from django.core.urlresolvers import set_script_prefix
from django.views.decorators.csrf import csrf_exempt

from djangorestframework.compat import View
from djangorestframework.response import Response, ErrorResponse
from djangorestframework.mixins import *
from djangorestframework import resources, renderers, parsers, authentication, permissions, status


__all__ = (
    'BaseView',
    'ModelView',
    'InstanceModelView',
    'ListModelView',
    'ListOrCreateModelView'
)



class BaseView(ResourceMixin, RequestMixin, ResponseMixin, AuthMixin, View):
    """
    Handles incoming requests and maps them to REST operations.
    Performs request deserialization, response serialization, authentication and input validation.
    """

    # Use the base resource by default
    resource = resources.Resource

    # List of renderers the resource can serialize the response with, ordered by preference.
    renderers = ( renderers.JSONRenderer,
                  renderers.DocumentingHTMLRenderer,
                  renderers.DocumentingXHTMLRenderer,
                  renderers.DocumentingPlainTextRenderer,
                  renderers.XMLRenderer )

    # List of parsers the resource can parse the request with.
    parsers = ( parsers.JSONParser,
                parsers.FormParser,
                parsers.MultiPartParser )

    # List of all authenticating methods to attempt.
    authentication = ( authentication.UserLoggedInAuthenticaton,
                       authentication.BasicAuthenticaton )
    
    # List of all permissions that must be checked.
    permissions = ( permissions.FullAnonAccess, )

    # Allow name and description for the Resource to be set explicitly,
    # overiding the default classname/docstring behaviour.
    # These are used for documentation in the standard html and text renderers.
    name = None
    description = None

    @property
    def allowed_methods(self):
        """
        Return the list of allowed HTTP methods, uppercased.
        """
        return [method.upper() for method in self.http_method_names if hasattr(self, method)]


    def http_method_not_allowed(self, request, *args, **kwargs):
        """
        Return an HTTP 405 error if an operation is called which does not have a handler method.        
        """
        raise ErrorResponse(status.HTTP_405_METHOD_NOT_ALLOWED,
                            {'detail': 'Method \'%s\' not allowed on this resource.' % self.method})


    # Note: session based authentication is explicitly CSRF validated,
    # all other authentication is CSRF exempt.
    @csrf_exempt
    def dispatch(self, request, *args, **kwargs):
        self.request = request
        self.args = args
        self.kwargs = kwargs

        # Calls to 'reverse' will not be fully qualified unless we set the scheme/host/port here.
        prefix = '%s://%s' % (request.is_secure() and 'https' or 'http', request.get_host())
        set_script_prefix(prefix)

        try:
            # Authenticate and check request has the relevant permissions
            self._check_permissions()

            # Get the appropriate handler method
            if self.method.lower() in self.http_method_names:
                handler = getattr(self, self.method.lower(), self.http_method_not_allowed)
            else:
                handler = self.http_method_not_allowed

            response_obj = handler(request, *args, **kwargs)

            # Allow return value to be either Response, or an object, or None
            if isinstance(response_obj, Response):
                response = response_obj
            elif response_obj is not None:
                response = Response(status.HTTP_200_OK, response_obj)
            else:
                response = Response(status.HTTP_204_NO_CONTENT)

            # Pre-serialize filtering (eg filter complex objects into natively serializable types)
            response.cleaned_content = self.filter_response(response.raw_content)
    
        except ErrorResponse, exc:
            response = exc.response

        # Always add these headers.
        #
        # TODO - this isn't actually the correct way to set the vary header,
        # also it's currently sub-obtimal for HTTP caching - need to sort that out. 
        response.headers['Allow'] = ', '.join(self.allowed_methods)
        response.headers['Vary'] = 'Authenticate, Accept'

        return self.render(response)
    


class ModelView(BaseView):
    """A RESTful view that maps to a model in the database."""
    resource = resources.ModelResource

class InstanceModelView(InstanceMixin, ReadModelMixin, UpdateModelMixin, DeleteModelMixin, ModelView):
    """A view which provides default operations for read/update/delete against a model instance."""
    pass

class ListModelView(ListModelMixin, ModelView):
    """A view which provides default operations for list, against a model in the database."""
    pass

class ListOrCreateModelView(ListModelMixin, CreateModelMixin, ModelView):
    """A view which provides default operations for list and create, against a model in the database."""
    pass