#!/usr/bin/env python
#
# Copyright 2018 Red Hat Inc.
#
# 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.
from __future__ import print_function
import logging
import os
import pwd
import stat
import sys

logging.basicConfig(stream=sys.stdout, level=logging.DEBUG)
LOG = logging.getLogger('nova_statedir')


class PathManager(object):
    """Helper class to manipulate ownership of a given path"""
    def __init__(self, path):
        self.path = path
        self._update()

    def _update(self):
        statinfo = os.stat(self.path)
        self.is_dir = stat.S_ISDIR(statinfo.st_mode)
        self.uid = statinfo.st_uid
        self.gid = statinfo.st_gid

    def __str__(self):
        return "uid: {} gid: {} path: {}{}".format(
            self.uid,
            self.gid,
            self.path,
            '/' if self.is_dir else ''
        )

    def has_owner(self, uid, gid):
        return self.uid == uid and self.gid == gid

    def has_either(self, uid, gid):
        return self.uid == uid or self.gid == gid

    def chown(self, uid, gid):
        target_uid = -1
        target_gid = -1
        if self.uid != uid:
            target_uid = uid
        if self.gid != gid:
            target_gid = gid
        if (target_uid, target_gid) != (-1, -1):
            LOG.info('Changing ownership of %s from %d:%d to %d:%d',
                     self.path,
                     self.uid,
                     self.gid,
                     self.uid if target_uid == -1 else target_uid,
                     self.gid if target_gid == -1 else target_gid)
            os.chown(self.path, target_uid, target_gid)
            self._update()
        else:
            LOG.info('Ownership of %s already %d:%d',
                     self.path,
                     uid,
                     gid)


class NovaStatedirOwnershipManager(object):
    """Class to manipulate the ownership of the nova statedir (/var/lib/nova).

       The nova uid/gid differ on the host and container images. An upgrade
       that switches from host systemd services to docker requires a change in
       ownership. Previously this was a naive recursive chown, however this
       causes issues if nova instance are shared via an NFS mount: any open
       filehandles in qemu/libvirt fail with an I/O error (LP1778465).

       Instead the upgrade/FFU ansible tasks now lay down a marker file when
       stopping and disabling the host systemd services. We use this file to
       determine the host nova uid/gid. We then walk the tree and update any
       files that have the host uid/gid to the docker nova uid/gid. As files
       owned by root/qemu etc... are ignored this avoids the issues with open
       filehandles. The marker is removed once the tree has been walked.

       For subsequent runs, or for a new deployment, we simply ensure that the
       docker nova user/group owns all directories. This is required as the
       directories are created with root ownership in host_prep_tasks (the
       docker nova uid/gid is not known in this context).
    """
    def __init__(self, statedir, upgrade_marker='upgrade_marker',
                 nova_user='nova'):
        self.statedir = statedir
        self.nova_user = nova_user

        self.upgrade_marker_path = os.path.join(statedir, upgrade_marker)
        self.upgrade = os.path.exists(self.upgrade_marker_path)

        self.target_uid, self.target_gid = self._get_nova_ids()
        self.previous_uid, self.previous_gid = self._get_previous_nova_ids()
        self.id_change = (self.target_uid, self.target_gid) != \
            (self.previous_uid, self.previous_gid)

    def _get_nova_ids(self):
        nova_uid, nova_gid = pwd.getpwnam(self.nova_user)[2:4]
        return nova_uid, nova_gid

    def _get_previous_nova_ids(self):
        if self.upgrade:
            statinfo = os.stat(self.upgrade_marker_path)
            return statinfo.st_uid, statinfo.st_gid
        else:
            return self._get_nova_ids()

    def _walk(self, top):
        for f in os.listdir(top):
            pathname = os.path.join(top, f)

            if pathname == self.upgrade_marker_path:
                continue

            pathinfo = PathManager(pathname)
            LOG.info("Checking %s", pathinfo)
            if pathinfo.is_dir:
                # Always chown the directories
                pathinfo.chown(self.target_uid, self.target_gid)
                self._walk(pathname)
            elif self.id_change:
                # Only chown files if it's an upgrade and the file is owned by
                # the host nova uid/gid
                pathinfo.chown(
                    self.target_uid if pathinfo.uid == self.previous_uid
                    else pathinfo.uid,
                    self.target_gid if pathinfo.gid == self.previous_gid
                    else pathinfo.gid
                )

    def run(self):
        LOG.info('Applying nova statedir ownership')
        LOG.info('Target ownership for %s: %d:%d',
                 self.statedir,
                 self.target_uid,
                 self.target_gid)

        pathinfo = PathManager(self.statedir)
        LOG.info("Checking %s", pathinfo)
        pathinfo.chown(self.target_uid, self.target_gid)

        self._walk(self.statedir)

        if self.upgrade:
            LOG.info('Removing upgrade_marker %s',
                     self.upgrade_marker_path)
            os.unlink(self.upgrade_marker_path)

        LOG.info('Nova statedir ownership complete')

if __name__ == '__main__':
    NovaStatedirOwnershipManager('/var/lib/nova').run()
