import os
from errno import ENOENT

from ._api import BaseFileLock
from ._util import raise_on_exist_ro_file

try:
    import msvcrt
except ImportError:
    msvcrt = None


class WindowsFileLock(BaseFileLock):
    """Uses the :func:`msvcrt.locking` function to hard lock the lock file on windows systems."""

    def _acquire(self):
        raise_on_exist_ro_file(self._lock_file)
        mode = (
            os.O_RDWR  # open for read and write
            | os.O_CREAT  # create file if not exists
            | os.O_TRUNC  # truncate file  if not empty
        )
        try:
            fd = os.open(self._lock_file, mode)
        except OSError as exception:
            if exception.errno == ENOENT:  # No such file or directory
                raise
        else:
            try:
                msvcrt.locking(fd, msvcrt.LK_NBLCK, 1)
            except (OSError, IOError):  # noqa: B014 # IOError is not OSError on python 2
                os.close(fd)
            else:
                self._lock_file_fd = fd

    def _release(self):
        fd = self._lock_file_fd
        self._lock_file_fd = None
        msvcrt.locking(fd, msvcrt.LK_UNLCK, 1)
        os.close(fd)

        try:
            os.remove(self._lock_file)
        # Probably another instance of the application hat acquired the file lock.
        except OSError:
            pass


__all__ = [
    "WindowsFileLock",
]