bound the downloads handed to the platform, and confirm bulk deletes

Two things a 3k-song playlist turned up, plus the hero's downloaded state.

- The platform runs about eight downloads at a time, but a bulk action handed it
  every song at once. Three thousand pending requests meant a notification flood,
  and a poll tick that rewrote every row's bytes/total, so the whole list churned
  ten times a second. Now a bulk action only records the songs and hands over at
  most IN_FLIGHT_LIMIT, oldest first, promoting the next as each finishes, so our
  row state mirrors what is actually running and a cancel only has to reach what
  is in flight.
- Cancelling was therefore unusable at that size. It now touches at most the
  in-flight requests instead of thousands, and the rows wait behind it.
- A queued row with no engine id is waiting its turn, not lost, so reconcile no
  longer re-enqueues the whole list on every pass; a row whose engine entry
  vanished goes back to waiting and the next promote picks it up. A song that
  cannot be handed over fails instead of being retried every tick.
- Requests follow the order the screen shows: artist songs resolve through the
  same albums ordering the artist page uses, so they were the one list that did
  not.
- The hero's fully-downloaded state shows the downloaded glyph rather than a bin,
  and tapping it asks before deleting, naming the album or playlist and the space
  it frees.

app/src/main/kotlin/com/subtracks/data/db/DownloadDao.kt

@@ -13,7 +13,7 @@ interface DownloadDao {
     @Query("SELECT * FROM song_downloads WHERE sourceId = :sourceId")
     fun downloads(sourceId: Long): Flow<List<SongDownload>>
 
-    @Query("SELECT * FROM song_downloads")
+    @Query("SELECT * FROM song_downloads ORDER BY rowid")
     suspend fun all(): List<SongDownload>
 
     @Query(

app/src/main/kotlin/com/subtracks/data/db/QueueDao.kt

@@ -163,9 +163,10 @@ interface QueueDao {
     ): List<String>
 
     @Query(
-        "SELECT id FROM songs WHERE sourceId = :sourceId " +
+        "SELECT songs.id FROM songs " +
-            "AND albumId IN (SELECT id FROM albums WHERE sourceId = :sourceId AND artistId = :artistId) " +
+            "JOIN albums ON albums.sourceId = songs.sourceId AND albums.id = songs.albumId " +
-            "ORDER BY albumId, disc, track, id",
+            "WHERE songs.sourceId = :sourceId AND albums.artistId = :artistId " +
+            "ORDER BY albums.year DESC, albums.name COLLATE NOCASE, albums.id, songs.disc, songs.track, songs.id",
     )
     suspend fun artistSongIds(
         sourceId: Long,

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

@@ -103,29 +103,64 @@ class DownloadRepository(
             showMessage(NO_ADDRESS)
             return@withContext
         }
-        if (!enqueueIfAbsent(sourceId, songId)) return@withContext
+        val promoted =
+            mutex.withLock {
+                if (!queueIfAbsentLocked(sourceId, songId)) return@withContext
+                promote()
+            }
         // The media is already with the platform, so this only has to happen while we are still
         // in the foreground: artwork is fetched by us, and it must not hold up the download.
-        fetchArtworkSafely(sourceId, listOf(songId))
+        fetchArtworkSafely(sourceId, promoted.map { it.songId })
     }
 
-    private suspend fun enqueueIfAbsent(
+    private suspend fun queueIfAbsentLocked(
-        sourceId: Long,
-        songId: String,
-    ): Boolean = mutex.withLock { enqueueIfAbsentLocked(sourceId, songId) }
-
-    private suspend fun enqueueIfAbsentLocked(
         sourceId: Long,
         songId: String,
     ): Boolean {
         if (alreadyDownloadingOrDownloaded(sourceId, songId)) return false
         val existing = db.downloadDao().find(sourceId, songId)
         existing?.engineId?.let(engine::cancel)
-        val url = sourceRepository.downloadUri(sourceId, songId) ?: return false
+        dir(sourceId).mkdirs()
-        enqueue(sourceId, songId, url)
+        file(sourceId, songId).delete()
+        db.downloadDao().upsert(SongDownload(sourceId = sourceId, songId = songId, status = DownloadStatus.Queued))
+        ensurePolling()
         return true
     }
 
