# Copyright (C) 2015 GRNET S.A.
#
# This program 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.
#
# This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.

from wsgiref.simple_server import make_server
from ws4py.websocket import WebSocket
from ws4py.server.wsgiutils import WebSocketWSGIApplication
from ws4py.server.wsgirefserver import WSGIServer, WebSocketWSGIRequestHandler
from hashlib import sha1
from threading import Thread
import sqlite3
import time
import os
import json
import logging
from agkyra.syncer import (
    syncer, setup, pithos_client, localfs_client, messaging)
from agkyra.config import AgkyraConfig, AGKYRA_DIR


LOG = logging.getLogger(__name__)


class SessionHelper(object):
    """Agkyra Helper Server sets a WebSocket server with the Helper protocol
    It also provided methods for running and killing the Helper server
    """
    session_timeout = 20

    def __init__(self, **kwargs):
        """Setup the helper server"""
        self.session_db = kwargs.get(
            'session_db', os.path.join(AGKYRA_DIR, 'session.db'))
        self.session_relation = kwargs.get('session_relation', 'heart')

        LOG.debug('Connect to db')
        self.db = sqlite3.connect(self.session_db)
        self._init_db_relation()
        self.session = self._load_active_session() or self._create_session()

    def _init_db_relation(self):
        self.db.execute('BEGIN')
        self.db.execute(
            'CREATE TABLE IF NOT EXISTS %s ('
            'ui_id VARCHAR(256), address text, beat VARCHAR(32)'
            ')' % self.session_relation)
        self.db.commit()

    def _load_active_session(self):
        """Load a session from db"""
        r = self.db.execute('SELECT * FROM %s' % self.session_relation)
        sessions = r.fetchall()
        if sessions:
            last = sessions[-1]
            now, last_beat = time.time(), float(last[2])
            if now - last_beat < self.session_timeout:
                # Found an active session
                return dict(ui_id=last[0], address=last[1])
        return None

    def _create_session(self):
        """Create session credentials"""
        ui_id = sha1(os.urandom(128)).hexdigest()

        WebSocketProtocol.ui_id = ui_id
        server = make_server(
            '', 0,
            server_class=WSGIServer,
            handler_class=WebSocketWSGIRequestHandler,
            app=WebSocketWSGIApplication(handler_cls=WebSocketProtocol))
        server.initialize_websockets_manager()
        address = 'ws://%s:%s' % (server.server_name, server.server_port)
        self.server = server

        self.db.execute('BEGIN')
        self.db.execute('DELETE FROM %s' % self.session_relation)
        self.db.execute('INSERT INTO %s VALUES ("%s", "%s", "%s")' % (
            self.session_relation, ui_id, address, time.time()))
        self.db.commit()

        return dict(ui_id=ui_id, address=address)

    def start(self):
        """Start the helper server in a thread"""
        if getattr(self, 'server', None):
            Thread(target=self.server.serve_forever).start()

    def shutdown(self):
        """Shutdown the server (needs another thread) and join threads"""
        if getattr(self, 'server', None):
            t = Thread(target=self.server.shutdown)
            t.start()
            t.join()


class WebSocketProtocol(WebSocket):
    """Helper-side WebSocket protocol for communication with GUI:

    -- INTERRNAL HANDSAKE --
    GUI: {"method": "post", "ui_id": <GUI ID>}
    HELPER: {"ACCEPTED": 202, "method": "post"}" or
        "{"REJECTED": 401, "action": "post ui_id"}

    -- SHUT DOWN --
    GUI: {"method": "post", "path": "shutdown"}

    -- PAUSE --
    GUI: {"method": "post", "path": "pause"}
    HELPER: {"OK": 200, "action": "post pause"} or error

    -- start --
    GUI: {"method": "post", "path": "start"}
    HELPER: {"OK": 200, "action": "post start"} or error

    -- GET SETTINGS --
    GUI: {"method": "get", "path": "settings"}
    HELPER:
        {
            "action": "get settings",
            "token": <user token>,
            "url": <auth url>,
            "container": <container>,
            "directory": <local directory>,
            "exclude": <file path>
        } or {<ERROR>: <ERROR CODE>}

    -- PUT SETTINGS --
    GUI: {
            "method": "put", "path": "settings",
            "token": <user token>,
            "url": <auth url>,
            "container": <container>,
            "directory": <local directory>,
            "exclude": <file path>
        }
    HELPER: {"CREATED": 201, "action": "put settings",} or
        {<ERROR>: <ERROR CODE>, "action": "get settings",}

