# Copyright (c) 2018, Ansible Project
# Simplified BSD License (see licenses/simplified_bsd.txt or https://opensource.org/licenses/BSD-2-Clause)

from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

import errno
import os
import stat
import re
import pwd
import grp
import time
import shutil
import tempfile
import traceback
import fcntl
import sys

from contextlib import contextmanager
from ansible.module_utils._text import to_bytes, to_native, to_text
from ansible.module_utils.six import b, binary_type

try:
    import selinux
    HAVE_SELINUX = True
except ImportError:
    HAVE_SELINUX = False


class LockTimeout(Exception):
    pass


class FileLock:
    '''
    Currently FileLock is implemented via fcntl.flock on a lock file, however this
    behaviour may change in the future. Avoid mixing lock types fcntl.flock,
    fcntl.lockf and module_utils.common.file.FileLock as it will certainly cause
    unwanted and/or unexpected behaviour
    '''
    def __init__(self):
        self.lockfd = None

    @contextmanager
    def lock_file(self, path, lock_timeout=None):
        '''
        Context for lock acquisition
        '''
        try:
            self.set_lock(path, lock_timeout)
            yield
        finally:
            self.unlock()

    def set_lock(self, path, lock_timeout=None):
        '''
        Create a lock file based on path with flock to prevent other processes
        using given path

        :kw path: Path (file) to lock
        :kw lock_timeout:
            Wait n seconds for lock acquisition, fail if timeout is reached.
            0 = Do not wait, fail if lock cannot be acquired immediately,
            Default is None, wait indefinitely until lock is released.
        :returns: True
        '''
        tmp_dir = tempfile.gettempdir()
        lock_path = os.path.join(tmp_dir, 'ansible-{0}.lock'.format(os.path.basename(path)))
        l_wait = 0.1
        r_exception = IOError
        if sys.version_info[0] == 3:
            r_exception = BlockingIOError

        self.lockfd = open(lock_path, 'w')

        if lock_timeout <= 0:
            fcntl.flock(self.lockfd, fcntl.LOCK_EX | fcntl.LOCK_NB)
            os.chmod(lock_path, stat.S_IWRITE | stat.S_IREAD)
            return True

        if lock_timeout:
            e_secs = 0
            while e_secs < lock_timeout:
                try:
                    fcntl.flock(self.lockfd, fcntl.LOCK_EX | fcntl.LOCK_NB)
                    os.chmod(lock_path, stat.S_IWRITE | stat.S_IREAD)
                    return True
                except r_exception:
                    time.sleep(l_wait)
                    e_secs += l_wait
                    continue

            self.lockfd.close()
            raise LockTimeout('{0} sec'.format(lock_timeout))

        fcntl.flock(self.lockfd, fcntl.LOCK_EX)
        os.chmod(lock_path, stat.S_IWRITE | stat.S_IREAD)

        return True

    def unlock(self):
        '''
        Unlock the file descriptor locked by set_lock

        :returns: True
        '''
        if not self.lockfd:
            return True

        try:
            fcntl.flock(self.lockfd, fcntl.LOCK_UN)
            self.lockfd.close()
        except ValueError:  # file wasn't opened, let context manager fail gracefully
            pass

        return True