# -*- encoding: utf-8 -*-
#
# Copyright © 2012 New Dream Network, LLC (DreamHost)
#
# Author: Doug Hellmann <doug.hellmann@dreamhost.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.
"""Base classes for storage engines
"""

import abc
import datetime
import math

from ceilometer.openstack.common import timeutils


def iter_period(start, end, period):
    """Split a time from start to end in periods of a number of seconds. This
    function yield the (start, end) time for each period composing the time
    passed as argument.

    :param start: When the period set start.
    :param end: When the period end starts.
    :param period: The duration of the period.

    """
    period_start = start
    increment = datetime.timedelta(seconds=period)
    for i in xrange(int(math.ceil(
            timeutils.delta_seconds(start, end)
            / float(period)))):
        next_start = period_start + increment
        yield (period_start, next_start)
        period_start = next_start


def _handle_sort_key(model_name, sort_key=None):
    """Generate sort keys according to the passed in sort key from user.

    :param model_name: Database model name be query.(alarm, meter, etc.)
    :param sort_key: sort key passed from user.
    return: sort keys list
    """
    sort_keys_extra = {'alarm': ['name', 'user_id', 'project_id'],
                       'meter': ['user_id', 'project_id'],
                       'resource': ['user_id', 'project_id'],
                       }

    sort_keys = sort_keys_extra[model_name]
    if not sort_key:
        return sort_keys
    # NOTE(Fengqian): We need to put the sort key from user
    #in the first place of sort keys list.
    try:
        sort_keys.remove(sort_key)
    except ValueError:
        pass
    finally:
        sort_keys.insert(0, sort_key)
    return sort_keys


class MultipleResultsFound(Exception):
    pass


class NoResultFound(Exception):
    pass


class Pagination(object):
    """Class for pagination query."""

    def __init__(self, limit=None, primary_sort_dir='desc', sort_keys=[],
                 sort_dirs=[], marker_value=None):
        """This puts all parameters used for paginate query together.

        :param limit: Maximum number of items to return;
        :param primary_sort_dir: Sort direction of primary key.
        :param marker_value: Value of primary key to identify the last item of
                             the previous page.
        :param sort_keys: Array of attributes passed in by users to sort the
                            results besides the primary key.
        :param sort_dirs: Per-column array of sort_dirs, corresponding to
                            sort_keys.
        """
        self.limit = limit
        self.primary_sort_dir = primary_sort_dir
        self.marker_value = marker_value
        self.sort_keys = sort_keys
        self.sort_dirs = sort_dirs


class StorageEngine(object):
    """Base class for storage engines."""

    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def get_connection(self, conf):
        """Return a Connection instance based on the configuration settings."""


class Connection(object):
    """Base class for storage system connections."""

    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def __init__(self, conf):
        """Constructor."""

    @abc.abstractmethod
    def upgrade(self):
        """Migrate the database to `version` or the most recent version."""

    @abc.abstractmethod
    def record_metering_data(self, data):
        """Write the data to the backend storage system.

        :param data: a dictionary such as returned by
                     ceilometer.meter.meter_message_from_counter

        All timestamps must be naive utc datetime object.
        """

    @abc.abstractmethod
    def clear_expired_metering_data(self, ttl):
        """Clear expired data from the backend storage system according to the
        time-to-live.

        :param ttl: Number of seconds to keep records for.

        """

    @abc.abstractmethod
    def get_users(self, source=None):
        """Return an iterable of user id strings.

        :param source: Optional source filter.
        """

    @abc.abstractmethod
    def get_projects(self, source=None):
        """Return an iterable of project id strings.

        :param source: Optional source filter.
        """

    @abc.abstractmethod
    def get_resources(self, user=None, project=None, source=None,
                      start_timestamp=None, start_timestamp_op=None,
                      end_timestamp=None, end_timestamp_op=None,
                      metaquery={}, resource=None, pagination=None):
        """Return an iterable of models.Resource instances containing
        resource information.

        :param user: Optional ID for user that owns the resource.
        :param project: Optional ID for project that owns the resource.
        :param source: Optional source filter.
        :param start_timestamp: Optional modified timestamp start range.
        :param start_timestamp_op: Optional timestamp start range operation.
        :param end_timestamp: Optional modified timestamp end range.
        :param end_timestamp_op: Optional timestamp end range operation.
        :param metaquery: Optional dict with metadata to match on.
        :param resource: Optional resource filter.
        :param pagination: Optional pagination query.
        """

    @abc.abstractmethod
    def get_meters(self, user=None, project=None, resource=None, source=None,
                   metaquery={}, pagination=None):
        """Return an iterable of model.Meter instances containing meter
        information.

        :param user: Optional ID for user that owns the resource.
        :param project: Optional ID for project that owns the resource.
        :param resource: Optional resource filter.
        :param source: Optional source filter.
        :param metaquery: Optional dict with metadata to match on.
        :param pagination: Optional pagination query.
        """

    @abc.abstractmethod
    def get_samples(self, sample_filter, limit=None):
        """Return an iterable of model.Sample instances.

        :param sample_filter: Filter.
        :param limit: Maximum number of results to return.
        """

    @abc.abstractmethod
    def get_meter_statistics(self, sample_filter, period=None, groupby=None):
        """Return an iterable of model.Statistics instances.

        The filter must have a meter value set.
        """

    @abc.abstractmethod
    def get_alarms(self, name=None, user=None,
                   project=None, enabled=True, alarm_id=None, pagination=None):
        """Yields a lists of alarms that match filters
        """

    @abc.abstractmethod
    def create_alarm(self, alarm):
        """Create an alarm. Returns the alarm as created.

        :param alarm: The alarm to create.
        """

    @abc.abstractmethod
    def update_alarm(self, alarm):
        """update alarm
        """

    @abc.abstractmethod
    def delete_alarm(self, alarm_id):
        """Delete a alarm
        """

    @abc.abstractmethod
    def get_alarm_changes(self, alarm_id, on_behalf_of,
                          user=None, project=None, type=None,
                          start_timestamp=None, start_timestamp_op=None,
                          end_timestamp=None, end_timestamp_op=None):
        """Yields list of AlarmChanges describing alarm history
        :param alarm_id: ID of alarm to return changes for
        :param on_behalf_of: ID of tenant to scope changes query (None for
                             administrative user, indicating all projects)
        :param user: Optional ID of user to return changes for
        :param project: Optional ID of project to return changes for
        :project type: Optional change type
        :param start_timestamp: Optional modified timestamp start range
        :param start_timestamp_op: Optional timestamp start range operation
        :param end_timestamp: Optional modified timestamp end range
        :param end_timestamp_op: Optional timestamp end range operation
        """

    @abc.abstractmethod
    def record_alarm_change(self, alarm_change):
        """Record alarm change event.
        """

    @abc.abstractmethod
    def clear(self):
        """Clear database."""

    @abc.abstractmethod
    def record_events(self, events):
        """Write the events to the backend storage system.

        :param events: a list of model.Event objects.
        """

    @abc.abstractmethod
    def get_events(self, event_filter):
        """Return an iterable of model.Event objects.
        """
