"""provide replacement classes for gae db module, so that a gae model can be

used as base for a cubicweb application by simply replacing ::

  from google.appengine.ext import db

by

  from cubicweb.goa import db

The db.model api should be fully featured by replacement classes, with the

following differences:

* all methods returning `google.appengine.ext.db.Model` instance(s) will return

  `cubicweb.goa.db.Model` instance instead (though you should see almost no

  difference since those instances have the same api)

* class methods returning model instance take a `req` as first argument, unless

  they are called through an instance, representing the current request

  (accessible through `self.req` on almost all objects)

* XXX no instance.<modelname>_set attributes, use instance.reverse_<attr name>

      instead

* XXX reference property always return a list of objects, not the instance

* XXX name/collection_name argument of properties constructor are ignored

* XXX ListProperty

:organization: Logilab

:copyright: 2008-2010 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.

:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr

:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses

"""

__docformat__ = "restructuredtext en"

from copy import deepcopy

from logilab.common.decorators import cached, iclassmethod

from cubicweb import Binary, entities

from cubicweb.req import RequestSessionBase

from cubicweb.rset import ResultSet

from cubicweb.entity import metaentity

from cubicweb.server.utils import crypt_password

from cubicweb.goa import MODE

from cubicweb.goa.dbinit import init_relations

from google.appengine.api.datastore import Get, Put, Key, Entity, Query

from google.appengine.api.datastore import NormalizeAndTypeCheck, RunInTransaction

from google.appengine.api.datastore_types import Text, Blob

from google.appengine.api.datastore_errors import BadKeyError

# XXX remove this dependancy

from google.appengine.ext import db

def rset_from_objs(req, objs, attrs=('eid',), rql=None, args=None):

    """return a ResultSet instance for list of objects"""

    if objs is None:

        objs = ()

    elif isinstance(objs, Entity):

        objs = (objs,)

    if rql is None:

        rql = 'Any X'

    rows = []

    description = []

    rset = ResultSet(rows, rql, args, description=description)

    vreg = req.vreg

    for i, obj in enumerate(objs):

        line = []

        linedescr = []

        eschema = vreg.schema.eschema(obj.kind())

        for j, attr in enumerate(attrs):

            if attr == 'eid':

                value = obj.key()

                obj.row, obj.col = i, j

                descr = eschema.type

                value = str(value)

            else:

                value = obj[attr]

                descr = str(eschema.destination(attr))

            line.append(value)

            linedescr.append(descr)

        rows.append(line)

        description.append(linedescr)

        for j, attr in enumerate(attrs):

            if attr == 'eid':

                entity = vreg.etype_class(eschema.type)(req, rset, i, j)

                rset._get_entity_cache_ = {(i, j): entity}

    rset.rowcount = len(rows)

    req.decorate_rset(rset)

    return rset

def needrequest(wrapped):

    def wrapper(cls, *args, **kwargs):

        req = kwargs.pop('req', None)

        if req is None and args and isinstance(args[0], RequestSessionBase):

            args = list(args)

            req = args.pop(0)

        if req is None:

            req = getattr(cls, 'req', None)

            if req is None:

                raise Exception('either call this method on an instance or '

                                'specify the req argument')

        return wrapped(cls, req, *args, **kwargs)

    return iclassmethod(wrapper)

class gaedbmetaentity(metaentity):

    """metaclass for goa.db.Model classes: filter entity / db model part,

    put aside the db model part for later creation of db model class.

    """

    def __new__(mcs, name, bases, classdict):

        if not 'id' in classdict:

            classdict['id'] = name

        entitycls = super(gaedbmetaentity, mcs).__new__(mcs, name, bases, classdict)

        return entitycls

TEST_MODELS = {}

def extract_dbmodel(entitycls):

    if MODE == 'test' and entitycls in TEST_MODELS:

        dbclassdict = TEST_MODELS[entitycls]

    else:

        dbclassdict = {}

        for attr, value in entitycls.__dict__.items():

            if isinstance(value, db.Property) or isinstance(value, ReferencePropertyStub):

                dbclassdict[attr] = value

                # don't remove attr from entitycls, this make tests fail, and it's anyway

                # overwritten by descriptor at class initialization time

                #delattr(entitycls, attr)

    if MODE == 'test':

        TEST_MODELS[entitycls] = dbclassdict

        dbclassdict = deepcopy(dbclassdict)

        for propname, prop in TEST_MODELS[entitycls].iteritems():

            if getattr(prop, 'reference_class', None) is db._SELF_REFERENCE:

                dbclassdict[propname].reference_class = db._SELF_REFERENCE

    return dbclassdict

class Model(entities.AnyEntity):

    id = 'Any'

    __metaclass__ = gaedbmetaentity

    row = col = 0

    @classmethod

    def __initialize__(cls):

        super(Model, cls).__initialize__()

        cls._attributes = frozenset(rschema for rschema in cls.e_schema.subject_relations()

                                    if rschema.final)

    def __init__(self, *args, **kwargs):

