#!/usr/bin/python3
#
# Unix SMB/CIFS implementation.
# Copyright (C) Andrew Bartlett <abartlet@samba.org> 2019
#
# Downgrade a database from 4.11 format to 4.7 format. 4.7 Format will
# run on any version of Samba AD, and Samba will repack/reconfigure the
# database if necessary.
#
# 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 3 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, see <http://www.gnu.org/licenses/>.
import optparse
import sys

# Find right directory when running from source tree
sys.path.insert(0, "bin/python")


import samba
import ldb
import urllib
import os
from samba import getopt as options
from samba.samdb import SamDB
from samba.dbchecker import dbcheck
from samba.credentials import Credentials
parser = optparse.OptionParser("samba_downgrade_db")
sambaopts = options.SambaOptions(parser)
parser.add_option_group(options.VersionOptions(parser))
parser.add_option("-H", "--URL", help="LDB URL for database",
                  type=str, metavar="URL", dest="H")
opts, args = parser.parse_args()

if len(args) != 0:
    parser.print_usage()
    sys.exit(1)

lp_ctx = sambaopts.get_loadparm()

if opts.H is None:
    url = lp_ctx.private_path("sam.ldb")
else:
    url = opts.H

samdb = ldb.Ldb(url=url,
                flags=ldb.FLG_DONT_CREATE_DB,
                options=["modules:"])

partitions = samdb.search(base="@PARTITION",
                          scope=ldb.SCOPE_BASE,
                          attrs=["backendStore", "partition"])

backend = str(partitions[0].get('backendStore', 'tdb'))

if backend == "mdb":
    samdb = None
    options = ["pack_format_override=%d" % ldb.PACKING_FORMAT]
    # We can't remove GUID indexes from LMDB in case there are very
    # long DNs, so we just move down the pack format, which also removes
    # references to ORDERED_INTEGER in @ATTRIBUTES.

    # Reopen the DB with pack_format_override set
    samdb = SamDB(url=url,
                  flags=ldb.FLG_DONT_CREATE_DB,
                  lp=lp_ctx,
                  options=options)
    samdb.transaction_start()
    samdb.transaction_commit()
    print("Your database has been downgraded to LDB pack format version %0x (v1)." % ldb.PACKING_FORMAT)

    print("NOTE: Any use of a Samba 4.11 tool that modifies the DB will "
          "auto-upgrade back to pack format version %0x (v2)" %
          ldb.PACKING_FORMAT_V2)
    exit(0);

# This is needed to force the @ATTRIBUTES and @INDEXLIST to be correct
lp_ctx.set("dsdb:guid index", "false")

modmsg = ldb.Message()
modmsg.dn = ldb.Dn(samdb, '@INDEXLIST')
modmsg.add(ldb.MessageElement(
    elements=[],
    flags=ldb.FLAG_MOD_REPLACE,
    name='@IDXGUID'))
modmsg.add(ldb.MessageElement(
    elements=[],
    flags=ldb.FLAG_MOD_REPLACE,
    name='@IDX_DN_GUID'))

samdb.transaction_start()
samdb.modify(modmsg)

privatedir = os.path.dirname(url)

dbs = []
for part in partitions[0]['partition']:
    dbname = str(part).split(":")[1]
    dbpath = os.path.join(privatedir, dbname)
    if os.path.isfile(dbpath):
        dbpath = "ldb://" + dbpath
    db = ldb.Ldb(url=dbpath,
                 options=["modules:"],
                 flags=ldb.FLG_DONT_CREATE_DB)
    db.transaction_start()
    db.modify(modmsg)
    dbs.append(db)

for db in dbs:
    db.transaction_commit()

samdb.transaction_commit()

print("Re-opening with the full DB stack")
samdb = SamDB(url=url,
              flags=ldb.FLG_DONT_CREATE_DB,
              lp=lp_ctx)
print("Re-triggering another re-index")
chk = dbcheck(samdb)

chk.reindex_database()

print("Your database has been downgraded to DN-based index values.")

print("NOTE: Any use of a Samba 4.8 or later tool including ldbsearch will "
      "auto-upgrade back to GUID index mode")