# Copyright 2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
# http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.
import inspect
import sys
import os
import errno
import socket

from botocore.compat import six


if sys.platform.startswith('win'):
    def rename_file(current_filename, new_filename):
        try:
            os.remove(new_filename)
        except OSError as e:
            if not e.errno == errno.ENOENT:
                # We only want to a ignore trying to remove
                # a file that does not exist.  If it fails
                # for any other reason we should be propagating
                # that exception.
                raise
        os.rename(current_filename, new_filename)
else:
    rename_file = os.rename

if six.PY3:
    def accepts_kwargs(func):
        # In python3.4.1, there's backwards incompatible
        # changes when using getargspec with functools.partials.
        return inspect.getfullargspec(func)[2]

    # In python3, socket.error is OSError, which is too general
    # for what we want (i.e FileNotFoundError is a subclass of OSError).
    # In py3 all the socket related errors are in a newly created
    # ConnectionError
    SOCKET_ERROR = ConnectionError
    MAXINT = None
else:
    def accepts_kwargs(func):
        return inspect.getargspec(func)[2]

    SOCKET_ERROR = socket.error
    MAXINT = sys.maxint


def seekable(fileobj):
    """Backwards compat function to determine if a fileobj is seekable

    :param fileobj: The file-like object to determine if seekable

    :returns: True, if seekable. False, otherwise.
    """
    # If the fileobj has a seekable attr, try calling the seekable()
    # method on it.
    if hasattr(fileobj, 'seekable'):
        return fileobj.seekable()
    # If there is no seekable attr, check if the object can be seeked
    # or telled. If it can, try to seek to the current position.
    elif hasattr(fileobj, 'seek') and hasattr(fileobj, 'tell'):
        try:
            fileobj.seek(0, 1)
            return True
        except (OSError, IOError):
            # If an io related error was thrown then it is not seekable.
            return False
    # Else, the fileobj is not seekable
    return False


def readable(fileobj):
    """Determines whether or not a file-like object is readable.

    :param fileobj: The file-like object to determine if readable

    :returns: True, if readable. False otherwise.
    """
    if hasattr(fileobj, 'readable'):
        return fileobj.readable()

    return hasattr(fileobj, 'read')


def fallocate(fileobj, size):
    if hasattr(os, 'posix_fallocate'):
        os.posix_fallocate(fileobj.fileno(), 0, size)
    else:
        fileobj.truncate(size)


if sys.version_info[:2] == (2, 6):
    # For Python 2.6, the start() method does not accept initializers.
    # So we backport the functionality. This is strictly a copy from the
    # Python 2.7 version.
    import multiprocessing
    import multiprocessing.managers
    import multiprocessing.connection
    import multiprocessing.util


    class BaseManager(multiprocessing.managers.BaseManager):
        def start(self, initializer=None, initargs=()):
            '''
            Spawn a server process for this manager object
            '''
            assert self._state.value == multiprocessing.managers.State.INITIAL

            if initializer is not None and not hasattr(initializer,
                                                       '__call__'):
                raise TypeError('initializer must be a callable')

            # pipe over which we will retrieve address of server
            reader, writer = multiprocessing.Pipe(duplex=False)

            # spawn process which runs a server
            self._process = multiprocessing.Process(
                target=type(self)._run_server,
                args=(self._registry, self._address, self._authkey,
                      self._serializer, writer, initializer, initargs),
            )
            ident = ':'.join(str(i) for i in self._process._identity)
            self._process.name = type(self).__name__ + '-' + ident
            self._process.start()

            # get address of server
            writer.close()
            self._address = reader.recv()
            reader.close()

            # register a finalizer
            self._state.value = multiprocessing.managers.State.STARTED
            self.shutdown = multiprocessing.util.Finalize(
                self, type(self)._finalize_manager,
                args=(self._process, self._address, self._authkey,
                      self._state, self._Client),
                exitpriority=0
            )

        @classmethod
        def _run_server(cls, registry, address, authkey, serializer,
                        writer,
                        initializer=None, initargs=()):
            '''
            Create a server, report its address and run it
            '''
            if initializer is not None:
                initializer(*initargs)

            # create server
            server = cls._Server(registry, address, authkey, serializer)

            # inform parent process of the server's address
            writer.send(server.address)
            writer.close()

            # run the manager
            multiprocessing.util.info('manager serving at %r', server.address)

            server.serve_forever()


else:
    from multiprocessing.managers import BaseManager