/brz/remove-bazaar

# Copyright (C) 2005 Canonical Ltd

# 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

from copy import deepcopy

from cStringIO import StringIO

from unittest import TestSuite

import xml.sax.saxutils

import bzrlib.bzrdir as bzrdir

from bzrlib.decorators import needs_read_lock, needs_write_lock

import bzrlib.errors as errors

from bzrlib.errors import InvalidRevisionId

from bzrlib.lockable_files import LockableFiles

from bzrlib.osutils import safe_unicode

from bzrlib.revision import NULL_REVISION

from bzrlib.store import copy_all

from bzrlib.store.weave import WeaveStore

from bzrlib.store.text import TextStore

from bzrlib.symbol_versioning import *

from bzrlib.trace import mutter

from bzrlib.tree import RevisionTree

from bzrlib.testament import Testament

from bzrlib.tree import EmptyTree

import bzrlib.xml5

class Repository(object):

    """Repository holding history for one or more branches.

    The repository holds and retrieves historical information including

    revisions and file history.  It's normally accessed only by the Branch,

    which views a particular line of development through that history.

    The Repository builds on top of Stores and a Transport, which respectively 

    describe the disk data format and the way of accessing the (possibly 

    remote) disk.

    """

    @needs_read_lock

    def _all_possible_ids(self):

        """Return all the possible revisions that we could find."""

        return self.get_inventory_weave().names()

    @needs_read_lock

    def all_revision_ids(self):

        """Returns a list of all the revision ids in the repository. 

        These are in as much topological order as the underlying store can 

        present: for weaves ghosts may lead to a lack of correctness until

        the reweave updates the parents list.

        """

        result = self._all_possible_ids()

        return self._eliminate_revisions_not_present(result)

    @needs_read_lock

    def _eliminate_revisions_not_present(self, revision_ids):

        """Check every revision id in revision_ids to see if we have it.

        Returns a set of the present revisions.

        """

        result = []

        for id in revision_ids:

            if self.has_revision(id):

               result.append(id)

        return result

    @staticmethod

    def create(a_bzrdir):

        """Construct the current default format repository in a_bzrdir."""

        return RepositoryFormat.get_default_format().initialize(a_bzrdir)

    def __init__(self, transport, branch_format, _format=None, a_bzrdir=None):

        object.__init__(self)

        if transport is not None:

            warn("Repository.__init__(..., transport=XXX): The transport parameter is "

                 "deprecated and was never in a supported release. Please use "

                 "bzrdir.open_repository() or bzrdir.open_branch().repository.",

                 DeprecationWarning,

                 stacklevel=2)

            self.control_files = LockableFiles(transport.clone(bzrlib.BZRDIR), 'README')

        else: 

            # TODO: clone into repository if needed

            self.control_files = LockableFiles(a_bzrdir.get_repository_transport(None), 'README')

        dir_mode = self.control_files._dir_mode

        file_mode = self.control_files._file_mode

        self._format = _format

        self.bzrdir = a_bzrdir

        def get_weave(name, prefixed=False):

            if name:

                name = safe_unicode(name)

            else:

                name = ''

            relpath = self.control_files._escape(name)

            weave_transport = self.control_files._transport.clone(relpath)

            ws = WeaveStore(weave_transport, prefixed=prefixed,

                            dir_mode=dir_mode,

                            file_mode=file_mode)

            if self.control_files._transport.should_cache():

                ws.enable_cache = True

            return ws

        def get_store(name, compressed=True, prefixed=False):

            # FIXME: This approach of assuming stores are all entirely compressed

            # or entirely uncompressed is tidy, but breaks upgrade from 

            # some existing branches where there's a mixture; we probably 

            # still want the option to look for both.

            if name:

                name = safe_unicode(name)

            else:

                name = ''

            relpath = self.control_files._escape(name)

            store = TextStore(self.control_files._transport.clone(relpath),

                              prefixed=prefixed, compressed=compressed,

                              dir_mode=dir_mode,

                              file_mode=file_mode)

            #if self._transport.should_cache():

            #    cache_path = os.path.join(self.cache_root, name)

            #    os.mkdir(cache_path)

            #    store = bzrlib.store.CachedStore(store, cache_path)

            return store

        if branch_format is not None:

