"""
Create backup for certain date for specified channel in slack
"""
from datetime import datetime
import getpass
import json
import logging
import os
import pprint

import slackclient
import sqlalchemy.orm.exc

from slack_backup import db
from slack_backup import objects as o
from slack_backup import download
from slack_backup import reporters


class Client(object):
    """
    This class is intended to provide an interface for getting, storing and
    querying data fetched out using Slack API.
    """
    def __init__(self, args):
        if 'token' in args:
            self.slack = slackclient.SlackClient(args.token)
            self.user = args.user
            self.password = args.password
            if not self.user and not self.password:
                logging.warning('No media will be downloaded, due to not '
                                'providing credentials for a slack account')
            elif not self.user and self.password:
                logging.warning('No media will be downloaded, due to not '
                                'providing username for a slack account')
            elif self.user and not self.password:
                self.password = getpass.getpass(prompt='Provide password for '
                                                'your slack account: ')
            dbpath = self._get_asset_dir(args.database)
            self.downloader = download.Download(args, dbpath)
        self.engine = db.connect(args.database)
        self.session = db.Session()
        self.selected_channels = args.channels
        self.q = self.session.query

        if 'format' in args:
            self.reporter = reporters.get_reporter(args, self.q)

    def update(self):
        """
        Perform an update, store data to db
        """
        self.downloader.authorize()
        self.update_users()
        self.update_channels()
        self.update_history()

    def update_channels(self):
        """Fetch and update channel list with current state in db"""
        logging.info("Fetching and update channels information in DB")
        result = self._channels_list()

        if not result:
            return

        for data in result:
            channel = self.q(o.Channel).\
                filter(o.Channel.slackid == data['id']).one_or_none()

            if not channel:
                channel = o.Channel()
                self.session.add(channel)

            self._update_channel(channel, data)

        self.session.commit()

    def update_users(self):
        """Fetch and update user list with current state in db"""
        result = self._users_list()

        if not result:
            return

        for user_data in result:
            user = self.q(o.User).\
                filter(o.User.slackid == user_data['id']).one_or_none()

            if user:
                user.update(user_data)
            else:
                user = o.User(user_data)
                self.session.add(user)
                self.session.flush()

            if user.profile.image_original:
                user.profile.image_path = self.downloader.\
                    download(user.profile.image_original, 'avatar')

        self.session.commit()

    def update_history(self):
        """
        Get the latest or all messages out of optionally selected channels
        """
        logging.info("Fetching and storing messages in DB")

        all_channels = self.q(o.Channel).all()
        if self.selected_channels:
            channels = [c for c in all_channels
                        if c.name in self.selected_channels]
        else:
            channels = all_channels

        for channel in channels:
            logging.info("Getting messages for channel `%s'", channel.name)
            latest = self.q(o.Message).\
                filter(o.Message.channel == channel).\
                order_by(o.Message.ts.desc()).first()
            # NOTE(gryf): Trick out the API, which by default (latest and
            # oldest parameters set to 0) return certain amount of latest
            # messages, while we'd like to have it from the beginning of the
            # available history, if there is no database records available. In
            # that case value of 1 here will force the API to get messages
            # starting from first January 1970.
            latest = latest and latest.ts or 1

            while True:
                logging.debug("Fetching another portion of messages")
                messages, latest = self._channels_history(channel, latest)

                for msg in messages:
                    self._create_message(msg, channel)

                if latest is None:
                    break

        self.session.commit()

    def generate_history(self):
        """
        Return a history accumulated in DB into desired format. Special format
        """
        self.reporter.generate()

    def _get_user(self, data):
        """
        Return an User object. It can be regular one, or a bot. In case of
        bot, check if it exists in db, and in case of failure - create it,
        since bots are not returned by user.list API method.
        """
        try:
            return self.q(o.User).filter(o.User.slackid == data['user']).one()
        except KeyError:
            pass

        try:
            return self.q(o.User).filter(o.User.slackid ==
                                         data['comment']['user']).one()
        except KeyError:
            pass

        try:
            return self.q(o.User).filter(o.User.slackid ==
                                         data['bot_id']).one()
        except KeyError:
            pass
        except sqlalchemy.orm.exc.NoResultFound:
            result = self.slack.api_call('bots.info', bot=data['bot_id'])
            if not result.get("ok"):
                logging.error(result['error'])
                return None

            user = o.User(result['bot'])
            user.real_name = result['bot']['name']
            self.session.add(user)
            self.session.flush()
            return user

        logging.exception('Failed on data: %s', pprint.pformat(data))
        raise ValueError('Cannot identify user out of given data.')

