localize transient messages and the download notification

Route user-facing messages produced below the UI through a typed UiMessage
(string-resource id plus format args) instead of pre-built English strings:
showMessage, SyncStatus.Failed, playback errors and download toasts now
resolve in the current locale at the UI edge. Subsonic and page-cap
exceptions carry a UiMessage alongside their developer message, and the
download progress notification is formatted from resources.

Internal invariants and log tags stay plain strings.

app/src/main/kotlin/com/subtracks/UiMessage.kt

@@ -0,0 +1,19 @@
+package com.subtracks
+
+import android.content.Context
+import android.content.res.Resources
+import androidx.annotation.StringRes
+
+data class UiMessage(
+    @param:StringRes val resId: Int,
+    val args: List<Any> = emptyList(),
+) {
+    fun resolve(resources: Resources): String = resources.getString(resId, *args.toTypedArray())
+
+    fun resolve(context: Context): String = resolve(context.resources)
+}
+
+class UiException(
+    val uiMessage: UiMessage,
+    message: String = "",
+) : Exception(message)

app/src/main/kotlin/com/subtracks/data/download/DownloadNotification.kt

@@ -1,5 +1,7 @@
 package com.subtracks.data.download
 
+import android.content.res.Resources
+import com.subtracks.R
 import com.subtracks.data.model.DownloadStatus
 import com.subtracks.data.model.SongDownload
 
@@ -9,14 +11,19 @@ data class DownloadNotification(
     val progress: Float?,
 )
 
-fun downloadNotification(rows: Collection<SongDownload>): DownloadNotification? {
+fun downloadNotification(
+    resources: Resources,
+    rows: Collection<SongDownload>,
+): DownloadNotification? {
     val active = rows.filter { it.status == DownloadStatus.Queued || it.status == DownloadStatus.Running }
     if (active.isEmpty()) return null
     val total = active.sumOf { it.total }
     val progress = if (total > 0) (active.sumOf { it.bytes }.toFloat() / total).coerceIn(0f, 1f) else null
     return DownloadNotification(
-        title = if (active.size == 1) "Downloading 1 song" else "Downloading ${active.size} songs",
-        text = progress?.let { "${(it * 100).toInt()}%" } ?: "In progress",
+        title = resources.getQuantityString(R.plurals.download_notification_title, active.size, active.size),
+        text =
+            progress?.let { resources.getString(R.string.download_notification_progress, (it * 100).toInt()) }
+                ?: resources.getString(R.string.download_notification_in_progress),
         progress = progress,
     )
 }

app/src/main/kotlin/com/subtracks/data/download/DownloadNotifier.kt

@@ -32,7 +32,7 @@ class DownloadNotifier(
         createChannel()
         scope.launch {
             repository.activeDownloads().collect { rows ->
-                val content = downloadNotification(rows)
+                val content = downloadNotification(context.resources, rows)
                 if (content == null) {
                     manager.cancel(ID)
                 } else if (manager.areNotificationsEnabled()) {

