#
# The Qubes OS Project, https://www.qubes-os.org/
#
# Copyright (C) 2013-2015  Joanna Rutkowska <joanna@invisiblethingslab.com>
# Copyright (C) 2013-2015  Marek Marczykowski-Górecki
#                              <marmarek@invisiblethingslab.com>
# Copyright (C) 2015  Wojtek Porczyk <woju@invisiblethingslab.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program 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 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.
#

""" Qubes storage system"""

from __future__ import absolute_import

import inspect
import os
import os.path
import string  # pylint: disable=deprecated-module
import time
from datetime import datetime

import asyncio
import lxml.etree
import pkg_resources
import qubes
import qubes.exc
import qubes.utils

STORAGE_ENTRY_POINT = 'qubes.storage'


class StoragePoolException(qubes.exc.QubesException):
    ''' A general storage exception '''
    pass


class BlockDevice(object):
    ''' Represents a storage block device. '''
    # pylint: disable=too-few-public-methods
    def __init__(self, path, name, script=None, rw=True, domain=None,
                 devtype='disk'):
        assert name, 'Missing device name'
        assert path, 'Missing device path'
        self.path = path
        self.name = name
        self.rw = rw
        self.script = script
        self.domain = domain
        self.devtype = devtype


class Volume(object):
    ''' Encapsulates all data about a volume for serialization to qubes.xml and
        libvirt config.


        Keep in mind!
        volatile        = not snap_on_start and not save_on_stop
        snapshot        =     snap_on_start and not save_on_stop
        origin          = not snap_on_start and     save_on_stop
        origin_snapshot =     snap_on_start and     save_on_stop
    '''

    devtype = 'disk'
    domain = None
    path = None
    script = None
    usage = 0

    def __init__(self, name, pool, vid, internal=False, removable=False,
            revisions_to_keep=0, rw=False, save_on_stop=False, size=0,
            snap_on_start=False, source=None, **kwargs):
        ''' Initialize a volume.

            :param str name: The domain name
            :param Pool pool: The pool object
            :param str vid:  Volume identifier needs to be unique in pool
            :param bool internal: If `True` volume is hidden when qvm-block ls
                is used
            :param bool removable: If `True` volume can be detached from vm at
                run time
            :param int revisions_to_keep: Amount of revisions to keep around
            :param bool rw: If true volume will be mounted read-write
            :param bool snap_on_start: Create a snapshot from source on start
            :param bool save_on_stop: Write changes to disk in vm.stop()
            :param Volume source: other volume in same pool, or None
            :param str/int size: Size of the volume

        '''

        super(Volume, self).__init__(**kwargs)
        assert isinstance(pool, Pool)
        assert source is None or (isinstance(source, Volume)
                                  and source.pool == pool)

        self.name = str(name)
        self.pool = pool
        self.internal = internal
        self.removable = removable
        self.revisions_to_keep = int(revisions_to_keep)
        self.rw = rw
        self.save_on_stop = save_on_stop
        self._size = int(size)
        self.snap_on_start = snap_on_start
        self.source = source
        self.vid = vid

    def __eq__(self, other):
        if isinstance(other, Volume):
            return other.pool == self.pool and other.vid == self.vid
        return NotImplemented

    def __hash__(self):
        return hash('%s:%s' % (self.pool, self.vid))

    def __neq__(self, other):
        return not self.__eq__(other)

    def __repr__(self):
        return '{!r}'.format(str(self.pool) + ':' + self.vid)

    def __str__(self):
        return str(self.vid)

    def __xml__(self):
        config = _sanitize_config(self.config)
        return lxml.etree.Element('volume', **config)

    def create(self):
        ''' Create the given volume on disk.

            This can be implemented as a coroutine.
        '''
        raise self._not_implemented("create")

    def remove(self):
        ''' Remove volume.

        This can be implemented as a coroutine.'''
        raise self._not_implemented("remove")

    def export(self):
        ''' Returns an object that can be `open()`. '''
        raise self._not_implemented("export")

    def import_data(self):
        ''' Returns an object that can be `open()`. '''
        raise self._not_implemented("import")

    def import_data_end(self, success):
        ''' End data import operation. This may be used by pool
        implementation to commit changes, cleanup temporary files etc.

        :param success: True if data import was successful, otherwise False
        '''
        # by default do nothing
        pass

    def import_volume(self, src_volume):
        ''' Imports data from a different volume (possibly in a different
        pool.

        The needs to be create()d first.

