# This file is part of Indico.
# Copyright (C) 2002 - 2017 European Organization for Nuclear Research (CERN).
#
# Indico 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 3 of the
# License, or (at your option) any later version.
#
# Indico 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 Indico; if not, see <http://www.gnu.org/licenses/>.

from __future__ import unicode_literals

from flask_pluginengine import depends, trim_docstring

from indico.core.plugins import IndicoPlugin, PluginCategory
from indico.util.date_time import now_utc
from indico.util.decorators import classproperty

from indico_livesync.forms import AgentForm
from indico_livesync.models.queue import LiveSyncQueueEntry
from indico_livesync.plugin import LiveSyncPlugin


@depends('livesync')
class LiveSyncPluginBase(IndicoPlugin):  # pragma: no cover
    """Base class for livesync plugins"""

    #: dict containing the backend(s) provided by the plugin; the keys are unique identifiers
    backend_classes = None
    category = PluginCategory.synchronization

    def init(self):
        super(LiveSyncPluginBase, self).init()
        for name, backend_class in self.backend_classes.iteritems():
            assert backend_class.plugin is None
            backend_class.plugin = type(self)
            LiveSyncPlugin.instance.register_backend_class(name, backend_class)


class LiveSyncBackendBase(object):
    """Base class for livesync backends"""

    #: the plugin containing the agent
    plugin = None  # set automatically when the agent is registered
    #: the Uploader to use. only needed if run and run_initial_export are not overridden
    uploader = None
    #: the form used when creating/editing the agent
    form = AgentForm

    @classproperty
    @classmethod
    def title(cls):
        parts = trim_docstring(cls.__doc__).split('\n', 1)
        return parts[0].strip()

    @classproperty
    @classmethod
    def description(cls):
        parts = trim_docstring(cls.__doc__).split('\n', 1)
        try:
            return parts[1].strip()
        except IndexError:
            return 'no description available'

    def __init__(self, agent):
        """
        :param agent: a `LiveSyncAgent` instance
        """
        self.agent = agent

    def fetch_records(self, count=None):
        query = (self.agent.queue
                 .filter_by(processed=False)
                 .order_by(LiveSyncQueueEntry.timestamp)
                 .limit(count))
        return query.all()

    def update_last_run(self):
        """Updates the last run timestamp.

        Don't forget to call this if you implement your own `run` method!
        """
        self.agent.last_run = now_utc()

    def run(self):
        """Runs the livesync export"""
        if self.uploader is None:  # pragma: no cover
            raise NotImplementedError

        records = self.fetch_records()
        uploader = self.uploader(self)
        LiveSyncPlugin.logger.info('Uploading %d records', len(records))
        uploader.run(records)
        self.update_last_run()

    def run_initial_export(self, events):
        """Runs the initial export.

        This process is expected to take a very long time.

        :param events: iterable of all events in this indico instance
        """
        if self.uploader is None:  # pragma: no cover
            raise NotImplementedError

        uploader = self.uploader(self)
        uploader.run_initial(events)