+    /**
+     * Hands the platform as many waiting songs as it can run, oldest first, so the queue it holds
+     * mirrors the list on screen rather than the whole library. Everything else waits as a row
+     * without an engine id, and the next tick promotes it.
+     */
+    private suspend fun promote(): List<SongDownload> {
+        val rows = db.downloadDao().all()
+        val free = IN_FLIGHT_LIMIT - rows.count { it.status.isActive && it.engineId != null }
+        if (free <= 0) return emptyList()
+        val promoted = ArrayList<SongDownload>()
+        rows
+            .filter { it.status == DownloadStatus.Queued && it.engineId == null }
+            .take(free)
+            .forEach { row ->
+                val url = sourceRepository.downloadUri(row.sourceId, row.songId) ?: return@forEach
+                val title = db.libraryDao().songOnce(row.sourceId, row.songId)?.title ?: row.songId
+                val engineId =
+                    try {
+                        engine.enqueue(
+                            EngineRequest(uri = url, path = enginePath(row.sourceId, row.songId), title = title),
+                        )
+                    } catch (e: CancellationException) {
+                        throw e
+                    } catch (_: Exception) {
+                        // Leave it failed rather than waiting, or the next tick would retry it forever.
+                        markFailed(row, STOPPED)
+                        return@forEach
+                    }
+                db.downloadDao().upsert(row.copy(engineId = engineId))
+                promoted += row
+            }
+        return promoted
+    }
+
     suspend fun remove(
         sourceId: Long,
         songId: String,
@@ -167,20 +202,23 @@ class DownloadRepository(
         }
         // Under one lock, so a cancel that lands mid-loop waits for the queue to be complete and
         // then removes all of it, rather than missing the songs enqueued after it looked.
-        // ponytail: the lock is held for the whole loop, so cancel latency and the poll tick scale
+        // ponytail: the lock is held for the whole insert pass, so cancel latency scales with the
-        // with the list length; a per-list cancel generation would lift that if it ever bites.
+        // list length; the promote below hands over at most IN_FLIGHT_LIMIT, which is what keeps
-        mutex.withLock {
+        // the platform's queue (and our poll writes) bounded.
-            songIds.forEach { songId ->
+        val promoted =
-                try {
+            mutex.withLock {
-                    enqueueIfAbsentLocked(sourceId, songId)
+                songIds.forEach { songId ->
-                } catch (e: CancellationException) {
+                    try {
-                    throw e
+                        queueIfAbsentLocked(sourceId, songId)
-                } catch (_: Exception) {
+                    } catch (e: CancellationException) {
-                    // One song failing to enqueue must not abandon the rest of the list.
+                        throw e
+                    } catch (_: Exception) {
+                        // One song failing to queue must not abandon the rest of the list.
+                    }
                 }
+                promote()
             }
-        }
+        fetchArtworkSafely(sourceId, promoted.map { it.songId })
-        fetchArtworkSafely(sourceId, songIds)
     }
 
     suspend fun applyAction(
@@ -194,6 +232,20 @@ class DownloadRepository(
         BulkDownloadAction.Delete -> deleteAll(sourceId, list, refId)
     }
 
+    suspend fun downloadedBytes(
+        sourceId: Long,
+        list: DownloadList,
+        refId: String,
+    ): Long =
+        withContext(dispatcher) {
+            val songIds = songIds(sourceId, list, refId).toHashSet()
+            db
+                .downloadDao()
+                .all()
+                .filter { it.sourceId == sourceId && it.songId in songIds && it.status == DownloadStatus.Completed }
+                .sumOf { file(it.sourceId, it.songId).length() }
+        }
+
     suspend fun cancelAll(
         sourceId: Long,
         list: DownloadList,
@@ -234,15 +286,15 @@ class DownloadRepository(
 
     suspend fun reconcile() =
         withContext(dispatcher) {
-            val resumed =
+            val promoted =
                 mutex.withLock {
                     val rows = db.downloadDao().all()
-                    val resumed = reconcileRows(rows)
+                    reconcileRows(rows)
                     sweep(rows)
                     ensurePolling()
-                    resumed
+                    promote()
                 }
-            resumed.forEach { fetchArtworkSafely(it.sourceId, listOf(it.songId)) }
+            warmArtwork(promoted)
         }
 
