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#
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# Copyright 2011 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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#   1. Redistributions of source code must retain the above
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#      copyright notice, this list of conditions and the following
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#      disclaimer.
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#
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#   2. Redistributions in binary form must reproduce the above
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#      copyright notice, this list of conditions and the following
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#      disclaimer in the documentation and/or other materials
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#      provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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from django import http
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from django.utils import simplejson as json
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from django.core.urlresolvers import reverse
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from django.http import HttpResponse
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from django.core.exceptions import ValidationError, NON_FIELD_ERRORS
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from snf_django.lib.astakos import get_user
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from django.conf import settings
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class View(object):
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    """
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    Intentionally simple parent class for all views. Only implements
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    dispatch-by-method and simple sanity checking.
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    """
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    method_names = ['GET', 'POST', 'DELETE', 'HEAD', 'OPTIONS', 'TRACE']
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    def __init__(self, *args, **kwargs):
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        """
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        Constructor. Called in the URLconf; can contain helpful extra
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        keyword arguments, and other things.
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        """
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        # Go through keyword arguments, and either save their values to our
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        # instance, or raise an error.
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        for key, value in kwargs.items():
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            if key in self.method_names:
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                raise TypeError(u"You tried to pass in the %s method name as a"
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                                u" keyword argument to %s(). Don't do that."
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                                % (key, self.__class__.__name__))
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            if hasattr(self, key):
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                setattr(self, key, value)
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            else:
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                raise TypeError(u"%s() received an invalid keyword %r" % (
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                    self.__class__.__name__,
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                    key,
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                ))
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    @classmethod
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    def as_view(cls, *initargs, **initkwargs):
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        """
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        Main entry point for a request-response process.
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        """
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        def view(request, *args, **kwargs):
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            get_user(request, settings.ASTAKOS_BASE_URL)
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            if not request.user_uniq:
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                return HttpResponse(status=401)
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            self = cls(*initargs, **initkwargs)
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            return self.dispatch(request, *args, **kwargs)
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        return view
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    def dispatch(self, request, *args, **kwargs):
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        # Try to dispatch to the right method for that; if it doesn't exist,
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        # raise a big error.
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        if hasattr(self, request.method.upper()):
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            self.request = request
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            self.args = args
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            self.kwargs = kwargs
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            data = request.body
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            if request.method.upper() in ['POST', 'PUT']:
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                # Expect json data
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                if request.META.get('CONTENT_TYPE').startswith(
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                        'application/json'):
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                    try:
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                        data = json.loads(data)
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                    except ValueError:
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                        return \
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                            http.HttpResponseServerError('Invalid JSON data.')
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                else:
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                    return http.HttpResponseServerError(
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                        'Unsupported Content-Type.')
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            try:
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                return getattr(self, request.method.upper())(
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                    request, data, *args, **kwargs)
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            except ValidationError, e:
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                # specific response for validation errors
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                return http.HttpResponseServerError(
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                    json.dumps({'errors': e.message_dict,
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                                'non_field_key': NON_FIELD_ERRORS}))
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        else:
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            allowed_methods = [m for m in self.method_names if hasattr(self, m)]
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            return http.HttpResponseNotAllowed(allowed_methods)
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class JSONRestView(View):
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    """
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    Class that provides helpers to produce a json response
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    """
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    url_name = None
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    def __init__(self, url_name, *args, **kwargs):
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        self.url_name = url_name
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        return super(JSONRestView, self).__init__(*args, **kwargs)
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    def update_instance(self, i, data, exclude_fields=[]):
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        update_keys = data.keys()
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        for field in i._meta.get_all_field_names():
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            if field in update_keys and (field not in exclude_fields):
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                i.__setattr__(field, data[field])
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        return i
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    def instance_to_dict(self, i, exclude_fields=[]):
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        """
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        Convert model instance to python dict
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        """
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        d = {}
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        d['uri'] = reverse(self.url_name, kwargs={'id': i.pk})
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        for field in i._meta.get_all_field_names():
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            if field in exclude_fields:
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                continue
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            d[field] = i.__getattribute__(field)
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        return d
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    def qs_to_dict_iter(self, qs, exclude_fields=[]):
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        """
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        Convert queryset to an iterator of model instances dicts
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        """
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        for i in qs:
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            yield self.instance_to_dict(i, exclude_fields)
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    def json_response(self, data):
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        return http.HttpResponse(json.dumps(data), mimetype="application/json")
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class ResourceView(JSONRestView):
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    method_names = ['GET', 'POST', 'PUT', 'DELETE']
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    model = None
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    exclude_fields = []
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    def queryset(self):
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        return self.model.objects.all()
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    def instance(self):
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        """
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        Retrieve selected instance based on url parameter
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        id parameter should be set in urlpatterns expression
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        """
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        try:
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            return self.queryset().get(pk=self.kwargs.get("id"))
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        except self.model.DoesNotExist:
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            raise http.Http404
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    def GET(self, request, data, *args, **kwargs):
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        return self.json_response(
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            self.instance_to_dict(self.instance(), self.exclude_fields))
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    def PUT(self, request, data, *args, **kwargs):
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        instance = self.instance()
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        self.update_instance(instance, data, self.exclude_fields)
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        instance.full_clean()
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        instance.save()
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        return self.GET(request, data, *args, **kwargs)
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    def DELETE(self, request, data, *args, **kwargs):
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        self.instance().delete()
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        return self.json_response("")
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class CollectionView(JSONRestView):
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    method_names = ['GET', 'POST']
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    model = None
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    exclude_fields = []
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    def queryset(self):
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        return self.model.objects.all()
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    def GET(self, request, data, *args, **kwargs):
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        return self.json_response(
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            list(self.qs_to_dict_iter(self.queryset(), self.exclude_fields)))
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    def POST(self, request, data, *args, **kwargs):
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        instance = self.model()
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        self.update_instance(instance, data, self.exclude_fields)
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        instance.full_clean()
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        instance.save()
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        return self.json_response(
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            self.instance_to_dict(instance, self.exclude_fields))
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class UserResourceView(ResourceView):
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    """
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    Filter resource queryset for request user entries
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    """
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    def queryset(self):
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        return super(UserResourceView,
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                     self).queryset().filter(user=self.request.user_uniq)
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class UserCollectionView(CollectionView):
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    """
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    Filter collection queryset for request user entries
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    """
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    def queryset(self):
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        return super(UserCollectionView,
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                     self).queryset().filter(user=self.request.user_uniq)
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    def POST(self, request, data, *args, **kwargs):
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        instance = self.model()
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        self.update_instance(instance, data, self.exclude_fields)
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        instance.user = request.user_uniq
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        instance.full_clean()
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        instance.save()
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        return self.json_response(
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            self.instance_to_dict(instance, self.exclude_fields))