            # circular dependencies:

            from bzrlib.branch import (BzrBranchFormat4,

                                       BzrBranchFormat5,

                                       BzrBranchFormat6,

                                       )

            if isinstance(branch_format, BzrBranchFormat4):

                self._format = RepositoryFormat4()

            elif isinstance(branch_format, BzrBranchFormat5):

                self._format = RepositoryFormat5()

            elif isinstance(branch_format, BzrBranchFormat6):

                self._format = RepositoryFormat6()

        if isinstance(self._format, RepositoryFormat4):

            self.inventory_store = get_store('inventory-store')

            self.text_store = get_store('text-store')

            self.revision_store = get_store('revision-store')

        elif isinstance(self._format, RepositoryFormat5):

            self.control_weaves = get_weave('')

            self.weave_store = get_weave('weaves')

            self.revision_store = get_store('revision-store', compressed=False)

        elif isinstance(self._format, RepositoryFormat6):

            self.control_weaves = get_weave('')

            self.weave_store = get_weave('weaves', prefixed=True)

            self.revision_store = get_store('revision-store', compressed=False,

                                            prefixed=True)

        elif isinstance(self._format, RepositoryFormat7):

            self.control_weaves = get_weave('')

            self.weave_store = get_weave('weaves', prefixed=True)

            self.revision_store = get_store('revision-store', compressed=False,

                                            prefixed=True)

        self.revision_store.register_suffix('sig')

    def lock_write(self):

        self.control_files.lock_write()

    def lock_read(self):

        self.control_files.lock_read()

    @needs_read_lock

    def missing_revision_ids(self, other, revision_id=None):

        """Return the revision ids that other has that this does not.

        These are returned in topological order.

        revision_id: only return revision ids included by revision_id.

        """

        if self._compatible_formats(other):

            # fast path for weave-inventory based stores.

            # we want all revisions to satisft revision_id in other.

            # but we dont want to stat every file here and there.

            # we want then, all revisions other needs to satisfy revision_id 

            # checked, but not those that we have locally.

            # so the first thing is to get a subset of the revisions to 

            # satisfy revision_id in other, and then eliminate those that

            # we do already have. 

            # this is slow on high latency connection to self, but as as this

            # disk format scales terribly for push anyway due to rewriting 

            # inventory.weave, this is considered acceptable.

            # - RBC 20060209

            if revision_id is not None:

                other_ids = other.get_ancestry(revision_id)

                assert other_ids.pop(0) == None

            else:

                other_ids = other._all_possible_ids()

            other_ids_set = set(other_ids)

            # other ids is the worst case to pull now.

            # now we want to filter other_ids against what we actually

            # have, but dont try to stat what we know we dont.

            my_ids = set(self._all_possible_ids())

            possibly_present_revisions = my_ids.intersection(other_ids_set)

            actually_present_revisions = set(self._eliminate_revisions_not_present(possibly_present_revisions))

            required_revisions = other_ids_set.difference(actually_present_revisions)

            required_topo_revisions = [rev_id for rev_id in other_ids if rev_id in required_revisions]

            if revision_id is not None:

                # we used get_ancestry to determine other_ids then we are assured all

                # revisions referenced are present as they are installed in topological order.

                return required_topo_revisions

            else:

                # we only have an estimate of whats available

                return other._eliminate_revisions_not_present(required_topo_revisions)

        # slow code path.

        my_ids = set(self.all_revision_ids())

        if revision_id is not None:

            other_ids = other.get_ancestry(revision_id)

            assert other_ids.pop(0) == None

        else:

            other_ids = other.all_revision_ids()

        result_set = set(other_ids).difference(my_ids)

        return [rev_id for rev_id in other_ids if rev_id in result_set]

    @staticmethod

    def open(base):

        """Open the repository rooted at base.

        For instance, if the repository is at URL/.bzr/repository,

        Repository.open(URL) -> a Repository instance.

