playback: reconcile detached items during offline transitions

app/src/main/kotlin/com/subtracks/playback/PlaybackController.kt

@@ -1192,6 +1192,7 @@ class PlaybackController(
         windowFiltered = false
         lastPosition = null
         lastEdit = null
+        clearDetached()
         player?.run {
             stop()
             clear()
@@ -1674,7 +1675,17 @@ class PlaybackController(
             if (snapshot.size == 0L) return@withMutationLock
             val current = currentQueuePosition() ?: return@withMutationLock
             val detached = detachedWindow && currentPosition() == null
+            val detachedItem = if (detached) player.currentItem else null
             windowJob?.cancel()
+            if (offline && detachedItem != null && downloads.localUri(detachedItem.id) == null) {
+                val target = downloadedAtOrAfter(snapshot, current)
+                if (target == null) {
+                    stopLocked()
+                } else {
+                    loadWindow(target, autoplay = player.playWhenReady, startPositionMs = 0)
+                }
+                return@withMutationLock
+            }
             val target =
                 if (offline) {
                     downloadedAtOrAfter(snapshot, current) ?: if (detached) {
@@ -1686,6 +1697,13 @@ class PlaybackController(
                 } else {
                     current
                 }
+            if (detachedItem != null) {
+                val isLocal = player.itemUris().getOrNull(player.currentIndex)?.startsWith(FILE_SCHEME) == true
+                if (!isLocal) {
+                    val replacement = queueItemAt(snapshot, current)?.takeIf { it.id == detachedItem.id } ?: detachedItem
+                    player.replaceItem(player.currentIndex, replacement)
+                }
+            }
             queueRepository.setCursor(target)
             if (preserveDetachedWindow(snapshot, target)) return@withMutationLock
             if (target == current) {

app/src/test/kotlin/com/subtracks/playback/PlaybackControllerTest.kt

@@ -1777,6 +1777,25 @@ class PlaybackControllerTest {
         assertEquals(null, controller.state.value.item)
     }
 
+    @Test
+    fun stoppingWhileDetachedClearsItsIdentityAndLaterPosition() {
+        seedPlaylist(3)
+        controller.playPlaylist(1, "p1", 1)
+        await { handle.currentItem?.id == "s2" }
+        val point = runBlocking { queues.captureResetPoint() }
+        setPlaylist("s1", "s3")
+        runBlocking { queues.resetChangedOrigins(setOf(QueueOrigin(QueueKind.Playlist, 1, "p1")), point) }
+        await { handle.currentItem?.id == "s2" && handle.items.any { it.id == "s3" } }
+
+        controller.playAlbum(1, "missing", 0)
+        await { handle.operations.contains("clear") }
+        controller.cycleRepeat()
+        handle.emitEvents()
+
+        assertNull(controller.state.value.item)
+        assertNull(controller.state.value.position)
+    }
+
     @Test
     fun restoringAQueueFromAnotherSourceStopsIt() {
         seedAlbum(3, sourceId = 1)
@@ -3394,6 +3413,57 @@ class PlaybackControllerTest {
         )
     }
 
+    @Test
+    fun offlineDetachedCurrentThatIsNotDownloadedMovesToTheSurvivor() {
+        seedPlaylist(3)
+        markDownloaded(1, "s3")
+        controller.playPlaylist(1, "p1", 1)
+        await { handle.currentItem?.id == "s2" }
+        val point = runBlocking { queues.captureResetPoint() }
+        setPlaylist("s1", "s3")
+        runBlocking { queues.resetChangedOrigins(setOf(QueueOrigin(QueueKind.Playlist, 1, "p1")), point) }
+        await { handle.currentItem?.id == "s2" && handle.items.any { it.id == "s3" } }
+
+        setOffline()
+
+        await { handle.currentItem?.id == "s3" }
+        assertEquals(1L, controller.state.value.position)
+    }
+
+    @Test
+    fun offlineDetachedCurrentWithoutADownloadedSurvivorStops() {
+        seedPlaylist(3)
+        controller.playPlaylist(1, "p1", 1)
+        await { handle.currentItem?.id == "s2" }
+        val point = runBlocking { queues.captureResetPoint() }
+        setPlaylist("s1", "s3")
+        runBlocking { queues.resetChangedOrigins(setOf(QueueOrigin(QueueKind.Playlist, 1, "p1")), point) }
+        await { handle.currentItem?.id == "s2" && handle.items.any { it.id == "s3" } }
+
+        setOffline()
+
+        await { controller.state.value.item == null && handle.itemCount == 0 }
+    }
+
+    @Test
+    fun offlineDetachedCurrentThatWasDownloadedReplacesItsStreamUri() {
+        seedPlaylist(3)
+        markDownloaded(1, "s2")
+        markDownloaded(1, "s3")
+        controller.playPlaylist(1, "p1", 1)
+        await { handle.currentItem?.id == "s2" }
+        val point = runBlocking { queues.captureResetPoint() }
+        setPlaylist("s1", "s3")
+        runBlocking { queues.resetChangedOrigins(setOf(QueueOrigin(QueueKind.Playlist, 1, "p1")), point) }
+        await { handle.currentItem?.id == "s2" && handle.items.any { it.id == "s3" } }
+        handle.operations.clear()
+
+        setOffline()
+
+        await { handle.operations.contains("replaceItem(0, s2)") }
+        assertEquals("s2", handle.currentItem?.id)
+    }
+
     @Test
     fun offlineNextCrossesTheLoadedWindowBoundary() {
         seedAlbum(30, sourceId = 1)