refactor(android): migrate 8 per-screen UiStates to shared UiState<T>

History/Hidden/Requests/PlaylistsList/AddToPlaylist/Home/Liked/Library
each had its own sealed interface with Loading/Empty/Success(payload)/
Error variants. Collapsed to the generic shared/UiState<T> introduced
in the prior commit. Library carries two lists (artists + albums) so
its payload is wrapped in a new LibraryData record; the test was
updated to assert against UiState.Success<LibraryData>.

The 3 detail screens (Artist/Album/Playlist Detail) keep their own
sealed interfaces for now since they include a Loading(seed: ...)
variant that does not fit UiState<T>.

android/app/src/main/java/com/fabledsword/minstrel/history/ui/HistoryTab.kt

@@ -23,6 +23,7 @@ import com.fabledsword.minstrel.history.data.HistoryEntry
 import com.fabledsword.minstrel.history.data.HistoryRepository
 import com.fabledsword.minstrel.models.TrackRef
 import com.fabledsword.minstrel.player.PlayerController
+import com.fabledsword.minstrel.shared.UiState
 import com.fabledsword.minstrel.shared.widgets.TrackRow
 import com.fabledsword.minstrel.shared.widgets.EmptyState
 import com.fabledsword.minstrel.shared.widgets.LoadingCentered
@@ -49,13 +50,6 @@ import javax.inject.Inject
 
 private const val SHARE_STOP_TIMEOUT_MS = 5_000L
 
-sealed interface HistoryUiState {
-    data object Loading : HistoryUiState
-    data object Empty : HistoryUiState
-    data class Success(val entries: List<HistoryEntry>) : HistoryUiState
-    data class Error(val message: String) : HistoryUiState
-}
-
 // ─── ViewModel ───────────────────────────────────────────────────────
 
 @HiltViewModel
@@ -72,18 +66,18 @@ class HistoryTabViewModel @Inject constructor(
      * only when there's nothing cached AND the refresh failed — a
      * failed refresh over a populated cache stays silent.
      */
-    val uiState: StateFlow<HistoryUiState> =
+    val uiState: StateFlow<UiState<List<HistoryEntry>>> =
         combine(repository.observeHistory(), refreshError) { page, err ->
             when {
-                page != null && page.entries.isNotEmpty() -> HistoryUiState.Success(page.entries)
+                page != null && page.entries.isNotEmpty() -> UiState.Success(page.entries)
-                page != null -> HistoryUiState.Empty
+                page != null -> UiState.Empty
-                err != null -> HistoryUiState.Error(err)
+                err != null -> UiState.Error(err)
-                else -> HistoryUiState.Loading
+                else -> UiState.Loading
             }
         }.stateIn(
             scope = viewModelScope,
             started = SharingStarted.WhileSubscribed(SHARE_STOP_TIMEOUT_MS),
-            initialValue = HistoryUiState.Loading,
+            initialValue = UiState.Loading,
         )
 
     init {
@@ -117,17 +111,17 @@ fun HistoryTab(
     val playingTrackId = playerState.currentTrack?.id
     PullToRefreshScaffold(onRefresh = { viewModel.refresh().join() }) {
         when (val s = state) {
-            HistoryUiState.Loading -> LoadingCentered()
+            UiState.Loading -> LoadingCentered()
-            HistoryUiState.Empty -> EmptyState(
+            UiState.Empty -> EmptyState(
                 title = "No listening history yet",
                 body = "Play something — your recent plays will show up here.",
             )
-            is HistoryUiState.Error -> EmptyState(
+            is UiState.Error -> EmptyState(
                 title = "Couldn't load history",
                 body = s.message,
             )
-            is HistoryUiState.Success -> HistoryList(
+            is UiState.Success -> HistoryList(
-                entries = s.entries,
+                entries = s.data,
                 playingTrackId = playingTrackId,
                 onPlay = viewModel::playTrack,
                 onNavigateToAlbum = onNavigateToAlbum,

android/app/src/main/java/com/fabledsword/minstrel/home/ui/HomeScreen.kt

@@ -67,6 +67,7 @@ import com.fabledsword.minstrel.playlists.data.PlaylistsRepository
 import com.fabledsword.minstrel.playlists.widgets.OfflinePoolCard
 import com.fabledsword.minstrel.playlists.widgets.PlaylistCard
 import com.fabledsword.minstrel.playlists.widgets.PlaylistPlaceholderCard
+import com.fabledsword.minstrel.shared.UiState
 import com.fabledsword.minstrel.shared.widgets.EmptyState
 import com.fabledsword.minstrel.shared.widgets.HorizontalScrollRow
 import com.fabledsword.minstrel.shared.widgets.MainAppBarActions
@@ -113,13 +114,6 @@ data class HomeSections(
             lastPlayedArtists.isEmpty()
 }
 
