toast a friendly message for playback connection errors

Map the Media3 network/HTTP error codes to readable text and show it as a toast, instead of leaving an opaque ERR_ code on the now playing screen.

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

@@ -45,7 +45,7 @@ fun appModule(
     single { SyncManager(get(), get(), get()) }
     single { QueueRepository(get()) }
     single<PlayerConnection> { MediaSessionConnection(context.applicationContext, get()) }
-    single { PlaybackController(get(), get(), get()) }
+    single { PlaybackController(get(), get(), get(), showMessage = toast) }
     viewModel { RootViewModel(get()) }
     viewModel { LibraryViewModel(get(), get(), get(), get(), get()) }
     viewModel { SettingsViewModel(get(), get()) }

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

@@ -111,7 +111,7 @@ class Media3PlayerHandle(
                         "Playback error ${error.errorCodeName} at ${controller.currentPosition}/${controller.duration}",
                         error,
                     )
-                    listener.onError(error.errorCodeName)
+                    listener.onError(playbackErrorMessage(error))
                 }
 
                 override fun onPlaybackStateChanged(playbackState: Int) {
@@ -171,3 +171,14 @@ class Media3PlayerHandle(
         const val EXTRA_DURATION_MS = "durationMs"
     }
 }
+
+internal fun playbackErrorMessage(error: PlaybackException): String =
+    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."
+
+        PlaybackException.ERROR_CODE_IO_BAD_HTTP_STATUS -> "The server refused to stream this track."
+
+        else -> error.errorCodeName
+    }

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

@@ -98,6 +98,7 @@ class PlaybackController(
     private val sourceRepository: SourceRepository,
     private val queueRepository: QueueRepository,
     private val connection: PlayerConnection,
+    private val showMessage: (String) -> Unit = {},
     dispatcher: CoroutineDispatcher = Dispatchers.Main.immediate,
 ) {
     private val scope = CoroutineScope(SupervisorJob() + dispatcher)
@@ -870,6 +871,7 @@ class PlaybackController(
 
             override fun onError(message: String) {
                 lastError = message
+                showMessage(message)
                 refresh()
             }
         }