# needs_restarting.py
# DNF plugin to check for running binaries in a need of restarting.
#
# Copyright (C) 2014 Red Hat, Inc.
#
# This copyrighted material is made available to anyone wishing to use,
# modify, copy, or redistribute it subject to the terms and conditions of
# the GNU General Public License v.2, or (at your option) any later version.
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY expressed or implied, including the implied warranties of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
# Public License for more details.  You should have received a copy of the
# GNU General Public License along with this program; if not, write to the
# Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.  Any Red Hat trademarks that are incorporated in the
# source code or documentation are not subject to the GNU General Public
# License and may only be used or replicated with the express permission of
# Red Hat, Inc.
#
# the mechanism of scanning smaps for opened files and matching them back to
# packages is heavily inspired by the original needs-restarting.py:
# http://yum.baseurl.org/gitweb?p=yum-utils.git;a=blob;f=needs-restarting.py

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from __future__ import unicode_literals
from dnfpluginscore import logger, _

import dnf
import dnf.cli
import dbus
import functools
import os
import re
import stat
import time


# For which package updates we should recommend a reboot
# Mostly taken from https://access.redhat.com/solutions/27943
NEED_REBOOT = ['kernel', 'kernel-rt', 'glibc', 'linux-firmware',
               'systemd', 'dbus', 'dbus-broker', 'dbus-daemon',
               'microcode_ctl']

NEED_REBOOT_DEPENDS_ON_DBUS = ['zlib']

def get_options_from_dir(filepath, base):
    """
    Provide filepath as string if single dir or list of strings
    Return set of package names contained in files under filepath
    """

    if not os.path.exists(filepath):
        return set()
    options = set()
    for file in os.listdir(filepath):
        if os.path.isdir(file) or not file.endswith('.conf'):
            continue

        with open(os.path.join(filepath, file)) as fp:
            for line in fp:
                options.add((line.rstrip(), file))

    packages = set()
    for pkg in base.sack.query().installed().filter(name={x[0] for x in options}):
        packages.add(pkg.name)
    for name, file in {x for x in options if x[0] not in packages}:
        logger.warning(
            _('No installed package found for package name "{pkg}" '
                'specified in needs-restarting file "{file}".'.format(pkg=name, file=file)))
    return packages


def list_opened_files(uid):
    for (pid, smaps) in list_smaps():
        try:
            if uid is not None and uid != owner_uid(smaps):
                continue
            with open(smaps, 'r', errors='replace') as smaps_file:
                lines = smaps_file.readlines()
        except EnvironmentError:
            logger.warning("Failed to read PID %d's smaps.", pid)
            continue

        for line in lines:
            ofile = smap2opened_file(pid, line)
            if ofile is not None:
                yield ofile


def list_smaps():
    for dir_ in os.listdir('/proc'):
        try:
            pid = int(dir_)
        except ValueError:
            continue
        smaps = '/proc/%d/smaps' % pid
        yield (pid, smaps)


def memoize(func):
    sentinel = object()
    cache = {}
    def wrapper(param):
        val = cache.get(param, sentinel)
        if val is not sentinel:
            return val
        val = func(param)
        cache[param] = val
        return val
    return wrapper


def owner_uid(fname):
    return os.stat(fname)[stat.ST_UID]


def owning_package(sack, fname):
    matches = sack.query().filter(file=fname).run()
    if matches:
        return matches[0]
    return None


def print_cmd(pid):
    cmdline = '/proc/%d/cmdline' % pid
    with open(cmdline) as cmdline_file:
        command = dnf.i18n.ucd(cmdline_file.read())
    command = ' '.join(command.split('\000'))
    print('%d : %s' % (pid, command))


def get_service_dbus(pid):
    bus = dbus.SystemBus()
    systemd_manager_object = bus.get_object(
        'org.freedesktop.systemd1',
        '/org/freedesktop/systemd1'
    )
    systemd_manager_interface = dbus.Interface(
        systemd_manager_object,
        'org.freedesktop.systemd1.Manager'
    )
    service_proxy = None
    try:
        service_proxy = bus.get_object(
            'org.freedesktop.systemd1',
            systemd_manager_interface.GetUnitByPID(pid)
        )
    except dbus.DBusException as e:
        # There is no unit for the pid. Usually error is 'NoUnitForPid'.
        # Considering what we do at the bottom (just return if not service)
        # Then there's really no reason to exit here on that exception.
        # Log what's happened then move on.
        msg = str(e)
        logger.warning("Failed to get systemd unit for PID {}: {}".format(pid, msg))
        return
    service_properties = dbus.Interface(
        service_proxy, dbus_interface="org.freedesktop.DBus.Properties")
    name = service_properties.Get(
        "org.freedesktop.systemd1.Unit",
        'Id'
    )
    if name.endswith(".service"):
        return name
    return

def smap2opened_file(pid, line):
    slash = line.find('/')
    if slash < 0:
        return None
    if line.find('00:') >= 0:
        # not a regular file
        return None
    fn = line[slash:].strip()
    suffix_index = fn.rfind(' (deleted)')
    if suffix_index < 0:
        return OpenedFile(pid, fn, False)
    else:
        return OpenedFile(pid, fn[:suffix_index], True)


class OpenedFile(object):
    RE_TRANSACTION_FILE = re.compile('^(.+);[0-9A-Fa-f]{8,}$')

    def __init__(self, pid, name, deleted):
        self.deleted = deleted
        self.name = name
        self.pid = pid

    @property
    def presumed_name(self):
        """Calculate the name of the file pre-transaction.

