data: handle network exceptions elegantly

examples/llama.android/app/src/main/java/com/example/llama/data/remote/HuggingFaceRemoteDataSource.kt

@@ -7,6 +7,8 @@ import android.util.Log
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.withContext
+import java.io.FileNotFoundException
+import java.io.IOException
 import javax.inject.Inject
 import javax.inject.Singleton
 
@@ -26,14 +28,14 @@ interface HuggingFaceRemoteDataSource {
         direction: String? = "-1",
         limit: Int? = SEARCH_RESULT_LIMIT,
         full: Boolean = true,
-    ): List<HuggingFaceModel>
+    ): Result<List<HuggingFaceModel>>
 
     suspend fun getModelDetails(modelId: String): HuggingFaceModelDetails
 
     /**
      * Obtain selected HuggingFace model's GGUF file size from HTTP header
      */
-    suspend fun getFileSize(modelId: String, filePath: String): Long?
+    suspend fun getFileSize(modelId: String, filePath: String): Result<Long>
 
     /**
      * Download selected HuggingFace model's GGUF file via DownloadManager
@@ -57,6 +59,7 @@ class HuggingFaceRemoteDataSourceImpl @Inject constructor(
         limit: Int?,
         full: Boolean,
     ) = withContext(Dispatchers.IO) {
+        try {
             apiService.getModels(
                 search = query,
                 filter = filter,
@@ -64,7 +67,15 @@ class HuggingFaceRemoteDataSourceImpl @Inject constructor(
                 direction = direction,
                 limit = limit,
                 full = full,
-        ).filter { it.gated != true && it.private != true && it.getGgufFilename() != null }
+            ).filter {
+                it.gated != true && it.private != true && it.getGgufFilename() != null
+            }.let {
+                if (it.isEmpty()) Result.failure(FileNotFoundException()) else Result.success(it)
+            }
+        } catch (e: Exception) {
+            Log.e(TAG, "Error searching for models on HuggingFace: ${e.message}")
+            Result.failure(e)
+        }
     }
 
     override suspend fun getModelDetails(
@@ -76,18 +87,26 @@ class HuggingFaceRemoteDataSourceImpl @Inject constructor(
     override suspend fun getFileSize(
         modelId: String,
         filePath: String
-    ): Long? = withContext(Dispatchers.IO) {
+    ): Result<Long> = withContext(Dispatchers.IO) {
         try {
-            apiService.getModelFileHeader(modelId, filePath).let {
+            apiService.getModelFileHeader(modelId, filePath).let { resp ->
-                if (it.isSuccessful) {
+                if (resp.isSuccessful) {
-                    it.headers()[HTTP_HEADER_CONTENT_LENGTH]?.toLongOrNull()
+                    resp.headers()[HTTP_HEADER_CONTENT_LENGTH]?.toLongOrNull()?.let {
+                        Result.success(it)
+                    } ?: Result.failure(IOException("Content-Length header missing"))
                 } else {
-                    null
+                    Result.failure(
+                        when (resp.code()) {
+                            401 -> SecurityException("Model requires authentication")
+                            404 -> FileNotFoundException("Model file not found")
+                            else -> IOException("Failed to get file info: HTTP ${resp.code()}")
+                        }
+                    )
                 }
             }
         } catch (e: Exception) {
             Log.e(TAG, "Error getting file size for $modelId: ${e.message}")
-            null
+            Result.failure(e)
         }
     }
 

examples/llama.android/app/src/main/java/com/example/llama/data/repository/ModelRepository.kt

@@ -86,7 +86,7 @@ interface ModelRepository {
     /**
      * Search models on HuggingFace
      */
-    suspend fun searchHuggingFaceModels(limit: Int = 20): List<HuggingFaceModel>
+    suspend fun searchHuggingFaceModels(limit: Int = 20): Result<List<HuggingFaceModel>>
 
     /**
      * Obtain the model details from HuggingFace
@@ -96,7 +96,7 @@ interface ModelRepository {
     /**
      * Obtain the model's size from HTTP response header
      */
-    suspend fun getHuggingFaceModelFileSize(downloadInfo: HuggingFaceDownloadInfo): Long?
+    suspend fun getHuggingFaceModelFileSize(downloadInfo: HuggingFaceDownloadInfo): Result<Long>
 
