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@@ -1,29 +1,32 @@
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import logging
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+import pickle
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from collections import defaultdict
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+from hashlib import sha1
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from flask import request, g
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-from rdflib.term import URIRef
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+from rdflib.term import Literal, URIRef, Variable
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from lakesuperior.dictionaries.namespaces import ns_collection as nsc
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from lakesuperior.store_layouts.rdf.base_rdf_layout import BaseRdfLayout
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-class Translator:
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+class Toolbox:
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'''
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- Utility class to perform translations of strings and their wrappers.
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- All static methods.
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+ Utility class to translate and generate strings and other objects.
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'''
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_logger = logging.getLogger(__name__)
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- @staticmethod
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- def base_url():
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- return request.host_url + g.url_prefix
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+ def __init__():
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+ '''
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+ Set the base URL for the requests. This class has to be instantiated
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+ within a request context.
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+ '''
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+ self.base_url = request.host_url + g.url_prefix
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- @staticmethod
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- def camelcase(word):
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+ def camelcase(self, word):
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'''
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Convert a string with underscores with a camel-cased one.
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@@ -32,17 +35,15 @@ class Translator:
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return ''.join(x.capitalize() or '_' for x in word.split('_'))
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- @staticmethod
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- def uuid_to_uri(uuid):
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+ def uuid_to_uri(self, uuid):
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'''Convert a UUID to a URI.
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@return URIRef
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'''
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- return URIRef('{}/{}'.format(Translator.base_url(), uuid))
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+ return URIRef('{}/{}'.format(self.base_url, uuid))
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- @staticmethod
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- def uri_to_uuid(uri):
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+ def uri_to_uuid(self, uri):
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'''Convert an absolute URI (internal or external) to a UUID.
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@return string
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@@ -50,23 +51,21 @@ class Translator:
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if uri.startswith(nsc['fcres']):
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return str(uri).replace(nsc['fcres'], '')
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else:
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- return str(uri).replace(Translator.base_url(), '')
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+ return str(uri).replace(self.base_url, '')
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- @staticmethod
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- def localize_string(s):
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+ def localize_string(self, s):
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'''Convert URIs into URNs in a string using the application base URI.
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@param string s Input string.
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@return string
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'''
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- return s.replace(Translator.base_url()+'/', str(nsc['fcres']))\
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- .replace(Translator.base_url(), str(nsc['fcres']))
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+ return s.replace(self.base_url+'/', str(nsc['fcres']))\
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+ .replace(self.base_url, str(nsc['fcres']))
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- @staticmethod
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- def localize_term(uri):
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+ def localize_term(self, uri):
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'''
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Convert an URI into an URN.
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@@ -74,25 +73,24 @@ class Translator:
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@return rdflib.term.URIRef
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'''
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- Translator._logger.debug('Input URI: {}'.format(uri))
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- if uri.strip('/') == Translator.base_url():
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+ self._logger.debug('Input URI: {}'.format(uri))
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+ if uri.strip('/') == self.base_url:
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return BaseRdfLayout.ROOT_NODE_URN
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- return URIRef(Translator.localize_string(str(uri)))
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+ return URIRef(self.localize_string(str(uri)))
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- @staticmethod
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- def globalize_string(s):
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+
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+ def globalize_string(self, s):
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'''Convert URNs into URIs in a string using the application base URI.
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@param string s Input string.
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@return string
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'''
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- return s.replace(str(nsc['fcres']), Translator.base_url() + '/')
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+ return s.replace(str(nsc['fcres']), self.base_url + '/')
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- @staticmethod
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- def globalize_term(urn):
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+ def globalize_term(self, urn):
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'''
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Convert an URN into an URI using the application base URI.
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@@ -102,7 +100,8 @@ class Translator:
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'''
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if urn == BaseRdfLayout.ROOT_NODE_URN:
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urn = nsc['fcres']
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- return URIRef(Translator.globalize_string(str(urn)))
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+
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+ return URIRef(self.globalize_string(str(urn)))
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@staticmethod
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@@ -129,8 +128,8 @@ class Translator:
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flt_g = g.query(q)
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for t in flt_g:
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- global_s = Translator.globalize_term(t[0])
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- global_o = Translator.globalize_term(t[2]) \
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+ global_s = self.globalize_term(t[0])
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+ global_o = self.globalize_term(t[2]) \
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if isinstance(t[2], URIRef) \
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else t[2]
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g.remove(t)
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@@ -139,22 +138,20 @@ class Translator:
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return g
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- @staticmethod
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- def globalize_rsrc(rsrc):
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+ def globalize_rsrc(self, rsrc):
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'''
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Globalize a resource.
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'''
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g = rsrc.graph
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urn = rsrc.identifier
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- global_g = Translator.globalize_graph(g)
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- global_uri = Translator.globalize_term(urn)
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+ global_g = self.globalize_graph(g)
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+ global_uri = self.globalize_term(urn)
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return global_g.resource(global_uri)
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- @staticmethod
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- def parse_rfc7240(h_str):
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+ def parse_rfc7240(self, h_str):
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'''
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Parse `Prefer` header as per https://tools.ietf.org/html/rfc7240
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@@ -191,3 +188,31 @@ class Translator:
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return parsed_hdr
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+ def rdf_cksum(self, g):
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+ '''
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+ Generate a checksum for a graph.
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+
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+ This is not straightforward because a graph is derived from an
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+ unordered data structure (RDF).
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+
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+ What this method does is ordering the graph by subject, predicate,
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+ object, then creating a pickle string and a checksum of it.
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+
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+ N.B. The context of the triples is ignored, so isomorphic graphs would
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+ have the same checksum regardless of the context(s) they are found in.
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+
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+ @TODO This can be later reworked to use a custom hashing algorithm.
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+
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+ @param rdflib.Graph g The graph to be hashed.
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+
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+ @return string SHA1 checksum.
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+ '''
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+ # Remove the messageDigest property, which very likely reflects the
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+ # previous state of the resource.
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+ g.remove((Variable('s'), nsc['premis'].messageDigest, Variable('o')))
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+
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+ ord_g = sorted(list(g), key=lambda x : (x[0], x[1], x[2]))
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+ hash = sha1(pickle.dumps(ord_g)).hexdigest()
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+
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+ return hash
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+
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Stefano Cossu