        This can be implemented as a coroutine. '''
        # pylint: disable=unused-argument
        raise self._not_implemented("import_volume")

    def is_dirty(self):
        ''' Return `True` if volume was not properly shutdown and commited '''
        raise self._not_implemented("is_dirty")

    def is_outdated(self):
        ''' Returns `True` if the currently used `volume.source` of a snapshot
            volume is outdated.
        '''
        raise self._not_implemented("is_outdated")

    def resize(self, size):
        ''' Expands volume, throws
            :py:class:`qubes.storage.StoragePoolException` if
            given size is less than current_size

            This can be implemented as a coroutine.
        '''
        # pylint: disable=unused-argument
        raise self._not_implemented("resize")

    def revert(self, revision=None):
        ''' Revert volume to previous revision  '''
        # pylint: disable=unused-argument
        raise self._not_implemented("revert")

    def start(self):
        ''' Do what ever is needed on start

        This can be implemented as a coroutine.'''
        raise self._not_implemented("start")

    def stop(self):
        ''' Do what ever is needed on stop

        This can be implemented as a coroutine.'''

    def verify(self):
        ''' Verifies the volume.

        This can be implemented as a coroutine.'''
        raise self._not_implemented("verify")

    def block_device(self):
        ''' Return :py:class:`BlockDevice` for serialization in
            the libvirt XML template as <disk>.
        '''
        return BlockDevice(self.path, self.name, self.script,
                                         self.rw, self.domain, self.devtype)

    @property
    def revisions(self):
        ''' Returns a `dict` containing revision identifiers and paths '''
        msg = "{!s} has revisions not implemented".format(self.__class__)
        raise NotImplementedError(msg)

    @property
    def size(self):
        return self._size

    @size.setter
    def size(self, size):
        # pylint: disable=attribute-defined-outside-init
        self._size = int(size)


    @property
    def config(self):
        ''' return config data for serialization to qubes.xml '''
        result = {
            'name': self.name,
            'pool': str(self.pool),
            'vid': self.vid,
            'internal': self.internal,
            'removable': self.removable,
            'revisions_to_keep': self.revisions_to_keep,
            'rw': self.rw,
            'save_on_stop': self.save_on_stop,
            'snap_on_start': self.snap_on_start,
        }

        if self.size:
            result['size'] = self.size

        if self.source:
            result['source'] = str(self.source)

        return result

    def _not_implemented(self, method_name):
        ''' Helper for emitting helpful `NotImplementedError` exceptions '''
        msg = "Volume {!s} has {!s}() not implemented"
        msg = msg.format(str(self.__class__.__name__), method_name)
        return NotImplementedError(msg)

class Storage(object):
    ''' Class for handling VM virtual disks.

    This is base class for all other implementations, mostly with Xen on Linux
    in mind.
    '''

    AVAILABLE_FRONTENDS = set(['xvd' + c for c in string.ascii_lowercase])

    def __init__(self, vm):
        #: Domain for which we manage storage
        self.vm = vm
        self.log = self.vm.log
        #: Additional drive (currently used only by HVM)
        self.drive = None

        if hasattr(vm, 'volume_config'):
            for name, conf in self.vm.volume_config.items():
                if 'source' in conf:
                    template = getattr(vm, 'template', None)
                    if template:
                        # we have no control over VM load order,
                        # so initialize storage recursively if needed
                        if template.storage is None:
                            template.storage = Storage(template)
                        # FIXME: this effectively ignore 'source' value;
                        # maybe we don't need it at all if it's always from
                        # VM's template?
                        conf['source'] = template.volumes[name]

                self.init_volume(name, conf)

    def init_volume(self, name, volume_config):
        ''' Initialize Volume instance attached to this domain '''
        assert 'pool' in volume_config, "Pool missing in volume_config " + str(
            volume_config)

        if 'name' not in volume_config:
            volume_config['name'] = name
        pool = self.vm.app.get_pool(volume_config['pool'])
        volume = pool.init_volume(self.vm, volume_config)
        self.vm.volumes[name] = volume
        return volume

    def attach(self, volume, rw=False):
        ''' Attach a volume to the domain '''
        assert self.vm.is_running()

        if self._is_already_attached(volume):
            self.vm.log.info("{!r} already attached".format(volume))
            return

