# https://github.com/pycontribs/tendo/blob/master/tendo/singleton.py


import logging
import os
import sys
import tempfile

logger = logging.getLogger('tendo.singleton')

if sys.platform != 'win32':
    import fcntl


class SingleInstanceException(BaseException):
    pass


class SingleInstance:
    """Class that can be instantiated only once per machine.

    If you want to prevent your script from running in parallel just instantiate SingleInstance() class. If is there
    another instance already running it will throw a `SingleInstanceException`.


    This option is very useful if you have scripts executed by crontab at small amounts of time.

    Remember that this works by creating a lock file with a filename based on the full path to the script file.

    Providing a flavor_id will augment the filename with the provided flavor_id, allowing you to create multiple
    singleton instances from the same file. This is particularly useful if you want specific functions to have their
    own singleton instances.
    """

    def __init__(self, flavor_id='', lockfile=''):
        self.initialized = False
        if lockfile:
            self.lockfile = lockfile
        else:
            basename = (
                os.path.splitext(os.path.abspath(sys.argv[0]))[0].replace('/', '-').replace(':', '').replace('\\', '-')
                + f'-{flavor_id}'
                + '.lock'
            )
            self.lockfile = os.path.normpath(f'{tempfile.gettempdir()}/{basename}')

        logger.debug(f'SingleInstance lockfile: {self.lockfile}')
        if sys.platform == 'win32':
            try:
                # file already exists, we try to remove (in case previous
                # execution was interrupted)
                if os.path.exists(self.lockfile):
                    os.unlink(self.lockfile)
                self.fd = os.open(self.lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
            except OSError as exc:
                type, e, tb = sys.exc_info()
                if e.errno == 13:
                    logger.error('Another instance is already running, quitting.')
                    raise SingleInstanceException() from exc
                print(e.errno)
                raise
        else:  # non Windows
            self.fp = open(self.lockfile, 'w')  # noqa: SIM115
            self.fp.flush()
            try:
                fcntl.lockf(self.fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
            except OSError as exc:
                logger.warning('Another instance is already running, quitting.')
                raise SingleInstanceException() from exc
        self.initialized = True

    def __del__(self):
        if not self.initialized:
            return
        try:
            if sys.platform == 'win32':
                if hasattr(self, 'fd'):
                    os.close(self.fd)
                    os.unlink(self.lockfile)
            else:
                fcntl.lockf(self.fp, fcntl.LOCK_UN)
                # os.close(self.fp)
                if os.path.isfile(self.lockfile):
                    os.unlink(self.lockfile)
        except Exception as e:
            if logger:
                logger.warning(e)
            else:
                print(f'Unloggable error: {e}', file=sys.stderr)
            sys.exit(-1)
