# Copyright (C) 2006 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

"""Implementation of Transport that prevents access to locations above a set
root.
"""
from urlparse import urlparse

from bzrlib import errors, urlutils
from bzrlib.transport import (
    get_transport,
    register_transport,
    Server,
    Transport,
    unregister_transport,
    )
from bzrlib.transport.decorator import TransportDecorator, DecoratorServer
from bzrlib.transport.memory import MemoryTransport


class ChrootServer(Server):
    """User space 'chroot' facility.
    
    The server's get_url returns the url for a chroot transport mapped to the
    backing transport. The url is of the form chroot-xxx:/// so parent
    directories of the backing transport are not visible. The chroot url will
    not allow '..' sequences to result in requests to the chroot affecting
    directories outside the backing transport.
    """

    def __init__(self, backing_transport):
        self.backing_transport = backing_transport

    def _factory(self, url):
        assert url.startswith(self.scheme)
        return ChrootTransport(self, url)

    def get_url(self):
        return self.scheme

    def setUp(self):
        self.scheme = 'chroot-%d:///' % id(self)
        register_transport(self.scheme, self._factory)

    def tearDown(self):
        unregister_transport(self.scheme, self._factory)


class ChrootTransport(Transport):
    """A ChrootTransport.

    Please see ChrootServer for details.
    """

    def __init__(self, server, base):
        self.server = server
        if not base.endswith('/'):
            base += '/'
        Transport.__init__(self, base)
        self.base_path = self.base[len(self.server.scheme)-1:]
        self.scheme = self.server.scheme

    def _call(self, methodname, relpath, *args):
        method = getattr(self.server.backing_transport, methodname)
        return method(self._safe_relpath(relpath), *args)

    def _safe_relpath(self, relpath):
        safe_relpath = self._combine_paths(self.base_path, relpath)
        assert safe_relpath.startswith('/')
        return safe_relpath[1:]

    # Transport methods
    def abspath(self, relpath):
        return self.scheme + self._safe_relpath(relpath)

    def append_file(self, relpath, f, mode=None):
        return self._call('append_file', relpath, f, mode)

    def _can_roundtrip_unix_modebits(self):
        return self.server.backing_transport._can_roundtrip_unix_modebits()

    def clone(self, relpath):
        return ChrootTransport(self.server, self.abspath(relpath))

    def delete(self, relpath):
        return self._call('delete', relpath)

    def delete_tree(self, relpath):
        return self._call('delete_tree', relpath)

    def external_url(self):
        """See bzrlib.transport.Transport.external_url."""
        # Chroots, like MemoryTransport depend on in-process
        # state and thus the base cannot simply be handed out.
        # See the base class docstring for more details and
        # possible directions. For now we return the chrooted
        # url. 
        return self.server.backing_transport.external_url()

    def get(self, relpath):
        return self._call('get', relpath)

    def has(self, relpath):
        return self._call('has', relpath)

    def iter_files_recursive(self):
        backing_transport = self.server.backing_transport.clone(
            self._safe_relpath('.'))
        return backing_transport.iter_files_recursive()

    def listable(self):
        return self.server.backing_transport.listable()

    def list_dir(self, relpath):
        return self._call('list_dir', relpath)

    def lock_read(self, relpath):
        return self._call('lock_read', relpath)

    def lock_write(self, relpath):
        return self._call('lock_write', relpath)

    def mkdir(self, relpath, mode=None):
        return self._call('mkdir', relpath, mode)

    def open_write_stream(self, relpath, mode=None):
        return self._call('open_write_stream', relpath, mode)

    def put_file(self, relpath, f, mode=None):
        return self._call('put_file', relpath, f, mode)

    def rename(self, rel_from, rel_to):
        return self._call('rename', rel_from, self._safe_relpath(rel_to))

    def rmdir(self, relpath):
        return self._call('rmdir', relpath)

    def stat(self, relpath):
        return self._call('stat', relpath)


class TestingChrootServer(ChrootServer):

    def __init__(self):
        """TestingChrootServer is not usable until setUp is called."""

    def setUp(self, backing_server=None):
        """Setup the Chroot on backing_server."""
        if backing_server is not None:
            self.backing_transport = get_transport(backing_server.get_url())
        else:
            self.backing_transport = get_transport('.')
        ChrootServer.setUp(self)


def get_test_permutations():
    """Return the permutations to be used in testing."""
    return [(ChrootTransport, TestingChrootServer),
            ]
