#
# The Qubes OS Project, https://www.qubes-os.org/
#
# Copyright (C) 2010-2015  Joanna Rutkowska <joanna@invisiblethingslab.com>
# Copyright (C) 2013-2015  Marek Marczykowski-Górecki
#                              <marmarek@invisiblethingslab.com>
# Copyright (C) 2014-2015  Wojtek Porczyk <woju@invisiblethingslab.com>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, see <https://www.gnu.org/licenses/>.
#

import asyncio
import hashlib
import logging
import random
import string
import os
import os.path
import socket
import subprocess
import tempfile
from contextlib import contextmanager, suppress

import pkg_resources

import docutils
import docutils.core
import docutils.io
import qubes.exc

LOGGER = logging.getLogger('qubes.utils')


def get_timezone():
    if os.path.islink('/etc/localtime'):
        tz_path = '/'.join(os.readlink('/etc/localtime').split('/'))
        return tz_path.split('zoneinfo/')[1]
    # last resort way, some applications makes /etc/localtime
    # hardlink instead of symlink...
    tz_info = os.stat('/etc/localtime')
    if not tz_info:
        return None
    if tz_info.st_nlink > 1:
        p = subprocess.Popen(['find', '/usr/share/zoneinfo',
            '-inum', str(tz_info.st_ino), '-print', '-quit'],
            stdout=subprocess.PIPE)
        tz_path = p.communicate()[0].strip()
        return tz_path.replace(b'/usr/share/zoneinfo/', b'')
    return None


def format_doc(docstring):
    '''Return parsed documentation string, stripping RST markup.
    '''

    if not docstring:
        return ''

    # pylint: disable=unused-variable
    output, pub = docutils.core.publish_programmatically(
        source_class=docutils.io.StringInput,
        source=' '.join(docstring.strip().split()),
        source_path=None,
        destination_class=docutils.io.NullOutput, destination=None,
        destination_path=None,
        reader=None, reader_name='standalone',
        parser=None, parser_name='restructuredtext',
        writer=None, writer_name='null',
        settings=None, settings_spec=None, settings_overrides=None,
        config_section=None, enable_exit_status=None)
    return pub.writer.document.astext()

def parse_size(size):
    units = [
        ('K', 1000), ('KB', 1000),
        ('M', 1000 * 1000), ('MB', 1000 * 1000),
        ('G', 1000 * 1000 * 1000), ('GB', 1000 * 1000 * 1000),
        ('Ki', 1024), ('KiB', 1024),
        ('Mi', 1024 * 1024), ('MiB', 1024 * 1024),
        ('Gi', 1024 * 1024 * 1024), ('GiB', 1024 * 1024 * 1024),
    ]

    size = size.strip().upper()
    if size.isdigit():
        return int(size)

    for unit, multiplier in units:
        if size.endswith(unit.upper()):
            size = size[:-len(unit)].strip()
            return int(size) * multiplier

    raise qubes.exc.QubesException("Invalid size: {0}.".format(size))

def mbytes_to_kmg(size):
    if size > 1024:
        return "%d GiB" % (size / 1024)

    return "%d MiB" % size


def kbytes_to_kmg(size):
    if size > 1024:
        return mbytes_to_kmg(size / 1024)

    return "%d KiB" % size


def bytes_to_kmg(size):
    if size > 1024:
        return kbytes_to_kmg(size / 1024)

    return "%d B" % size


def size_to_human(size):
    """Humane readable size, with 1/10 precision"""
    if size < 1024:
        return str(size)
    if size < 1024 * 1024:
        return str(round(size / 1024.0, 1)) + ' KiB'
    if size < 1024 * 1024 * 1024:
        return str(round(size / (1024.0 * 1024), 1)) + ' MiB'

    return str(round(size / (1024.0 * 1024 * 1024), 1)) + ' GiB'


def urandom(size):
    rand = os.urandom(size)
    if rand is None:
        raise IOError('failed to read urandom')
    return hashlib.sha512(rand).digest()


