"""Permanent deletion shared by the trash API and scheduled retention cleanup."""
from django.db import transaction
from .models import DriveItem, UploadSession
from .services import descendant_files
from .storage_layout import disk_path, file_location


def has_active_uploads_in_tree(item):
    """Do not purge directories while a resumable upload targets a descendant."""
    if not item.is_folder:
        return False
    pending = [item.pk]
    while pending:
        batch, pending = pending[:250], pending[250:]
        if UploadSession.objects.filter(parent_id__in=batch).exists():
            return True
        pending.extend(DriveItem.objects.filter(parent_id__in=batch, is_folder=True).values_list('pk', flat=True))
    return False


def delete_trashed_item(item):
    """Delete the SQL tree, then its tracked files after commit.

    Untracked files and directories are not erased. Failures resolving a stored
    path abort before the SQL delete; missing physical files are tolerated.
    """
    if item.trashed_at is None:
        raise ValueError('L’élément doit être dans la corbeille.')
    if has_active_uploads_in_tree(item):
        raise ValueError('Un transfert est encore en cours dans ce dossier.')
    files = [disk_path(key) for key in descendant_files(item)]
    folder = disk_path(file_location(item.space, item.parent, item.name)) if item.is_folder else None
    with transaction.atomic():
        item.delete()
        def remove_files():
            for path in files:
                path.unlink(missing_ok=True)
            if folder and folder.is_dir() and not folder.is_symlink():
                # Only remove empty directories, never user data untracked by SQL.
                for candidate in sorted(folder.rglob('*'), key=lambda p:len(p.parts), reverse=True):
                    if candidate.is_dir() and not candidate.is_symlink():
                        try: candidate.rmdir()
                        except OSError: pass
                try: folder.rmdir()
                except OSError: pass
        transaction.on_commit(remove_files)