apps/dcmeta/models.py

   1 from django.db import models
   2 import eav.models
   3 import pdb
   4
   5 # Some monkey patches to EAV:
   6
   7 # Allow dots & stuff
   8 eav.models.slugify = lambda x: x
   9
  10 # Allow more characters
  11 eav.models.BaseSchema._meta.get_field_by_name("name")[0].max_length = 200
  12
  13 from django.contrib.auth.models import User
  14 from django.contrib.contenttypes.generic import GenericRelation, GenericForeignKey
  15 from django.contrib.contenttypes.models import ContentType
  16
  17 from lxml import etree
  18 from dcmeta.utils import RDFNS, common_prefixes, NamespaceDescriptor
  19 import logging
  20
  21 logger = logging.getLogger("django.dcmeta")
  22
  23 class Description(eav.models.BaseEntity):
  24     """Collection of meta-data that can be assigned to an entity."""
  25     object_id = models.PositiveIntegerField(blank=True, null=True)
  26     content_type = models.ForeignKey(ContentType, blank=True, null=True)
  27
  28     about = GenericForeignKey()
  29     about_uri = models.TextField()
  30
  31     attrs = GenericRelation('Attr', object_id_field="entity_id", content_type_field="entity_type")
  32
  33     # shortcuts to EAV attributes
  34     dublincore = NamespaceDescriptor('http://purl.org/dc/elements/1.1/')
  35     marcrel = NamespaceDescriptor('http://www.loc.gov/loc.terms/relators/')
  36
  37     @classmethod
  38     def get_schemata_for_model(self):
  39         return Schema.objects.all()
  40
  41     @classmethod
  42     def import_rdf(cls, text):
  43         doc = etree.fromstring(text)
  44         xml_desc = doc.xpath('/rdf:RDF/rdf:Description', namespaces={"rdf": RDFNS.uri})
  45
  46         if not xml_desc:
  47             raise ValueError("Invalid document structure.")
  48
  49         xml_desc = xml_desc[0]
  50
  51         desc = Description.objects.create(about_uri=xml_desc.get(RDFNS("about")))
  52
  53         for xml_property in xml_desc.iterchildren():
  54             property, _created = Schema.objects.get_or_create(
  55                                 name=xml_property.tag, datatype=Schema.TYPE_TEXT)
  56             property.save_attr(desc, xml_property.text)
  57
  58         desc = Description.objects.get(pk=desc.pk)
  59         return desc
  60
  61     def __getitem__(self, key):
  62         if not isinstance(key, tuple):
  63             raise ValueError
  64         ns, attr = key
  65
  66         if ns in common_prefixes: # URI given, value stored as prefix
  67             ns = common_prefixes[ns]
  68
  69         return getattr(self, "{%s}%s" % (ns, attr))
  70
  71     def __setitem__(self, key, value):
  72         return setattr(self, "dc_" + key, value)
  73
  74 class Schema(eav.models.BaseSchema):
  75     pass
  76
  77 class Choice(eav.models.BaseChoice):
  78     """
  79         For properties with multiply values.
  80     """
  81     schema = models.ForeignKey(Schema, related_name='choices')
  82
  83 class Attr(eav.models.BaseAttribute):
  84     schema = models.ForeignKey(Schema, related_name='attrs')
  85     choice = models.ForeignKey(Choice, blank=True, null=True)