-sealed interface HomeUiState {
-    data object Loading : HomeUiState
-    data object Empty : HomeUiState
-    data class Success(val sections: HomeSections) : HomeUiState
-    data class Error(val message: String) : HomeUiState
-}
-
 // ─── ViewModel ───────────────────────────────────────────────────────
 
 @HiltViewModel
@@ -204,10 +198,10 @@ class HomeViewModel @Inject constructor(
         status.join()
     }
 
-    val uiState: StateFlow<HomeUiState> = combineHomeFlows().stateIn(
+    val uiState: StateFlow<UiState<HomeSections>> = combineHomeFlows().stateIn(
         scope = viewModelScope,
         started = SharingStarted.WhileSubscribed(SHARE_STOP_TIMEOUT_MS),
-        initialValue = HomeUiState.Loading,
+        initialValue = UiState.Loading,
     )
 
     /**
@@ -236,8 +230,8 @@ class HomeViewModel @Inject constructor(
     private fun combineHomeFlows() =
         observeHomeSections().combine(playlistsRepository.observeAll()) { sections, playlists ->
             val merged = sections.copy(playlists = playlists)
-            if (merged.isAllEmpty) HomeUiState.Empty else HomeUiState.Success(merged)
+            if (merged.isAllEmpty) UiState.Empty else UiState.Success(merged)
-        }.catch { e -> emit(HomeUiState.Error(ErrorCopy.fromThrowable(e))) }
+        }.catch { e -> emit(UiState.Error(ErrorCopy.fromThrowable(e))) }
 }
 
 // ─── Screen ──────────────────────────────────────────────────────────
@@ -276,19 +270,19 @@ fun HomeScreen(
         ) {
             Crossfade(targetState = state, label = "home-state") { s ->
                 when (s) {
-                    HomeUiState.Loading -> HomeSkeletonContent()
+                    UiState.Loading -> HomeSkeletonContent()
-                    HomeUiState.Empty -> EmptyState(
+                    UiState.Empty -> EmptyState(
                         title = "Welcome to Minstrel",
                         body = "Nothing to show yet — scan a folder in your server " +
                             "settings, then come back here for system playlists " +
                             "and recommendations.",
                     )
-                    is HomeUiState.Error -> EmptyState(
+                    is UiState.Error -> EmptyState(
                         title = "Couldn't load home",
                         body = s.message,
                     )
-                    is HomeUiState.Success -> HomeSuccessContent(
+                    is UiState.Success -> HomeSuccessContent(
-                        sections = s.sections,
+                        sections = s.data,
                         systemStatus = systemStatus,
                         offline = offline,
                         onAlbumClick = { id -> navController.navigate(AlbumDetail(id)) },

android/app/src/main/java/com/fabledsword/minstrel/library/ui/LibraryScreen.kt

@@ -46,6 +46,7 @@ import com.fabledsword.minstrel.nav.ArtistDetail
 import com.fabledsword.minstrel.nav.Library
 import com.composables.icons.lucide.Lucide
 import com.composables.icons.lucide.Shuffle
+import com.fabledsword.minstrel.shared.UiState
 import com.fabledsword.minstrel.shared.widgets.EmptyState
 import com.fabledsword.minstrel.shared.widgets.ErrorRetry
 import com.fabledsword.minstrel.shared.widgets.MainAppBarActions
@@ -151,18 +152,18 @@ private fun ArtistsTab(
     PullToRefreshScaffold(onRefresh = { viewModel.refresh().join() }) {
         Crossfade(targetState = state, label = "library-artists") { s ->
             when (s) {
-                LibraryUiState.Loading -> SkeletonArtistsGrid()
+                UiState.Loading -> SkeletonArtistsGrid()
-                LibraryUiState.Empty -> EmptyState(
+                UiState.Empty -> EmptyState(
                     title = "No artists yet",
                     body = "Scan a folder in your server settings to " +
                         "populate the library.",
                 )
-                is LibraryUiState.Error -> ErrorRetry(
+                is UiState.Error -> ErrorRetry(
                     message = s.message,
                     onRetry = { viewModel.refresh() },
                 )
-                is LibraryUiState.Success -> ArtistsGrid(
+                is UiState.Success -> ArtistsGrid(
-                    artists = s.artists,
+                    artists = s.data.artists,
                     onArtistClick = { id -> navController.navigate(ArtistDetail(id)) },
                 )
             }
@@ -179,18 +180,18 @@ private fun AlbumsTab(
     PullToRefreshScaffold(onRefresh = { viewModel.refresh().join() }) {
         Crossfade(targetState = state, label = "library-albums") { s ->
             when (s) {
-                LibraryUiState.Loading -> SkeletonAlbumsGrid()
+                UiState.Loading -> SkeletonAlbumsGrid()
-                LibraryUiState.Empty -> EmptyState(
+                UiState.Empty -> EmptyState(
                     title = "No albums yet",
                     body = "Scan a folder in your server settings to " +
                         "populate the library.",
                 )
-                is LibraryUiState.Error -> ErrorRetry(
+                is UiState.Error -> ErrorRetry(
                     message = s.message,
                     onRetry = { viewModel.refresh() },
                 )
-                is LibraryUiState.Success -> AlbumsGrid(
+                is UiState.Success -> AlbumsGrid(
-                    albums = s.albums,
+                    albums = s.data.albums,
                     onAlbumClick = { id -> navController.navigate(AlbumDetail(id)) },
                 )
             }

