# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.
"""Fake LDAP server for test harness.

This class does very little error checking, and knows nothing about ldap
class definitions.  It implements the minimum emulation of the python ldap
library to work with nova.

"""

import logging
import re
import shelve

from ldap import (dn, filter, modlist,
    SCOPE_BASE, SCOPE_ONELEVEL, SCOPE_SUBTREE, MOD_ADD, MOD_DELETE, MOD_REPLACE,
    NO_SUCH_OBJECT, OBJECT_CLASS_VIOLATION, SERVER_DOWN, NO_SUCH_ATTRIBUTE,
    ALREADY_EXISTS)


scope_names = {
    SCOPE_BASE: 'SCOPE_BASE',
    SCOPE_ONELEVEL: 'SCOPE_ONELEVEL',
    SCOPE_SUBTREE: 'SCOPE_SUBTREE',
}


LOG = logging.getLogger('keystone.backends.ldap.fakeldap')


def initialize(uri):
    """Opens a fake connection with an LDAP server."""
    return FakeLDAP(uri)


def _match_query(query, attrs):
    """Match an ldap query to an attribute dictionary.

    The characters &, |, and ! are supported in the query. No syntax checking
    is performed, so malformed querys will not work correctly.
    """
    # cut off the parentheses
    inner = query[1:-1]
    if inner.startswith('&'):
        # cut off the &
        l, r = _paren_groups(inner[1:])
        return _match_query(l, attrs) and _match_query(r, attrs)
    if inner.startswith('|'):
        # cut off the |
        l, r = _paren_groups(inner[1:])
        return _match_query(l, attrs) or _match_query(r, attrs)
    if inner.startswith('!'):
        # cut off the ! and the nested parentheses
        return not _match_query(query[2:-1], attrs)

    (k, _sep, v) = inner.partition('=')
    return _match(k, v, attrs)


def _paren_groups(source):
    """Split a string into parenthesized groups."""
    count = 0
    start = 0
    result = []
    for pos in xrange(len(source)):
        if source[pos] == '(':
            if count == 0:
                start = pos
            count += 1
        if source[pos] == ')':
            count -= 1
            if count == 0:
                result.append(source[start:pos + 1])
    return result


def _match(key, value, attrs):
    """Match a given key and value against an attribute list."""
    if key not in attrs:
        return False
    # This is a wild card search. Implemented as all or nothing for now.
    if value == "*":
        return True
    if key != "objectclass":
        return value in attrs[key]
    # it is an objectclass check, so check subclasses
    values = _subs(value)
    for v in values:
        if v in attrs[key]:
            return True
    return False


def _subs(value):
    """Returns a list of subclass strings.

    The strings represent the ldap objectclass plus any subclasses that
    inherit from it. Fakeldap doesn't know about the ldap object structure,
    so subclasses need to be defined manually in the dictionary below.

    """
    subs = {'groupOfNames': ['keystoneTenant', 'keystoneRole', 'keystoneTenantRole']}
    if value in subs:
        return [value] + subs[value]
    return [value]


server_fail = False


class FakeLDAP(object):
    """Fake LDAP connection."""

    def __init__(self, url):
        LOG.debug("FakeLDAP initialize url=%s" % (url,))
        self.db = shelve.open(url[7:])

    def simple_bind_s(self, dn, password):
        """This method is ignored, but provided for compatibility."""
        if server_fail:
            raise SERVER_DOWN
        LOG.debug("FakeLDAP bind dn=%s" % (dn,))

    def unbind_s(self):
        """This method is ignored, but provided for compatibility."""
        if server_fail:
            raise SERVER_DOWN
        pass

    def add_s(self, dn, attrs):
        """Add an object with the specified attributes at dn."""
        if server_fail:
            raise SERVER_DOWN

        key = "%s%s" % (self.__prefix, dn)
        LOG.debug("FakeLDAP add item: dn=%s, attrs=%s" % (dn, attrs))
        if self.db.has_key(key):
            LOG.error("FakeLDAP add item failed: dn '%s' is already in store." %
                        (dn,))
            raise ALREADY_EXISTS
        self.db[key] = dict([(k, v if isinstance(v, list) else [v])
                             for k, v in attrs])
        self.db.sync()

    def delete_s(self, dn):
        """Remove the ldap object at specified dn."""
        if server_fail:
            raise SERVER_DOWN

        key = "%s%s" % (self.__prefix, dn)
        LOG.debug("FakeLDAP delete item: dn=%s" % (dn,))
        try:
            del self.db[key]
        except KeyError:
            LOG.error("FakeLDAP delete item failed: dn '%s' not found." % (dn,))
            raise NO_SUCH_OBJECT
        self.db.sync()

    def modify_s(self, dn, attrs):
        """Modify the object at dn using the attribute list.

