fix(util): is folder writable anr

[alperozturk96]

Issue

ANR error caused by executing I/O on the main thread.

 #00  pc 0x000000000009f7dc  /apex/com.android.runtime/lib64/bionic/libc.so (syscall+28)
  #01  pc 0x0000000000201434  /apex/com.android.art/lib64/libart.so (art::ConditionVariable::WaitHoldingLocks+136)
  #02  pc 0x000000000064a824  /apex/com.android.art/lib64/libart.so (art::JNI<false>::NewStringUTF+3972)
  #03  pc 0x00000000000242a8  /apex/com.android.art/lib64/libopenjdk.so (Java_java_io_UnixFileSystem_list0+420)
  at java.io.UnixFileSystem.list0 (Native method)
  at java.io.UnixFileSystem.list (UnixFileSystem.java:402)
  at java.io.File.list (File.java:1145)
  at java.io.File.listFiles (File.java:1230)
  at com.owncloud.android.utils.FileStorageUtils.isFolderWritable (FileStorageUtils.java:795)
  at com.owncloud.android.ui.activity.UploadFilesActivity.checkWritableFolder (UploadFilesActivity.java:599)
  at com.owncloud.android.ui.activity.UploadFilesActivity.pushDirname (UploadFilesActivity.java:465)
  at com.owncloud.android.ui.activity.UploadFilesActivity.onDirectoryClick (UploadFilesActivity.java:593)
  at com.owncloud.android.ui.fragment.LocalFileListFragment.onItemClicked (LocalFileListFragment.java:179)
  at com.owncloud.android.ui.adapter.LocalFileListAdapter.lambda$onBindViewHolder$1 (LocalFileListAdapter.java:254)
  at com.owncloud.android.ui.adapter.LocalFileListAdapter.$r8$lambda$QpkUeU_0knpa_PBZ0Gk2E9oqku4 (unavailable)
  at com.owncloud.android.ui.adapter.LocalFileListAdapter$$ExternalSyntheticLambda4.onClick (D8$$SyntheticClass)
  at android.view.View.performClick (View.java:8229)
  at android.view.View.performClickInternal (View.java:8206)
  at android.view.View.-$$Nest$mperformClickInternal (unavailable)
  at android.view.View$PerformClick.run (View.java:32007)
  at android.os.Handler.handleCallback (Handler.java:1095)
  at android.os.Handler.dispatchMessageImpl (Handler.java:135)
  at android.os.Handler.dispatchMessage (Handler.java:125)
  at android.os.Looper.loopOnce (Looper.java:269)
  at android.os.Looper.loop (Looper.java:367)
  at android.app.ActivityThread.main (ActivityThread.java:9333)
  at java.lang.reflect.Method.invoke (Native method)
  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run (RuntimeInit.java:566)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:929)

Changes

• Removes isFolderWritable FileStorageUtils.java and add inside FileUtils.java since FileUtils much smaller class.
• Converts FileUtils.java to Kotlin to handle thread management easily and write tests easily
• Removes unused getFilenameFromPathString function and tests
• Adds tests for isFolderWritable
• Instead of using listFiles which is very expensive operation, just tries to create temp dir then creates the temp file in temp dir then tries to delete all

This way in future we can slowly use our util functions inside FileUtils.kt then gain performance, safety.

[github-actions]

APK file: https://github.com/nextcloud/android/actions/runs/24077570029/artifacts/6304182028
To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.
(please click on link to get QR code displayed)

[github-actions]

Codacy

SpotBugs

Category	Base	New
Bad practice	36	36
Correctness	69	69
Dodgy code	229	229
Experimental	1	1
Internationalization	7	7
Malicious code vulnerability	2	2
Multithreaded correctness	34	34
Performance	42	42
Security	16	16
Total	436	436

[github-actions]

APK file: https://github.com/nextcloud/android/actions/runs/24078527579/artifacts/6304561069
To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.
(please click on link to get QR code displayed)

[github-actions]

blue-Light-Screenshot test failed, but no output was generated. Maybe a preliminary stage failed.