android/app/src/main/java/com/fabledsword/minstrel/library/ui/LibraryUiState.kt

@@ -4,23 +4,12 @@ import com.fabledsword.minstrel.models.AlbumRef
 import com.fabledsword.minstrel.models.ArtistRef
 
 /**
- * UI state for the Library screen. Sealed interface — each composable
+ * Payload carried by `UiState.Success` for the Library screen. The
- * branch handles exactly the cases it cares about; the compiler
+ * grid renders artists and albums side-by-side, so the state wraps
- * enforces exhaustiveness.
+ * both lists into a single value; the generic `shared/UiState<T>` then
- *
+ * provides Loading / Empty / Error around it.
- * - Loading: initial state before the first DAO emission.
- * - Empty: DAO emitted but the cache holds no artists and no albums
- *   (fresh install, never synced).
- * - Success: DAO emitted with content.
- * - Error: an exception bubbled from the DAO/repository layer; the
- *   message is surfaced as-is in the empty-state copy.
  */
-sealed interface LibraryUiState {
+data class LibraryData(
-    data object Loading : LibraryUiState
+    val artists: List<ArtistRef>,
-    data object Empty : LibraryUiState
+    val albums: List<AlbumRef>,
-    data class Success(
+)
-        val artists: List<ArtistRef>,
-        val albums: List<AlbumRef>,
-    ) : LibraryUiState
-    data class Error(val message: String) : LibraryUiState
-}

android/app/src/main/java/com/fabledsword/minstrel/library/ui/LibraryViewModel.kt

@@ -5,6 +5,7 @@ import androidx.lifecycle.viewModelScope
 import com.fabledsword.minstrel.api.ErrorCopy
 import com.fabledsword.minstrel.cache.sync.SyncController
 import com.fabledsword.minstrel.library.data.LibraryRepository
+import com.fabledsword.minstrel.shared.UiState
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.SharingStarted
@@ -24,24 +25,24 @@ class LibraryViewModel @Inject constructor(
     private val player: com.fabledsword.minstrel.player.PlayerController,
 ) : ViewModel() {
 
-    val uiState: StateFlow<LibraryUiState> =
+    val uiState: StateFlow<UiState<LibraryData>> =
         combine(
             repository.observeArtists(),
             repository.observeAlbums(),
         ) { artists, albums ->
             if (artists.isEmpty() && albums.isEmpty()) {
-                LibraryUiState.Empty
+                UiState.Empty
             } else {
-                LibraryUiState.Success(artists, albums)
+                UiState.Success(LibraryData(artists, albums))
             }
         }
             .catch { e ->
-                emit(LibraryUiState.Error(ErrorCopy.fromThrowable(e)))
+                emit(UiState.Error(ErrorCopy.fromThrowable(e)))
             }
             .stateIn(
                 scope = viewModelScope,
                 started = SharingStarted.WhileSubscribed(SHARE_STOP_TIMEOUT_MS),
-                initialValue = LibraryUiState.Loading,
+                initialValue = UiState.Loading,
             )
 