     @OptIn(ExperimentalCoroutinesApi::class)
@@ -316,59 +368,38 @@ class DownloadRepository(
                     .toSet()
             }
 
-    private suspend fun enqueue(
+    private suspend fun recover(row: SongDownload) {
-        sourceId: Long,
-        songId: String,
-        url: String,
-    ) {
-        dir(sourceId).mkdirs()
-        file(sourceId, songId).delete()
-        val title = db.libraryDao().songOnce(sourceId, songId)?.title ?: songId
-        val engineId =
-            engine.enqueue(
-                EngineRequest(uri = url, path = enginePath(sourceId, songId), title = title),
-            )
-        db.downloadDao().upsert(
-            SongDownload(sourceId = sourceId, songId = songId, status = DownloadStatus.Queued, engineId = engineId),
-        )
-        ensurePolling()
-    }
-
-    private suspend fun recover(row: SongDownload): Boolean =
         when (row.status) {
             DownloadStatus.Completed -> {
                 if (!file(row.sourceId, row.songId).exists()) markFailed(row, MISSING_FILE)
-                false
             }
 
+            // Waiting rows have no engine id by design; the next promote hands them over.
             DownloadStatus.Queued -> {
-                if (sourceRepository.activeSourceIdOnce() != row.sourceId) return false
+                if (row.engineId != null) db.downloadDao().upsert(row.copy(engineId = null))
-                val url = sourceRepository.downloadUri(row.sourceId, row.songId) ?: return false
-                enqueue(row.sourceId, row.songId, url)
-                true
             }
 
             DownloadStatus.Running -> {
                 markFailed(row, STOPPED)
-                false
             }
 
             DownloadStatus.Failed -> {
-                false
+                Unit
             }
         }
+    }
 
-    private suspend fun reconcileRows(rows: List<SongDownload>): List<SongDownload> {
+    private suspend fun reconcileRows(rows: List<SongDownload>) {
-        val resumed = ArrayList<SongDownload>()
         rows.forEach { row ->
             val state = row.engineId?.let(engine::download)
-            if (state == null) {
+            if (state == null) recover(row) else apply(row, state)
-                if (recover(row)) resumed += row
+        }
-            } else {
+    }
-                apply(row, state)
+
-            }
+    private suspend fun warmArtwork(promoted: List<SongDownload>) {
+        promoted.groupBy { it.sourceId }.forEach { (sourceId, rows) ->
+            fetchArtworkSafely(sourceId, rows.map { it.songId })
         }
-        return resumed
     }
 
     private suspend fun removeRow(
@@ -458,16 +489,19 @@ class DownloadRepository(
             scope.launch {
                 while (true) {
                     delay(POLL_MS)
-                    val resumed =
+                    val promoted =
                         mutex.withLock {
                             val sourceId = sourceRepository.activeSourceIdOnce()
                             val active = db.downloadDao().all().filter { it.status.isActive && it.sourceId == sourceId }
                             if (active.isEmpty()) return@launch
                             reconcileRows(active)
+                            promote()
                         }
                     // Fetching artwork here would hold up the next tick, and with it the progress
                     // the queue is mirrored from.
-                    resumed.forEach { row -> scope.launch { fetchArtworkSafely(row.sourceId, listOf(row.songId)) } }
+                    promoted.groupBy { it.sourceId }.forEach { (sourceId, rows) ->
+                        scope.launch { fetchArtworkSafely(sourceId, rows.map { it.songId }) }
+                    }
                 }
             }
     }
@@ -507,6 +541,7 @@ class DownloadRepository(
         const val ENGINE_DIR = "downloads"
         const val NO_MEDIA = ".nomedia"
         const val POLL_MS = 1_000L
+        const val IN_FLIGHT_LIMIT = 8
         const val MISSING_FILE = "The downloaded file is missing"
         const val NO_ADDRESS = "Can't download: the server address is unavailable"
         const val EMPTY_LIST = "Nothing left to download from this list"

