#
#

# Copyright (C) 2010 Google Inc.
#
# 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.

"""Module implementing configuration details at runtime.

"""


import grp
import pwd
import threading
import platform

from ganeti import constants
from ganeti import errors
from ganeti import utils


_priv = None
_priv_lock = threading.Lock()

#: Architecture information
_arch = None


def GetUid(user, _getpwnam):
  """Retrieve the uid from the database.

  @type user: string
  @param user: The username to retrieve
  @return: The resolved uid

  """
  try:
    return _getpwnam(user).pw_uid
  except KeyError, err:
    raise errors.ConfigurationError("User '%s' not found (%s)" % (user, err))


def GetGid(group, _getgrnam):
  """Retrieve the gid from the database.

  @type group: string
  @param group: The group name to retrieve
  @return: The resolved gid

  """
  try:
    return _getgrnam(group).gr_gid
  except KeyError, err:
    raise errors.ConfigurationError("Group '%s' not found (%s)" % (group, err))


class GetentResolver:
  """Resolves Ganeti uids and gids by name.

  @ivar masterd_uid: The resolved uid of the masterd user
  @ivar masterd_gid: The resolved gid of the masterd group
  @ivar confd_uid: The resolved uid of the confd user
  @ivar confd_gid: The resolved gid of the confd group
  @ivar luxid_uid: The resolved uid of the luxid user
  @ivar luxid_gid: The resolved gid of the luxid group
  @ivar rapi_uid: The resolved uid of the rapi user
  @ivar rapi_gid: The resolved gid of the rapi group
  @ivar noded_uid: The resolved uid of the noded user
  @ivar daemons_gid: The resolved gid of the daemons group
  @ivar admin_gid: The resolved gid of the admin group

  """
  def __init__(self, _getpwnam=pwd.getpwnam, _getgrnam=grp.getgrnam):
    """Initialize the resolver.

    """
    # Daemon pairs
    self.masterd_uid = GetUid(constants.MASTERD_USER, _getpwnam)
    self.masterd_gid = GetGid(constants.MASTERD_GROUP, _getgrnam)

    self.confd_uid = GetUid(constants.CONFD_USER, _getpwnam)
    self.confd_gid = GetGid(constants.CONFD_GROUP, _getgrnam)

    self.luxid_uid = GetUid(constants.LUXID_USER, _getpwnam)
    self.luxid_gid = GetGid(constants.LUXID_GROUP, _getgrnam)

    self.rapi_uid = GetUid(constants.RAPI_USER, _getpwnam)
    self.rapi_gid = GetGid(constants.RAPI_GROUP, _getgrnam)

    self.noded_uid = GetUid(constants.NODED_USER, _getpwnam)
    self.noded_gid = GetGid(constants.NODED_GROUP, _getgrnam)

    self.mond_uid = GetUid(constants.MOND_USER, _getpwnam)
    self.mond_gid = GetGid(constants.MOND_GROUP, _getgrnam)

    # Misc Ganeti groups
    self.daemons_gid = GetGid(constants.DAEMONS_GROUP, _getgrnam)
    self.admin_gid = GetGid(constants.ADMIN_GROUP, _getgrnam)

    self._uid2user = {
      self.masterd_uid: constants.MASTERD_USER,
      self.confd_uid: constants.CONFD_USER,
      self.luxid_uid: constants.LUXID_USER,
      self.rapi_uid: constants.RAPI_USER,
      self.noded_uid: constants.NODED_USER,
      self.mond_uid: constants.MOND_USER,
      }

    self._gid2group = {
      self.masterd_gid: constants.MASTERD_GROUP,
      self.confd_gid: constants.CONFD_GROUP,
      self.luxid_gid: constants.LUXID_GROUP,
      self.rapi_gid: constants.RAPI_GROUP,
      self.noded_gid: constants.NODED_GROUP,
      self.mond_gid: constants.MOND_GROUP,
      self.daemons_gid: constants.DAEMONS_GROUP,
      self.admin_gid: constants.ADMIN_GROUP,
      }

    self._user2uid = utils.InvertDict(self._uid2user)
    self._group2gid = utils.InvertDict(self._gid2group)

  def LookupUid(self, uid):
    """Looks which Ganeti user belongs to this uid.

    @param uid: The uid to lookup
    @returns The user name associated with that uid

    """
    try:
      return self._uid2user[uid]
    except KeyError:
      raise errors.ConfigurationError("Unknown Ganeti uid '%d'" % uid)

  def LookupGid(self, gid):
    """Looks which Ganeti group belongs to this gid.

    @param gid: The gid to lookup
    @returns The group name associated with that gid

    """
    try:
      return self._gid2group[gid]
    except KeyError:
      raise errors.ConfigurationError("Unknown Ganeti gid '%d'" % gid)

  def LookupUser(self, name):
    """Looks which uid belongs to this name.

    @param name: The name to lookup
    @returns The uid associated with that user name

    """
    try:
      return self._user2uid[name]
    except KeyError:
      raise errors.ConfigurationError("Unknown Ganeti user '%s'" % name)

  def LookupGroup(self, name):
    """Looks which gid belongs to this name.

    @param name: The name to lookup
    @returns The gid associated with that group name

    """
    try:
      return self._group2gid[name]
    except KeyError:
      raise errors.ConfigurationError("Unknown Ganeti group '%s'" % name)


def GetEnts(resolver=GetentResolver):
  """Singleton wrapper around resolver instance.

  As this method is accessed by multiple threads at the same time
  we need to take thread-safety carefully.

  """
  # We need to use the global keyword here
  global _priv # pylint: disable=W0603

  if not _priv:
    _priv_lock.acquire()
    try:
      if not _priv:
        # W0621: Redefine '_priv' from outer scope (used for singleton)
        _priv = resolver() # pylint: disable=W0621
    finally:
      _priv_lock.release()

  return _priv


def InitArchInfo():
  """Initialize architecture information.

  We can assume this information never changes during the lifetime of a
  process, therefore the information can easily be cached.

  @note: This function uses C{platform.architecture} to retrieve the Python
    binary architecture and does so by forking to run C{file} (see Python
    documentation for more information). Therefore it must not be used in a
    multi-threaded environment.

  """
  global _arch # pylint: disable=W0603

  if _arch is not None:
    raise errors.ProgrammerError("Architecture information can only be"
                                 " initialized once")

  _arch = (platform.architecture()[0], platform.machine())


def GetArchInfo():
  """Returns previsouly initialized architecture information.

  """
  if _arch is None:
    raise errors.ProgrammerError("Architecture information hasn't been"
                                 " initialized")

  return _arch