#
# Copyright 2013 Rackspace Hosting.
#
# Author: Monsyne Dragon <mdragon@rackspace.com>
#
# 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.

import fnmatch
import os

import jsonpath_rw
from oslo.config import cfg
from oslo.utils import timeutils
import six
import yaml

from ceilometer.openstack.common.gettextutils import _
from ceilometer.openstack.common import log
from ceilometer.storage import models

OPTS = [
    cfg.StrOpt('definitions_cfg_file',
               default="event_definitions.yaml",
               help="Configuration file for event definitions."
               ),
    cfg.BoolOpt('drop_unmatched_notifications',
                default=False,
                help='Drop notifications if no event definition matches. '
                '(Otherwise, we convert them with just the default traits)'),

]

cfg.CONF.register_opts(OPTS, group='event')

LOG = log.getLogger(__name__)


class EventDefinitionException(Exception):
    def __init__(self, message, definition_cfg):
        super(EventDefinitionException, self).__init__(message)
        self.definition_cfg = definition_cfg

    def __str__(self):
        return '%s %s: %s' % (self.__class__.__name__,
                              self.definition_cfg, self.message)


class TraitDefinition(object):

    def __init__(self, name, trait_cfg, plugin_manager):
        self.cfg = trait_cfg
        self.name = name

        type_name = trait_cfg.get('type', 'text')

        if 'plugin' in trait_cfg:
            plugin_cfg = trait_cfg['plugin']
            if isinstance(plugin_cfg, six.string_types):
                plugin_name = plugin_cfg
                plugin_params = {}
            else:
                try:
                    plugin_name = plugin_cfg['name']
                except KeyError:
                    raise EventDefinitionException(
                        _('Plugin specified, but no plugin name supplied for '
                          'trait %s') % name, self.cfg)
                plugin_params = plugin_cfg.get('parameters')
                if plugin_params is None:
                    plugin_params = {}
            try:
                plugin_ext = plugin_manager[plugin_name]
            except KeyError:
                raise EventDefinitionException(
                    _('No plugin named %(plugin)s available for '
                      'trait %(trait)s') % dict(plugin=plugin_name,
                                                trait=name), self.cfg)
            plugin_class = plugin_ext.plugin
            self.plugin = plugin_class(**plugin_params)
        else:
            self.plugin = None

        if 'fields' not in trait_cfg:
            raise EventDefinitionException(
                _("Required field in trait definition not specified: "
                  "'%s'") % 'fields',
                self.cfg)

        fields = trait_cfg['fields']
        if not isinstance(fields, six.string_types):
            # NOTE(mdragon): if not a string, we assume a list.
            if len(fields) == 1:
                fields = fields[0]
            else:
                fields = '|'.join('(%s)' % path for path in fields)
        try:
            self.fields = jsonpath_rw.parse(fields)
        except Exception as e:
            raise EventDefinitionException(
                _("Parse error in JSONPath specification "
                  "'%(jsonpath)s' for %(trait)s: %(err)s")
                % dict(jsonpath=fields, trait=name, err=e), self.cfg)
        self.trait_type = models.Trait.get_type_by_name(type_name)
        if self.trait_type is None:
            raise EventDefinitionException(
                _("Invalid trait type '%(type)s' for trait %(trait)s")
                % dict(type=type_name, trait=name), self.cfg)

    def _get_path(self, match):
        if match.context is not None:
            for path_element in self._get_path(match.context):
                yield path_element
            yield str(match.path)

    def to_trait(self, notification_body):
        values = [match for match in self.fields.find(notification_body)
                  if match.value is not None]

        if self.plugin is not None:
            value_map = [('.'.join(self._get_path(match)), match.value) for
                         match in values]
            value = self.plugin.trait_value(value_map)
        else:
            value = values[0].value if values else None

        if value is None:
            return None

        # NOTE(mdragon): some openstack projects (mostly Nova) emit ''
        # for null fields for things like dates.
        if self.trait_type != models.Trait.TEXT_TYPE and value == '':
            return None

        value = models.Trait.convert_value(self.trait_type, value)
        return models.Trait(self.name, self.trait_type, value)


class EventDefinition(object):

