# copyright 2003-2012 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

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

#

# This file is part of CubicWeb.

#

# CubicWeb is free software: you can redistribute it and/or modify it under the

# terms of the GNU Lesser General Public License as published by the Free

# Software Foundation, either version 2.1 of the License, or (at your option)

# any later version.

#

# CubicWeb 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 Lesser General Public License for more

# details.

#

# You should have received a copy of the GNU Lesser General Public License along

# with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.

"""json export views"""

__docformat__ = "restructuredtext en"

from cubicweb import _

from cubicweb.uilib import rest_traceback

from cubicweb.utils import json_dumps

from cubicweb.predicates import ExpectedValuePredicate, any_rset, empty_rset

from cubicweb.view import EntityView, AnyRsetView

from cubicweb.web.application import anonymized_request

from cubicweb.web.views import basecontrollers, management

class JsonpController(basecontrollers.ViewController):

    """The jsonp controller is the same as a ViewController but :

    - anonymize request (avoid CSRF attacks)

    - if ``vid`` parameter is passed, make sure it's sensible (i.e. either

      "jsonexport" or "ejsonexport")

    - if ``callback`` request parameter is passed, it's used as json padding

    Response's content-type will either be ``application/javascript`` or

    ``application/json`` depending on ``callback`` parameter presence or not.

    """

    __regid__ = 'jsonp'

    def publish(self, rset=None):

        if 'vid' in self._cw.form:

            vid = self._cw.form['vid']

            if vid not in ('jsonexport', 'ejsonexport'):

                self.warning("vid %s can't be used with jsonp controller, "

                             "falling back to jsonexport", vid)

                self._cw.form['vid'] = 'jsonexport'

        else: # if no vid is specified, use jsonexport

            self._cw.form['vid'] = 'jsonexport'

        if self._cw.vreg.config['anonymize-jsonp-queries']:

            with anonymized_request(self._cw):

                return self._get_json_data(rset)

        else:

            return self._get_json_data(rset)

    def _get_json_data(self, rset):

        json_data = super(JsonpController, self).publish(rset)

        if 'callback' in self._cw.form: # jsonp

            json_padding = self._cw.form['callback'].encode('ascii')

            # use ``application/javascript`` if ``callback`` parameter is

            # provided, keep ``application/json`` otherwise

            self._cw.set_content_type('application/javascript')

            json_data = json_padding + b'(' + json_data + b')'

        return json_data

class JsonMixIn(object):

    """mixin class for json views

    Handles the following optional request parameters:

    - ``_indent`` : must be an integer. If found, it is used to pretty print

      json output

    """

    templatable = False

    content_type = 'application/json'

    binary = True

    def wdata(self, data):

        if '_indent' in self._cw.form:

            indent = int(self._cw.form['_indent'])

        else:

            indent = None

        # python's json.dumps escapes non-ascii characters

        self.w(json_dumps(data, indent=indent).encode('ascii'))

class JsonRsetView(JsonMixIn, AnyRsetView):

    """dumps raw result set in JSON format"""

    __regid__ = 'jsonexport'

    __select__ = any_rset() # means rset might be empty or have any shape

    title = _('json-export-view')

    def call(self):

        # XXX mimic w3c recommandations to serialize SPARQL results in json?

        #     http://www.w3.org/TR/rdf-sparql-json-res/

        self.wdata(self.cw_rset.rows)

class JsonEntityView(JsonMixIn, EntityView):

    """dumps rset entities in JSON

    The following additional metadata is added to each row :

    - ``__cwetype__`` : entity type

    """

    __regid__ = 'ejsonexport'

    __select__ = EntityView.__select__ | empty_rset()

    title = _('json-entities-export-view')

    def call(self):

        entities = []

        for entity in self.cw_rset.entities():

            entity.complete() # fetch all attributes

            # hack to add extra metadata

            entity.cw_attr_cache.update({

                    '__cwetype__': entity.cw_etype,

                    })

            entities.append(entity)

        self.wdata(entities)

class _requested_vid(ExpectedValuePredicate):

    """predicate that checks vid parameter value

    It differs from ``match_view`` in that it doesn't expect a ``view``

    parameter to be given to ``select`` but will rather check

    ``req.form['vid']`` to match expected vid.

    """

    def __call__(self, cls, req, rset=None, **kwargs):

        return req.form.get('vid') in self.expected

class JsonErrorView(JsonMixIn, management.ErrorView):

    """custom error view selected when client asks for a json view

    The returned json object will contain err / traceback informations.

    """

    __select__ = (management.ErrorView.__select__ &

                  _requested_vid('jsonexport', 'ejsonexport'))

    def call(self):

        errmsg, exclass, excinfo = self._excinfo()

        self.wdata({

            'errmsg': errmsg,

            'exclass': exclass,

            'traceback': rest_traceback(excinfo, errmsg),

            })