data: allow canceling the ongoing model import

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

@@ -16,7 +16,10 @@ import com.example.llama.revamp.util.extractQuantizationFromFilename
 import com.example.llama.revamp.util.getFileNameFromUri
 import com.example.llama.revamp.util.getFileSizeFromUri
 import dagger.hilt.android.qualifiers.ApplicationContext
+import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.cancel
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flow
@@ -34,10 +37,16 @@ import javax.inject.Singleton
  * Repository for managing available models on local device.
  */
 interface ModelRepository {
+    /**
+     * Obtain the current status of local storage and available models.
+     */
     fun getStorageMetrics(): Flow<StorageMetrics>
     fun getModels(): Flow<List<ModelInfo>>
     suspend fun getModelById(id: String): ModelInfo?
 
+    /**
+     * Import a local model file from device storage.
+     */
     suspend fun importModel(
         uri: Uri,
         name: String? = null,
@@ -45,14 +54,29 @@ interface ModelRepository {
         progressTracker: ImportProgressTracker? = null
     ): ModelInfo
 
-    suspend fun updateModelLastUsed(modelId: String)
-
-    suspend fun deleteModel(modelId: String)
-    suspend fun deleteModels(modelIds: List<String>)
-
     fun interface ImportProgressTracker {
         fun onProgress(progress: Float) // 0.0f to 1.0f
     }
+
+    /**
+     * Cancels any ongoing local model import operation.
+     *
+     * @return null if no import is in progress,
+     *         true if successfully canceled,
+     *         false if cancellation failed
+     */
+    suspend fun cancelImport(): Boolean?
+
+    /**
+     * Update a model's last used timestamp.
+     */
+    suspend fun updateModelLastUsed(modelId: String)
+
+    /**
+     * Delete a model or in batches
+     */
+    suspend fun deleteModel(modelId: String)
+    suspend fun deleteModels(modelIds: List<String>)
 }
 
 @Singleton
@@ -93,16 +117,27 @@ class ModelRepositoryImpl @Inject constructor(
     override suspend fun getModelById(id: String) =
         modelDao.getModelById(id)?.toModelInfo()
 
+
+    private var importJob: Job? = null
+    private var currentModelFile: File? = null
+
     override suspend fun importModel(
         uri: Uri,
         name: String?,
         size: Long?,
         progressTracker: ImportProgressTracker?
     ): ModelInfo = withContext(Dispatchers.IO) {
+        if (importJob != null && importJob?.isActive == true) {
+            throw IllegalStateException("Another import is already in progress!")
+        }
+
         val fileName = name ?: getFileNameFromUri(context, uri) ?: throw FileNotFoundException("Filename N/A")
         val fileSize = size ?: getFileSizeFromUri(context, uri) ?: throw FileNotFoundException("File size N/A")
         val modelFile = File(modelsDir, fileName)
 
+        importJob = coroutineContext[Job]
+        currentModelFile = modelFile
+
         try {
             val inputStream = context.contentResolver.openInputStream(uri)
                 ?: throw IOException("Failed to open input stream")
@@ -163,12 +198,74 @@ class ModelRepositoryImpl @Inject constructor(
                 dateAdded = System.currentTimeMillis()
             ).let {
                 modelDao.insertModel(it)
+
+                importJob = null
+                currentModelFile = null
+
                 it.toModelInfo()
             }
-        } catch (e: Exception) {
-            // Clean up partially downloaded file if error occurs
-            if (modelFile.exists()) { modelFile.delete() }
+
+        } catch (e: CancellationException) {
+            Log.i(TAG, "Import was cancelled for $fileName: ${e.message}")
+            cleanupPartialFile(modelFile)
             throw e
+
+        } catch (e: Exception) {
+            Log.e(TAG, "Import failed for $fileName: ${e.message}")
+            cleanupPartialFile(modelFile)
+            throw e
+
+        } finally {
+            importJob = null
+            currentModelFile = null
+        }
+    }
+
+    override suspend fun cancelImport(): Boolean? = withContext(Dispatchers.IO) {
+        val job = importJob
+        val file = currentModelFile
+
+        return@withContext when {
+            // No import in progress
+            job == null -> null
+
+            // Job already completed or cancelled
+            !job.isActive -> {
+                importJob = null
+                currentModelFile = null
+                null
+            }
+
+            // Job in progress
+            else -> try {
+                // Attempt to cancel the job
+                job.cancel("Import cancelled by user")
+
+                // Give the job a moment to clean up
+                delay(CANCEL_LOCAL_MODEL_IMPORT_TIMEOUT)
+
+                // Clean up the partial file (as a safety measure)
+                cleanupPartialFile(file)
+
+                // Reset state
+                importJob = null
+                currentModelFile = null
+
+                true // Successfully cancelled
+            } catch (e: Exception) {
+                Log.e(TAG, "Failed to cancel import: ${e.message}")
+                false
+            }
+        }
+    }
+
+    private fun cleanupPartialFile(file: File?) {
+        try {
+            if (file?.exists() == true && !file.delete()) {
+                Log.e(TAG, "Failed to delete partial file: ${file.absolutePath}")
+            }
+        } catch (e: Exception) {
+            Log.e(TAG, "Error cleaning up partial file: ${e.message}")
         }
     }
 
@@ -212,6 +309,7 @@ class ModelRepositoryImpl @Inject constructor(
 
         private const val INTERNAL_STORAGE_PATH = "models"
 
+        private const val STORAGE_METRICS_UPDATE_INTERVAL = 5_000L
         private const val BYTES_IN_GB = 1024f * 1024f * 1024f
 
         private const val LARGE_MODEL_THRESHOLD_SIZE = 1024 * 1024 * 1024
@@ -219,8 +317,8 @@ class ModelRepositoryImpl @Inject constructor(
         private const val NIO_YIELD_SIZE = 128 * 1024 * 1024
         private const val DEFAULT_BUFFER_SIZE = 4 * 1024 * 1024
         private const val DEFAULT_YIELD_SIZE = 16 * 1024 * 1024
+        private const val CANCEL_LOCAL_MODEL_IMPORT_TIMEOUT = 500L
 
-        private const val STORAGE_METRICS_UPDATE_INTERVAL = 5_000L
         private const val DEFAULT_CONTEXT_SIZE = 8192
 
     }