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

@@ -1,6 +1,8 @@
 package com.subtracks.data.repo
 
 import android.net.Uri
+import com.subtracks.R
+import com.subtracks.UiMessage
 import com.subtracks.data.db.SubtracksDatabase
 import com.subtracks.data.download.ArtworkFetcher
 import com.subtracks.data.download.ArtworkStore
@@ -48,7 +50,7 @@ class DownloadRepository(
     private val downloadsDir: File,
     private val artworkStore: ArtworkStore,
     private val artworkFetcher: ArtworkFetcher,
-    private val showMessage: (String) -> Unit = {},
+    private val showMessage: (UiMessage) -> Unit = {},
     private val dispatcher: CoroutineDispatcher = Dispatchers.IO,
     private val scope: CoroutineScope = CoroutineScope(SupervisorJob() + dispatcher),
 ) {
@@ -111,11 +113,11 @@ class DownloadRepository(
         songId: String,
     ) = withContext(dispatcher) {
         if (sourceRepository.activeSourceIdOnce() != sourceId) {
-            showMessage(NOT_ACTIVE)
+            showMessage(UiMessage(R.string.error_download_inactive_source))
             return@withContext
         }
         if (sourceRepository.downloadUri(sourceId, songId) == null) {
-            showMessage(NO_ADDRESS)
+            showMessage(UiMessage(R.string.error_download_no_address))
             return@withContext
         }
         val promoted =
@@ -243,16 +245,16 @@ class DownloadRepository(
         refId: String,
     ) = withContext(dispatcher) {
         if (sourceRepository.activeSourceIdOnce() != sourceId) {
-            showMessage(NOT_ACTIVE)
+            showMessage(UiMessage(R.string.error_download_inactive_source))
             return@withContext
         }
         val songIds = songIds(sourceId, list, refId)
         if (songIds.isEmpty()) {
-            showMessage(EMPTY_LIST)
+            showMessage(UiMessage(R.string.error_download_nothing_left))
             return@withContext
         }
         if (sourceRepository.downloadUri(sourceId, songIds.first()) == null) {
-            showMessage(NO_ADDRESS)
+            showMessage(UiMessage(R.string.error_download_no_address))
             return@withContext
         }
         // Under one lock, so a cancel that lands mid-loop waits for the queue to be complete and
@@ -655,10 +657,6 @@ class DownloadRepository(
         const val POLL_MS = 1_000L
         const val IN_FLIGHT_LIMIT = 8
         const val DELETE_CHUNK = 900
-        const val NO_ADDRESS = "Can't download: the server address is unavailable"
-        const val EMPTY_LIST = "Nothing left to download from this list"
-        const val STOPPED = "The download stopped unexpectedly"
-        const val NOT_ACTIVE = "Can't download from a source that isn't active"
         const val ART_TIMEOUT_MS = 60_000L
     }
 }

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

@@ -4,6 +4,8 @@ import androidx.paging.Pager
 import androidx.paging.PagingConfig
 import androidx.paging.PagingData
 import androidx.paging.PagingSource
+import com.subtracks.R
+import com.subtracks.UiMessage
 import com.subtracks.data.db.SubtracksDatabase
 import com.subtracks.data.db.albumsDefaultQuery
 import com.subtracks.data.db.artistsDefaultQuery
@@ -38,7 +40,7 @@ class LibraryRepository(
     private val db: SubtracksDatabase,
     private val sourceRepository: SourceRepository,
     private val serverActions: ServerActionSink,
-    private val showMessage: (String) -> Unit = {},
+    private val showMessage: (UiMessage) -> Unit = {},
     private val scope: CoroutineScope = CoroutineScope(SupervisorJob() + Dispatchers.IO),
 ) {
     val activeSourceId: Flow<Long?> = sourceRepository.activeSourceId()
@@ -444,7 +446,7 @@ class LibraryRepository(
             throw cancellation
         } catch (failure: Exception) {
             withContext(NonCancellable) { updateStarred(sourceId, type, id, previous) }
-            showMessage("Could not update star")
+            showMessage(UiMessage(R.string.star_update_failed))
             Result.failure(failure)
         }
     }

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

@@ -1,5 +1,8 @@
 package com.subtracks.data.repo
 
+import com.subtracks.R
+import com.subtracks.UiException
+import com.subtracks.UiMessage
 import com.subtracks.data.db.SubtracksDatabase
 import com.subtracks.data.download.ArtworkStore
 import com.subtracks.data.model.CoverArtRef
@@ -35,7 +38,7 @@ class SourceRepository(
     private val prefs: UserPreferences,
     private val artworkStore: ArtworkStore,
     networkMode: Flow<NetworkMode> = flowOf(NetworkMode.Wifi),
-    private val showMessage: (String) -> Unit = {},
+    private val showMessage: (UiMessage) -> Unit = {},
     private val scope: CoroutineScope = CoroutineScope(SupervisorJob() + Dispatchers.Default),
 ) {
     private data class ActiveSource(
@@ -222,7 +225,7 @@ class SourceRepository(
         useTokenAuth: Boolean,
     ): Result<Boolean> =
         if (_offline.value) {
-            Result.failure(IllegalStateException("Offline mode is on"))
+            Result.failure(UiException(UiMessage(R.string.sync_offline), "Offline mode is on"))
         } else {
             withContext(Dispatchers.IO) {
                 var fellBack = false
@@ -262,7 +265,7 @@ class SourceRepository(
     private fun disableTokenAuth(sourceId: Long) {
         scope.launch {
             db.sourcesDao().disableTokenAuth(sourceId)
-            showMessage("Server does not support token auth; using the password instead")
+            showMessage(UiMessage(R.string.connection_token_fallback))
         }
     }
 