     /**

android/app/src/main/java/com/fabledsword/minstrel/likes/ui/LikedTab.kt

@@ -35,6 +35,7 @@ import com.fabledsword.minstrel.models.TrackRef
 import com.fabledsword.minstrel.nav.AlbumDetail
 import com.fabledsword.minstrel.nav.ArtistDetail
 import com.fabledsword.minstrel.player.PlayerController
+import com.fabledsword.minstrel.shared.UiState
 import com.fabledsword.minstrel.shared.widgets.TrackRow
 import com.fabledsword.minstrel.shared.widgets.EmptyState
 import com.fabledsword.minstrel.shared.widgets.HorizontalScrollRow
@@ -66,13 +67,6 @@ data class LikedSections(
         get() = artists.isEmpty() && albums.isEmpty() && tracks.isEmpty()
 }
 
-sealed interface LikedTabUiState {
-    data object Loading : LikedTabUiState
-    data object Empty : LikedTabUiState
-    data class Success(val sections: LikedSections) : LikedTabUiState
-    data class Error(val message: String) : LikedTabUiState
-}
-
 // ─── ViewModel ───────────────────────────────────────────────────────
 
 @HiltViewModel
@@ -99,19 +93,19 @@ class LikedTabViewModel @Inject constructor(
         }
     }
 
-    val uiState: StateFlow<LikedTabUiState> = combine(
+    val uiState: StateFlow<UiState<LikedSections>> = combine(
         repository.observeLikedArtists(),
         repository.observeLikedAlbums(),
         repository.observeLikedTracks(),
     ) { artists, albums, tracks ->
         val sections = LikedSections(artists, albums, tracks)
-        if (sections.isAllEmpty) LikedTabUiState.Empty else LikedTabUiState.Success(sections)
+        if (sections.isAllEmpty) UiState.Empty else UiState.Success(sections)
     }
-        .catch { e -> emit(LikedTabUiState.Error(ErrorCopy.fromThrowable(e))) }
+        .catch { e -> emit(UiState.Error(ErrorCopy.fromThrowable(e))) }
         .stateIn(
             scope = viewModelScope,
             started = SharingStarted.WhileSubscribed(SHARE_STOP_TIMEOUT_MS),
-            initialValue = LikedTabUiState.Loading,
+            initialValue = UiState.Loading,
         )
 
     /**
@@ -141,23 +135,23 @@ fun LikedTab(
     val playingTrackId = playerState.currentTrack?.id
     PullToRefreshScaffold(onRefresh = { viewModel.refresh().join() }) {
         when (val s = state) {
-            LikedTabUiState.Loading -> LoadingCentered()
+            UiState.Loading -> LoadingCentered()
-            LikedTabUiState.Empty -> EmptyState(
+            UiState.Empty -> EmptyState(
                 title = "No likes yet",
                 body = "Tap the heart on an artist, album, or track to start " +
                     "building your liked collection.",
             )
-            is LikedTabUiState.Error -> EmptyState(
+            is UiState.Error -> EmptyState(
                 title = "Couldn't load likes",
                 body = s.message,
             )
-            is LikedTabUiState.Success -> LikedContent(
+            is UiState.Success -> LikedContent(
-                sections = s.sections,
+                sections = s.data,
                 playingTrackId = playingTrackId,
                 onArtistClick = { id -> navController.navigate(ArtistDetail(id)) },
                 onAlbumClick = { id -> navController.navigate(AlbumDetail(id)) },
                 onTrackClick = { index ->
-                    viewModel.playTracks(s.sections.tracks, index)
+                    viewModel.playTracks(s.data.tracks, index)
                 },
                 onUnlike = viewModel::unlikeTrack,
                 onNavigateToAlbum = { id -> navController.navigate(AlbumDetail(id)) },

android/app/src/main/java/com/fabledsword/minstrel/playlists/ui/PlaylistsListScreen.kt

@@ -29,6 +29,7 @@ import com.fabledsword.minstrel.models.PlaylistRef
 import com.fabledsword.minstrel.nav.PlaylistDetail
 import com.fabledsword.minstrel.nav.Playlists
 import com.fabledsword.minstrel.playlists.data.PlaylistsRepository
+import com.fabledsword.minstrel.shared.UiState
 import com.fabledsword.minstrel.playlists.widgets.PlaylistCard
 import com.fabledsword.minstrel.shared.widgets.EmptyState
 import com.fabledsword.minstrel.shared.widgets.LoadingCentered
@@ -49,13 +50,6 @@ private const val SHARE_STOP_TIMEOUT_MS = 5_000L
 
