import logging from pprint import pformat from uuid import uuid4 from rdflib import Graph, parser, plugin, serializer from rdflib.resource import Resource from rdflib.namespace import RDF from lakesuperior.model.ldpr import Ldpr from lakesuperior.model.ldp_nr import LdpNr from lakesuperior.model.ldp_rs import LdpRs, Ldpc, LdpDc, LdpIc from lakesuperior.config_parser import config from lakesuperior.env import env from lakesuperior.dictionaries.namespaces import ns_collection as nsc from lakesuperior.exceptions import ( IncompatibleLdpTypeError, InvalidResourceError, ResourceExistsError, ResourceNotExistsError, TombstoneError) LDP_NR_TYPE = nsc['ldp'].NonRDFSource LDP_RS_TYPE = nsc['ldp'].RDFSource rdfly = env.app_globals.rdfly logger = logging.getLogger(__name__) class LdpFactory: ''' Generate LDP instances. The instance classes are based on provided client data or on stored data. ''' @staticmethod def new_container(uid): if not uid.startswith('/') or uid == '/': raise InvalidResourceError(uid) if rdfly.ask_rsrc_exists(uid): raise ResourceExistsError(uid) rsrc = Ldpc(uid, provided_imr=Resource(Graph(), nsc['fcres'][uid])) return rsrc @staticmethod def from_stored(uid, repr_opts={}, **kwargs): ''' Create an instance for retrieval purposes. This factory method creates and returns an instance of an LDPR subclass based on information that needs to be queried from the underlying graph store. N.B. The resource must exist. @param uid UID of the instance. ''' #logger.info('Retrieving stored resource: {}'.format(uid)) imr_urn = nsc['fcres'][uid] rsrc_meta = rdfly.get_metadata(uid) #logger.debug('Extracted metadata: {}'.format( # pformat(set(rsrc_meta.graph)))) rdf_types = set(rsrc_meta.graph[imr_urn : RDF.type]) if LDP_NR_TYPE in rdf_types: logger.info('Resource is a LDP-NR.') rsrc = LdpNr(uid, repr_opts, **kwargs) elif LDP_RS_TYPE in rdf_types: logger.info('Resource is a LDP-RS.') rsrc = LdpRs(uid, repr_opts, **kwargs) else: raise ResourceNotExistsError(uid) # Sneak in the already extracted metadata to save a query. rsrc._metadata = rsrc_meta return rsrc @staticmethod def from_provided(uid, mimetype, stream=None, **kwargs): ''' Determine LDP type from request content. @param uid (string) UID of the resource to be created or updated. @param mimetype (string) The provided content MIME type. @param stream (IOStream | None) The provided data stream. This can be RDF or non-RDF content, or None. In the latter case, an empty container is created. ''' uri = nsc['fcres'][uid] if not stream: # Create empty LDPC. logger.info('No data received in request. ' 'Creating empty container.') inst = Ldpc(uid, provided_imr=Resource(Graph(), uri), **kwargs) elif __class__.is_rdf_parsable(mimetype): # Create container and populate it with provided RDF data. input_rdf = stream.read() gr = Graph().parse(data=input_rdf, format=mimetype, publicID=uri) #logger.debug('Provided graph: {}'.format( # pformat(set(provided_gr)))) provided_imr = Resource(gr, uri) # Determine whether it is a basic, direct or indirect container. if Ldpr.MBR_RSRC_URI in gr.predicates() and \ Ldpr.MBR_REL_URI in gr.predicates(): if Ldpr.INS_CNT_REL_URI in gr.predicates(): cls = LdpIc else: cls = LdpDc else: cls = Ldpc inst = cls(uid, provided_imr=provided_imr, **kwargs) # Make sure we are not updating an LDP-RS with an LDP-NR. if inst.is_stored and LDP_NR_TYPE in inst.ldp_types: raise IncompatibleLdpTypeError(uid, mimetype) if kwargs.get('handling', 'strict') != 'none': inst._check_mgd_terms(inst.provided_imr.graph) else: # Create a LDP-NR and equip it with the binary file provided. provided_imr = Resource(Graph(), uri) inst = LdpNr(uid, stream=stream, mimetype=mimetype, provided_imr=provided_imr, **kwargs) # Make sure we are not updating an LDP-NR with an LDP-RS. if inst.is_stored and LDP_RS_TYPE in inst.ldp_types: raise IncompatibleLdpTypeError(uid, mimetype) logger.info('Creating resource of type: {}'.format( inst.__class__.__name__)) try: types = inst.types except (TombstoneError, ResourceNotExistsError): types = set() return inst @staticmethod def is_rdf_parsable(mimetype): ''' Checks whether a MIME type support RDF parsing by a RDFLib plugin. @param mimetype (string) MIME type to check. ''' try: plugin.get(mimetype, parser.Parser) except plugin.PluginException: return False else: return True @staticmethod def is_rdf_serializable(mimetype): ''' Checks whether a MIME type support RDF serialization by a RDFLib plugin @param mimetype (string) MIME type to check. ''' try: plugin.get(mimetype, serializer.Serializer) except plugin.PluginException: return False else: return True @staticmethod def mint_uid(parent_uid, path=None): ''' Mint a new resource UID based on client directives. This method takes a parent ID and a tentative path and returns an LDP resource UID. This may raise an exception resulting in a 404 if the parent is not found or a 409 if the parent is not a valid container. @param parent_uid (string) UID of the parent resource. It must be an existing LDPC. @param path (string) path to the resource, relative to the parent. @return string The confirmed resource UID. This may be different from what has been indicated. ''' def split_if_legacy(uid): if config['application']['store']['ldp_rs']['legacy_ptree_split']: uid = tbox.split_uuid(uid) return uid if path and path.startswith('/'): raise ValueError('Slug cannot start with a slash.') # Shortcut! if not path and parent_uid == '/': return split_if_legacy(str(uuid4())) if not parent_uid.startswith('/'): raise ValueError('Invalid parent UID: {}'.format(parent_uid)) parent = LdpFactory.from_stored(parent_uid) if nsc['ldp'].Container not in parent.types: raise InvalidResourceError(parent_uid, 'Parent {} is not a container.') pfx = parent_uid.rstrip('/') + '/' if path: cnd_uid = pfx + path if not rdfly.ask_rsrc_exists(cnd_uid): return cnd_uid return pfx + split_if_legacy(str(uuid4()))