app/src/main/kotlin/com/subtracks/data/source/subsonic/SubsonicClient.kt

@@ -1,5 +1,7 @@
 package com.subtracks.data.source.subsonic
 
+import com.subtracks.R
+import com.subtracks.UiMessage
 import okhttp3.HttpUrl
 import okhttp3.OkHttpClient
 import okhttp3.Request
@@ -9,6 +11,7 @@ import java.security.MessageDigest
 open class SubsonicException(
     val code: Int,
     message: String,
+    val uiMessage: UiMessage? = null,
 ) : Exception(message)
 
 class SubsonicClient(
@@ -77,7 +80,7 @@ class SubsonicClient(
                 .build()
         http.newCall(request).execute().use { response ->
             if (!response.isSuccessful) {
-                throw SubsonicException(-1, "HTTP ${response.code}")
+                throw SubsonicException(-1, "HTTP ${response.code}", UiMessage(R.string.error_http, listOf(response.code)))
             }
             return body(response.body.byteStream())
         }

app/src/main/kotlin/com/subtracks/data/source/subsonic/SubsonicSource.kt

@@ -1,5 +1,7 @@
 package com.subtracks.data.source.subsonic
 
+import com.subtracks.R
+import com.subtracks.UiMessage
 import com.subtracks.data.model.Album
 import com.subtracks.data.model.Artist
 import com.subtracks.data.model.Playlist
@@ -282,7 +284,13 @@ class SubsonicSource(
         return supported
     }
 
-    private fun pageCapExceeded() = PageCapExceeded("Library is too large to sync: it exceeds ${maxPages.toLong() * PAGE_SIZE} rows")
+    private fun pageCapExceeded(): PageCapExceeded {
+        val rows = maxPages.toLong() * PAGE_SIZE
+        return PageCapExceeded(
+            "Library is too large to sync: it exceeds $rows rows",
+            UiMessage(R.string.error_library_too_large, listOf(rows)),
+        )
+    }
 
     private fun <T> entityBatches(
         method: String,
@@ -336,4 +344,5 @@ class SubsonicSource(
 
 private class PageCapExceeded(
     message: String,
-) : SubsonicException(-1, message)
+    uiMessage: UiMessage,
+) : SubsonicException(-1, message, uiMessage)

app/src/main/kotlin/com/subtracks/data/source/subsonic/SubsonicXml.kt

@@ -1,5 +1,7 @@
 package com.subtracks.data.source.subsonic
 
+import com.subtracks.R
+import com.subtracks.UiMessage
 import com.subtracks.data.model.Album
 import com.subtracks.data.model.Artist
 import com.subtracks.data.model.Playlist
@@ -224,6 +226,7 @@ private const val ROOT_TAG = "subsonic-response"
 private class XmlFailure(
     val code: Int,
     message: String,
+    val uiMessage: UiMessage? = null,
 ) : RuntimeException(message)
 
 private class StopReading : RuntimeException()
@@ -240,7 +243,7 @@ private open class SubsonicResponseHandler : DefaultHandler() {
     ) {
         depth++
         if (depth == 1) {
-            if (qName != ROOT_TAG) throw XmlFailure(-1, "Unexpected response from the server")
+            if (qName != ROOT_TAG) throw XmlFailure(-1, "Unexpected response from the server", UiMessage(R.string.error_server_unexpected))
             if (attributes.getValue("status") == "failed") statusFailed = true
         }
         if (qName == "error") {
@@ -262,7 +265,7 @@ private open class SubsonicResponseHandler : DefaultHandler() {
     }
 
     override fun endDocument() {
-        if (statusFailed) throw XmlFailure(-1, "Unknown error")
+        if (statusFailed) throw XmlFailure(-1, "Unknown error", UiMessage(R.string.error_server_unknown))
     }
 
