address review: renumber moves from the window start and version the length cache

app/src/main/kotlin/com/subtracks/data/repo/QueueRepository.kt

@@ -21,6 +21,7 @@ const val QUEUE_CHUNK = 60
 private const val LENGTH_CACHE_LIMIT = 512
 
 private data class EntryLengthKey(
+    val version: Long,
     val sourceId: Long,
     val kind: QueueKind,
     val refId: String,
@@ -147,7 +148,7 @@ class QueueRepository(
         val loaded =
             db.useReaderConnection { transactor ->
                 transactor.deferredTransaction {
-                    val entries = dao.entries().map { ResolvedQueueEntry(it, lengthOf(it)) }
+                    val entries = dao.entries().map { ResolvedQueueEntry(it, lengthOf(it, version)) }
                     val row = dao.cursor()
                     val shuffled = row?.shuffleEnabled == true
                     val order = if (shuffled) loadShuffleOrder(row.shuffleSeed, entries.sumOf { it.length }) else null
@@ -386,8 +387,11 @@ class QueueRepository(
             }
         }
 
-    private suspend fun lengthOf(entry: QueueEntry): Long {
+    private suspend fun lengthOf(
-        val key = entry.lengthKey()
+        entry: QueueEntry,
+        version: Long,
+    ): Long {
+        val key = entry.lengthKey(version)
         lengthCache[key]?.let { return it }
         val length = entry.resolvedLength()
         if (lengthCache.size >= LENGTH_CACHE_LIMIT) lengthCache.clear()
@@ -395,8 +399,9 @@ class QueueRepository(
         return length
     }
 
-    private fun QueueEntry.lengthKey() =
+    private fun QueueEntry.lengthKey(version: Long) =
         EntryLengthKey(
+            version = version,
             sourceId = sourceId,
             kind = kind,
             refId = refId,

app/src/main/kotlin/com/subtracks/ui/playback/QueueScreen.kt

@@ -184,7 +184,7 @@ class QueueViewModel(
         viewModelScope.launch {
             playbackController.move(from, to)
             mutex.withLock {
-                val base = rows.firstOrNull()?.position ?: return@withLock
+                val base = rows.minOfOrNull { it.position } ?: return@withLock
                 // The loaded order already reflects the move, so only the positions need updating.
                 val updated =
                     rows.mapIndexed { index, row ->

app/src/test/kotlin/com/subtracks/ui/playback/QueueViewModelTest.kt

@@ -199,8 +199,30 @@ class QueueViewModelTest {
             viewModel.rows[13]
                 .song.song.id,
         )
-        assertEquals(QUEUE_WINDOW_ROWS, viewModel.rows.size)
+        assertEquals((220L..399L).toList(), viewModel.rows.map { it.position })
-        assertContiguous()
+    }
+
+    @Test
+    fun movingTheTopRowDownRenumbersFromTheWindowStart() {
+        runBlocking { seedSongs(400) }
+        controller.playAlbum(1, "al1", 100)
+        await { controller.state.value.position == 100L }
+
+        viewModel.open()
+        await { viewModel.ready }
+        extendToEnd()
+        assertEquals((220L..399L).toList(), viewModel.rows.map { it.position })
+
+        val from = viewModel.rows.first().position
+        viewModel.reorder(0, 5)
+        val to = dropTarget(viewModel.rows, index = 5, from = from)
+        viewModel.move(from, to)
+        await {
+            viewModel.rows.firstOrNull()?.position == 220L &&
+                viewModel.rows.lastOrNull()?.position == 399L
+        }
+
+        assertEquals((220L..399L).toList(), viewModel.rows.map { it.position })
     }
 
     @Test