        In case of a file that got deleted during the transactionm, possibly
        just because of an upgrade to a newer version of the same file, RPM
        renames the old file to the same name with a hexadecimal suffix just
        before delting it.

        """

        if self.deleted:
            match = self.RE_TRANSACTION_FILE.match(self.name)
            if match:
                return match.group(1)
        return self.name


class ProcessStart(object):
    def __init__(self):
        self.boot_time = self.get_boot_time()
        self.sc_clk_tck = self.get_sc_clk_tck()

    @staticmethod
    def get_boot_time():
        """
        We have two sources from which to derive the boot time. These values vary
        depending on containerization, existence of a Real Time Clock, etc.
        For our purposes we want the latest derived value.
        - st_mtime of /proc/1
             Reflects the time the first process was run after booting
             This works for all known cases except machines without
             a RTC - they awake at the start of the epoch.
        - /proc/uptime
             Seconds field of /proc/uptime subtracted from the current time
             Works for machines without RTC iff the current time is reasonably correct.
             Does not work on containers which share their kernel with the
             host - there the host kernel uptime is returned
        """

        proc_1_boot_time = int(os.stat('/proc/1').st_mtime)
        if os.path.isfile('/proc/uptime'):
            with open('/proc/uptime', 'rb') as f:
                uptime = f.readline().strip().split()[0].strip()
                proc_uptime_boot_time = int(time.time() - float(uptime))
                return max(proc_1_boot_time, proc_uptime_boot_time)
        return proc_1_boot_time

    @staticmethod
    def get_sc_clk_tck():
        return os.sysconf(os.sysconf_names['SC_CLK_TCK'])

    def __call__(self, pid):
        stat_fn = '/proc/%d/stat' % pid
        with open(stat_fn) as stat_file:
            stats = stat_file.read().strip().split()
        ticks_after_boot = int(stats[21])
        secs_after_boot = ticks_after_boot // self.sc_clk_tck
        return self.boot_time + secs_after_boot


@dnf.plugin.register_command
class NeedsRestartingCommand(dnf.cli.Command):
    aliases = ('needs-restarting',)
    summary = _('determine updated binaries that need restarting')

    @staticmethod
    def set_argparser(parser):
        parser.add_argument('-u', '--useronly', action='store_true',
                            help=_("only consider this user's processes"))
        parser.add_argument('-r', '--reboothint', action='store_true',
                            help=_("only report whether a reboot is required "
                                   "(exit code 1) or not (exit code 0)"))
        parser.add_argument('-s', '--services', action='store_true',
                            help=_("only report affected systemd services"))

    def configure(self):
        demands = self.cli.demands
        demands.sack_activation = True

    def run(self):
        process_start = ProcessStart()
        owning_pkg_fn = functools.partial(owning_package, self.base.sack)
        owning_pkg_fn = memoize(owning_pkg_fn)

        opt = get_options_from_dir(os.path.join(
            self.base.conf.installroot,
            "etc/dnf/plugins/needs-restarting.d/"),
            self.base)
        NEED_REBOOT.extend(opt)
        if self.opts.reboothint:
            need_reboot = set()
            need_reboot_depends_on_dbus = set()
            installed = self.base.sack.query().installed()
            for pkg in installed.filter(name=NEED_REBOOT):
                if pkg.installtime > process_start.boot_time:
                    need_reboot.add(pkg.name)

            dbus_installed = installed.filter(name=['dbus', 'dbus-daemon', 'dbus-broker'])
            if len(dbus_installed) != 0:
                for pkg in installed.filter(name=NEED_REBOOT_DEPENDS_ON_DBUS):
                    if pkg.installtime > process_start.boot_time:
                        need_reboot_depends_on_dbus.add(pkg.name)
            if need_reboot or need_reboot_depends_on_dbus:
                print(_('Core libraries or services have been updated '
                        'since boot-up:'))
                for name in sorted(need_reboot):
                    print('  * %s' % name)
                for name in sorted(need_reboot_depends_on_dbus):
                    print('  * %s (dependency of dbus. Recommending reboot of dbus)' % name)
                print()
                print(_('Reboot is required to fully utilize these updates.'))
                print(_('More information:'),
                      'https://access.redhat.com/solutions/27943')
                raise dnf.exceptions.Error()  # Sets exit code 1
            else:
                print(_('No core libraries or services have been updated '
                        'since boot-up.'))
                print(_('Reboot should not be necessary.'))
                return None

        stale_pids = set()
        uid = os.geteuid() if self.opts.useronly else None
        for ofile in list_opened_files(uid):
            pkg = owning_pkg_fn(ofile.presumed_name)
            if pkg is None:
                continue
            if pkg.installtime > process_start(ofile.pid):
                stale_pids.add(ofile.pid)

        if self.opts.services:
            names = set([get_service_dbus(pid) for pid in sorted(stale_pids)])
            for name in names:
                if name is not None:
                    print(name)
            return 0
        for pid in sorted(stale_pids):
            print_cmd(pid)