        try:
            frontend = self.unused_frontend()
        except IndexError:
            raise StoragePoolException("No unused frontend found")
        disk = lxml.etree.Element("disk")
        disk.set('type', 'block')
        disk.set('device', 'disk')
        lxml.etree.SubElement(disk, 'driver').set('name', 'phy')
        lxml.etree.SubElement(disk, 'source').set('dev', '/dev/%s' % volume.vid)
        lxml.etree.SubElement(disk, 'target').set('dev', frontend)
        if not rw:
            lxml.etree.SubElement(disk, 'readonly')

        if volume.domain is not None:
            lxml.etree.SubElement(disk, 'backenddomain').set(
                'name', volume.domain.name)

        xml_string = lxml.etree.tostring(disk, encoding='utf-8')
        self.vm.libvirt_domain.attachDevice(xml_string)
        # trigger watches to update device status
        # FIXME: this should be removed once libvirt will report such
        # events itself
        # self.vm.qdb.write('/qubes-block-devices', '') ← do we need this?

    def _is_already_attached(self, volume):
        ''' Checks if the given volume is already attached '''
        parsed_xml = lxml.etree.fromstring(self.vm.libvirt_domain.XMLDesc())
        disk_sources = parsed_xml.xpath("//domain/devices/disk/source")
        for source in disk_sources:
            if source.get('dev') == '/dev/%s' % volume.vid:
                return True
        return False

    def detach(self, volume):
        ''' Detach a volume from domain '''
        parsed_xml = lxml.etree.fromstring(self.vm.libvirt_domain.XMLDesc())
        disks = parsed_xml.xpath("//domain/devices/disk")
        for disk in disks:
            source = disk.xpath('source')[0]
            if source.get('dev') == '/dev/%s' % volume.vid:
                disk_xml = lxml.etree.tostring(disk, encoding='utf-8')
                self.vm.libvirt_domain.detachDevice(disk_xml)
                return
        raise StoragePoolException('Volume {!r} is not attached'.format(volume))

    @property
    def kernels_dir(self):
        '''Directory where kernel resides.

        If :py:attr:`self.vm.kernel` is :py:obj:`None`, the this points inside
        :py:attr:`self.vm.dir_path`
        '''
        assert 'kernel' in self.vm.volumes, "VM has no kernel volume"
        return self.vm.volumes['kernel'].kernels_dir

    def get_disk_utilization(self):
        ''' Returns summed up disk utilization for all domain volumes '''
        result = 0
        for volume in self.vm.volumes.values():
            result += volume.usage
        return result

    @asyncio.coroutine
    def resize(self, volume, size):
        ''' Resizes volume a read-writable volume '''
        if isinstance(volume, str):
            volume = self.vm.volumes[volume]
        ret = volume.resize(size)
        if asyncio.iscoroutine(ret):
            yield from ret
        if self.vm.is_running():
            yield from self.vm.run_service_for_stdio('qubes.ResizeDisk',
                input=volume.name.encode(),
                user='root')

    @asyncio.coroutine
    def create(self):
        ''' Creates volumes on disk '''
        old_umask = os.umask(0o002)

        coros = []
        for volume in self.vm.volumes.values():
            # launch the operation, if it's asynchronous, then append to wait
            #  for them at the end
            ret = volume.create()
            if asyncio.iscoroutine(ret):
                coros.append(ret)
        if coros:
            yield from asyncio.wait(coros)

        os.umask(old_umask)

    @asyncio.coroutine
    def clone_volume(self, src_vm, name):
        ''' Clone single volume from the specified vm

        :param QubesVM src_vm: source VM
        :param str name: name of volume to clone ('root', 'private' etc)
        :return cloned volume object
        '''
        config = self.vm.volume_config[name]
        dst_pool = self.vm.app.get_pool(config['pool'])
        dst = dst_pool.init_volume(self.vm, config)
        src_volume = src_vm.volumes[name]
        msg = "Importing volume {!s} from vm {!s}"
        self.vm.log.info(msg.format(src_volume.name, src_vm.name))
        clone_op_ret = dst.import_volume(src_volume)

        # clone/import functions may be either synchronous or asynchronous
        # in the later case, we need to wait for them to finish
        if asyncio.iscoroutine(clone_op_ret):
            clone_op_ret = yield from clone_op_ret
        self.vm.volumes[name] = clone_op_ret
        return self.vm.volumes[name]

    @asyncio.coroutine
    def clone(self, src_vm):
        ''' Clone volumes from the specified vm '''

        self.vm.volumes = {}
        with VmCreationManager(self.vm):
            yield from asyncio.wait(self.clone_volume(src_vm, vol_name)
                for vol_name in self.vm.volume_config.keys())

    @property
    def outdated_volumes(self):
        ''' Returns a list of outdated volumes '''
        result = []
        if self.vm.is_halted():
            return result

        volumes = self.vm.volumes
        for volume in volumes.values():
            if volume.is_outdated():
                result += [volume]

        return result

    @asyncio.coroutine
    def verify(self):
        '''Verify that the storage is sane.