 // ─── State ───────────────────────────────────────────────────────────
 
-sealed interface PlaylistsListUiState {
-    data object Loading : PlaylistsListUiState
-    data object Empty : PlaylistsListUiState
-    data class Success(val playlists: List<PlaylistRef>) : PlaylistsListUiState
-    data class Error(val message: String) : PlaylistsListUiState
-}
-
 // ─── ViewModel ───────────────────────────────────────────────────────
 
 @HiltViewModel
@@ -80,22 +74,22 @@ class PlaylistsListViewModel @Inject constructor(
         runCatching { repository.refreshList() }
     }
 
-    val uiState: StateFlow<PlaylistsListUiState> =
+    val uiState: StateFlow<UiState<List<PlaylistRef>>> =
         repository.observeAll()
             .map { list ->
                 if (list.isEmpty()) {
-                    PlaylistsListUiState.Empty
+                    UiState.Empty
                 } else {
-                    PlaylistsListUiState.Success(list)
+                    UiState.Success(list)
                 }
             }
             .catch { e ->
-                emit(PlaylistsListUiState.Error(ErrorCopy.fromThrowable(e)))
+                emit(UiState.Error(ErrorCopy.fromThrowable(e)))
             }
             .stateIn(
                 scope = viewModelScope,
                 started = SharingStarted.WhileSubscribed(SHARE_STOP_TIMEOUT_MS),
-                initialValue = PlaylistsListUiState.Loading,
+                initialValue = UiState.Loading,
             )
 }
 
@@ -127,19 +121,19 @@ fun PlaylistsListScreen(
             modifier = Modifier.fillMaxSize().padding(inner),
         ) {
             when (val s = state) {
-                PlaylistsListUiState.Loading -> LoadingCentered()
+                UiState.Loading -> LoadingCentered()
-                PlaylistsListUiState.Empty -> EmptyState(
+                UiState.Empty -> EmptyState(
                     title = "No playlists yet",
                     body = "System playlists (For You / Discover / Songs like…) " +
                         "appear once your library has enough plays. Create your " +
                         "own playlist from any album or track in the meantime.",
                 )
-                is PlaylistsListUiState.Error -> EmptyState(
+                is UiState.Error -> EmptyState(
                     title = "Couldn't load playlists",
                     body = s.message,
                 )
-                is PlaylistsListUiState.Success -> PlaylistsGrid(
+                is UiState.Success -> PlaylistsGrid(
-                    playlists = s.playlists,
+                    playlists = s.data,
                     onPlaylistClick = { id -> navController.navigate(PlaylistDetail(id)) },
                 )
             }

android/app/src/main/java/com/fabledsword/minstrel/quarantine/ui/HiddenTab.kt

@@ -25,6 +25,7 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.composables.icons.lucide.ArchiveRestore
 import com.composables.icons.lucide.Lucide
 import com.fabledsword.minstrel.models.QuarantineRef
+import com.fabledsword.minstrel.shared.UiState
 import com.fabledsword.minstrel.shared.widgets.EmptyState
 import com.fabledsword.minstrel.shared.widgets.LoadingCentered
 import com.fabledsword.minstrel.shared.widgets.PullToRefreshScaffold
@@ -35,19 +36,19 @@ fun HiddenTab(viewModel: HiddenTabViewModel = hiltViewModel()) {
     val state by viewModel.uiState.collectAsStateWithLifecycle()
     PullToRefreshScaffold(onRefresh = { viewModel.refresh().join() }) {
         when (val s = state) {
-            HiddenTabUiState.Loading -> LoadingCentered()
+            UiState.Loading -> LoadingCentered()
-            HiddenTabUiState.Empty -> EmptyState(
+            UiState.Empty -> EmptyState(
                 title = "No hidden tracks",
                 body = "Flag a track from its menu (bad rip, wrong tags, etc.) " +
                     "and it'll show up here. The track stays out of system " +
                     "playlists until you unhide it.",
             )
-            is HiddenTabUiState.Error -> EmptyState(
+            is UiState.Error -> EmptyState(
                 title = "Couldn't load hidden tracks",
                 body = s.message,
             )
-            is HiddenTabUiState.Success -> HiddenList(
+            is UiState.Success -> HiddenList(
-                rows = s.rows,
+                rows = s.data,
                 onUnflag = viewModel::unflag,
             )
         }

android/app/src/main/java/com/fabledsword/minstrel/quarantine/ui/HiddenTabViewModel.kt