app/src/main/kotlin/com/subtracks/ui/components/DeleteDownloadsDialog.kt

@@ -0,0 +1,40 @@
+package com.subtracks.ui.components
+
+import androidx.compose.material3.AlertDialog
+import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
+import androidx.compose.runtime.Composable
+
+fun formatBytes(bytes: Long): String {
+    val units = listOf("B", "kB", "MB", "GB", "TB")
+    var value = bytes.toDouble()
+    var unit = 0
+    while (value >= 1000 && unit < units.lastIndex) {
+        value /= 1000
+        unit++
+    }
+    return if (unit == 0) "$bytes ${units[unit]}" else "${"%.1f".format(value)} ${units[unit]}"
+}
+
+@Composable
+fun DeleteDownloadsDialog(
+    name: String,
+    bytes: Long,
+    onConfirm: () -> Unit,
+    onDismiss: () -> Unit,
+) {
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text("Delete downloads") },
+        text = { Text("Delete the downloaded songs of \"$name\"? This frees ${formatBytes(bytes)}.") },
+        confirmButton = {
+            TextButton(
+                onClick = {
+                    onConfirm()
+                    onDismiss()
+                },
+            ) { Text("Delete") }
+        },
+        dismissButton = { TextButton(onClick = onDismiss) { Text("Cancel") } },
+    )
+}

app/src/main/kotlin/com/subtracks/ui/components/HeroDetailScaffold.kt

@@ -28,8 +28,8 @@ import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.rounded.ArrowBack
 import androidx.compose.material.icons.rounded.Close
-import androidx.compose.material.icons.rounded.Delete
 import androidx.compose.material.icons.rounded.Download
+import androidx.compose.material.icons.rounded.DownloadDone
 import androidx.compose.material.icons.rounded.MoreHoriz
 import androidx.compose.material.icons.rounded.PlayArrow
 import androidx.compose.material.icons.rounded.Shuffle
@@ -291,7 +291,11 @@ fun HeroHeader(
             ) {
                 when (downloadStatus.action()) {
                     BulkDownloadAction.Delete -> {
-                        Icon(Icons.Rounded.Delete, contentDescription = "Delete download", modifier = Modifier.offset(y = 1.5.dp))
+                        Icon(
+                            imageVector = Icons.Rounded.DownloadDone,
+                            contentDescription = "Delete download",
+                            modifier = Modifier.size(28.dp).offset(y = 1.5.dp),
+                        )
                     }
 