        On success, returns normally. On failure, raises exception.
        '''
        if not os.path.exists(self.vm.dir_path):
            raise qubes.exc.QubesVMError(
                self.vm,
                'VM directory does not exist: {}'.format(self.vm.dir_path))
        futures = []
        for volume in self.vm.volumes.values():
            ret = volume.verify()
            if asyncio.iscoroutine(ret):
                futures.append(ret)
        if futures:
            yield from asyncio.wait(futures)
        self.vm.fire_event('domain-verify-files')
        return True

    @asyncio.coroutine
    def remove(self):
        ''' Remove all the volumes.

            Errors on removal are catched and logged.
        '''
        futures = []
        for name, volume in self.vm.volumes.items():
            self.log.info('Removing volume %s: %s' % (name, volume.vid))
            try:
                ret = volume.remove()
                if asyncio.iscoroutine(ret):
                    futures.append(ret)
            except (IOError, OSError) as e:
                self.vm.log.exception("Failed to remove volume %s", name, e)

        if futures:
            try:
                yield from asyncio.wait(futures)
            except (IOError, OSError) as e:
                self.vm.log.exception("Failed to remove some volume", e)

    @asyncio.coroutine
    def start(self):
        ''' Execute the start method on each pool '''
        futures = []
        for volume in self.vm.volumes.values():
            ret = volume.start()
            if asyncio.iscoroutine(ret):
                futures.append(ret)

        if futures:
            yield from asyncio.wait(futures)

    @asyncio.coroutine
    def stop(self):
        ''' Execute the start method on each pool '''
        futures = []
        for volume in self.vm.volumes.values():
            ret = volume.stop()
            if asyncio.iscoroutine(ret):
                futures.append(ret)

        if futures:
            yield from asyncio.wait(futures)

    def unused_frontend(self):
        ''' Find an unused device name '''
        unused_frontends = self.AVAILABLE_FRONTENDS.difference(
            self.used_frontends)
        return sorted(unused_frontends)[0]

    @property
    def used_frontends(self):
        ''' Used device names '''
        xml = self.vm.libvirt_domain.XMLDesc()
        parsed_xml = lxml.etree.fromstring(xml)
        return set([target.get('dev', None)
                    for target in parsed_xml.xpath(
                        "//domain/devices/disk/target")])

    def export(self, volume):
        ''' Helper function to export volume (pool.export(volume))'''
        assert isinstance(volume, (Volume, str)), \
            "You need to pass a Volume or pool name as str"
        if isinstance(volume, Volume):
            return volume.export()

        return self.vm.volumes[volume].export()

    def import_data(self, volume):
        ''' Helper function to import volume data (pool.import_data(volume))'''
        assert isinstance(volume, (Volume, str)), \
            "You need to pass a Volume or pool name as str"
        if isinstance(volume, Volume):
            return volume.import_data()

        return self.vm.volumes[volume].import_data()

    def import_data_end(self, volume, success):
        ''' Helper function to finish/cleanup data import
        (pool.import_data_end( volume))'''
        assert isinstance(volume, (Volume, str)), \
            "You need to pass a Volume or pool name as str"
        if isinstance(volume, Volume):
            return volume.import_data_end(volume,
                success=success)

        return self.vm.volumes[volume].import_data_end(success=success)


class VolumesCollection(object):
    '''Convenient collection wrapper for pool.get_volume and
    pool.list_volumes
    '''
    def __init__(self, pool):
        self._pool = pool

    def __getitem__(self, item):
        ''' Get a single volume with given Volume ID.

        You can also a Volume instance to get the same Volume or KeyError if
        Volume no longer exists.