    DEFAULT_TRAITS = dict(
        service=dict(type='text', fields='publisher_id'),
        request_id=dict(type='text', fields='_context_request_id'),
        tenant_id=dict(type='text', fields=['payload.tenant_id',
                                            '_context_tenant']),
    )

    def __init__(self, definition_cfg, trait_plugin_mgr):
        self._included_types = []
        self._excluded_types = []
        self.traits = dict()
        self.cfg = definition_cfg

        try:
            event_type = definition_cfg['event_type']
            traits = definition_cfg['traits']
        except KeyError as err:
            raise EventDefinitionException(
                _("Required field %s not specified") % err.args[0], self.cfg)

        if isinstance(event_type, six.string_types):
            event_type = [event_type]

        for t in event_type:
            if t.startswith('!'):
                self._excluded_types.append(t[1:])
            else:
                self._included_types.append(t)

        if self._excluded_types and not self._included_types:
            self._included_types.append('*')

        for trait_name in self.DEFAULT_TRAITS:
            self.traits[trait_name] = TraitDefinition(
                trait_name,
                self.DEFAULT_TRAITS[trait_name],
                trait_plugin_mgr)
        for trait_name in traits:
            self.traits[trait_name] = TraitDefinition(
                trait_name,
                traits[trait_name],
                trait_plugin_mgr)

    def included_type(self, event_type):
        for t in self._included_types:
            if fnmatch.fnmatch(event_type, t):
                return True
        return False

    def excluded_type(self, event_type):
        for t in self._excluded_types:
            if fnmatch.fnmatch(event_type, t):
                return True
        return False

    def match_type(self, event_type):
        return (self.included_type(event_type)
                and not self.excluded_type(event_type))

    @property
    def is_catchall(self):
        return '*' in self._included_types and not self._excluded_types

    @staticmethod
    def _extract_when(body):
        """Extract the generated datetime from the notification."""
        # NOTE: I am keeping the logic the same as it was in the collector,
        # However, *ALL* notifications should have a 'timestamp' field, it's
        # part of the notification envelope spec. If this was put here because
        # some openstack project is generating notifications without a
        # timestamp, then that needs to be filed as a bug with the offending
        # project (mdragon)
        when = body.get('timestamp', body.get('_context_timestamp'))
        if when:
            return timeutils.normalize_time(timeutils.parse_isotime(when))

        return timeutils.utcnow()

    def to_event(self, notification_body):
        event_type = notification_body['event_type']
        message_id = notification_body['message_id']
        when = self._extract_when(notification_body)

        traits = (self.traits[t].to_trait(notification_body)
                  for t in self.traits)
        # Only accept non-None value traits ...
        traits = [trait for trait in traits if trait is not None]
        event = models.Event(message_id, event_type, when, traits)
        return event


class NotificationEventsConverter(object):
    """Notification Event Converter

    The NotificationEventsConverter handles the conversion of Notifications
    from openstack systems into Ceilometer Events.

    The conversion is handled according to event definitions in a config file.

    The config is a list of event definitions. Order is significant, a
    notification will be processed according to the LAST definition that
    matches it's event_type. (We use the last matching definition because that
    allows you to use YAML merge syntax in the definitions file.)
    Each definition is a dictionary with the following keys (all are
    required):

    - event_type: this is a list of notification event_types this definition
      will handle. These can be wildcarded with unix shell glob (not regex!)
      wildcards.
      An exclusion listing (starting with a '!') will exclude any types listed
      from matching. If ONLY exclusions are listed, the definition will match
      anything not matching the exclusions.
      This item can also be a string, which will be taken as equivalent to 1
      item list.

                Examples:

                * ['compute.instance.exists'] will only match
                  compute.intance.exists notifications
                * "compute.instance.exists"   Same as above.
                * ["image.create", "image.delete"]  will match
                  image.create and image.delete, but not anything else.
                * "compute.instance.*" will match
                  compute.instance.create.start but not image.upload
                * ['*.start','*.end', '!scheduler.*'] will match
                  compute.instance.create.start, and image.delete.end,
                  but NOT compute.instance.exists or
                  scheduler.run_instance.start
                * '!image.*' matches any notification except image
                  notifications.
                * ['*', '!image.*']  same as above.