        """

        control = bzrdir.BzrDir.open(base)

        return control.open_repository()

    def _compatible_formats(self, other):

        """Return True if the stores in self and other are 'compatible'

        'compatible' means that they are both the same underlying type

        i.e. both weave stores, or both knits and thus support fast-path

        operations."""

        return (isinstance(self._format, (RepositoryFormat5,

                                          RepositoryFormat6,

                                          RepositoryFormat7)) and

                isinstance(other._format, (RepositoryFormat5,

                                           RepositoryFormat6,

                                           RepositoryFormat7)))

    @needs_read_lock

    def copy_content_into(self, destination, revision_id=None, basis=None):

        """Make a complete copy of the content in self into destination."""

        destination.lock_write()

        try:

            # optimised paths:

            # compatible stores

            if self._compatible_formats(destination):

                if basis is not None:

                    # copy the basis in, then fetch remaining data.

                    basis.copy_content_into(destination, revision_id)

                    destination.fetch(self, revision_id=revision_id)

                else:

                    # FIXME do not peek!

                    if self.control_files._transport.listable():

                        destination.control_weaves.copy_multi(self.control_weaves,

                                                              ['inventory'])

                        copy_all(self.weave_store, destination.weave_store)

                        copy_all(self.revision_store, destination.revision_store)

                    else:

                        destination.fetch(self, revision_id=revision_id)

            # compatible v4 stores

            elif isinstance(self._format, RepositoryFormat4):

                if not isinstance(destination._format, RepositoryFormat4):

                    raise BzrError('cannot copy v4 branches to anything other than v4 branches.')

                store_pairs = ((self.text_store,      destination.text_store),

                               (self.inventory_store, destination.inventory_store),

                               (self.revision_store,  destination.revision_store))

                try:

                    for from_store, to_store in store_pairs: 

                        copy_all(from_store, to_store)

                except UnlistableStore:

                    raise UnlistableBranch(from_store)

            # fallback - 'fetch'

            else:

                destination.fetch(self, revision_id=revision_id)

        finally:

            destination.unlock()

    @needs_write_lock

    def fetch(self, source, revision_id=None):

        """Fetch the content required to construct revision_id from source.

        If revision_id is None all content is copied.

        """

        from bzrlib.fetch import RepoFetcher

        mutter("Using fetch logic to copy between %s(%s) and %s(%s)",

               source, source._format, self, self._format)

        RepoFetcher(to_repository=self, from_repository=source, last_revision=revision_id)

    def unlock(self):

        self.control_files.unlock()

    @needs_read_lock

    def clone(self, a_bzrdir, revision_id=None, basis=None):

        """Clone this repository into a_bzrdir using the current format.

        Currently no check is made that the format of this repository and

        the bzrdir format are compatible. FIXME RBC 20060201.

        """

        if not isinstance(a_bzrdir._format, self.bzrdir._format.__class__):

            # use target default format.

            result = a_bzrdir.create_repository()

        # FIXME RBC 20060209 split out the repository type to avoid this check ?

        elif isinstance(a_bzrdir._format,

                      (bzrdir.BzrDirFormat4,

                       bzrdir.BzrDirFormat5,

                       bzrdir.BzrDirFormat6)):

            result = a_bzrdir.open_repository()

        else:

            result = self._format.initialize(a_bzrdir)

        self.copy_content_into(result, revision_id, basis)

        return result

    def has_revision(self, revision_id):

        """True if this branch has a copy of the revision.

        This does not necessarily imply the revision is merge

        or on the mainline."""

        return (revision_id is None

                or self.revision_store.has_id(revision_id))

    @needs_read_lock

    def get_revision_xml_file(self, revision_id):

        """Return XML file object for revision object."""

        if not revision_id or not isinstance(revision_id, basestring):

            raise InvalidRevisionId(revision_id=revision_id, branch=self)

        try:

            return self.revision_store.get(revision_id)

        except (IndexError, KeyError):

            raise bzrlib.errors.NoSuchRevision(self, revision_id)

    @needs_read_lock

    def get_revision_xml(self, revision_id):

        return self.get_revision_xml_file(revision_id).read()

    @needs_read_lock

    def get_revision(self, revision_id):

        """Return the Revision object for a named revision"""

        xml_file = self.get_revision_xml_file(revision_id)

        try:

            r = bzrlib.xml5.serializer_v5.read_revision(xml_file)

        except SyntaxError, e:

            raise bzrlib.errors.BzrError('failed to unpack revision_xml',

                                         [revision_id,

                                          str(e)])

        assert r.revision_id == revision_id

        return r

    @needs_read_lock

    def get_revision_sha1(self, revision_id):

        """Hash the stored value of a revision, and return it."""

