Initial internal download continue incomplete download

android/app/src/main/java/com/audiobookshelf/app/managers/DownloadItemManager.kt

@@ -19,7 +19,6 @@ import com.fasterxml.jackson.core.json.JsonReadFeature
 import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
 import com.getcapacitor.JSObject
 import java.io.File
-import java.io.FileOutputStream
 import java.util.*
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.GlobalScope
@@ -113,7 +112,6 @@ class DownloadItemManager(
     val file = File(downloadItemPart.finalDestinationPath)
     file.parentFile?.mkdirs()
 
-    val fileOutputStream = FileOutputStream(downloadItemPart.finalDestinationPath)
     val internalProgressCallback =
             object : InternalProgressCallback {
               override fun onProgress(totalBytesWritten: Long, progress: Long) {
@@ -131,7 +129,11 @@ class DownloadItemManager(
             tag,
             "Start internal download to destination path ${downloadItemPart.finalDestinationPath} from ${downloadItemPart.serverUrl}"
     )
-    InternalDownloadManager(fileOutputStream, internalProgressCallback)
+    InternalDownloadManager(
+                    mainActivity,
+                    downloadItemPart.finalDestinationUri,
+                    internalProgressCallback
+            )
             .download(downloadItemPart.serverUrl)
     downloadItemPart.downloadId = 1
     currentDownloadItemParts.add(downloadItemPart)

android/app/src/main/java/com/audiobookshelf/app/managers/InternalDownloadManager.kt

@@ -1,5 +1,7 @@
 package com.audiobookshelf.app.managers
 
+import android.content.Context
+import android.net.Uri
 import android.util.Log
 import java.io.*
 import java.util.concurrent.TimeUnit
@@ -12,14 +14,14 @@ import okhttp3.*
  * @property progressCallback The callback to report download progress.
  */
 class InternalDownloadManager(
-        private val outputStream: FileOutputStream,
+        private val context: Context,
+        private val fileUri: Uri,
         private val progressCallback: DownloadItemManager.InternalProgressCallback
 ) : AutoCloseable {
 
   private val tag = "InternalDownloadManager"
   private val client: OkHttpClient =
           OkHttpClient.Builder().connectTimeout(30, TimeUnit.SECONDS).build()
-  private val writer = BinaryFileWriter(outputStream, progressCallback)
 
   /**
    * Downloads a file from the given URL.
@@ -29,69 +31,108 @@ class InternalDownloadManager(
    */
   @Throws(IOException::class)
   fun download(url: String) {
-    val request: Request = Request.Builder().url(url).build()
-    client.newCall(request)
-            .enqueue(
-                    object : Callback {
-                      override fun onFailure(call: Call, e: IOException) {
-                        Log.e(tag, "Download URL $url FAILED", e)
-                        progressCallback.onComplete(true)
-                      }
+    try {
+      val existingSize = getInternalFileSize(fileUri)
+      Log.d(tag, "Existing file size: $existingSize bytes")
 
-                      override fun onResponse(call: Call, response: Response) {
-                        response.body?.let { responseBody ->
-                          val length: Long = response.header("Content-Length")?.toLongOrNull() ?: 0L
-                          writer.write(responseBody.byteStream(), length)
+      val request =
+              Request.Builder()
+                      .url(url)
+                      .apply {
+                        if (existingSize > 0) {
+                          addHeader("Range", "bytes=$existingSize-") // Resume download
                         }
-                                ?: run {
-                                  Log.e(tag, "Response doesn't contain a file")
-                                  progressCallback.onComplete(true)
-                                }
                       }
-                    }
-            )
+                      .build()
+
+      client.newCall(request)
+              .enqueue(
+                      object : Callback {
+                        override fun onFailure(call: Call, e: IOException) {
+                          Log.e(tag, "Download failed: $url", e)
+                          progressCallback.onComplete(true)
+                        }
+
+                        override fun onResponse(call: Call, response: Response) {
+                          if (!response.isSuccessful) {
+                            Log.e(tag, "Failed to download: ${response.code}")
+                            progressCallback.onComplete(true)
+                            return
+                          }
+
+                          response.body?.let { responseBody ->
+                            val totalLength =
+                                    (response.header("Content-Length")?.toLongOrNull()
+                                            ?: 0L) + existingSize
+                            val outputStream = getOutputStream(fileUri, existingSize)
+
+                            outputStream?.let {
+                              BinaryFileWriter(it, progressCallback, existingSize).use { writer ->
+                                writer.write(responseBody.byteStream(), totalLength)
+                              }
+                            }
+                                    ?: run {
+                                      Log.e(tag, "Failed to open output stream")
+                                      progressCallback.onComplete(true)
+                                    }
+                          }
+                                  ?: run {
+                                    Log.e(tag, "Response doesn't contain a file")
+                                    progressCallback.onComplete(true)
+                                  }
+                        }
+                      }
+              )
+    } catch (e: Exception) {
+      Log.e(tag, "Download error", e)
+      progressCallback.onComplete(true)
+    }
   }
 
-  /**
-   * Closes the download manager and releases resources.
-   *
-   * @throws Exception If an error occurs during closing.
-   */
-  @Throws(Exception::class)
-  override fun close() {
-    writer.close()
+  private fun getInternalFileSize(uri: Uri): Long {
+    val file = File(uri.path!!)
+    return if (file.exists()) file.length() else 0L
   }
+
+  private fun getOutputStream(uri: Uri, existingSize: Long): OutputStream? {
+    val file = File(uri.path!!)
+    return if (file.exists()) {
+      FileOutputStream(file, true).apply {
+        channel.position(existingSize) // Move to the end of the file to append
+      }
+    } else {
+      FileOutputStream(file) // Create a new file if it doesn't exist
+    }
+  }
+
+  @Throws(Exception::class) override fun close() {}
 }
 
-/**
- * Writes binary data to an output stream.
- *
- * @property outputStream The output stream to write the data to.
- * @property progressCallback The callback to report write progress.
- */
 class BinaryFileWriter(
         private val outputStream: OutputStream,
-        private val progressCallback: DownloadItemManager.InternalProgressCallback
+        private val progressCallback: DownloadItemManager.InternalProgressCallback,
+        private val existingSize: Long
 ) : AutoCloseable {
 
   /**
    * Writes data from the input stream to the output stream.
    *
    * @param inputStream The input stream to read the data from.
-   * @param length The total length of the data to be written.
+   * @param totalLength The total length of the data to be written.
    * @return The total number of bytes written.
    * @throws IOException If an I/O error occurs.
    */
   @Throws(IOException::class)
-  fun write(inputStream: InputStream, length: Long): Long {
+  fun write(inputStream: InputStream, totalLength: Long): Long {
     BufferedInputStream(inputStream).use { input ->
       val dataBuffer = ByteArray(CHUNK_SIZE)
-      var totalBytes: Long = 0
+      var totalBytes = existingSize
       var readBytes: Int
+
       while (input.read(dataBuffer).also { readBytes = it } != -1) {
         totalBytes += readBytes
         outputStream.write(dataBuffer, 0, readBytes)
-        progressCallback.onProgress(totalBytes, (totalBytes * 100L) / length)
+        progressCallback.onProgress(totalBytes, (totalBytes * 100L) / totalLength)
       }
       progressCallback.onComplete(false)
       return totalBytes