        Args:
        dn -- a dn
        attrs -- a list of tuples in the following form:
            ([MOD_ADD | MOD_DELETE | MOD_REPACE], attribute, value)

        """
        if server_fail:
            raise SERVER_DOWN

        key = "%s%s" % (self.__prefix, dn)
        LOG.debug("FakeLDAP modify item: dn=%s attrs=%s" % (dn, attrs))
        try:
            entry = self.db[key]
        except KeyError:
            LOG.error("FakeLDAP modify item failed: dn '%s' not found." % (dn,))
            raise NO_SUCH_OBJECT

        for cmd, k, v in attrs:
            values = entry.setdefault(k, [])
            if cmd == MOD_ADD:
                if isinstance(v, list):
                    values += v
                else:
                    values.append(v)
            elif cmd == MOD_REPLACE:
                values[:] = v if isinstance(v, list) else [v]
            elif cmd == MOD_DELETE:
                if v is None:
                    if len(values) == 0:
                        LOG.error("FakeLDAP modify item failed: "
                                  "item has no attribute '%s' to delete" % (k,))
                        raise NO_SUCH_ATTRIBUTE
                    values[:] = []
                else:
                    if not isinstance(v,list):
                        v = [v]
                    for val in v:
                        try:
                            values.remove(val)
                        except ValueError:
                            LOG.error("FakeLDAP modify item failed: "
                                      "item has no attribute '%s' with value '%s'"
                                      " to delete" % (k, val))
                            raise NO_SUCH_ATTRIBUTE
            else:
                LOG.error("FakeLDAP modify item failed: unknown command %s" % (cmd,))
                raise NotImplementedError( \
                    "modify_s action %s not implemented" % (cmd,))
        self.db[key] = entry
        self.db.sync()

    def search_s(self, dn, scope, query=None, fields=None):
        """Search for all matching objects under dn using the query.

        Args:
        dn -- dn to search under
        scope -- only SCOPE_BASE and SCOPE_SUBTREE are supported
        query -- query to filter objects by
        fields -- fields to return. Returns all fields if not specified

        """
        if server_fail:
            raise SERVER_DOWN

        LOG.debug("FakeLDAP search at dn=%s scope=%s query='%s'" %
                    (dn, scope_names.get(scope, scope), query))
        if scope == SCOPE_BASE:
            try:
                item_dict = self.db["%s%s" % (self.__prefix, dn)]
            except KeyError:
                LOG.debug("FakeLDAP search fail: dn not found for SCOPE_BASE")
                raise NO_SUCH_OBJECT
            results = [(dn, item_dict)]
        elif scope == SCOPE_SUBTREE:
            results = [(k[len(self.__prefix):], v)
                       for k, v in self.db.iteritems()
                       if re.match("%s.*,%s" % (self.__prefix, dn), k)]
        elif scope == SCOPE_ONELEVEL:
            results = [(k[len(self.__prefix):], v)
                       for k, v in self.db.iteritems()
                       if re.match("%s\w+=[^,]+,%s" % (self.__prefix, dn), k)]
        else:
            LOG.error("FakeLDAP search fail: unknown scope %s" % (scope,))
            raise NotImplementedError("Search scope %s not implemented." % 
                                                                    (scope,))

        objects = []
        for dn, attrs in results:
            # filter the objects by query
            if not query or _match_query(query, attrs):
                # filter the attributes by fields
                attrs = dict([(k, v) for k, v in attrs.iteritems()
                              if not fields or k in fields])
                objects.append((dn, attrs))
            # pylint: enable=E1103
        LOG.debug("FakeLDAP search result: %s" % (objects,))
        return objects

    @property
    def __prefix(self):  # pylint: disable=R0201
        """Get the prefix to use for all keys."""
        return 'ldap:'