        # In the future, revision entries will be signed. At that

        # point, it is probably best *not* to include the signature

        # in the revision hash. Because that lets you re-sign

        # the revision, (add signatures/remove signatures) and still

        # have all hash pointers stay consistent.

        # But for now, just hash the contents.

        return bzrlib.osutils.sha_file(self.get_revision_xml_file(revision_id))

    @needs_write_lock

    def store_revision_signature(self, gpg_strategy, plaintext, revision_id):

        self.revision_store.add(StringIO(gpg_strategy.sign(plaintext)), 

                                revision_id, "sig")

    def fileid_involved_between_revs(self, from_revid, to_revid):

        """Find file_id(s) which are involved in the changes between revisions.

        This determines the set of revisions which are involved, and then

        finds all file ids affected by those revisions.

        """

        # TODO: jam 20060119 This code assumes that w.inclusions will

        #       always be correct. But because of the presence of ghosts

        #       it is possible to be wrong.

        #       One specific example from Robert Collins:

        #       Two branches, with revisions ABC, and AD

        #       C is a ghost merge of D.

        #       Inclusions doesn't recognize D as an ancestor.

        #       If D is ever merged in the future, the weave

        #       won't be fixed, because AD never saw revision C

        #       to cause a conflict which would force a reweave.

        w = self.get_inventory_weave()

        from_set = set(w.inclusions([w.lookup(from_revid)]))

        to_set = set(w.inclusions([w.lookup(to_revid)]))

        included = to_set.difference(from_set)

        changed = map(w.idx_to_name, included)

        return self._fileid_involved_by_set(changed)

    def fileid_involved(self, last_revid=None):

        """Find all file_ids modified in the ancestry of last_revid.

        :param last_revid: If None, last_revision() will be used.

        """

        w = self.get_inventory_weave()

        if not last_revid:

            changed = set(w._names)

        else:

            included = w.inclusions([w.lookup(last_revid)])

            changed = map(w.idx_to_name, included)

        return self._fileid_involved_by_set(changed)

    def fileid_involved_by_set(self, changes):

        """Find all file_ids modified by the set of revisions passed in.

        :param changes: A set() of revision ids

        """

        # TODO: jam 20060119 This line does *nothing*, remove it.

        #       or better yet, change _fileid_involved_by_set so

        #       that it takes the inventory weave, rather than

        #       pulling it out by itself.

        return self._fileid_involved_by_set(changes)

    def _fileid_involved_by_set(self, changes):

        """Find the set of file-ids affected by the set of revisions.

        :param changes: A set() of revision ids.

        :return: A set() of file ids.

        This peaks at the Weave, interpreting each line, looking to

        see if it mentions one of the revisions. And if so, includes

        the file id mentioned.

        This expects both the Weave format, and the serialization

        to have a single line per file/directory, and to have

        fileid="" and revision="" on that line.

        """

        assert isinstance(self._format, (RepositoryFormat5,

                                         RepositoryFormat6,

                                         RepositoryFormat7)), \

            "fileid_involved only supported for branches which store inventory as unnested xml"

        w = self.get_inventory_weave()

        file_ids = set()

        for line in w._weave:

            # it is ugly, but it is due to the weave structure

            if not isinstance(line, basestring): continue

            start = line.find('file_id="')+9

            if start < 9: continue

            end = line.find('"', start)

            assert end>= 0

            file_id = xml.sax.saxutils.unescape(line[start:end])

            # check if file_id is already present

            if file_id in file_ids: continue

            start = line.find('revision="')+10

            if start < 10: continue

            end = line.find('"', start)

            assert end>= 0

            revision_id = xml.sax.saxutils.unescape(line[start:end])

            if revision_id in changes:

                file_ids.add(file_id)

        return file_ids

    @needs_read_lock

    def get_inventory_weave(self):

        return self.control_weaves.get_weave('inventory',

            self.get_transaction())

    @needs_read_lock

    def get_inventory(self, revision_id):