    - traits: (dict) The keys are trait names, the values are the trait
      definitions. Each trait definition is a dictionary with the following
      keys:

      - type (optional): The data type for this trait. (as a string)
        Valid options are: 'text', 'int', 'float' and 'datetime', defaults to
        'text' if not specified.
      - fields:  a path specification for the field(s) in the notification you
        wish to extract. The paths can be specified with a dot syntax
        (e.g. 'payload.host') or dictionary syntax (e.g. 'payload[host]') is
        also supported.
        In either case, if the key for the field you are looking for contains
        special characters, like '.', it will need to be quoted (with double
        or single quotes) like so::

         "payload.image_meta.'org.openstack__1__architecture'"

        The syntax used for the field specification is a variant of JSONPath,
        and is fairly flexible.
        (see: https://github.com/kennknowles/python-jsonpath-rw for more info)
        Specifications can be written to match multiple possible fields, the
        value for the trait will be derived from the matching fields that
        exist and have a non-null (i.e. is not None) values in the
        notification.
        By default the value will be the first such field. (plugins can alter
        that, if they wish)

        This configuration value is normally a string, for convenience, it can
        be specified as a list of specifications, which will be OR'ed together
        (a union query in jsonpath terms)
    - plugin (optional): (dictionary) with the following keys:

      - name: (string) name of a plugin to load
      - parameters: (optional) Dictionary of keyword args to pass
        to the plugin on initialization. See documentation on each plugin to
        see what arguments it accepts.

      For convenience, this value can also be specified as a string, which is
      interpreted as a plugin name, which will be loaded with no parameters.

    """

    def __init__(self, events_config, trait_plugin_mgr, add_catchall=True):
        self.definitions = [
            EventDefinition(event_def, trait_plugin_mgr)
            for event_def in reversed(events_config)]
        if add_catchall and not any(d.is_catchall for d in self.definitions):
            event_def = dict(event_type='*', traits={})
            self.definitions.append(EventDefinition(event_def,
                                                    trait_plugin_mgr))

    def to_event(self, notification_body):
        event_type = notification_body['event_type']
        message_id = notification_body['message_id']
        edef = None
        for d in self.definitions:
            if d.match_type(event_type):
                edef = d
                break

        if edef is None:
            msg = (_('Dropping Notification %(type)s (uuid:%(msgid)s)')
                   % dict(type=event_type, msgid=message_id))
            if cfg.CONF.event.drop_unmatched_notifications:
                LOG.debug(msg)
            else:
                # If drop_unmatched_notifications is False, this should
                # never happen. (mdragon)
                LOG.error(msg)
            return None

        return edef.to_event(notification_body)


def get_config_file():
    config_file = cfg.CONF.event.definitions_cfg_file
    if not os.path.exists(config_file):
        config_file = cfg.CONF.find_file(config_file)
    return config_file


def setup_events(trait_plugin_mgr):
    """Setup the event definitions from yaml config file."""
    config_file = get_config_file()
    if config_file is not None:
        LOG.debug(_("Event Definitions configuration file: %s"), config_file)

        with open(config_file) as cf:
            config = cf.read()

        try:
            events_config = yaml.safe_load(config)
        except yaml.YAMLError as err:
            if hasattr(err, 'problem_mark'):
                mark = err.problem_mark
                errmsg = (_("Invalid YAML syntax in Event Definitions file "
                            "%(file)s at line: %(line)s, column: %(column)s.")
                          % dict(file=config_file,
                                 line=mark.line + 1,
                                 column=mark.column + 1))
            else:
                errmsg = (_("YAML error reading Event Definitions file "
                            "%(file)s")
                          % dict(file=config_file))
            LOG.error(errmsg)
            raise

    else:
        LOG.debug(_("No Event Definitions configuration file found!"
                  " Using default config."))
        events_config = []

    LOG.info(_("Event Definitions: %s"), events_config)

    allow_drop = cfg.CONF.event.drop_unmatched_notifications
    return NotificationEventsConverter(events_config,
                                       trait_plugin_mgr,
                                       add_catchall=not allow_drop)
