""" A plugin to fetch data from a LDAP directory """

import imp
import os
import sys
import time
import traceback
from functools import partial

import Bcfg2.Options
import Bcfg2.Server.Cache
import Bcfg2.Server.Plugin
from Bcfg2.Logger import Debuggable
from Bcfg2.Utils import ClassName, safe_module_name

try:
    import ldap
    HAS_LDAP = True
except ImportError:
    HAS_LDAP = False


class ConfigFile(Bcfg2.Server.Plugin.FileBacked):
    """ Config file for the Ldap plugin  """

    def __init__(self, name, core, plugin):
        Bcfg2.Server.Plugin.FileBacked.__init__(self, name)
        self.core = core
        self.plugin = plugin
        self.queries = list()
        self.fam.AddMonitor(name, self)

    def Index(self):
        """ Get the queries from the config file """
        try:
            module_name = os.path.splitext(os.path.basename(self.name))[0]
            module = imp.load_source(safe_module_name('Ldap', module_name),
                                     self.name)
        except:  # pylint: disable=W0702
            err = sys.exc_info()[1]
            self.logger.error("Ldap: Failed to import %s: %s" %
                              (self.name, err))
            return

        if not hasattr(module, "__queries__"):
            self.logger.error("Ldap: %s has no __queries__ list" % self.name)
            return

        self.queries = list()
        for query in module.__queries__:
            try:
                self.queries.append(getattr(module, query))
            except AttributeError:
                self.logger.warning(
                    "Ldap: %s exports %s, but has no such attribute" %
                    (self.name, query))

        if self.core.metadata_cache_mode in ['cautious', 'aggressive']:
            self.core.metadata_cache.expire()

        self.plugin.expire_cache()


class Ldap(Bcfg2.Server.Plugin.Plugin,
           Bcfg2.Server.Plugin.ClientRunHooks,
           Bcfg2.Server.Plugin.Connector):
    """ The Ldap plugin allows adding data from an LDAP server
    to your metadata. """
    __rmi__ = Bcfg2.Server.Plugin.Plugin.__rmi__ + ['expire_cache']

    experimental = True

    options = [
        Bcfg2.Options.Option(
            cf=('ldap', 'retries'), type=int, default=3,
            dest='ldap_retries',
            help='The number of times to retry reaching the '
                 'LDAP server if a connection is broken'),
        Bcfg2.Options.Option(
            cf=('ldap', 'retry_delay'), type=float, default=5.0,
            dest='ldap_retry_delay',
            help='The time in seconds betreen retries'),
        Bcfg2.Options.BooleanOption(
            cf=('ldap', 'cache'), default=None, dest='ldap_cache',
            help='Cache the results of the LDAP Queries until they '
                 'are expired using the XML-RPC RMI')]

    def __init__(self, core):
        Bcfg2.Server.Plugin.Plugin.__init__(self, core)
        Bcfg2.Server.Plugin.Connector.__init__(self)

        if not HAS_LDAP:
            msg = "Python ldap module is required for Ldap plugin"
            self.logger.error(msg)
            raise Bcfg2.Server.Plugin.PluginInitError(msg)

        self.config = ConfigFile(os.path.join(self.data, 'config.py'),
                                 core, self)
        self._hosts = dict()

    def _cache(self, query_name):
        """ Return the :class:`Cache <Bcfg2.Server.Cache>` for the
        given query name. """
        return Bcfg2.Server.Cache.Cache('Ldap', 'results', query_name)

    def _execute_query(self, query, metadata):
        """ Return the cached result of the given query for this host or
        execute the given query and cache the result. """
        result = None

        if Bcfg2.Options.setup.ldap_cache is not False:
            cache = self._cache(query.name)
            result = cache.get(metadata.hostname, None)

        if result is None:
            try:
                self.debug_log("Processing query '%s'" % query.name)
                result = query.get_result(metadata)
                if Bcfg2.Options.setup.ldap_cache is not False:
                    cache[metadata.hostname] = result
            except:  # pylint: disable=W0702
                self.logger.error(
                    "Exception during processing of query named '%s', query "
                    "results will be empty and may cause bind failures" %
                    query.name)
                for line in traceback.format_exc().split('\n'):
                    self.logger.error(line)
        return result

    def get_additional_data(self, metadata):
        data = {}
        self.debug_log("Found queries %s" % self.config.queries)
        for query_class in self.config.queries:
            try:
                query = query_class()
                if query.is_applicable(metadata):
                    self.debug_log("Processing query '%s'" % query.name)
                    data[query.name] = partial(
                        self._execute_query, query, metadata)
                else:
                    self.debug_log("query '%s' not applicable to host '%s'" %
                                   (query.name, metadata.hostname))
            except:  # pylint: disable=W0702
                self.logger.error(
                    "Exception during preparation of query named '%s'. "
                    "Query will be ignored." % query_class.__name__)
                for line in traceback.format_exc().split('\n'):
                    self.logger.error(line)

        return Bcfg2.Server.Plugin.CallableDict(**data)