    -- GET STATUS --
    GUI: {"method": "get", "path": "status"}
    HELPER: {
        "can_sync": <boolean>,
        "progress": <int>,
        "paused": <boolean>,
        "action": "get status"} or
        {<ERROR>: <ERROR CODE>, "action": "get status"}
    """

    ui_id = None
    accepted = False
    settings = dict(
        token=None, url=None,
        container=None, directory=None,
        exclude=None)
    status = dict(
        progress=0, synced=0, unsynced=0, paused=True, can_sync=False)
    file_syncer = None
    cnf = AgkyraConfig()
    essentials = ('url', 'token', 'container', 'directory')

    def _get_default_sync(self):
        """Get global.default_sync or pick the first sync as default
        If there are no syncs, create a 'default' sync.
        """
        sync = self.cnf.get('global', 'default_sync')
        if not sync:
            for sync in self.cnf.keys('sync'):
                break
            self.cnf.set('global', 'default_sync', sync or 'default')
        return sync or 'default'

    def _get_sync_cloud(self, sync):
        """Get the <sync>.cloud or pick the first cloud and use it
        In case of cloud picking, set the cloud as the <sync>.cloud for future
        sessions.
        If no clouds are found, create a 'default' cloud, with an empty url.
        """
        try:
            cloud = self.cnf.get_sync(sync, 'cloud')
        except KeyError:
            cloud = None
        if not cloud:
            for cloud in self.cnf.keys('cloud'):
                break
            self.cnf.set_sync(sync, 'cloud', cloud or 'default')
        return cloud or 'default'

    def _load_settings(self):
        LOG.debug('Start loading settings')
        sync = self._get_default_sync()
        cloud = self._get_sync_cloud(sync)

        try:
            self.settings['url'] = self.cnf.get_cloud(cloud, 'url')
        except Exception:
            self.settings['url'] = None
        try:
            self.settings['token'] = self.cnf.get_cloud(cloud, 'token')
        except Exception:
            self.settings['url'] = None

        for option in ('container', 'directory', 'exclude'):
            try:
                self.settings[option] = self.cnf.get_sync(sync, option)
            except KeyError:
                LOG.debug('No %s is set' % option)

        LOG.debug('Finished loading settings')

    def _dump_settings(self):
        LOG.debug('Saving settings')
        if not self.settings.get('url', None):
            LOG.debug('No settings to save')
            return

        sync = self._get_default_sync()
        cloud = self._get_sync_cloud(sync)

        try:
            old_url = self.cnf.get_cloud(cloud, 'url') or ''
        except KeyError:
            old_url = self.settings['url']

        while old_url != self.settings['url']:
            cloud = '%s_%s' % (cloud, sync)
            try:
                self.cnf.get_cloud(cloud, 'url')
            except KeyError:
                break

        self.cnf.set_cloud(cloud, 'url', self.settings['url'])
        self.cnf.set_cloud(cloud, 'token', self.settings['token'] or '')
        self.cnf.set_sync(sync, 'cloud', cloud)

        for option in ('directory', 'container', 'exclude'):
            self.cnf.set_sync(sync, option, self.settings[option] or '')

        self.cnf.write()
        LOG.debug('Settings saved')

    def _essentials_changed(self, new_settings):
        """Check if essential settings have changed in new_settings"""
        return all([
            self.settings[e] == self.settings[e] for e in self.essentials])

    def _update_statistics(self):
        """Update statistics by consuming and understanding syncer messages"""
        if self.can_sync():
            msg = self.syncer.get_next_message()
            if not msg:
                if self.status['unsynced'] == self.status['synced']:
                    self.status['unsynced'] = 0
                    self.status['synced'] = 0
            while (msg):
                if isinstance(msg, messaging.SyncMessage):
                    LOG.info('Start syncing "%s"' % msg.objname)
                    self.status['unsynced'] += 1
                elif isinstance(msg, messaging.AckSyncMessage):
                    LOG.info('Finished syncing "%s"' % msg.objname)
                    self.status['synced'] += 1
                elif isinstance(msg, messaging.CollisionMessage):
                    LOG.info('Collision for "%s"' % msg.objname)
                elif isinstance(msg, messaging.ConflictStashMessage):
                    LOG.info('Conflict for "%s"' % msg.objname)
                else:
                    LOG.debug('Consumed msg %s' % msg)
                msg = self.syncer.get_next_message()

