"""Base class for request/session

:organization: Logilab
:copyright: 2001-2009 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
:license: Library General Public License version 2 - http://www.gnu.org/licenses
"""
__docformat__ = "restructuredtext en"

from urllib import quote as urlquote, unquote as urlunquote
from datetime import time, datetime, timedelta

from logilab.common.decorators import cached
from logilab.common.deprecation import deprecated

from cubicweb import Unauthorized, RegistryException, typed_eid
from cubicweb.rset import ResultSet
from cubicweb.utils import ustrftime, strptime, todate, todatetime

ONESECOND = timedelta(0, 1, 0)
CACHE_REGISTRY = {}


class Cache(dict):
    def __init__(self):
        super(Cache, self).__init__()
        _now = datetime.now()
        self.cache_creation_date = _now
        self.latest_cache_lookup = _now


class RequestSessionBase(object):
    """base class containing stuff shared by server session and web request

    request/session is the main resources accessor, mainly through it's vreg
    attribute:
    :vreg:
      the instance's registry
    :vreg.schema:
      the instance's schema
    :vreg.config:
      the instance's configuration
    """
    def __init__(self, vreg):
        self.vreg = vreg
        try:
            encoding = vreg.property_value('ui.encoding')
        except: # no vreg or property not registered
            encoding = 'utf-8'
        self.encoding = encoding
        # cache result of execution for (rql expr / eids),
        # should be emptied on commit/rollback of the server session / web
        # connection
        self.local_perm_cache = {}
        self._ = unicode

    def property_value(self, key):
        """return value of the property with the given key, giving priority to
        user specific value if any, else using site value
        """
        if self.user:
            return self.user.property_value(key)
        return self.vreg.property_value(key)

    def etype_rset(self, etype, size=1):
        """return a fake result set for a particular entity type"""
        rset = ResultSet([('A',)]*size, '%s X' % etype,
                         description=[(etype,)]*size)
        def get_entity(row, col=0, etype=etype, req=self, rset=rset):
            return req.vreg.etype_class(etype)(req, rset, row, col)
        rset.get_entity = get_entity
        return self.decorate_rset(rset)

    def eid_rset(self, eid, etype=None):
        """return a result set for the given eid without doing actual query
        (we have the eid, we can suppose it exists and user has access to the
        entity)
        """
        eid = typed_eid(eid)
        if etype is None:
            etype = self.describe(eid)[0]
        rset = ResultSet([(eid,)], 'Any X WHERE X eid %(x)s', {'x': eid},
                         [(etype,)])
        return self.decorate_rset(rset)

    def empty_rset(self):
        """return a result set for the given eid without doing actual query
        (we have the eid, we can suppose it exists and user has access to the
        entity)
        """
        return self.decorate_rset(ResultSet([], 'Any X WHERE X eid -1'))

    def entity_from_eid(self, eid, etype=None):
        """return an entity instance for the given eid. No query is done"""
        try:
            return self.entity_cache(eid)
        except KeyError:
            rset = self.eid_rset(eid, etype)
            entity = rset.get_entity(0, 0)
            self.set_entity_cache(entity)
            return entity

    def entity_cache(self, eid):
        raise KeyError

    def set_entity_cache(self, entity):
        pass

    # XXX move to CWEntityManager or even better as factory method (unclear
    # where yet...)

    def create_entity(self, etype, _cw_unsafe=False, **kwargs):
        """add a new entity of the given type

        Example (in a shell session):

        c = create_entity('Company', name=u'Logilab')
        create_entity('Person', works_for=c, firstname=u'John', lastname=u'Doe')