     protected open fun onElementStart(
@@ -328,12 +331,12 @@ private fun parse(
     try {
         secureParserFactory().newSAXParser().parse(input, handler)
     } catch (failure: XmlFailure) {
-        throw SubsonicException(failure.code, failure.message ?: "Unknown error")
+        throw SubsonicException(failure.code, failure.message ?: "Unknown error", failure.uiMessage)
     } catch (_: StopReading) {
     } catch (failure: SAXException) {
-        throw SubsonicException(-1, failure.message ?: "Malformed response from the server")
+        throw SubsonicException(-1, failure.message ?: "Malformed response from the server", UiMessage(R.string.error_server_malformed))
     } catch (failure: IOException) {
-        throw SubsonicException(-1, failure.message ?: "Truncated response from the server")
+        throw SubsonicException(-1, failure.message ?: "Truncated response from the server", UiMessage(R.string.error_server_truncated))
     }
 }
 

app/src/main/kotlin/com/subtracks/data/sync/SyncManager.kt

@@ -1,9 +1,13 @@
 package com.subtracks.data.sync
 
 import android.util.Log
+import com.subtracks.R
+import com.subtracks.UiException
+import com.subtracks.UiMessage
 import com.subtracks.data.db.SubtracksDatabase
 import com.subtracks.data.repo.QueueRepository
 import com.subtracks.data.repo.SourceRepository
+import com.subtracks.data.source.subsonic.SubsonicException
 import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -21,7 +25,7 @@ sealed interface SyncStatus {
     data object Success : SyncStatus
 
     data class Failed(
-        val message: String,
+        val message: UiMessage,
     ) : SyncStatus
 }
 
@@ -29,7 +33,7 @@ class SyncManager(
     private val db: SubtracksDatabase,
     private val sourceRepository: SourceRepository,
     private val queueRepository: QueueRepository,
-    private val showMessage: (String) -> Unit = {},
+    private val showMessage: (UiMessage) -> Unit = {},
     private val scope: CoroutineScope = CoroutineScope(SupervisorJob() + Dispatchers.Default),
 ) {
     private val requests = Channel<Unit>(Channel.CONFLATED)
@@ -48,22 +52,37 @@ class SyncManager(
 
     private suspend fun runSync() {
         if (sourceRepository.offline.value) {
-            showMessage("Offline mode is on")
-            _status.value = SyncStatus.Failed("Offline mode is on")
+            val offline = UiMessage(R.string.sync_offline)
+            showMessage(offline)
+            _status.value = SyncStatus.Failed(offline)
             return
         }
         _status.value = SyncStatus.Running
         val result =
             try {
-                val source = sourceRepository.activeMusicSource() ?: error("No server configured")
+                val source = sourceRepository.activeMusicSource() ?: throw NoServerException()
                 SyncService(db, source).sync()
                 SyncStatus.Success
             } catch (cancellation: CancellationException) {
                 throw cancellation
             } catch (failure: Exception) {
                 Log.w(TAG, "Sync failed", failure)
-                val message = failure.message ?: "unknown error"
-                showMessage("Sync failed: $message")
+                val message =
+                    when (failure) {
+                        is NoServerException -> {
+                            UiMessage(R.string.error_no_server)
+                        }
+
+                        is UiException -> {
+                            failure.uiMessage
+                        }
+
+                        else -> {
+                            (failure as? SubsonicException)?.uiMessage
+                                ?: UiMessage(R.string.sync_failed_detail, listOf(failure.message ?: ""))
+                        }
+                    }
+                showMessage(message)
                 SyncStatus.Failed(message)
             }
         queueRepository.invalidateLibraryCache()
@@ -74,3 +93,5 @@ class SyncManager(
         const val TAG = "SubtracksSync"
     }
 }
+
+private class NoServerException : IllegalStateException()

app/src/main/kotlin/com/subtracks/di/AppModule.kt

@@ -6,6 +6,7 @@ import android.os.Handler
 import android.os.Looper
 import android.widget.Toast
 import com.subtracks.R
+import com.subtracks.UiMessage
 import com.subtracks.data.db.createAndroidDatabase
 import com.subtracks.data.download.ArtworkFetcher
 import com.subtracks.data.download.ArtworkStore
@@ -55,8 +56,8 @@ fun appModule(
     http: OkHttpClient,
 ) = module {
     val mainHandler = Handler(Looper.getMainLooper())
-    val toast: (String) -> Unit = { message ->
-        mainHandler.post { Toast.makeText(context, message, Toast.LENGTH_SHORT).show() }
+    val toast: (UiMessage) -> Unit = { message ->
+        mainHandler.post { Toast.makeText(context, message.resolve(context), Toast.LENGTH_SHORT).show() }
     }
     single { createAndroidDatabase(context) }
     single { http }