@@ -5,6 +5,7 @@ import androidx.lifecycle.viewModelScope
 import com.fabledsword.minstrel.api.ErrorCopy
 import com.fabledsword.minstrel.events.EventsStream
 import com.fabledsword.minstrel.models.QuarantineRef
+import com.fabledsword.minstrel.shared.UiState
 import com.fabledsword.minstrel.quarantine.data.QuarantineRepository
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.Job
@@ -19,13 +20,6 @@ import javax.inject.Inject
 
 private const val SHARE_STOP_TIMEOUT_MS = 5_000L
 
-sealed interface HiddenTabUiState {
-    data object Loading : HiddenTabUiState
-    data object Empty : HiddenTabUiState
-    data class Success(val rows: List<QuarantineRef>) : HiddenTabUiState
-    data class Error(val message: String) : HiddenTabUiState
-}
-
 @HiltViewModel
 class HiddenTabViewModel @Inject constructor(
     private val repository: QuarantineRepository,
@@ -41,17 +35,17 @@ class HiddenTabViewModel @Inject constructor(
      * refresh failed. Optimistic flag/unflag write the cache, so the
      * list updates without waiting on the server.
      */
-    val uiState: StateFlow<HiddenTabUiState> =
+    val uiState: StateFlow<UiState<List<QuarantineRef>>> =
         combine(repository.observeMine(), refreshError) { rows, err ->
             when {
-                rows.isNotEmpty() -> HiddenTabUiState.Success(rows)
+                rows.isNotEmpty() -> UiState.Success(rows)
-                err != null -> HiddenTabUiState.Error(err)
+                err != null -> UiState.Error(err)
-                else -> HiddenTabUiState.Empty
+                else -> UiState.Empty
             }
         }.stateIn(
             scope = viewModelScope,
             started = SharingStarted.WhileSubscribed(SHARE_STOP_TIMEOUT_MS),
-            initialValue = HiddenTabUiState.Loading,
+            initialValue = UiState.Loading,
         )
 
     init {

android/app/src/main/java/com/fabledsword/minstrel/requests/ui/RequestsScreen.kt

@@ -46,6 +46,7 @@ import com.composables.icons.lucide.X
 import com.fabledsword.minstrel.models.RequestRef
 import com.fabledsword.minstrel.models.RequestStatus
 import com.fabledsword.minstrel.nav.AlbumDetail
+import com.fabledsword.minstrel.shared.UiState
 import com.fabledsword.minstrel.nav.ArtistDetail
 import com.fabledsword.minstrel.nav.Requests
 import com.fabledsword.minstrel.shared.widgets.EmptyState
@@ -84,18 +85,18 @@ fun RequestsScreen(
             modifier = Modifier.fillMaxSize().padding(inner),
         ) {
             when (val s = state) {
-                RequestsUiState.Loading -> LoadingCentered()
+                UiState.Loading -> LoadingCentered()
-                RequestsUiState.Empty -> EmptyState(
+                UiState.Empty -> EmptyState(
                     title = "Nothing requested yet",
                     body = "Use Discover to ask Lidarr for new music; your " +
                         "requests show up here.",
                 )
-                is RequestsUiState.Error -> EmptyState(
+                is UiState.Error -> EmptyState(
                     title = "Couldn't load requests",
                     body = s.message,
                 )
-                is RequestsUiState.Success -> RequestList(
+                is UiState.Success -> RequestList(
-                    rows = s.requests,
+                    rows = s.data,
                     onCancel = viewModel::cancel,
                     onListen = { id -> navController.navigate(id) },
                 )

android/app/src/main/java/com/fabledsword/minstrel/requests/ui/RequestsViewModel.kt

@@ -6,6 +6,7 @@ import com.fabledsword.minstrel.api.ErrorCopy
 import com.fabledsword.minstrel.events.EventsStream
 import com.fabledsword.minstrel.models.RequestRef
 import com.fabledsword.minstrel.requests.data.RequestsRepository
+import com.fabledsword.minstrel.shared.UiState
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -18,21 +19,14 @@ import javax.inject.Inject
 
 private val RELEVANT_EVENT_KINDS = setOf("request.status_changed")
 
-sealed interface RequestsUiState {
-    data object Loading : RequestsUiState
-    data object Empty : RequestsUiState
-    data class Success(val requests: List<RequestRef>) : RequestsUiState
-    data class Error(val message: String) : RequestsUiState
-}
-
 @HiltViewModel
 class RequestsViewModel @Inject constructor(
     private val repository: RequestsRepository,
     private val eventsStream: EventsStream,
 ) : ViewModel() {
 