        """Get Inventory object by hash."""

        xml = self.get_inventory_xml(revision_id)

        return bzrlib.xml5.serializer_v5.read_inventory_from_string(xml)

    @needs_read_lock

    def get_inventory_xml(self, revision_id):

        """Get inventory XML as a file object."""

        try:

            assert isinstance(revision_id, basestring), type(revision_id)

            iw = self.get_inventory_weave()

            return iw.get_text(iw.lookup(revision_id))

        except IndexError:

            raise bzrlib.errors.HistoryMissing(self, 'inventory', revision_id)

    @needs_read_lock

    def get_inventory_sha1(self, revision_id):

        """Return the sha1 hash of the inventory entry

        """

        return self.get_revision(revision_id).inventory_sha1

    @needs_read_lock

    def get_revision_inventory(self, revision_id):

        """Return inventory of a past revision."""

        # TODO: Unify this with get_inventory()

        # bzr 0.0.6 and later imposes the constraint that the inventory_id

        # must be the same as its revision, so this is trivial.

        if revision_id is None:

            # This does not make sense: if there is no revision,

            # then it is the current tree inventory surely ?!

            # and thus get_root_id() is something that looks at the last

            # commit on the branch, and the get_root_id is an inventory check.

            raise NotImplementedError

            # return Inventory(self.get_root_id())

        else:

            return self.get_inventory(revision_id)

    @needs_read_lock

    def revision_tree(self, revision_id):

        """Return Tree for a revision on this branch.

        `revision_id` may be None for the null revision, in which case

        an `EmptyTree` is returned."""

        # TODO: refactor this to use an existing revision object

        # so we don't need to read it in twice.

        if revision_id is None or revision_id == NULL_REVISION:

            return EmptyTree()

        else:

            inv = self.get_revision_inventory(revision_id)

            return RevisionTree(self, inv, revision_id)

    @needs_read_lock

    def get_ancestry(self, revision_id):

        """Return a list of revision-ids integrated by a revision.

        This is topologically sorted.

        """

        if revision_id is None:

            return [None]

        if not self.has_revision(revision_id):

            raise errors.NoSuchRevision(self, revision_id)

        w = self.get_inventory_weave()

        return [None] + map(w.idx_to_name,

                            w.inclusions([w.lookup(revision_id)]))

    @needs_read_lock

    def print_file(self, file, revision_id):

        """Print `file` to stdout.

        FIXME RBC 20060125 as John Meinel points out this is a bad api

        - it writes to stdout, it assumes that that is valid etc. Fix

        by creating a new more flexible convenience function.

        """

        tree = self.revision_tree(revision_id)

        # use inventory as it was in that revision

        file_id = tree.inventory.path2id(file)

        if not file_id:

            raise BzrError("%r is not present in revision %s" % (file, revno))

            try:

                revno = self.revision_id_to_revno(revision_id)

            except errors.NoSuchRevision:

                # TODO: This should not be BzrError,

                # but NoSuchFile doesn't fit either

                raise BzrError('%r is not present in revision %s' 

                                % (file, revision_id))

            else:

                raise BzrError('%r is not present in revision %s'

                                % (file, revno))

        tree.print_file(file_id)

    def get_transaction(self):

        return self.control_files.get_transaction()

    @needs_write_lock

    def sign_revision(self, revision_id, gpg_strategy):

        plaintext = Testament.from_revision(self, revision_id).as_short_text()

        self.store_revision_signature(gpg_strategy, plaintext, revision_id)

class RepositoryFormat(object):

    """A repository format.

    Formats provide three things:

     * An initialization routine to construct repository data on disk.

     * a format string which is used when the BzrDir supports versioned

       children.

     * an open routine which returns a Repository instance.

    Formats are placed in an dict by their format string for reference 

    during opening. These should be subclasses of RepositoryFormat

    for consistency.

    Once a format is deprecated, just deprecate the initialize and open

    methods on the format class. Do not deprecate the object, as the 

    object will be created every system load.

    Common instance attributes:

    _matchingbzrdir - the bzrdir format that the repository format was

    originally written to work with. This can be used if manually

    constructing a bzrdir and repository, or more commonly for test suite

    parameterisation.

    """

    _default_format = None

    """The default format used for new repositories."""