        # db.Model prototype:

        #   __init__(self, parent=None, key_name=None, **kw)

        #

        # Entity prototype:

        #   __init__(self, req, rset, row=None, col=0)

        if args and isinstance(args[0], RequestSessionBase) or 'req' in kwargs:

            super(Model, self).__init__(*args, **kwargs)

            self._gaeinitargs = None

        else:

            super(Model, self).__init__(None, None)

            # if Model instances are given in kwargs, turn them into db model

            for key, val in kwargs.iteritems():

                if key in self.e_schema.subject_relations() and not self.e_schema.schema[key].final:

                    if isinstance(kwargs, (list, tuple)):

                        val = [isinstance(x, Model) and x._dbmodel or x for x in val]

                    elif isinstance(val, Model):

                        val = val._dbmodel

                    kwargs[key] = val.key()

            self._gaeinitargs = (args, kwargs)

    def __repr__(self):

        return '<ModelEntity %s %s %s at %s>' % (

            self.e_schema, self.eid, self.keys(), id(self))

    def _cubicweb_to_datastore(self, attr, value):

        attr = attr[2:] # remove 's_' / 'o_' prefix

        if attr in self._attributes:

            tschema = self.e_schema.destination(attr)

            if tschema == 'String':

                if len(value) > 500:

                    value = Text(value)

            elif tschema == 'Password':

                # if value is a Binary instance, this mean we got it

                # from a query result and so it is already encrypted

                if isinstance(value, Binary):

                    value = value.getvalue()

                else:

                    value = crypt_password(value)

            elif tschema == 'Bytes':

                if isinstance(value, Binary):

                    value = value.getvalue()

                value = Blob(value)

        else:

            value = Key(value)

        return value

    def _to_gae_dict(self, convert=True):

        gaedict = {}

        for attr, value in self.iteritems():

            attr = 's_' + attr

            if value is not None and convert:

                value = self._cubicweb_to_datastore(attr, value)

            gaedict[attr] = value

        return gaedict

    def to_gae_model(self):

        dbmodel = self._dbmodel

        dbmodel.update(self._to_gae_dict())

        return dbmodel

    @property

    @cached

    def _dbmodel(self):

        if self.has_eid():

            assert self._gaeinitargs is None

            try:

                return self.req.datastore_get(self.eid)

            except AttributeError: # self.req is not a server session

                return Get(self.eid)

        self.set_defaults()

        values = self._to_gae_dict(convert=False)

        parent = key_name = _app = None

        if self._gaeinitargs is not None:

            args, kwargs = self._gaeinitargs

            args = list(args)

            if args:

                parent = args.pop(0)

            if args:

                key_name = args.pop(0)

            if args:

                _app = args.pop(0)

            assert not args

            if 'parent' in kwargs:

                assert parent is None

                parent = kwargs.pop('parent')

            if 'key_name' in kwargs:

                assert key_name is None

                key_name = kwargs.pop('key_name')

            if '_app' in kwargs:

                assert _app is None

                _app = kwargs.pop('_app')

            for key, value in kwargs.iteritems():

                if key in self._attributes:

                    values['s_'+key] = value

        else:

            kwargs = None

        if key_name is None:

            key_name = self.db_key_name()

            if key_name is not None:

                key_name = 'key_' + key_name

        for key, value in values.iteritems():

            if value is None:

                continue

            values[key] = self._cubicweb_to_datastore(key, value)

        entity = Entity(self.id, parent, _app, key_name)

        entity.update(values)

        init_relations(entity, self.e_schema)

        return entity

    def db_key_name(self):

        """override this method to control datastore key name that should be

        used at entity creation.

        Note that if this function return something else than None, the returned

        value will be prefixed by 'key_' to build the actual key name.

        """

        return None

    def metainformation(self):

        return {'type': self.id, 'source': {'uri': 'system'}, 'extid': None}

    def view(self, vid, __registry='views', **kwargs):

        """shortcut to apply a view on this entity"""

        return self.vreg[__registry].render(vid, self.req, rset=self.rset,

                                           row=self.row, col=self.col, **kwargs)

    @classmethod

    def _rest_attr_info(cls):

        mainattr, needcheck = super(Model, cls)._rest_attr_info()

        if needcheck:

            return 'eid', False

        return mainattr, needcheck

    def get_value(self, name):

        try:

            value = self[name]

        except KeyError:

            if not self.has_eid():

                return None

            value = self._dbmodel.get('s_'+name)

            if value is not None:

                if isinstance(value, Text):

                    value = unicode(value)

                elif isinstance(value, Blob):

                    value = Binary(str(value))

            self[name] = value

        return value

    def has_eid(self):

        if self.eid is None:

            return False

        try:

            Key(self.eid)

            return True

        except BadKeyError:

            return False

    def complete(self, skip_bytes=True):

        pass

    def unrelated(self, rtype, targettype, role='subject', limit=None,

                  ordermethod=None):

        # XXX dumb implementation

        if limit is not None:

            objs = Query(str(targettype)).Get(limit)

        else:

            objs = Query(str(targettype)).Run()

        return rset_from_objs(self.req, objs, ('eid',),

                              'Any X WHERE X is %s' % targettype)

    def key(self):

        return Key(self.eid)