        :param item: a Volume ID (str) or a Volume instance
        '''
        if isinstance(item, Volume):
            if item.pool == self._pool:
                return self[item.vid]
            else:
                raise KeyError(item)
        try:
            return self._pool.get_volume(item)
        except NotImplementedError:
            for vol in self:
                if vol.vid == item:
                    return vol
            # if list_volumes is not implemented too, it will raise
            # NotImplementedError again earlier
            raise KeyError(item)

    def __iter__(self):
        ''' Get iterator over pool's volumes '''
        return iter(self._pool.list_volumes())

    def __contains__(self, item):
        ''' Check if given volume (either Volume ID or Volume instance) is
        present in the pool
        '''
        try:
            return self[item] is not None
        except KeyError:
            return False

    def keys(self):
        ''' Return list of volume IDs '''
        return [vol.vid for vol in self]

    def values(self):
        ''' Return list of Volumes'''
        return [vol for vol in self]


class Pool(object):
    ''' A Pool is used to manage different kind of volumes (File
        based/LVM/Btrfs/...).

        3rd Parties providing own storage implementations will need to extend
        this class.
    '''  # pylint: disable=unused-argument
    private_img_size = qubes.config.defaults['private_img_size']
    root_img_size = qubes.config.defaults['root_img_size']

    def __init__(self, name, revisions_to_keep=1, **kwargs):
        super(Pool, self).__init__(**kwargs)
        self._volumes_collection = VolumesCollection(self)
        self.name = name
        self.revisions_to_keep = revisions_to_keep
        kwargs['name'] = self.name

    def __eq__(self, other):
        if isinstance(other, Pool):
            return self.name == other.name
        elif isinstance(other, str):
            return self.name == other
        return NotImplemented

    def __neq__(self, other):
        return not self.__eq__(other)

    def __str__(self):
        return self.name

    def __hash__(self):
        return hash(self.name)

    def __xml__(self):
        config = _sanitize_config(self.config)
        return lxml.etree.Element('pool', **config)

    @property
    def config(self):
        ''' Returns the pool config to be written to qubes.xml '''
        raise self._not_implemented("config")

    def destroy(self):
        ''' Called when removing the pool. Use this for implementation specific
            clean up.
        '''
        raise self._not_implemented("destroy")

    def init_volume(self, vm, volume_config):
        ''' Initialize a :py:class:`qubes.storage.Volume` from `volume_config`.
        '''
        raise self._not_implemented("init_volume")

    def setup(self):
        ''' Called when adding a pool to the system. Use this for implementation
            specific set up.
        '''
        raise self._not_implemented("setup")

    @property
    def volumes(self):
        ''' Return a collection of volumes managed by this pool '''
        return self._volumes_collection

    def list_volumes(self):
        ''' Return a list of volumes managed by this pool '''
        raise self._not_implemented("list_volumes")

    def get_volume(self, vid):
        ''' Return a volume with *vid* from this pool

        :raise KeyError: if no volume is found
        '''
        raise self._not_implemented("get_volume")

    def _not_implemented(self, method_name):
        ''' Helper for emitting helpful `NotImplementedError` exceptions '''
        msg = "Pool driver {!s} has {!s}() not implemented"
        msg = msg.format(str(self.__class__.__name__), method_name)
        return NotImplementedError(msg)


def _sanitize_config(config):
    ''' Helper function to convert types to appropriate strings
    '''  # FIXME: find another solution for serializing basic types
    result = {}
    for key, value in config.items():
        if isinstance(value, bool):
            if value:
                result[key] = 'True'
        else:
            result[key] = str(value)
    return result


def pool_drivers():
    """ Return a list of EntryPoints names """
    return [ep.name
            for ep in pkg_resources.iter_entry_points(STORAGE_ENTRY_POINT)]


def driver_parameters(name):
    ''' Get __init__ parameters from a driver with out `self` & `name`. '''
    init_function = qubes.utils.get_entry_point_one(
        qubes.storage.STORAGE_ENTRY_POINT, name).__init__
    params = init_function.func_code.co_varnames
    ignored_params = ['self', 'name']
    return [p for p in params if p not in ignored_params]


def isodate(seconds=time.time()):
    ''' Helper method which returns an iso date '''
    return datetime.utcfromtimestamp(seconds).isoformat("T")


class VmCreationManager(object):
    ''' A `ContextManager` which cleans up if volume creation fails.
    '''  # pylint: disable=too-few-public-methods
    def __init__(self, vm):
        self.vm = vm

    def __enter__(self):
        pass

    def __exit__(self, type, value, tb):  # pylint: disable=redefined-builtin
        if type is not None and value is not None and tb is not None:
            for volume in self.vm.volumes.values():
                try:
                    volume.remove()
                except Exception:  # pylint: disable=broad-except
                    pass
            os.rmdir(self.vm.dir_path)