        """
        if _cw_unsafe:
            execute = self.unsafe_execute
        else:
            execute = self.execute
        rql = 'INSERT %s X' % etype
        relations = []
        restrictions = set()
        cachekey = []
        pending_relations = []
        for attr, value in kwargs.items():
            if isinstance(value, (tuple, list, set, frozenset)):
                if len(value) == 1:
                    value = iter(value).next()
                else:
                    del kwargs[attr]
                    pending_relations.append( (attr, value) )
                    continue
            if hasattr(value, 'eid'): # non final relation
                rvar = attr.upper()
                # XXX safer detection of object relation
                if attr.startswith('reverse_'):
                    relations.append('%s %s X' % (rvar, attr[len('reverse_'):]))
                else:
                    relations.append('X %s %s' % (attr, rvar))
                restriction = '%s eid %%(%s)s' % (rvar, attr)
                if not restriction in restrictions:
                    restrictions.add(restriction)
                cachekey.append(attr)
                kwargs[attr] = value.eid
            else: # attribute
                relations.append('X %s %%(%s)s' % (attr, attr))
        if relations:
            rql = '%s: %s' % (rql, ', '.join(relations))
        if restrictions:
            rql = '%s WHERE %s' % (rql, ', '.join(restrictions))
        created = execute(rql, kwargs, cachekey).get_entity(0, 0)
        for attr, values in pending_relations:
            if attr.startswith('reverse_'):
                restr = 'Y %s X' % attr[len('reverse_'):]
            else:
                restr = 'X %s Y' % attr
            execute('SET %s WHERE X eid %%(x)s, Y eid IN (%s)' % (
                restr, ','.join(str(r.eid) for r in values)),
                         {'x': created.eid}, 'x')
        return created

    def ensure_ro_rql(self, rql):
        """raise an exception if the given rql is not a select query"""
        first = rql.split(' ', 1)[0].lower()
        if first in ('insert', 'set', 'delete'):
            raise Unauthorized(self._('only select queries are authorized'))

    def get_cache(self, cachename):
        """
        NOTE: cachename should be dotted names as in :
        - cubicweb.mycache
        - cubes.blog.mycache
        - etc.
        """
        if cachename in CACHE_REGISTRY:
            cache = CACHE_REGISTRY[cachename]
        else:
            cache = CACHE_REGISTRY[cachename] = Cache()
        _now = datetime.now()
        if _now > cache.latest_cache_lookup + ONESECOND:
            ecache = self.execute(
                'Any C,T WHERE C is CWCache, C name %(name)s, C timestamp T',
                {'name':cachename}).get_entity(0,0)
            cache.latest_cache_lookup = _now
            if not ecache.valid(cache.cache_creation_date):
                cache.clear()
                cache.cache_creation_date = _now
        return cache

    # url generation methods ##################################################

    def build_url(self, *args, **kwargs):
        """return an absolute URL using params dictionary key/values as URL
        parameters. Values are automatically URL quoted, and the
        publishing method to use may be specified or will be guessed.
        """
        # use *args since we don't want first argument to be "anonymous" to
        # avoid potential clash with kwargs
        if args:
            assert len(args) == 1, 'only 0 or 1 non-named-argument expected'
            method = args[0]
        else:
            method = None
        # XXX I (adim) think that if method is passed explicitly, we should
        #     not try to process it and directly call req.build_url()
        if method is None:
            if self.from_controller() == 'view' and not '_restpath' in kwargs:
                method = self.relative_path(includeparams=False) or 'view'
            else:
                method = 'view'
        base_url = kwargs.pop('base_url', None)
        if base_url is None:
            base_url = self.base_url()
        if '_restpath' in kwargs:
            assert method == 'view', method
            path = kwargs.pop('_restpath')
        else:
            path = method
        if not kwargs:
            return u'%s%s' % (base_url, path)
        return u'%s%s?%s' % (base_url, path, self.build_url_params(**kwargs))


    def build_url_params(self, **kwargs):
        """return encoded params to incorporate them in an URL"""
        args = []
        for param, values in kwargs.items():
            if not isinstance(values, (list, tuple)):
                values = (values,)
            for value in values:
                args.append(u'%s=%s' % (param, self.url_quote(value)))
        return '&'.join(args)

    def url_quote(self, value, safe=''):
        """urllib.quote is not unicode safe, use this method to do the
        necessary encoding / decoding. Also it's designed to quote each
        part of a url path and so the '/' character will be encoded as well.
        """
        if isinstance(value, unicode):
            quoted = urlquote(value.encode(self.encoding), safe=safe)
            return unicode(quoted, self.encoding)
        return urlquote(str(value), safe=safe)

    def url_unquote(self, quoted):
        """returns a unicode unquoted string

        decoding is based on `self.encoding` which is the encoding
        used in `url_quote`
        """
        if isinstance(quoted, unicode):
            quoted = quoted.encode(self.encoding)
        try:
            return unicode(urlunquote(quoted), self.encoding)
        except UnicodeDecodeError: # might occurs on manually typed URLs
            return unicode(urlunquote(quoted), 'iso-8859-1')

