetch
+        // the same /Users/{userId}/Views response a second time per refresh.
+        val filteredLibraries = librariesState.value
+        val url = serverUrl()
         val latestLibraryContents = filteredLibraries.associate { library ->
             val latestFromLibrary = runCatching { jellyfinApiClient.getLatestFromLibrary(library.id) }
                 .getOrElse { error ->
                     handleRefreshFailure(error, "Unable to load latest items for library ${library.id}")
                 }
-            library.id to when (library.collectionType) {
-                CollectionType.MOVIES -> latestFromLibrary.map {
-                    val movie = it.toMovie(serverUrl())
+            library.id to when (library.type) {
+                LibraryKind.MOVIES -> latestFromLibrary.map {
+                    val movie = it.toMovie(url)
                     Media.MovieMedia(movieId = movie.id)
                 }
-                CollectionType.TVSHOWS -> latestFromLibrary.map {
+                LibraryKind.SERIES -> latestFromLibrary.map {
                     when (it.type) {
                         BaseItemKind.SERIES -> {
-                            val series = it.toSeries(serverUrl())
+                            val series = it.toSeries(url)
                             Media.SeriesMedia(seriesId = series.id)
                         }
                         BaseItemKind.SEASON -> {
@@ -331,13 +328,12 @@ class InMemoryAppContentRepository @Inject constructor(
                             Media.SeasonMedia(seasonId = season.id, seriesId = season.seriesId)
                         }
                         BaseItemKind.EPISODE -> {
-                            val episode = it.toEpisode(serverUrl())
+                            val episode = it.toEpisode(url)
                             Media.EpisodeMedia(episodeId = episode.id, seriesId = episode.seriesId)
                         }
                         else -> throw UnsupportedOperationException("Unsupported item type: ${it.type}")
                     }
                 }
-                else -> throw UnsupportedOperationException("Unsupported library type: ${library.collectionType}")
             }
         }
         latestLibraryContentState.value = latestLibraryContents

data/src/main/java/hu/bbara/purefin/data/jellyfin/playback/SyncPlaybackPositionsHomeRefreshSideEffect.kt

@@ -1,5 +1,6 @@
 package hu.bbara.purefin.data.jellyfin.playback
 
+import android.os.SystemClock
 import hu.bbara.purefin.core.Offline
 import hu.bbara.purefin.core.Online
 import hu.bbara.purefin.core.data.LocalMediaRepository
@@ -15,6 +16,9 @@ import org.jellyfin.sdk.model.api.BaseItemDto
 import timber.log.Timber
 import java.util.UUID
 import javax.inject.Inject
+import kotlin.concurrent.atomics.AtomicLong
+import kotlin.concurrent.atomics.ExperimentalAtomicApi
+import kotlin.concurrent.atomics.fetchAndIncrement
 import kotlin.math.roundToLong
 
 class SyncPlaybackPositionsHomeRefreshSideEffect @Inject constructor(
@@ -25,17 +29,44 @@ class SyncPlaybackPositionsHomeRefreshSideEffect @Inject constructor(
     @param:Online private val onlineRepository: LocalMediaRepository,
 ) : HomeRefreshSideEffect {
 
+    // Tracks the last time the sync actually ran. Using an AtomicLong keeps the
+    // timestamp race-free across coroutines; the debounce compares against
+    // SystemClock.elapsedRealtime() and skips when the window has not elapsed.
+    @OptIn(ExperimentalAtomicApi::class)
+    private val lastRunAtElapsedMs = AtomicLong(0L)
+
+    // Rotates the slice of items synced on each successful run. Without this,
+    // sortedBy+take(25) would re-fetch the same lexicographically lowest UUIDs
+    // forever and the rest of the offline library would never be reconciled.
+    @OptIn(ExperimentalAtomicApi::class)
+    private val nextWindowIndex = AtomicLong(0L)
+
+    @OptIn(ExperimentalAtomicApi::class)
     override suspend fun run() {
         if (!networkMonitor.isOnline.first()) return
 
-        val localPlaybackPositions = buildList {
-            addAll(offlineRepository.movies.first().values.map { it.toLocalPlaybackPosition() })
-            addAll(offlineRepository.episodes.first().values.map { it.toLocalPlaybackPosition() })
+        val now = SystemClock.elapsedRealtime()
+        if (now - lastRunAtElapsedMs.load() < MIN_INTERVAL_MS) {
+            Timber.tag(TAG).d("Skipping playback position sync (rate-limited)")
+            return
         }
 
-        localPlaybackPositions.forEach { localPlaybackPosition ->
-            syncPlaybackPosition(localPlaybackPosition)
+        val sorted = buildList {
+            addAll(offlineRepository.movies.first().values.map { it.toLocalPlaybackPosition() })
+            addAll(offlineRepository.episodes.first().values.map { it.toLocalPlaybackPosition() })
+        }.sortedBy { it.mediaId }
+
+        val total = sorted.size
+        if (total > 0) {
+            val windowCount = (total + MAX_PER_RUN - 1) / MAX_PER_RUN
+            val windowIndex = Math.floorMod(nextWindowIndex.fetchAndIncrement(), windowCount.toLong()).toInt()
+            val start = windowIndex * MAX_PER_RUN
+            val end = minOf(start + MAX_PER_RUN, total)
+            val window = sorted.subList(start, end)
+            window.forEach { syncPlaybackPosition(it) }
         }
+
+        lastRunAtElapsedMs.store(SystemClock.elapsedRealtime())
     }
 
     private suspend fun syncPlaybackPosition(localPlaybackPosition: LocalPlaybackPosition) {
@@ -151,5 +182,11 @@ class SyncPlaybackPositionsHomeRefreshSideEffect @Inject constructor(
     private companion object {
         const val TAG = "PlaybackPositionSync"
         const val PROGRESS_TOLERANCE_PERCENT = 0.5
+        // At most one full sweep every 6 hours; combined with MAX_PER_RUN this
+        // bounds the request count regardless of how many downloads the user has.
+        const val MIN_INTERVAL_MS = 6L * 60L * 60L * 1000L
+        // Cap the number of getItemInfo calls per refresh so a user with many
+        // downloads does not trigger N requests on every resume.
+        const val MAX_PER_RUN = 25
     }
 }