                     BulkDownloadAction.Cancel -> {

app/src/main/kotlin/com/subtracks/ui/library/AlbumDetailScreen.kt

@@ -13,7 +13,10 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.text.font.FontWeight
@@ -31,12 +34,14 @@ import com.subtracks.data.model.SongDownload
 import com.subtracks.data.source.StarType
 import com.subtracks.playback.PlaybackController
 import com.subtracks.ui.components.ContextMenuHost
+import com.subtracks.ui.components.DeleteDownloadsDialog
 import com.subtracks.ui.components.HeroDetailScaffold
 import com.subtracks.ui.components.HeroHeader
 import com.subtracks.ui.components.ItemActions
 import com.subtracks.ui.components.MenuTarget
 import com.subtracks.ui.theme.ArtworkColors
 import com.subtracks.ui.theme.rememberArtworkColors
+import kotlinx.coroutines.launch
 import org.koin.compose.koinInject
 import org.koin.compose.viewmodel.koinViewModel
 import org.koin.core.parameter.parametersOf
@@ -60,6 +65,8 @@ fun AlbumDetailRoute(
     val discs by viewModel.discs.collectAsStateWithLifecycle(initialValue = emptyList())
     val downloads by viewModel.downloads.collectAsStateWithLifecycle()
     val downloadStatus by viewModel.downloadStatus.collectAsStateWithLifecycle()
+    val scope = rememberCoroutineScope()
+    var pendingDelete by remember { mutableStateOf<Long?>(null) }
     val playback by playbackController.state.collectAsStateWithLifecycle()
     val context = playback.context
     val shortcutArt = remember(coverArtId) { coverArtId?.let { viewModel.coverArt(it, true) } }
@@ -84,7 +91,13 @@ fun AlbumDetailRoute(
         artwork = rememberArtworkColors(shortcutArt ?: viewModel.coverArt(album?.coverArt, true), THEME_TRANSITION_MS),
         downloads = downloads,
         downloadStatus = downloadStatus,
-        onDownloadAction = viewModel::onDownloadAction,
+        onDownloadAction = { action ->
+            if (action == BulkDownloadAction.Delete) {
+                scope.launch { pendingDelete = viewModel.downloadedBytes() }
+            } else {
+                viewModel.onDownloadAction(action)
+            }
+        },
         onBack = onBack,
         onSongClick = viewModel::play,
         onSongLongClick = { contextMenuHost?.show(it, actions) },
@@ -98,6 +111,15 @@ fun AlbumDetailRoute(
                 ?.let { id -> { onViewArtist(id) } },
         playingSongId = playback.item?.id.takeIf { context?.kind == QueueKind.Album && context.refId == albumId },
     )
+
+    pendingDelete?.let { bytes ->
+        DeleteDownloadsDialog(
+            name = album?.name.orEmpty(),
+            bytes = bytes,
+            onConfirm = { viewModel.onDownloadAction(BulkDownloadAction.Delete) },
+            onDismiss = { pendingDelete = null },
+        )
+    }
 }
 
 @Composable

app/src/main/kotlin/com/subtracks/ui/library/AlbumDetailViewModel.kt

@@ -47,6 +47,8 @@ class AlbumDetailViewModel(
             .flatMapLatest { downloadRepository.status(it, DownloadList.Album, albumId) }
             .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), ListDownloadStatus())
 
+    suspend fun downloadedBytes(): Long = downloadRepository.downloadedBytes(sourceId.first(), DownloadList.Album, albumId)
+
     fun onDownloadAction(action: BulkDownloadAction) {
         viewModelScope.launch {
             downloadRepository.applyAction(sourceId.first(), DownloadList.Album, albumId, action)

