from django.contrib.sites.models import Site from django.core.urlresolvers import reverse from django.http import HttpResponse from djangorestframework import emitters, parsers, authenticators from djangorestframework.response import status, Response, ResponseException from decimal import Decimal import re # TODO: Figure how out references and named urls need to work nicely # TODO: POST on existing 404 URL, PUT on existing 404 URL # # NEXT: Exceptions on func() -> 500, tracebacks emitted if settings.DEBUG # __all__ = ['Resource'] class Resource(object): """Handles incoming requests and maps them to REST operations, performing authentication, input deserialization, input validation, output serialization.""" # List of RESTful operations which may be performed on this resource. allowed_methods = ('GET',) anon_allowed_methods = () # List of emitters the resource can serialize the response with, ordered by preference emitters = ( emitters.JSONEmitter, emitters.DocumentingHTMLEmitter, emitters.DocumentingXHTMLEmitter, emitters.DocumentingPlainTextEmitter, emitters.XMLEmitter ) # List of content-types the resource can read from parsers = ( parsers.JSONParser, parsers.XMLParser, parsers.FormParser ) # List of all authenticating methods to attempt authenticators = ( authenticators.UserLoggedInAuthenticator, authenticators.BasicAuthenticator ) # Optional form for input validation and presentation of HTML formatted responses. form = None # Map standard HTTP methods to function calls callmap = { 'GET': 'get', 'POST': 'post', 'PUT': 'put', 'DELETE': 'delete' } # Some reserved parameters to allow us to use standard HTML forms with our resource # Override any/all of these with None to disable them, or override them with another value to rename them. ACCEPT_QUERY_PARAM = '_accept' # Allow override of Accept header in URL query params METHOD_PARAM = '_method' # Allow POST overloading in form params CONTENTTYPE_PARAM = '_contenttype' # Allow override of Content-Type header in form params (allows sending arbitrary content with standard forms) CONTENT_PARAM = '_content' # Allow override of body content in form params (allows sending arbitrary content with standard forms) CSRF_PARAM = 'csrfmiddlewaretoken' # Django's CSRF token used in form params def __new__(cls, *args, **kwargs): """Make the class callable so it can be used as a Django view.""" self = object.__new__(cls) if args: request = args[0] self.__init__(request) return self._handle_request(request, *args[1:], **kwargs) else: self.__init__() return self def __init__(self, request=None): """""" # Setup the resource context self.request = request self.response = None self.form_instance = None # These sets are determined now so that overridding classes can modify the various parameter names, # or set them to None to disable them. self.RESERVED_FORM_PARAMS = set((self.METHOD_PARAM, self.CONTENTTYPE_PARAM, self.CONTENT_PARAM, self.CSRF_PARAM)) self.RESERVED_QUERY_PARAMS = set((self.ACCEPT_QUERY_PARAM)) self.RESERVED_FORM_PARAMS.discard(None) self.RESERVED_QUERY_PARAMS.discard(None) @property def name(self): """Provide a name for the resource. By default this is the class name, with 'CamelCaseNames' converted to 'Camel Case Names'.""" class_name = self.__class__.__name__ return re.sub('(((?<=[a-z])[A-Z])|([A-Z](?![A-Z]|$)))', ' \\1', class_name).strip() @property def description(self): """Provide a description for the resource. By default this is the class's docstring with leading line spaces stripped.""" return re.sub(re.compile('^ +', re.MULTILINE), '', self.__doc__) @property def emitted_media_types(self): """Return an list of all the media types that this resource can emit.""" return [emitter.media_type for emitter in self.emitters] @property def default_emitter(self): """Return the resource's most prefered emitter. (This emitter is used if the client does not send and Accept: header, or sends Accept: */*)""" return self.emitters[0] @property def parsed_media_types(self): """Return an list of all the media types that this resource can emit.""" return [parser.media_type for parser in self.parsers] @property def default_parser(self): """Return the resource's most prefered emitter. (This has no behavioural effect, but is may be used by documenting emitters)""" return self.parsers[0] def get(self, request, auth, *args, **kwargs): """Must be subclassed to be implemented.""" self.not_implemented('GET') def post(self, request, auth, content, *args, **kwargs): """Must be subclassed to be implemented.""" self.not_implemented('POST') def put(self, request, auth, content, *args, **kwargs): """Must be subclassed to be implemented.""" self.not_implemented('PUT') def delete(self, request, auth, *args, **kwargs): """Must be subclassed to be implemented.""" self.not_implemented('DELETE') def reverse(self, view, *args, **kwargs): """Return a fully qualified URI for a given view or resource. Add the domain using the Sites framework if possible, otherwise fallback to using the current request.""" return self.add_domain(reverse(view, args=args, kwargs=kwargs)) def not_implemented(self, operation): """Return an HTTP 500 server error if an operation is called which has been