playback: preserve null keys and ranged duplicate ranks

app/src/test/kotlin/com/subtracks/data/repo/QueueKeysetTest.kt

@@ -150,6 +150,18 @@ class QueueKeysetTest {
             assertTrue("backward keyset seeks", repository.keysetSeeks > beforeBackward)
         }
 
+    @Test
+    fun scanningAnAlbumWithNullDiscAndTrackForwardFallsBackToOffsetRows() =
+        runTest {
+            seedLibrary()
+            repository.replace(listOf(repository.albumEntry(1, "mixed")))
+            val snapshot = repository.snapshot()
+
+            val resolved = (0 until snapshot.size).map { repository.itemAt(snapshot, it)?.song?.id }
+
+            assertEquals(listOf("n1", "n2", "s1", "s2"), resolved)
+        }
+
     @Test
     fun scanningAnAlbumWithNullDiscAndTrackBackwardsResolvesEveryRow() =
         runTest {

app/src/test/kotlin/com/subtracks/data/repo/QueueRepositoryTest.kt

@@ -895,6 +895,24 @@ class QueueRepositoryTest {
             assertEquals(1L, repository.combinedContextIndexOf(snapshot, "s1"))
         }
 
+    @Test
+    fun contextIndexFindsADuplicateInsideTheEntryRange() =
+        runTest {
+            seedLibrary()
+            db.libraryDao().upsertPlaylists(listOf(playlist("duplicates", "Duplicates")))
+            db.libraryDao().upsertPlaylistSongs(
+                listOf(
+                    PlaylistSong(1, "duplicates", "s2", 10),
+                    PlaylistSong(1, "duplicates", "s1", 20),
+                    PlaylistSong(1, "duplicates", "s2", 30),
+                ),
+            )
+            val entry = repository.playlistEntry(1, "duplicates").copy(rangeStart = 1, rangeEnd = 2)
+            val snapshot = repository.snapshotAfter(listOf(entry))
+
+            assertEquals(1L, repository.combinedContextIndexOf(snapshot, "s2"))
+        }
+
     @Test
     fun contextIndexFallsBackToBoundedRowsForGenre() =
         runTest {