    _formats = {}

    """The known formats."""

    @classmethod

    def find_format(klass, a_bzrdir):

        """Return the format for the repository object in a_bzrdir."""

        try:

            transport = a_bzrdir.get_repository_transport(None)

            format_string = transport.get("format").read()

            return klass._formats[format_string]

        except errors.NoSuchFile:

            raise errors.NoRepositoryPresent(a_bzrdir)

        except KeyError:

            raise errors.UnknownFormatError(format_string)

    @classmethod

    def get_default_format(klass):

        """Return the current default format."""

        return klass._default_format

    def get_format_string(self):

        """Return the ASCII format string that identifies this format.

        Note that in pre format ?? repositories the format string is 

        not permitted nor written to disk.

        """

        raise NotImplementedError(self.get_format_string)

    def initialize(self, a_bzrdir, shared=False):

        """Initialize a repository of this format in a_bzrdir.

        :param a_bzrdir: The bzrdir to put the new repository in it.

        :param shared: The repository should be initialized as a sharable one.

        This may raise UninitializableFormat if shared repository are not

        compatible the a_bzrdir.

        """

    def is_supported(self):

        """Is this format supported?

        Supported formats must be initializable and openable.

        Unsupported formats may not support initialization or committing or 

        some other features depending on the reason for not being supported.

        """

        return True

    def open(self, a_bzrdir, _found=False):

        """Return an instance of this format for the bzrdir a_bzrdir.

        _found is a private parameter, do not use it.

        """

        if not _found:

            # we are being called directly and must probe.

            raise NotImplementedError

        return Repository(None, branch_format=None, _format=self, a_bzrdir=a_bzrdir)

    @classmethod

    def register_format(klass, format):

        klass._formats[format.get_format_string()] = format

    @classmethod

    def set_default_format(klass, format):

        klass._default_format = format

    @classmethod

    def unregister_format(klass, format):

        assert klass._formats[format.get_format_string()] is format

        del klass._formats[format.get_format_string()]

class PreSplitOutRepositoryFormat(RepositoryFormat):

    """Base class for the pre split out repository formats."""

    def initialize(self, a_bzrdir, shared=False, _internal=False):

        """Create a weave repository.

        TODO: when creating split out bzr branch formats, move this to a common

        base for Format5, Format6. or something like that.

        """

        from bzrlib.weavefile import write_weave_v5

        from bzrlib.weave import Weave

        if shared:

            raise errors.IncompatibleFormat(self, a_bzrdir._format)

        if not _internal:

            # always initialized when the bzrdir is.

            return Repository(None, branch_format=None, _format=self, a_bzrdir=a_bzrdir)

        # Create an empty weave

        sio = StringIO()

        bzrlib.weavefile.write_weave_v5(Weave(), sio)

        empty_weave = sio.getvalue()

        mutter('creating repository in %s.', a_bzrdir.transport.base)

        dirs = ['revision-store', 'weaves']

        lock_file = 'branch-lock'

        files = [('inventory.weave', StringIO(empty_weave)), 

                 ]

        # FIXME: RBC 20060125 dont peek under the covers

        # NB: no need to escape relative paths that are url safe.

        control_files = LockableFiles(a_bzrdir.transport, 'branch-lock')

        control_files.lock_write()

        control_files._transport.mkdir_multi(dirs,

                mode=control_files._dir_mode)

        try:

            for file, content in files:

                control_files.put(file, content)

        finally:

            control_files.unlock()

        return Repository(None, branch_format=None, _format=self, a_bzrdir=a_bzrdir)

class RepositoryFormat4(PreSplitOutRepositoryFormat):

    """Bzr repository format 4.

    This repository format has:

     - flat stores

     - TextStores for texts, inventories,revisions.

    This format is deprecated: it indexes texts using a text id which is

    removed in format 5; initializationa and write support for this format

    has been removed.

    """

    def __init__(self):

        super(RepositoryFormat4, self).__init__()

        self._matchingbzrdir = bzrdir.BzrDirFormat4()

    def initialize(self, url, shared=False, _internal=False):

        """Format 4 branches cannot be created."""

        raise errors.UninitializableFormat(self)

    def is_supported(self):