-    private val internal = MutableStateFlow<RequestsUiState>(RequestsUiState.Loading)
+    private val internal = MutableStateFlow<UiState<List<RequestRef>>>(UiState.Loading)
-    val uiState: StateFlow<RequestsUiState> = internal.asStateFlow()
+    val uiState: StateFlow<UiState<List<RequestRef>>> = internal.asStateFlow()
 
     init {
         refresh()
@@ -44,18 +38,18 @@ class RequestsViewModel @Inject constructor(
     }
 
     fun refresh(): Job = viewModelScope.launch {
-        internal.value = RequestsUiState.Loading
+        internal.value = UiState.Loading
         try {
             val rows = repository.listMine()
             internal.value = if (rows.isEmpty()) {
-                RequestsUiState.Empty
+                UiState.Empty
             } else {
-                RequestsUiState.Success(rows)
+                UiState.Success(rows)
             }
         } catch (
             @Suppress("TooGenericExceptionCaught") e: Throwable,
         ) {
-            internal.value = RequestsUiState.Error(ErrorCopy.fromThrowable(e))
+            internal.value = UiState.Error(ErrorCopy.fromThrowable(e))
         }
     }
 
@@ -67,12 +61,12 @@ class RequestsViewModel @Inject constructor(
      */
     fun cancel(id: String) {
         val before = internal.value
-        if (before is RequestsUiState.Success) {
+        if (before is UiState.Success) {
-            val filtered = before.requests.filterNot { it.id == id }
+            val filtered = before.data.filterNot { it.id == id }
             internal.value = if (filtered.isEmpty()) {
-                RequestsUiState.Empty
+                UiState.Empty
             } else {
-                RequestsUiState.Success(filtered)
+                UiState.Success(filtered)
             }
         }
         viewModelScope.launch {
@@ -80,11 +74,11 @@ class RequestsViewModel @Inject constructor(
                 val (_, updated) = repository.cancel(id)
                 if (updated != null) {
                     internal.update { state ->
-                        if (state !is RequestsUiState.Success) {
+                        if (state !is UiState.Success) {
                             // Mid-refresh — let the refresh result win, but
                             // splice the cancelled row in so it shows the new
                             // status if the user re-pulls.
-                            RequestsUiState.Success(listOf(updated))
+                            UiState.Success(listOf(updated))
                         } else {
                             // Re-insert the cancelled row in its old position
                             // would require remembering the prior ordering;

android/app/src/main/java/com/fabledsword/minstrel/shared/widgets/trackactions/AddToPlaylistSheet.kt

@@ -27,6 +27,7 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.composables.icons.lucide.ListMusic
 import com.composables.icons.lucide.Lucide
 import com.fabledsword.minstrel.models.PlaylistRef
+import com.fabledsword.minstrel.shared.UiState
 
 /**
  * ModalBottomSheet that lists the caller's user-owned playlists and
@@ -55,16 +56,16 @@ fun AddToPlaylistSheet(
                 modifier = Modifier.padding(horizontal = 20.dp, vertical = 8.dp),
             )
             when (val s = state) {
-                AddToPlaylistUiState.Loading -> Box(
+                UiState.Loading -> Box(
                     modifier = Modifier.fillMaxWidth().padding(24.dp),
                     contentAlignment = Alignment.Center,
                 ) { CircularProgressIndicator(color = MaterialTheme.colorScheme.primary) }
-                is AddToPlaylistUiState.Error -> Text(
+                is UiState.Error -> Text(
                     text = s.message,
                     color = MaterialTheme.colorScheme.error,
                     modifier = Modifier.padding(horizontal = 20.dp, vertical = 12.dp),
                 )
-                is AddToPlaylistUiState.Success -> if (s.playlists.isEmpty()) {
+                is UiState.Success -> if (s.data.isEmpty()) {
                     Text(
                         text = "You haven't created any playlists yet.",
                         color = MaterialTheme.colorScheme.onSurfaceVariant,
@@ -72,7 +73,7 @@ fun AddToPlaylistSheet(
                     )
                 } else {
                     LazyColumn(modifier = Modifier.fillMaxWidth()) {
-                        items(items = s.playlists, key = { it.id }) { p ->
+                        items(items = s.data, key = { it.id }) { p ->
                             PlaylistPickRow(playlist = p, onClick = { onPick(p.id) })
                         }
                     }

android/app/src/main/java/com/fabledsword/minstrel/shared/widgets/trackactions/AddToPlaylistViewModel.kt