    def start_client_run(self, metadata):
        if Bcfg2.Options.setup.ldap_cache is None:
            self.expire_cache(hostname=metadata.hostname)

    def expire_cache(self, query=None, hostname=None):
        """ Expire the cache. You can select the items to purge
        per query and/or per host, or you can purge all cached
        data. This is exposed as an XML-RPC RMI. """

        tags = ['Ldap', 'results']
        if query:
            tags.append(query)
        if hostname:
            tags.append(hostname)

        return Bcfg2.Server.Cache.expire(*tags)


class LdapConnection(Debuggable):
    """ Connection to an LDAP server. """

    def __init__(self, host="localhost", port=389, uri=None, options=None,
                 binddn=None, bindpw=None):
        Debuggable.__init__(self)

        if HAS_LDAP:
            msg = "Python ldap module is required for Ldap plugin"
            self.logger.error(msg)
            raise Bcfg2.Server.Plugin.PluginInitError(msg)

        self.host = host
        self.port = port
        self.uri = uri
        self.options = options
        self.binddn = binddn
        self.bindpw = bindpw
        self.conn = None

        self.__scopes__ = {
            'base': ldap.SCOPE_BASE,
            'one': ldap.SCOPE_ONELEVEL,
            'sub': ldap.SCOPE_SUBTREE,
        }

    def __del__(self):
        """ Disconnection if the instance is destroyed. """
        self.disconnect()

    def disconnect(self):
        """ If a connection to an LDAP server is available, disconnect it. """
        if self.conn:
            self.conn.unbund()
            self.conn = None

    def connect(self):
        """ Open a connection to the configured LDAP server, and do a simple
        bind ff both binddn and bindpw are set. """
        self.disconnect()
        self.conn = ldap.initialize(self.get_uri())

        if self.options is not None:
            for (option, value) in self.options.items():
                self.conn.set_option(option, value)

        if self.binddn is not None and self.bindpw is not None:
            self.conn.simple_bind_s(self.binddn, self.bindpw)

    def run_query(self, query):
        """ Connect to the server and execute the query. If the server is
        down, wait the configured amount and try to reconnect.

        :param query: The query to execute on the LDAP server.
        :type query: Bcfg.Server.Plugins.Ldap.LdapQuery
        """
        for attempt in range(Bcfg2.Options.setup.ldap_retries + 1):
            try:
                if not self.conn:
                    self.connect()

                return self.conn.search_s(
                    query.base, self.__scopes__[query.scope],
                    query.filter.replace('\\', '\\\\'), query.attrs)

            except ldap.SERVER_DOWN:
                self.conn = None
                self.logger.error(
                    "LdapConnection: Server %s down. Retry %d/%d in %.2fs." %
                    (self.get_uri(), attempt + 1,
                     Bcfg2.Options.setup.ldap_retries,
                     Bcfg2.Options.setup.ldap_retry_delay))
                time.sleep(Bcfg2.Options.setup.ldap_retry_delay)

        return None

    def get_uri(self):
        """ The URL of the LDAP server. """
        if self.uri is None:
            if self.port == 636:
                return "ldaps://%s" % self.host
            return "ldap://%s:%d" % (self.host, self.port)
        return self.uri


class LdapQuery(object):
    """ Query referencing an LdapConnection and providing several
    methods for query manipulation. """

    #: Name of the Query, used to register it in additional data.
    name = ClassName()

    base = ""
    scope = "sub"
    filter = "(objectClass=*)"
    attrs = None
    connection = None
    result = None

    def __unicode__(self):
        return "LdapQuery: %s" % self.name

    def is_applicable(self, metadata):  # pylint: disable=W0613
        """ Check is the query should be executed for a given metadata
        object.

        :param metadata: The client metadata
        :type metadata: Bcfg2.Server.Plugins.Metadata.ClientMetadata
        """
        return True

    def prepare_query(self, metadata, **kwargs):  # pylint: disable=W0613
        """ Prepares the query based on the client metadata. You can
        for example modify the filter based on the client hostname.

        :param metadata: The client metadata
        :type metadata: Bcfg2.Server.Plugins.Metadata.ClientMetadata
        """
        pass

    def process_result(self, metadata, **kwargs):  # pylint: disable=W0613
        """ Post-process the query result.

        :param metadata: The client metadata
        :type metadata: Bcfg2.Server.Plugins.Metadata.ClientMetadata
        """
        return self.result

    def get_result(self, metadata, **kwargs):
        """ Handle the perparation, execution and processing of the query.

        :param metadata: The client metadata
        :type metadata: Bcfg2.Server.Plugins.Metadata.ClientMetadata
        :raises: :class:`Bcfg2.Server.Plugin.exceptions.PluginExecutionError`
        """

        if self.connection is not None:
            self.prepare_query(metadata, **kwargs)
            self.result = self.connection.run_query(self)
            self.result = self.process_result(metadata, **kwargs)
        else:
            raise Bcfg2.Server.Plugin.PluginExecutionError(
                'No connection defined for %s' % self.name)

        return self.result