forked from mirrors/bookwyrm
119 lines
3.4 KiB
Python
119 lines
3.4 KiB
Python
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''' basics for an activitypub serializer '''
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from dataclasses import dataclass, fields, MISSING
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from json import JSONEncoder
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from django.db.models.fields.related_descriptors \
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import ForwardManyToOneDescriptor
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class ActivityEncoder(JSONEncoder):
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''' used to convert an Activity object into json '''
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def default(self, o):
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return o.__dict__
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@dataclass
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class Image:
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''' image block '''
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mediaType: str
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url: str
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type: str = 'Image'
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@dataclass
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class PublicKey:
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''' public key block '''
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id: str
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owner: str
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publicKeyPem: str
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@dataclass
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class Signature:
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''' public key block '''
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creator: str
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created: str
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signatureValue: str
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type: str = 'RsaSignature2017'
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@dataclass(init=False)
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class ActivityObject:
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''' actor activitypub json '''
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id: str
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type: str
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def __init__(self, **kwargs):
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''' this lets you pass in an object with fields
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that aren't in the dataclass, which it ignores.
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Any field in the dataclass is required or has a
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default value '''
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for field in fields(self):
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try:
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value = kwargs[field.name]
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except KeyError:
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if field.default == MISSING:
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raise TypeError('Missing required field: %s' % field.name)
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value = field.default
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setattr(self, field.name, value)
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def to_model(self, model, instance=None):
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''' convert from an activity to a model '''
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if not isinstance(self, model.activity_serializer):
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raise TypeError('Wrong activity type for model')
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model_fields = [m.name for m in model._meta.get_fields()]
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mapped_fields = {}
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for mapping in model.activity_mappings:
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if mapping.model_key not in model_fields:
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continue
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# value is None if there's a default that isn't supplied
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# in the activity but is supplied in the formatter
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value = None
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if mapping.activity_key:
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value = getattr(self, mapping.activity_key)
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model_field = getattr(model, mapping.model_key)
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# remote_id -> foreign key resolver
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if isinstance(model_field, ForwardManyToOneDescriptor) and value:
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fk_model = model_field.field.related_model
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value = resolve_foreign_key(fk_model, value)
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mapped_fields[mapping.model_key] = mapping.model_formatter(value)
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# updating an existing model isntance
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if instance:
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for k, v in mapped_fields.items():
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setattr(instance, k, v)
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instance.save()
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return instance
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# creating a new model instance
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return model.objects.create(**mapped_fields)
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def serialize(self):
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''' convert to dictionary with context attr '''
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data = self.__dict__
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data['@context'] = 'https://www.w3.org/ns/activitystreams'
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return data
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def resolve_foreign_key(model, remote_id):
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''' look up the remote_id on an activity json field '''
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result = model.objects
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if hasattr(model.objects, 'select_subclasses'):
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result = result.select_subclasses()
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result = result.filter(
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remote_id=remote_id
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).first()
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if not result:
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raise ValueError('Could not resolve remote_id in %s model: %s' % \
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(model.__name__, remote_id))
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return result
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