def get_entry_point_one(group, name):
    epoints = tuple(pkg_resources.iter_entry_points(group, name))
    if not epoints:
        raise KeyError(name)
    if len(epoints) > 1:
        raise TypeError(
            'more than 1 implementation of {!r} found: {}'.format(name,
                ', '.join('{}.{}'.format(ep.module_name, '.'.join(ep.attrs))
                    for ep in epoints)))
    return epoints[0].load()


def random_string(length=5):
    ''' Return random string consisting of ascii_leters and digits '''
    return ''.join(random.choice(string.ascii_letters + string.digits)
                   for _ in range(length))

def systemd_notify():
    '''Notify systemd'''
    nofity_socket = os.getenv('NOTIFY_SOCKET')
    if not nofity_socket:
        return
    if nofity_socket.startswith('@'):
        nofity_socket = '\0' + nofity_socket[1:]
    sock = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
    sock.connect(nofity_socket)
    sock.sendall(b'READY=1')
    sock.close()

def match_vm_name_with_special(vm, name):
    '''Check if *vm* matches given name, which may be specified as @tag:...
    or @type:...'''
    if name.startswith('@tag:'):
        return name[len('@tag:'):] in vm.tags
    if name.startswith('@type:'):
        return name[len('@type:'):] == vm.__class__.__name__
    return name == vm.name

@contextmanager
def replace_file(dst, *, permissions, close_on_success=True,
                 logger=LOGGER, log_level=logging.DEBUG):
    ''' Yield a tempfile whose name starts with dst. If the block does
        not raise an exception, apply permissions and persist the
        tempfile to dst (which is allowed to already exist). Otherwise
        ensure that the tempfile is cleaned up.
    '''
    tmp_dir, prefix = os.path.split(dst + '~')
    tmp = tempfile.NamedTemporaryFile(dir=tmp_dir, prefix=prefix, delete=False)
    try:
        yield tmp
        tmp.flush()
        os.fchmod(tmp.fileno(), permissions)
        os.fsync(tmp.fileno())
        if close_on_success:
            tmp.close()
        rename_file(tmp.name, dst, logger=logger, log_level=log_level)
    except:
        try:
            tmp.close()
        finally:
            remove_file(tmp.name, logger=logger, log_level=log_level)
        raise

def rename_file(src, dst, *, logger=LOGGER, log_level=logging.DEBUG):
    ''' Durably rename src to dst. '''
    os.rename(src, dst)
    dst_dir = os.path.dirname(dst)
    src_dir = os.path.dirname(src)
    fsync_path(dst_dir)
    if src_dir != dst_dir:
        fsync_path(src_dir)
    logger.log(log_level, 'Renamed file: %r -> %r', src, dst)

def remove_file(path, *, logger=LOGGER, log_level=logging.DEBUG):
    ''' Durably remove the file at path, if it exists. Return whether
        we removed it. '''
    with suppress(FileNotFoundError):
        os.remove(path)
        fsync_path(os.path.dirname(path))
        logger.log(log_level, 'Removed file: %r', path)
        return True
    return False

def fsync_path(path):
    fd = os.open(path, os.O_RDONLY)  # works for a file or a directory
    try:
        os.fsync(fd)
    finally:
        os.close(fd)

@asyncio.coroutine
def coro_maybe(value):
    if asyncio.iscoroutine(value):
        return (yield from value)
    return value

@asyncio.coroutine
def void_coros_maybe(values):
    ''' Ignore elements of the iterable values that are not coroutine
        objects. Run all coroutine objects to completion, concurrent
        with each other. If there were exceptions, raise the leftmost
        one (not necessarily chronologically first). Return nothing.
    '''
    coros = [val for val in values if asyncio.iscoroutine(val)]
    if coros:
        done, _ = yield from asyncio.wait(coros)
        for task in done:
            task.result()  # re-raises exception if task failed