# Copyright 2012 Michael Still and Canonical Inc
# 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. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License 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.

"""Config Drive v2 helper."""

import os
import shutil
import tempfile

from oslo.config import cfg
from oslo.utils import strutils
from oslo.utils import units

from nova import exception
from nova.i18n import _LW
from nova.openstack.common import fileutils
from nova.openstack.common import log as logging
from nova import utils
from nova import version

LOG = logging.getLogger(__name__)

configdrive_opts = [
    cfg.StrOpt('config_drive_format',
               default='iso9660',
               help='Config drive format. One of iso9660 (default) or vfat'),
    cfg.StrOpt('config_drive_tempdir',
               default=tempfile.tempdir,
               help=('DEPRECATED (not needed any more): '
                     ' Where to put temporary files associated with '
                     'config drive creation')),
    # force_config_drive is a string option, to allow for future behaviors
    #  (e.g. use config_drive based on image properties)
    cfg.StrOpt('force_config_drive',
               help='Set to force injection to take place on a config drive '
                    '(if set, valid options are: always)'),
    cfg.StrOpt('mkisofs_cmd',
               default='genisoimage',
               help='Name and optionally path of the tool used for '
                    'ISO image creation')
    ]

CONF = cfg.CONF
CONF.register_opts(configdrive_opts)

# Config drives are 64mb, if we can't size to the exact size of the data
CONFIGDRIVESIZE_BYTES = 64 * units.Mi


class ConfigDriveBuilder(object):
    """Build config drives, optionally as a context manager."""

    def __init__(self, instance_md=None):
        self.imagefile = None
        self.mdfiles = []

        if instance_md is not None:
            self.add_instance_metadata(instance_md)

    def __enter__(self):
        return self

    def __exit__(self, exctype, excval, exctb):
        if exctype is not None:
            # NOTE(mikal): this means we're being cleaned up because an
            # exception was thrown. All bets are off now, and we should not
            # swallow the exception
            return False
        self.cleanup()

    def _add_file(self, basedir, path, data):
        filepath = os.path.join(basedir, path)
        dirname = os.path.dirname(filepath)
        fileutils.ensure_tree(dirname)
        with open(filepath, 'wb') as f:
            f.write(data)

    def add_instance_metadata(self, instance_md):
        for (path, data) in instance_md.metadata_for_config_drive():
            self.mdfiles.append((path, data))

    def _write_md_files(self, basedir):
        for data in self.mdfiles:
            self._add_file(basedir, data[0], data[1])

    def _make_iso9660(self, path, tmpdir):
        publisher = "%(product)s %(version)s" % {
            'product': version.product_string(),
            'version': version.version_string_with_package()
            }

        utils.execute(CONF.mkisofs_cmd,
                      '-o', path,
                      '-ldots',
                      '-allow-lowercase',
                      '-allow-multidot',
                      '-l',
                      '-publisher',
                      publisher,
                      '-quiet',
                      '-J',
                      '-r',
                      '-V', 'config-2',
                      tmpdir,
                      attempts=1,
                      run_as_root=False)

    def _make_vfat(self, path, tmpdir):
        # NOTE(mikal): This is a little horrible, but I couldn't find an
        # equivalent to genisoimage for vfat filesystems.
        with open(path, 'wb') as f:
            f.truncate(CONFIGDRIVESIZE_BYTES)

        utils.mkfs('vfat', path, label='config-2')

        with utils.tempdir() as mountdir:
            mounted = False
            try:
                _, err = utils.trycmd(
                    'mount', '-o', 'loop,uid=%d,gid=%d' % (os.getuid(),
                                                           os.getgid()),
                    path,
                    mountdir,
                    run_as_root=True)
                if err:
                    raise exception.ConfigDriveMountFailed(operation='mount',
                                                           error=err)
                mounted = True

                # NOTE(mikal): I can't just use shutils.copytree here,
                # because the destination directory already
                # exists. This is annoying.
                for ent in os.listdir(tmpdir):
                    shutil.copytree(os.path.join(tmpdir, ent),
                                    os.path.join(mountdir, ent))

            finally:
                if mounted:
                    utils.execute('umount', mountdir, run_as_root=True)

    def make_drive(self, path):
        """Make the config drive.

        :param path: the path to place the config drive image at

        :raises ProcessExecuteError if a helper process has failed.
        """
        with utils.tempdir() as tmpdir:
            self._write_md_files(tmpdir)

            if CONF.config_drive_format == 'iso9660':
                self._make_iso9660(path, tmpdir)
            elif CONF.config_drive_format == 'vfat':
                self._make_vfat(path, tmpdir)
            else:
                raise exception.ConfigDriveUnknownFormat(
                    format=CONF.config_drive_format)

    def cleanup(self):
        if self.imagefile:
            fileutils.delete_if_exists(self.imagefile)

    def __repr__(self):
        return "<ConfigDriveBuilder: " + str(self.mdfiles) + ">"


def required_by(instance):

    image_prop = utils.instance_sys_meta(instance).get(
        utils.SM_IMAGE_PROP_PREFIX + 'img_config_drive', 'optional')
    if image_prop not in ['optional', 'mandatory']:
        LOG.warn(_LW('Image config drive option %(image_prop)s is invalid '
                        'and will be ignored') %
                        {'image_prop': image_prop},
                  instance=instance)

    return (instance.get('config_drive') or
            'always' == CONF.force_config_drive or
            strutils.bool_from_string(CONF.force_config_drive) or
            image_prop == 'mandatory'
            )