     /**
      * Download a HuggingFace model via system download manager
@@ -351,7 +351,7 @@ class ModelRepositoryImpl @Inject constructor(
 
     override suspend fun searchHuggingFaceModels(
         limit: Int
-    ): List<HuggingFaceModel> = withContext(Dispatchers.IO) {
+    ) = withContext(Dispatchers.IO) {
         huggingFaceRemoteDataSource.searchModels(limit = limit)
     }
 
@@ -363,7 +363,7 @@ class ModelRepositoryImpl @Inject constructor(
 
     override suspend fun getHuggingFaceModelFileSize(
         downloadInfo: HuggingFaceDownloadInfo,
-    ): Long? = withContext(Dispatchers.IO) {
+    ): Result<Long> = withContext(Dispatchers.IO) {
         huggingFaceRemoteDataSource.getFileSize(downloadInfo.modelId, downloadInfo.filename)
     }
 

examples/llama.android/app/src/main/java/com/example/llama/viewmodel/ModelsManagementViewModel.kt

@@ -38,6 +38,9 @@ import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
 import java.io.FileNotFoundException
+import java.io.IOException
+import java.net.SocketTimeoutException
+import java.net.UnknownHostException
 import javax.inject.Inject
 
 @HiltViewModel
@@ -246,11 +249,23 @@ class ModelsManagementViewModel @Inject constructor(
         huggingFaceQueryJob = viewModelScope.launch {
             _managementState.emit(Download.Querying)
             try {
-                val models = modelRepository.searchHuggingFaceModels()
+                modelRepository.searchHuggingFaceModels().fold(
+                    onSuccess = { models ->
                         Log.d(TAG, "Fetched ${models.size} models from HuggingFace:")
                         _managementState.emit(Download.Ready(models))
+                    },
+                    onFailure = { throw it }
+                )
             } catch (_: CancellationException) {
                 // no-op
+            } catch (_: UnknownHostException) {
+                _managementState.value = Download.Error(message = "No internet connection")
+            } catch (_: SocketTimeoutException) {
+                _managementState.value = Download.Error(message = "Connection timed out")
+            } catch (e: IOException) {
+                _managementState.value = Download.Error(message = "Network error: ${e.message}")
+            } catch (_: FileNotFoundException) {
+                _managementState.emit(Download.Error(message = "No eligible models"))
             } catch (e: Exception) {
                 _managementState.emit(Download.Error(message = e.message ?: "Unknown error"))
             }
@@ -267,17 +282,24 @@ class ModelsManagementViewModel @Inject constructor(
             val downloadInfo = model.toDownloadInfo()
             requireNotNull(downloadInfo) { "Download URL is missing!" }
 
-            val actualSize = modelRepository.getHuggingFaceModelFileSize(downloadInfo)
+            modelRepository.getHuggingFaceModelFileSize(downloadInfo).fold(
-            requireNotNull(actualSize) { "Unknown model file size!" }
+                onSuccess = { actualSize ->
                     Log.d(TAG, "Model file size: ${formatFileByteSize(actualSize)}")
-
                     modelRepository.downloadHuggingFaceModel(downloadInfo, actualSize)
                         .onSuccess { downloadId ->
                             activeDownloads[downloadId] = model
                             _managementState.value = Download.Dispatched(downloadInfo)
                         }
                         .onFailure { throw it }
-
+                },
+                onFailure = { throw it }
+            )
+        } catch (_: UnknownHostException) {
+            _managementState.value = Download.Error(message = "No internet connection")
+        } catch (_: SocketTimeoutException) {
+            _managementState.value = Download.Error(message = "Connection timed out")
+        } catch (e: IOException) {
+            _managementState.value = Download.Error(message = "Network error: ${e.message}")
         } catch (e: InsufficientStorageException) {
             _managementState.value = Download.Error(
                 message = e.message ?: "Insufficient storage space to download ${model.modelId}",
@@ -343,7 +365,6 @@ class ModelsManagementViewModel @Inject constructor(
     companion object {
         private val TAG = ModelsManagementViewModel::class.java.simpleName
 
-        private const val SUBSCRIPTION_TIMEOUT_MS = 5000L
         private const val SUCCESS_RESET_TIMEOUT_MS = 1000L
     }
 }