@@ -5,6 +5,7 @@ import androidx.lifecycle.viewModelScope
 import com.fabledsword.minstrel.api.ErrorCopy
 import com.fabledsword.minstrel.models.PlaylistRef
 import com.fabledsword.minstrel.playlists.data.PlaylistsRepository
+import com.fabledsword.minstrel.shared.UiState
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
@@ -17,12 +18,6 @@ import javax.inject.Inject
 
 private const val SHARE_STOP_TIMEOUT_MS = 5_000L
 
-sealed interface AddToPlaylistUiState {
-    data object Loading : AddToPlaylistUiState
-    data class Success(val playlists: List<PlaylistRef>) : AddToPlaylistUiState
-    data class Error(val message: String) : AddToPlaylistUiState
-}
-
 /**
  * Backs [AddToPlaylistSheet] with the caller's user-owned playlists.
  * System playlists (For You / Discover / etc.) are filtered out at
@@ -33,9 +28,9 @@ class AddToPlaylistViewModel @Inject constructor(
     repository: PlaylistsRepository,
 ) : ViewModel() {
 
-    val uiState: StateFlow<AddToPlaylistUiState> = repository
+    val uiState: StateFlow<UiState<List<PlaylistRef>>> = repository
         .observeUserPlaylists()
-        .map { list -> AddToPlaylistUiState.Success(list) as AddToPlaylistUiState }
+        .map { list -> UiState.Success(list) as UiState<List<PlaylistRef>> }
         .onStart {
             // Best-effort refresh so the sheet reflects newly-created
             // playlists from another device. Cached list shows first;
@@ -43,12 +38,12 @@ class AddToPlaylistViewModel @Inject constructor(
             viewModelScope.launch {
                 runCatching { repository.refreshList() }
             }
-            emit(AddToPlaylistUiState.Loading)
+            emit(UiState.Loading)
         }
-        .catch { e -> emit(AddToPlaylistUiState.Error(ErrorCopy.fromThrowable(e))) }
+        .catch { e -> emit(UiState.Error(ErrorCopy.fromThrowable(e))) }
         .stateIn(
             scope = viewModelScope,
             started = SharingStarted.WhileSubscribed(SHARE_STOP_TIMEOUT_MS),
-            initialValue = AddToPlaylistUiState.Loading,
+            initialValue = UiState.Loading,
         )
 }

android/app/src/test/java/com/fabledsword/minstrel/library/ui/LibraryViewModelTest.kt

@@ -6,6 +6,7 @@ import com.fabledsword.minstrel.library.data.LibraryRepository
 import com.fabledsword.minstrel.models.AlbumRef
 import com.fabledsword.minstrel.models.ArtistRef
 import com.fabledsword.minstrel.player.PlayerController
+import com.fabledsword.minstrel.shared.UiState
 import com.fabledsword.minstrel.testutil.MainDispatcherExtension
 import io.mockk.every
 import io.mockk.mockk
@@ -32,7 +33,7 @@ class LibraryViewModelTest {
             mockk<PlayerController>(relaxed = true),
         )
 
-        assertEquals(LibraryUiState.Loading, vm.uiState.value)
+        assertEquals(UiState.Loading, vm.uiState.value)
     }
 
     // Note: tests below collect the resolved state directly. With
@@ -55,7 +56,7 @@ class LibraryViewModelTest {
         )
 
         vm.uiState.test {
-            assertEquals(LibraryUiState.Empty, awaitItem())
+            assertEquals(UiState.Empty, awaitItem())
             cancelAndConsumeRemainingEvents()
         }
     }
@@ -75,11 +76,11 @@ class LibraryViewModelTest {
         )
 
         vm.uiState.test {
-            val success = awaitItem() as LibraryUiState.Success
+            val success = awaitItem() as UiState.Success<LibraryData>
-            assertEquals(1, success.artists.size)
+            assertEquals(1, success.data.artists.size)
-            assertEquals(1, success.albums.size)
+            assertEquals(1, success.data.albums.size)
-            assertEquals("a1", success.artists[0].id)
+            assertEquals("a1", success.data.artists[0].id)
-            assertEquals("al1", success.albums[0].id)
+            assertEquals("al1", success.data.albums[0].id)
             cancelAndConsumeRemainingEvents()
         }
     }
@@ -98,7 +99,7 @@ class LibraryViewModelTest {
         )
 
         vm.uiState.test {
-            val error = awaitItem() as LibraryUiState.Error
+            val error = awaitItem() as UiState.Error
             // ErrorCopy maps a non-HTTP/non-IO throwable to the generic
             // fallback rather than leaking the raw exception text.
             assertEquals("Something went wrong.", error.message)