import errno
import logging
import os
import shutil
import stat
import time

"""
File system utilities, copied from mozfile.
"""

LOG = logging.getLogger(__name__)


def _call_windows_retry(func, args=(), retry_max=5, retry_delay=0.5):
    """
    It's possible to see spurious errors on Windows due to various things
    keeping a handle to the directory open (explorer, virus scanners, etc)
    So we try a few times if it fails with a known error.
    """
    retry_count = 0
    while True:
        try:
            func(*args)
        except OSError as e:
            # Error codes are defined in:
            # http://docs.python.org/2/library/errno.html#module-errno
            if e.errno not in (errno.EACCES, errno.ENOTEMPTY):
                raise

            if retry_count == retry_max:
                raise

            retry_count += 1

            LOG.info('%s() failed for "%s". Reason: %s (%s). Retrying...',
                     func.__name__, args, e.strerror, e.errno)
            time.sleep(retry_delay)
        else:
            # If no exception has been thrown it should be done
            break


def remove(path):
    """Removes the specified file, link, or directory tree.

    This is a replacement for shutil.rmtree that works better under
    windows. It does the following things:

     - check path access for the current user before trying to remove
     - retry operations on some known errors due to various things keeping
       a handle on file paths - like explorer, virus scanners, etc. The
       known errors are errno.EACCES and errno.ENOTEMPTY, and it will
       retry up to 5 five times with a delay of 0.5 seconds between each
       attempt.

    Note that no error will be raised if the given path does not exists.

    :param path: path to be removed
    """

    def _call_with_windows_retry(*args, **kwargs):
        try:
            _call_windows_retry(*args, **kwargs)
        except OSError as e:
            # The file or directory to be removed doesn't exist anymore
            if e.errno != errno.ENOENT:
                raise

    def _update_permissions(path):
        """Sets specified pemissions depending on filetype"""
        if os.path.islink(path):
            # Path is a symlink which we don't have to modify
            # because it should already have all the needed permissions
            return

        stats = os.stat(path)

        if os.path.isfile(path):
            mode = stats.st_mode | stat.S_IWUSR
        elif os.path.isdir(path):
            mode = stats.st_mode | stat.S_IWUSR | stat.S_IXUSR
        else:
            # Not supported type
            return

        _call_with_windows_retry(os.chmod, (path, mode))

    if not os.path.exists(path):
        return

    if os.path.isfile(path) or os.path.islink(path):
        # Verify the file or link is read/write for the current user
        _update_permissions(path)
        _call_with_windows_retry(os.remove, (path,))

    elif os.path.isdir(path):
        # Verify the directory is read/write/execute for the current user
        _update_permissions(path)

        # We're ensuring that every nested item has writable permission.
        for root, dirs, files in os.walk(path):
            for entry in dirs + files:
                _update_permissions(os.path.join(root, entry))
        _call_with_windows_retry(shutil.rmtree, (path,))


def move(src, dst):
    """
    Move a file or directory path.

    This is a replacement for shutil.move that works better under windows,
    retrying operations on some known errors due to various things keeping
    a handle on file paths.
    """
    _call_windows_retry(shutil.move, (src, dst))