    def _create_message(self, data, channel):
        """
        Create message with corresponding possible metadata, like reactions,
        files etc.
        """
        if data['type'] != 'message':
            logging.info("Skipping message of type `%s'.", data['type'])
            return

        logging.debug('Message data: %s', json.dumps(data))

        user = self._get_user(data)

        if not any((data.get('attachments'), data['text'].strip())):
            logging.info("Skipping message from `%s' since it's empty",
                         user.name)
            return

        message = o.Message(data)
        message.channel = channel
        message.user = user

        if data.get('is_starred'):
            message.is_starred = True

        if 'reactions' in data:
            for reaction_data in data['reactions']:
                message.reactions.append(o.Reaction(reaction_data))

        if data.get('subtype') == 'file_share':
            self._file_data(message, data['file'], data['file']['is_external'])
        elif data.get('subtype') == 'pinned_item':
            if data.get('attachments'):
                self._att_data(message, data['attachments'])
            elif data.get('item'):
                self._file_data(message, data['item'],
                                data['item']['is_external'])
        elif data.get('attachments'):
            self._att_data(message, data['attachments'])

        self.session.add(message)

    def _file_data(self, message, data, is_external=True):
        """
        Process file data. Could be either represented as 'file' object or
        'item' object in case of pinned items
        """
        message.file = o.File(data)
        if data.get('is_starred'):
            message.is_starred = True

        if is_external:
            logging.debug("Found external file `%s'", data['url_private'])
            message.file.url = data['url_private']
        else:
            logging.debug("Found internal file `%s'",
                          data['url_private_download'])
            priv_url = data['url_private_download']
            message.file.filepath = self.downloader.download(priv_url, 'file')
        self.session.add(message.file)

    def _att_data(self, message, data):
        """
        Process attachments
        """
        for att in data:
            attachment = o.Attachment(att)
            message.attachments.append(attachment)

    def _get_create_obj(self, data, classobj, channel):
        """
        Return object if exist in appropriate table (Topic or Purpose),
        compared to the data provided, create it otherwise.
        """
        if not data['value']:
            return

        user = self.q(o.User).filter(o.User.slackid ==
                                     data['creator']).one_or_none()

        try:
            obj = self.q(classobj).\
                filter(classobj.last_set ==
                       datetime.fromtimestamp(data['last_set'])).\
                filter(classobj.value == data['value']).\
                filter(classobj.creator == user).one_or_none()
        except OSError:
            logging.exception('Failed on data: %s', pprint.pformat(data))
            raise

        if not obj:
            # break channel relation
            for obj in self.q(classobj).filter(classobj.channel ==
                                               channel).all():
                obj.channel = None

            # create new object
            obj = classobj(data)
            obj.creator = user
            self.session.flush()

        return obj

    def _update_channel(self, channel, data):
        """Update a channel with provided data"""
        logging.info("Update channel `%s' information in DB", data['name'])

        channel.update(data)
        channel.user = self.q(o.User).filter(o.User.slackid ==
                                             data['creator']).one_or_none()
        channel.purpose = self._get_create_obj(data['purpose'], o.Purpose,
                                               channel)
        channel.topic = self._get_create_obj(data['topic'], o.Topic, channel)
        self.session.flush()

    def _get_asset_dir(self, database):
        """
        Get absolute assets directory using sqlite database path as a
        reference.
        """
        if not database:
            return 'assets'

        path = os.path.dirname(database)
        return os.path.join(path, 'assets')

    def _channels_list(self):
        """
        Get channel list using Slack API. Return list of channel data or None
        in case of error.
        """
        result = self.slack.api_call("channels.list")

        if not result.get("ok"):
            logging.error(result['error'])
            return None

        return result['channels']

    def _users_list(self):
        """
        Get users list using Slack API. Return list of channel data or None
        in case of error.
        """
        logging.info("Fetching and updating user information in DB")
        result = self.slack.api_call("users.list")

        if not result.get("ok"):
            logging.error(result['error'])
            return None

        return result['members']

    def _channels_history(self, channel, latest):
        """
        Get list of messages using Slack API. Return tuple containing:
         - list of messages data and returned timestramp if has_more is set
           to true,
         - list of messages data and None if has_more is set to false,
         - empty list and None if there is no messages
        """
        result = self.slack.api_call("channels.history",
                                     channel=channel.slackid, count=1000,
                                     oldest=latest)

        if not result.get("ok"):
            logging.error(result['error'])
            return None, None

        if result['messages']:
            if result['has_more']:
                # TODO: this one might be not true, if API will return
                # messages not sorted by timestamp in descending order
                return result['messages'], result['messages'][0]['ts']
            else:
                return result['messages'], None

        return [], None