app/src/main/kotlin/com/subtracks/ui/library/PlaylistDetailScreen.kt

@@ -5,6 +5,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
@@ -21,12 +22,14 @@ import com.subtracks.data.model.SongDownload
 import com.subtracks.data.source.StarType
 import com.subtracks.playback.PlaybackController
 import com.subtracks.ui.components.ContextMenuHost
+import com.subtracks.ui.components.DeleteDownloadsDialog
 import com.subtracks.ui.components.HeroDetailScaffold
 import com.subtracks.ui.components.HeroHeader
 import com.subtracks.ui.components.ItemActions
 import com.subtracks.ui.components.MenuTarget
 import com.subtracks.ui.theme.ArtworkColors
 import com.subtracks.ui.theme.rememberArtworkColors
+import kotlinx.coroutines.launch
 import org.koin.compose.koinInject
 import org.koin.compose.viewmodel.koinViewModel
 import org.koin.core.parameter.parametersOf
@@ -48,6 +51,8 @@ fun PlaylistDetailRoute(
     val playlist by viewModel.playlist.collectAsStateWithLifecycle(initialValue = null)
     val downloads by viewModel.downloads.collectAsStateWithLifecycle()
     val downloadStatus by viewModel.downloadStatus.collectAsStateWithLifecycle()
+    val scope = rememberCoroutineScope()
+    var pendingDelete by remember { mutableStateOf<Long?>(null) }
     val playback by playbackController.state.collectAsStateWithLifecycle()
     val context = playback.context
     val actions =
@@ -70,7 +75,13 @@ fun PlaylistDetailRoute(
         artwork = rememberArtworkColors(viewModel.coverArt(playlist?.coverArt, true), THEME_TRANSITION_MS),
         downloads = downloads,
         downloadStatus = downloadStatus,
-        onDownloadAction = viewModel::onDownloadAction,
+        onDownloadAction = { action ->
+            if (action == BulkDownloadAction.Delete) {
+                scope.launch { pendingDelete = viewModel.downloadedBytes() }
+            } else {
+                viewModel.onDownloadAction(action)
+            }
+        },
         onBack = onBack,
         onSongClick = viewModel::play,
         onSongLongClick = { contextMenuHost?.show(it, actions) },
@@ -79,6 +90,15 @@ fun PlaylistDetailRoute(
         onMore = { playlist?.let { contextMenuHost?.show(MenuTarget.Playlist(it, viewModel.coverArt(it.coverArt, true)), actions) } },
         playingSongId = playback.item?.id.takeIf { context?.kind == QueueKind.Playlist && context.refId == playlistId },
     )
+
+    pendingDelete?.let { bytes ->
+        DeleteDownloadsDialog(
+            name = playlist?.name.orEmpty(),
+            bytes = bytes,
+            onConfirm = { viewModel.onDownloadAction(BulkDownloadAction.Delete) },
+            onDismiss = { pendingDelete = null },
+        )
+    }
 }
 
 @Composable

app/src/main/kotlin/com/subtracks/ui/library/PlaylistDetailViewModel.kt

@@ -51,6 +51,8 @@ class PlaylistDetailViewModel(
             .flatMapLatest { downloadRepository.status(it, DownloadList.Playlist, playlistId) }
             .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), ListDownloadStatus())
 
+    suspend fun downloadedBytes(): Long = downloadRepository.downloadedBytes(sourceId.first(), DownloadList.Playlist, playlistId)
+
     fun onDownloadAction(action: BulkDownloadAction) {
         viewModelScope.launch {
             downloadRepository.applyAction(sourceId.first(), DownloadList.Playlist, playlistId, action)

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

@@ -560,11 +560,10 @@ class DownloadRepositoryTest {
     fun cancellingWhileAListIsStillQueuingRemovesTheWholeList() =
         runTest {
             seedLibrary()
-            seedSongs(3..40)
+            seedSongs(3..400)
-            engine.enqueueDelayMs = 1
 
             val queuing = launch(Dispatchers.IO) { repository.downloadAll(1, DownloadList.Album, "al1") }
-            await { engine.requests.size >= 3 }
+            await { allRows().size >= 50 }
             val cancelling = launch(Dispatchers.IO) { repository.cancelAll(1, DownloadList.Album, "al1") }
             queuing.join()
             cancelling.join()
@@ -572,6 +571,50 @@ class DownloadRepositoryTest {
             assertTrue("expected the whole list cancelled, ${db.downloadDao().all().size} rows left", db.downloadDao().all().isEmpty())
         }
 
+    @Test
+    fun aLongListHandsThePlatformOnlyTheInFlightLimit() =
+        runTest {
+            seedLibrary()
+            seedSongs(3..40)
+
+            runBlocking { repository.downloadAll(1, DownloadList.Album, "al1") }
+
+            assertEquals(8, engine.requests.size)
+            assertEquals(32, db.downloadDao().all().count { it.status == DownloadStatus.Queued && it.engineId == null })
+        }
+
+    @Test
+    fun finishingADownloadHandsOverTheNextSongInListOrder() =
+        runTest {
+            seedLibrary()
+            seedSongs(3..12)
+            runBlocking { repository.downloadAll(1, DownloadList.Album, "al1") }
+            val first = engine.requests.first()
+
+            engine.complete(first.first, total = 10)
+            writeFile(1, first.second.path.substringAfterLast('/'), "audio")
+            runBlocking { repository.reconcile() }
+
+            assertEquals(9, engine.requests.size)
+            assertEquals((1..9).map { "s$it" }, requestedSongIds())
+        }
+
+    @Test
+    fun reconcilingAWaitingListDoesNotHandItOverWholesale() =
+        runTest {
+            seedLibrary()
+            seedSongs(3..40)
+            runBlocking {
+                (1..40).forEach { track ->
+                    db.downloadDao().upsert(SongDownload(1, "s$track", DownloadStatus.Queued))
+                }
+            }
+
+            runBlocking { repository.reconcile() }
+
+            assertEquals(8, engine.requests.size)
+        }
+
     @Test
     fun oneSongFailingToQueueDoesNotAbandonTheRest() =
         runTest {
@@ -613,6 +656,19 @@ class DownloadRepositoryTest {
             assertNull(row(1, "s2"))
         }
 