app/src/main/kotlin/com/subtracks/playback/Media3PlayerHandle.kt

@@ -11,6 +11,8 @@ import androidx.media3.common.PlaybackException
 import androidx.media3.common.Player
 import androidx.media3.common.util.UnstableApi
 import androidx.media3.session.MediaController
+import com.subtracks.R
+import com.subtracks.UiMessage
 import com.subtracks.data.model.AudioEncoding
 import com.subtracks.data.repo.DownloadRepository
 import com.subtracks.data.repo.SourceRepository
@@ -235,13 +237,13 @@ internal fun queueMediaItem(
     return builder.build()
 }
 
-internal fun playbackErrorMessage(error: PlaybackException): String =
+internal fun playbackErrorMessage(error: PlaybackException): UiMessage =
     when (error.errorCode) {
         PlaybackException.ERROR_CODE_IO_NETWORK_CONNECTION_FAILED,
         PlaybackException.ERROR_CODE_IO_NETWORK_CONNECTION_TIMEOUT,
-        -> "Can't reach the server. Check your connection."
+        -> UiMessage(R.string.playback_error_network)
 
-        PlaybackException.ERROR_CODE_IO_BAD_HTTP_STATUS -> "The server refused to stream this track."
+        PlaybackException.ERROR_CODE_IO_BAD_HTTP_STATUS -> UiMessage(R.string.playback_error_refused)
 
-        else -> error.errorCodeName
+        else -> UiMessage(R.string.playback_error, listOf(error.errorCodeName))
     }

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

@@ -1,5 +1,6 @@
 package com.subtracks.playback
 
+import com.subtracks.UiMessage
 import com.subtracks.data.model.AudioEncoding
 import com.subtracks.data.model.CoverArtRef
 import com.subtracks.data.model.QueueEntry
@@ -108,7 +109,7 @@ class PlaybackController(
     private val queueRepository: QueueRepository,
     private val connection: PlayerConnection,
     private val downloads: DownloadRepository,
-    private val showMessage: (String) -> Unit = {},
+    private val showMessage: (UiMessage) -> Unit = {},
     private val scope: CoroutineScope = CoroutineScope(SupervisorJob() + Dispatchers.Main.immediate),
 ) {
     private val _state = MutableStateFlow(PlaybackState())
@@ -1414,7 +1415,7 @@ class PlaybackController(
                 refresh()
             }
 
-            override fun onError(message: String) {
+            override fun onError(message: UiMessage) {
                 showMessage(message)
                 refresh()
             }

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

@@ -1,5 +1,6 @@
 package com.subtracks.playback
 
+import com.subtracks.UiMessage
 import com.subtracks.data.model.AudioEncoding
 
 interface PlayerHandle {
@@ -75,7 +76,7 @@ interface PlayerHandle {
 
         fun onEvents()
 
-        fun onError(message: String) {
+        fun onError(message: UiMessage) {
         }
     }
 }

app/src/main/kotlin/com/subtracks/ui/settings/AddSourceViewModel.kt

@@ -4,6 +4,7 @@ import android.content.res.Resources
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import com.subtracks.R
+import com.subtracks.UiException
 import com.subtracks.data.repo.DownloadRepository
 import com.subtracks.data.repo.SourceRepository
 import com.subtracks.data.sync.SyncManager
@@ -99,7 +100,10 @@ class AddSourceViewModel(
                                     resources.getString(R.string.connection_ok)
                                 }
                             },
-                            { error -> resources.getString(R.string.connection_failed, error.message) },
+                            { error ->
+                                (error as? UiException)?.uiMessage?.resolve(resources)
+                                    ?: resources.getString(R.string.connection_failed, error.message)
+                            },
                         ),
                     isError = result.isFailure,
                 )