    def can_sync(self):
        """Check if settings are enough to setup a syncing proccess"""
        return all([self.settings[e] for e in self.essentials])

    def init_sync(self):
        """Initialize syncer"""
        sync = self._get_default_sync()
        syncer_settings = setup.SyncerSettings(
            sync,
            self.settings['url'], self.settings['token'],
            self.settings['container'], self.settings['directory'],
            agkyra_path=AGKYRA_DIR,
            ignore_ssl=True)
        master = pithos_client.PithosFileClient(syncer_settings)
        slave = localfs_client.LocalfsFileClient(syncer_settings)
        self.syncer = syncer.FileSyncer(syncer_settings, master, slave)
        self.syncer_settings = syncer_settings
        self.syncer.initiate_probe()

    # Syncer-related methods
    def get_status(self):
        if self.can_sync():
            self._update_statistics()
            self.status['paused'] = self.syncer.paused
            self.status['can_sync'] = self.can_sync()
        else:
            self.status = dict(
                progress=0, synced=0, unsynced=0, paused=True, can_sync=False)
        return self.status

    def get_settings(self):
        return self.settings

    def set_settings(self, new_settings):
        # Prepare setting save
        could_sync = self.can_sync()
        was_active = False
        if could_sync and not self.syncer.paused:
            was_active = True
            self.pause_sync()
        must_reset_syncing = self._essentials_changed(new_settings)

        # save settings
        self.settings = new_settings
        self._dump_settings()

        # Restart
        if self.can_sync():
            if must_reset_syncing or not could_sync:
                self.init_sync()
            elif was_active:
                self.start_sync()

    def pause_sync(self):
        self.syncer.stop_decide()
        LOG.debug('Wait open syncs to complete')
        self.syncer.wait_sync_threads()

    def start_sync(self):
        self.syncer.start_decide()

    # WebSocket connection methods
    def opened(self):
        LOG.debug('Helper: connection established')

    def closed(self, *args):
        LOG.debug('Helper: connection closed')

    def send_json(self, msg):
        LOG.debug('send: %s' % msg)
        self.send(json.dumps(msg))

    # Protocol handling methods
    def _post(self, r):
        """Handle POST requests"""
        if self.accepted:
            action = r['path']
            if action == 'shutdown':
                if self.can_sync():
                    self.syncer.stop_all_daemons()
                    LOG.debug('Wait open syncs to complete')
                    self.syncer.wait_sync_threads()
                self.close()
                return
            {
                'start': self.start_sync,
                'pause': self.pause_sync
            }[action]()
            self.send_json({'OK': 200, 'action': 'post %s' % action})
        elif r['ui_id'] == self.ui_id:
            self._load_settings()
            self.accepted = True
            self.send_json({'ACCEPTED': 202, 'action': 'post ui_id'})
            if self.can_sync():
                self.init_sync()
                self.pause_sync()
        else:
            action = r.get('path', 'ui_id')
            self.send_json({'REJECTED': 401, 'action': 'post %s' % action})
            self.terminate()

    def _put(self, r):
        """Handle PUT requests"""
        if self.accepted:
            LOG.debug('put %s' % r)
            action = r.pop('path')
            self.set_settings(r)
            r.update({'CREATED': 201, 'action': 'put %s' % action})
            self.send_json(r)
        else:
            action = r['path']
            self.send_json({'UNAUTHORIZED': 401, 'action': 'put %s' % action})
            self.terminate()

    def _get(self, r):
        """Handle GET requests"""
        action = r.pop('path')
        if not self.accepted:
            self.send_json({'UNAUTHORIZED': 401, 'action': 'get %s' % action})
            self.terminate()
        else:
            data = {
                'settings': self.get_settings,
                'status': self.get_status,
            }[action]()
            data['action'] = 'get %s' % action
            self.send_json(data)

    def received_message(self, message):
        """Route requests to corresponding handling methods"""
        LOG.debug('recv: %s' % message)
        try:
            r = json.loads('%s' % message)
        except ValueError as ve:
            self.send_json({'BAD REQUEST': 400})
            LOG.error('JSON ERROR: %s' % ve)
            return
        try:
            method = r.pop('method')
            {
                'post': self._post,
                'put': self._put,
                'get': self._get
            }[method](r)
        except KeyError as ke:
            self.send_json({'BAD REQUEST': 400})
            LOG.error('KEY ERROR: %s' % ke)
        except Exception as e:
            self.send_json({'INTERNAL ERROR': 500})
            LOG.error('EXCEPTION: %s' % e)
            self.terminate()