    # bound user related methods ###############################################

    @cached
    def user_data(self):
        """returns a dictionnary with this user's information"""
        userinfo = {}
        if self.is_internal_session:
            userinfo['login'] = "cubicweb"
            userinfo['name'] = "cubicweb"
            userinfo['email'] = ""
            return userinfo
        user = self.actual_session().user
        userinfo['login'] = user.login
        userinfo['name'] = user.name()
        userinfo['email'] = user.get_email()
        return userinfo

    def is_internal_session(self):
        """overrided on the server-side"""
        return False

    # formating methods #######################################################

    def view(self, __vid, rset=None, __fallback_oid=None, __registry='views',
             initargs=None, **kwargs):
        """Select object with the given id (`__oid`) then render it.  If the
        object isn't selectable, try to select fallback object if
        `__fallback_oid` is specified.

        If specified `initargs` is expected to be a dictionnary containing
        arguments that should be given to selection (hence to object's __init__
        as well), but not to render(). Other arbitrary keyword arguments will be
        given to selection *and* to render(), and so should be handled by
        object's call or cell_call method..
        """
        if initargs is None:
            initargs = kwargs
        else:
            initargs.update(kwargs)
        try:
            view =  self.vreg[__registry].select(__vid, self, rset=rset, **initargs)
        except RegistryException:
            view =  self.vreg[__registry].select(__fallback_oid, self,
                                                 rset=rset, **initargs)
        return view.render(**kwargs)

    def format_date(self, date, date_format=None, time=False):
        """return a string for a date time according to instance's
        configuration
        """
        if date:
            if date_format is None:
                if time:
                    date_format = self.property_value('ui.datetime-format')
                else:
                    date_format = self.property_value('ui.date-format')
            return ustrftime(date, date_format)
        return u''

    def format_time(self, time):
        """return a string for a time according to instance's
        configuration
        """
        if time:
            return ustrftime(time, self.property_value('ui.time-format'))
        return u''

    def format_float(self, num):
        """return a string for floating point number according to instance's
        configuration
        """
        if num:
            return self.property_value('ui.float-format') % num
        return u''

    def parse_datetime(self, value, etype='Datetime'):
        """get a datetime or time from a string (according to etype)
        Datetime formatted as Date are accepted
        """
        assert etype in ('Datetime', 'Date', 'Time'), etype
        # XXX raise proper validation error
        if etype == 'Datetime':
            format = self.property_value('ui.datetime-format')
            try:
                return todatetime(strptime(value, format))
            except ValueError:
                pass
        elif etype == 'Time':
            format = self.property_value('ui.time-format')
            try:
                # (adim) I can't find a way to parse a Time with a custom format
                date = strptime(value, format) # this returns a DateTime
                return time(date.hour, date.minute, date.second)
            except ValueError:
                raise ValueError(self._('can\'t parse %(value)r (expected %(format)s)')
                                 % {'value': value, 'format': format})
        try:
            format = self.property_value('ui.date-format')
            dt = strptime(value, format)
            if etype == 'Datetime':
                return todatetime(dt)
            return todate(dt)
        except ValueError:
            raise ValueError(self._('can\'t parse %(value)r (expected %(format)s)')
                             % {'value': value, 'format': format})

    # abstract methods to override according to the web front-end #############

    def base_url(self):
        """return the root url of the instance"""
        raise NotImplementedError

    def decorate_rset(self, rset):
        """add vreg/req (at least) attributes to the given result set """
        raise NotImplementedError

    def describe(self, eid):
        """return a tuple (type, sourceuri, extid) for the entity with id <eid>"""
        raise NotImplementedError

    @property
    @deprecated('[3.6] use _cw.vreg.config')
    def config(self):
        return self.vreg.config

    @property
    @deprecated('[3.6] use _cw.vreg.schema')
    def schema(self):
        return self.vreg.schema