Introduce device specific writable directory (MAC address)

Also adds temporary method to move the fetched files from the legacy path to the new one which does not include the device name.
Also moves the FileIndex to the end of the cached files to allow for easier sorting.

Cherry-picked from 525b395c01ce57449ee9a8f74af663595223279e and adapted

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/AbstractDeviceCoordinator.java

@@ -80,6 +80,7 @@ import nodomain.freeyourgadget.gadgetbridge.model.StressSample;
 import nodomain.freeyourgadget.gadgetbridge.model.TemperatureSample;
 import nodomain.freeyourgadget.gadgetbridge.service.ServiceDeviceSupport;
 import nodomain.freeyourgadget.gadgetbridge.service.SleepAsAndroidSender;
+import nodomain.freeyourgadget.gadgetbridge.util.FileUtils;
 import nodomain.freeyourgadget.gadgetbridge.util.GBPrefs;
 import nodomain.freeyourgadget.gadgetbridge.util.Prefs;
 
@@ -296,6 +297,18 @@ public abstract class AbstractDeviceCoordinator implements DeviceCoordinator {
         return null;
     }
 
+    @Override
+    public File getWritableExportDirectory(final GBDevice device) throws IOException {
+        File dir;
+        dir = new File(FileUtils.getExternalFilesDir() + File.separator + device.getAddress());
+        if (!dir.isDirectory()) {
+            if (!dir.mkdir()) {
+                throw new IOException("Cannot create device specific directory for " + device.getName());
+            }
+        }
+        return dir;
+    }
+
     @Override
     public String getAppCacheSortFilename() {
         return null;

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/devices/DeviceCoordinator.java

@@ -458,6 +458,11 @@ public interface DeviceCoordinator {
      */
     File getAppCacheDir() throws IOException;
 
+    /**
+     * Returns the dedicated writable export directory for this device.
+     */
+    File getWritableExportDirectory(GBDevice device) throws IOException;
+
     /**
      * Returns a String containing the device app sort order filename.
      */

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/garmin/FileTransferHandler.java

@@ -338,7 +338,7 @@ public class FileTransferHandler implements MessageHandler {
         public String getFileName() {
             SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd_HH-mm-ss");
             String dateString = dateFormat.format(fileDate);
-            return getFiletype().name() + "_" + getFileIndex() + "_" + dateString + (getFiletype().isFitFile() ? ".fit" : ".bin");
+            return getFiletype().name() + "_" + dateString + "_" + getFileIndex() + (getFiletype().isFitFile() ? ".fit" : ".bin");
         }
 
         @NonNull

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/devices/garmin/GarminSupport.java

@@ -445,6 +445,9 @@ public class GarminSupport extends AbstractBTLEDeviceSupport implements ICommuni
     }
 
     private void processDownloadQueue() {
+
+        moveFilesFromLegacyCache(); //TODO: remove before merging
+
         if (!filesToDownload.isEmpty() && !fileTransferHandler.isDownloading()) {
             if (!gbDevice.isBusy()) {
                 GB.updateTransferNotification(getContext().getString(R.string.busy_task_fetch_activity_data), "", true, 0, getContext());
@@ -484,6 +487,36 @@ public class GarminSupport extends AbstractBTLEDeviceSupport implements ICommuni
         }
     }
 
+    private void moveFilesFromLegacyCache() { //TODO: remove before merging
+        File legacyDir;
+        try {
+            legacyDir = new File(FileUtils.getExternalFilesDir() + "/" + FileUtils.makeValidFileName(getDevice().getName() + "_" + getDevice().getAddress()));
+
+            if (legacyDir.isDirectory()) {
+                final File newDir = getWritableExportDirectory();
+                File[] files = legacyDir.listFiles();
+
+                for (File file : files) {
+                    if (file.isFile()) {
+                        File destFile = new File(newDir, file.getName());
+                        boolean success = file.renameTo(destFile);
+                        if (!success) {
+                            LOG.error("Failed to move file {}", file.getName());
+                        } else {
+                            LOG.info("Moved file {} to new cache directory", file.getName());
+                        }
+                    }
+                }
+                boolean removed = legacyDir.delete();
+                if (!removed) {
+                    LOG.error("Failed to remove legacy directory: {}", legacyDir);
+                }
+            }
+        } catch (IOException e) {
+            LOG.error(e.getMessage());
+        }
+    }
+
     private void enableBatteryLevelUpdate() {
         final ProtobufMessage batteryLevelProtobufRequest = protocolBufferHandler.prepareProtobufRequest(GdiSmartProto.Smart.newBuilder()
                 .setDeviceStatusService(
@@ -597,14 +630,7 @@ public class GarminSupport extends AbstractBTLEDeviceSupport implements ICommuni
     }
 
     public File getWritableExportDirectory() throws IOException {
-        File dir;
+        return getDevice().getDeviceCoordinator().getWritableExportDirectory(getDevice());
-        dir = new File(FileUtils.getExternalFilesDir() + "/" + FileUtils.makeValidFileName(getDevice().getName() + "_" + getDevice().getAddress()));
-        if (!dir.isDirectory()) {
-            if (!dir.mkdir()) {
-                throw new IOException("Cannot create device specific directory for " + getDevice().getName());
-            }
-        }
-        return dir;
     }
 
     @Override