allowed by allowed_methods, but which has not been implemented.""" raise ResponseException(status.HTTP_500_INTERNAL_SERVER_ERROR, {'detail': '%s operation on this resource has not been implemented' % (operation, )}) def add_domain(self, path): """Given a path, return an fully qualified URI. Use the Sites framework if possible, otherwise fallback to using the domain from the current request.""" # Note that out-of-the-box the Sites framework uses the reserved domain 'example.com' # See RFC 2606 - http://www.faqs.org/rfcs/rfc2606.html try: site = Site.objects.get_current() if site.domain and site.domain != 'example.com': return 'http://%s%s' % (site.domain, path) except: pass return self.request.build_absolute_uri(path) def determine_method(self, request): """Determine the HTTP method that this request should be treated as. Allows PUT and DELETE tunneling via the _method parameter if METHOD_PARAM is set.""" method = request.method.upper() if method == 'POST' and self.METHOD_PARAM and request.POST.has_key(self.METHOD_PARAM): method = request.POST[self.METHOD_PARAM].upper() return method def authenticate(self, request): """Attempt to authenticate the request, returning an authentication context or None. An authentication context may be any object, although in many cases it will be a User instance.""" # Attempt authentication against each authenticator in turn, # and return None if no authenticators succeed in authenticating the request. for authenticator in self.authenticators: auth_context = authenticator(self).authenticate(request) if auth_context: return auth_context return None def check_method_allowed(self, method, auth): """Ensure the request method is permitted for this resource, raising a ResourceException if it is not.""" if not method in self.callmap.keys(): raise ResponseException(status.HTTP_501_NOT_IMPLEMENTED, {'detail': 'Unknown or unsupported method \'%s\'' % method}) if not method in self.allowed_methods: raise ResponseException(status.HTTP_405_METHOD_NOT_ALLOWED, {'detail': 'Method \'%s\' not allowed on this resource.' % method}) if auth is None and not method in self.anon_allowed_methods: raise ResponseException(status.HTTP_403_FORBIDDEN, {'detail': 'You do not have permission to access this resource. ' + 'You may need to login or otherwise authenticate the request.'}) def get_form(self, data=None): """Optionally return a Django Form instance, which may be used for validation and/or rendered by an HTML/XHTML emitter. If data is not None the form will be bound to data.""" if self.form: if data: return self.form(data) else: return self.form() return None def cleanup_request(self, data, form_instance): """Perform any resource-specific data deserialization and/or validation after the initial HTTP content-type deserialization has taken place. Returns a tuple containing the cleaned up data, and optionally a form bound to that data. By default this uses form validation to filter the basic input into the required types.""" if form_instance is None: return data # Default form validation does not check for additional invalid fields non_existent_fields = [] for key in set(data.keys()) - set(form_instance.fields.keys()): non_existent_fields.append(key) if not form_instance.is_valid() or non_existent_fields: if not form_instance.errors and not non_existent_fields: # If no data was supplied the errors property will be None details = 'No content was supplied' else: # Add standard field errors details = dict((key, map(unicode, val)) for (key, val) in form_instance.errors.iteritems() if key != '__all__') # Add any non-field errors if form_instance.non_field_errors(): details['errors'] = form_instance.non_field_errors() # Add any non-existent field errors for key in non_existent_fields: details[key] = ['This field does not exist'] # Bail. Note that we will still serialize this response with the appropriate content type raise ResponseException(status.HTTP_400_BAD_REQUEST, {'detail': details}) return form_instance.cleaned_data def cleanup_response(self, data): """Perform any resource-specific data filtering prior to the standard HTTP content-type serialization. Eg filter complex objects that cannot be serialized by json/xml/etc into basic objects that can.""" return data def determine_parser(self, request): """Return the appropriate parser for the input, given the client's 'Content-Type' header, and the content types that this Resource knows how to parse.""" content_type = request.META.get('CONTENT_TYPE', 'application/x-www-form-urlencoded') raw_content = request.raw_post_data split = content_type.split(';', 1) if len(split) > 1: content_type = split[0] content_type = content_type.strip() # If CONTENTTYPE_PARAM is turned on, and this is a standard POST form then allow the content type to be overridden if (content_type == 'application/x-www-form-urlencoded' and request.method == 'POST' and self.CONTENTTYPE_PARAM and self.CONTENT_PARAM and request.POST.get(self.CONTENTTYPE_PARAM, None) and request.POST.get(self.CONTENT_PARAM, None)): raw_content = request.POST[self.CONTENT_PARAM] content_type = request.POST[self.CONTENTTYPE_PARAM] # Create a list of list of (media_type, Parser) tuples media_type_to_parser = dict([(parser.media_type, parser) for parser in self.parsers]) try: return (media_type_to_parser[content_type], raw_content) except KeyError: raise ResponseException(status.HTTP_415_UNSUPPORTED_MEDIA_TYPE, {'detail': 'Unsupported media type \'%s\'' % content_type}) def determine_emitter(self, request): """Return the appropriate emitter for the output, given the client's 'Accept' header, and the content types that this Resource knows how to serve. See: RFC 2616, Section 14 - http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html""" if self.ACCEPT_QUERY_PARAM and request.GET.get(self.ACCEPT_QUERY_PARAM, None): # Use _accept parameter override accept_list = [request.GET.get(self.ACCEPT_QUERY_PARAM)] elif request.META.has_key('HTTP_ACCEPT'): # Use standard HTTP Accept negotiation accept_list = request.META["HTTP_ACCEPT"].split(',') else: # No accept header specified return self.default_emitter # Parse the accept header into a dict of {qvalue: set of media types} # We ignore mietype parameters accept_dict = {} for token in accept_list: components = token.split(';') mimetype = components[0].strip() qvalue = Decimal('1.0') if len(components) > 1: # Parse items that have a qvalue eg text/html;q=0.9 try: (q, num) = components[-1].split('=') if q == 'q': qvalue = Decimal(num) except: # Skip malformed entries continue if accept_dict.has_key(qvalue): accept_dict[qvalue].add(mimetype) else: accept_dict[qvalue] = set((mimetype,)) # Convert to a list of sets ordered by qvalue (highest first) accept_sets = [accept_dict[qvalue] for qvalue in sorted(accept_dict.keys(), reverse=True)] for accept_set in accept_sets: # Return any exact match for emitter in self.emitters: if emitter.media_type in accept_set: return emitter # Return any subtype match for emitter in self.emitters: if emitter.media_type.split('/')[0] + '/*' in accept_set: return emitter # Return default if '*/*' in accept_set: return self.default_emitter raise ResponseException(status.HTTP_406_NOT_ACCEPTABLE, {'detail': 'Could not statisfy the client\'s Accept header', 'available_types': self.emitted_media_types}) def _handle_request(self, request, *args, **kwargs): """This method is the core of Resource, through which all requests are passed. Broadly this consists of the following procedure: 0. ensure the operation is permitted 1. deserialize request content into request data, using standard HTTP content types (PUT/POST only) 2. cleanup and validate request data (PUT/POST only) 3. call the core method to get the response data 4. cleanup the response data 5. serialize response data into response content, using standard HTTP content negotiation """ emitter = None method = self.determine_method(request) try: # Before we attempt anything else determine what format to emit our response data with. emitter = self.determine_emitter(request) # Authenticate the request, and store any context so that the resource operations can # do more fine grained authentication if required. # # Typically the context will be a user, or None if this is an anonymous request, # but it could potentially be more complex (eg the context of a request key which # has been signed against a particular set of permissions) auth_context = self.authenticate(request) # Ensure the requested operation is permitted on this resource self.check_method_allowed(method, auth_context) # Get the appropriate create/read/update/delete function func = getattr(self, self.callmap.get(method, None)) # Either generate the response data, deserializing and validating any request data # TODO: Add support for message bodys on other HTTP methods, as it is valid. if method in ('PUT', 'POST'): (parser, raw_content) = self.determine_parser(request) data = parser(self).parse(raw_content) self.form_instance = self.get_form(data) data = self.cleanup_request(data, self.form_instance) response = func(request, auth_context, data, *args, **kwargs) else: response = func(request, auth_context, *args, **kwargs) # Allow return value to be either Response, or an object, or None if isinstance(response, Response): self.response = response elif response is not None: self.response = Response(status.HTTP_200_OK, response) else: self.response = Response(status.HTTP_204_NO_CONTENT) # Pre-serialize filtering (eg filter complex objects into natively serializable types) self.response.cleaned_content = self.cleanup_response(self.response.raw_content) except ResponseException, exc: self.response = exc.response # Fall back to the default emitter if we failed to perform content negotiation if emitter is None: emitter = self.default_emitter # Always add these headers self.response.headers['Allow'] = ', '.join(self.allowed_methods) self.response.headers['Vary'] = 'Authenticate, Allow' # Serialize the response content if self.response.has_content_body: content = emitter(self).emit(output=self.response.cleaned_content) else: content = emitter(self).emit() # Build the HTTP Response # TODO: Check if emitter.mimetype is underspecified, or if a content-type header has been set resp = HttpResponse(content, mimetype=emitter.media_type, status=self.response.status) for (key, val) in self.response.headers.items(): resp[key] = val return resp