import warnings
import logging
from contextlib import contextmanager

from pyramid.compat import pickle
from pyramid.session import SignedCookieSessionFactory

from cubicweb import Binary


log = logging.getLogger(__name__)


def logerrors(logger):
    def wrap(fn):
        def newfn(*args, **kw):
            try:
                return fn(*args, **kw)
            except:
                logger.exception("Error in %s" % fn.__name__)
        return newfn
    return wrap


@contextmanager
def unsafe_cnx_context_manager(request):
    """Return a connection for use as a context manager, with security disabled

    If request has an attached connection, its security will be deactived in the context manager's
    scope, else a new internal connection is returned.
    """
    cnx = request.cw_cnx
    if cnx is None:
        with request.registry['cubicweb.repository'].internal_cnx() as cnx:
            yield cnx
    else:
        with cnx.security_enabled(read=False, write=False):
            yield cnx


def CWSessionFactory(
        secret,
        cookie_name='session',
        max_age=None,
        path='/',
        domain=None,
        secure=False,
        httponly=True,
        set_on_exception=True,
        timeout=1200,
        reissue_time=120,
        hashalg='sha512',
        salt='pyramid.session.',
        serializer=None):
    """ A pyramid session factory that store session data in the CubicWeb
    database.

    Storage is done with the 'CWSession' entity, which is provided by the
    'pyramid' cube.

    .. warning::

        Although it provides a sane default behavior, this session storage has
        a serious overhead because it uses RQL to access the database.

        Using pure SQL would improve a bit (it is roughly twice faster), but it
        is still pretty slow and thus not an immediate priority.

        It is recommended to use faster session factory
        (pyramid_redis_sessions_ for example) if you need speed.

    .. _pyramid_redis_sessions: http://pyramid-redis-sessions.readthedocs.org/
                                en/latest/index.html
    """

    SignedCookieSession = SignedCookieSessionFactory(
        secret,
        cookie_name=cookie_name,
        max_age=max_age,
        path=path,
        domain=domain,
        secure=secure,
        httponly=httponly,
        set_on_exception=set_on_exception,
        timeout=timeout,
        reissue_time=reissue_time,
        hashalg=hashalg,
        salt=salt,
        serializer=serializer)

    class CWSession(SignedCookieSession):
        def __init__(self, request):
            # _set_accessed will be called by the super __init__.
            # Setting _loaded to True inhibates it.
            self._loaded = True

            # the super __init__ will load a single value in the dictionnary,
            # the session id.
            super(CWSession, self).__init__(request)

            # Remove the session id from the dict
            self.sessioneid = self.pop('sessioneid', None)
            self.repo = request.registry['cubicweb.repository']

            # We need to lazy-load only for existing sessions
            self._loaded = self.sessioneid is None

        @logerrors(log)
        def _set_accessed(self, value):
            self._accessed = value

            if self._loaded:
                return

            with unsafe_cnx_context_manager(self.request) as cnx:
                value_rset = cnx.execute('Any D WHERE X eid %(x)s, X cwsessiondata D',
                                         {'x': self.sessioneid})
                value = value_rset[0][0]
                if value:
                    # Use directly dict.update to avoir _set_accessed to be
                    # recursively called
                    dict.update(self, pickle.load(value))

            self._loaded = True

        def _get_accessed(self):
            return self._accessed

        accessed = property(_get_accessed, _set_accessed)

        @logerrors(log)
        def _set_cookie(self, response):
            # Save the value in the database
            data = Binary(pickle.dumps(dict(self)))
            sessioneid = self.sessioneid

            with unsafe_cnx_context_manager(self.request) as cnx:
                if not sessioneid:
                    session = cnx.create_entity(
                        'CWSession', cwsessiondata=data)
                    sessioneid = session.eid
                else:
                    session = cnx.entity_from_eid(sessioneid)
                    session.cw_set(cwsessiondata=data)
                cnx.commit()

            # Only if needed actually set the cookie
            if self.new or self.accessed - self.renewed > self._reissue_time:
                dict.clear(self)
                dict.__setitem__(self, 'sessioneid', sessioneid)
                return super(CWSession, self)._set_cookie(response)

            return True

    return CWSession


def includeme(config):
    """ Activate the CubicWeb session factory.

    Usually called via ``config.include('cubicweb.pyramid.auth')``.

    See also :ref:`defaults_module`
    """
    settings = config.registry.settings
    secret = settings.get('cubicweb.session.secret', '')
    if not secret:
        secret = config.registry['cubicweb.config'].get('pyramid-session-secret')
        warnings.warn('''
        Please migrate pyramid-session-secret from
        all-in-one.conf to cubicweb.session.secret config entry in
        your pyramid.ini file.
        ''')
    if not secret:
        secret = 'notsosecret'
        warnings.warn('''

            !! WARNING !! !! WARNING !!

            The session cookies are signed with a static secret key.
            To put your own secret key, edit your pyramid.ini file
            and set the 'cubicweb.session.secret' key.

            YOU SHOULD STOP THIS INSTANCE unless your really know what you
            are doing !!

        ''')
    session_factory = CWSessionFactory(secret)
    config.set_session_factory(session_factory)