+    @Test
+    fun downloadedBytesCountsTheCompletedFilesOfTheList() =
+        runTest {
+            seedLibrary()
+            writeFile(1, "s1", "12345")
+            db.downloadDao().upsert(SongDownload(1, "s1", DownloadStatus.Completed, engineId = 11))
+            writeFile(1, "s2", "1234")
+            db.downloadDao().upsert(SongDownload(1, "s2", DownloadStatus.Running, engineId = 22))
+            writeFile(1, "s3", "123")
+
+            assertEquals(5L, repository.downloadedBytes(1, DownloadList.Album, "al1"))
+        }
+
     private fun requestedSongIds(): List<String> = engine.requests.map { it.second.path.substringAfterLast('/') }
 
     private fun seedSongs(tracks: IntRange) {

app/src/test/kotlin/com/subtracks/ui/components/DeleteDownloadsDialogTest.kt

@@ -0,0 +1,69 @@
+package com.subtracks.ui.components
+
+import androidx.activity.ComponentActivity
+import androidx.compose.ui.test.assertIsDisplayed
+import androidx.compose.ui.test.junit4.v2.createAndroidComposeRule
+import androidx.compose.ui.test.onNodeWithText
+import androidx.compose.ui.test.performClick
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.subtracks.ui.theme.SubtracksTheme
+import org.junit.Assert.assertEquals
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.annotation.GraphicsMode
+
+@RunWith(AndroidJUnit4::class)
+@GraphicsMode(GraphicsMode.Mode.NATIVE)
+class DeleteDownloadsDialogTest {
+    @get:Rule
+    val composeRule = createAndroidComposeRule<ComponentActivity>()
+
+    @Test
+    fun theDialogNamesTheThingAndTheSpaceItFrees() {
+        render(bytes = 1_500_000)
+
+        composeRule.onNodeWithText("Kid A", substring = true).assertIsDisplayed()
+        composeRule.onNodeWithText("1.5 MB", substring = true).assertIsDisplayed()
+    }
+
+    @Test
+    fun deleteConfirms() {
+        var confirms = 0
+        render(onConfirm = { confirms++ })
+
+        composeRule.onNodeWithText("Delete").performClick()
+
+        assertEquals(1, confirms)
+    }
+
+    @Test
+    fun cancelDismisses() {
+        var dismisses = 0
+        render(onDismiss = { dismisses++ })
+
+        composeRule.onNodeWithText("Cancel").performClick()
+
+        assertEquals(1, dismisses)
+    }
+
+    @Test
+    fun bytesReadAsUnits() {
+        assertEquals("512 B", formatBytes(512))
+        assertEquals("1.0 kB", formatBytes(1_024))
+        assertEquals("1.5 MB", formatBytes(1_500_000))
+        assertEquals("2.0 GB", formatBytes(2_000_000_000))
+    }
+
+    private fun render(
+        bytes: Long = 0,
+        onConfirm: () -> Unit = {},
+        onDismiss: () -> Unit = {},
+    ) {
+        composeRule.setContent {
+            SubtracksTheme {
+                DeleteDownloadsDialog(name = "Kid A", bytes = bytes, onConfirm = onConfirm, onDismiss = onDismiss)
+            }
+        }
+    }
+}