import shutil

from django.core.management.base import BaseCommand, CommandError
from django.db import connection, transaction

from openslides.utils.main import get_database_path_from_settings


class Command(BaseCommand):
    """
    Command to backup the SQLite3 database.
    """

    help = "Backups the SQLite3 database."

    def add_arguments(self, parser):
        parser.add_argument(
            "--path",
            default="database_backup.sqlite",
            help="Path for the backup file (Default: database_backup.sqlite).",
        )

    def handle(self, *args, **options):
        path = options.get("path")

        @transaction.atomic
        def do_backup(src_path, dest_path):
            # perform a simple file-copy backup of the database
            # first we need a shared lock on the database, issuing a select()
            # will do this for us
            cursor = connection.cursor()
            cursor.execute("SELECT count(*) from sqlite_master")
            # now copy the file
            try:
                shutil.copy(src_path, dest_path)
            except IOError:
                # TODO: use the IOError message as message for the user
                raise CommandError("Database backup failed.")

        database_path = get_database_path_from_settings()
        if database_path:
            do_backup(database_path, path)
            self.stdout.write(
                self.style.SUCCESS(
                    f"Database {database_path} successfully stored at {path}."
                )
            )
        else:
            raise CommandError(
                "Default database is not SQLite3. Only SQLite3 databases"
                "can currently be backuped."
            )