moviewyrm/bookwyrm/activitypub/base_activity.py
2020-12-12 15:44:17 -08:00

213 lines
7.3 KiB
Python

''' basics for an activitypub serializer '''
from dataclasses import dataclass, fields, MISSING
from json import JSONEncoder
from django.apps import apps
from django.db import transaction
from django.db.models.fields.files import ImageFileDescriptor
from django.db.models.fields.related_descriptors import ManyToManyDescriptor
from bookwyrm.connectors import ConnectorException, get_data
from bookwyrm.tasks import app
class ActivitySerializerError(ValueError):
''' routine problems serializing activitypub json '''
class ActivityEncoder(JSONEncoder):
''' used to convert an Activity object into json '''
def default(self, o):
return o.__dict__
@dataclass
class Link:
''' for tagging a book in a status '''
href: str
name: str
type: str = 'Link'
@dataclass
class Mention(Link):
''' a subtype of Link for mentioning an actor '''
type: str = 'Mention'
@dataclass
class Signature:
''' public key block '''
creator: str
created: str
signatureValue: str
type: str = 'RsaSignature2017'
@dataclass(init=False)
class ActivityObject:
''' actor activitypub json '''
id: str
type: str
def __init__(self, **kwargs):
''' this lets you pass in an object with fields that aren't in the
dataclass, which it ignores. Any field in the dataclass is required or
has a default value '''
for field in fields(self):
try:
value = kwargs[field.name]
except KeyError:
if field.default == MISSING and \
field.default_factory == MISSING:
raise ActivitySerializerError(\
'Missing required field: %s' % field.name)
value = field.default
setattr(self, field.name, value)
@transaction.atomic
def to_model(self, model, instance=None, save=True):
''' convert from an activity to a model instance '''
if not isinstance(self, model.activity_serializer):
raise ActivitySerializerError(
'Wrong activity type "%s" for model "%s" (expects "%s")' % \
(self.__class__,
model.__name__,
model.activity_serializer)
)
# check for an existing instance, if we're not updating a known obj
if not instance:
instance = model.find_existing(self.serialize()) or model()
many_to_many_fields = {}
image_fields = {}
for field in model._meta.get_fields():
# check if it's an activitypub field
if not hasattr(field, 'field_to_activity'):
continue
# call the formatter associated with the model field class
value = field.field_from_activity(
getattr(self, field.get_activitypub_field())
)
if value is None or value is MISSING:
continue
model_field = getattr(model, field.name)
if isinstance(model_field, ManyToManyDescriptor):
# status mentions book/users for example, stash this for later
many_to_many_fields[field.name] = value
elif isinstance(model_field, ImageFileDescriptor):
# image fields need custom handling
image_fields[field.name] = value
else:
# just a good old fashioned model.field = value
setattr(instance, field.name, value)
# if this isn't here, it messes up saving users. who even knows.
for (model_key, value) in image_fields.items():
getattr(instance, model_key).save(*value, save=save)
if not save:
# we can't set many to many and reverse fields on an unsaved object
return instance
instance.save()
# add many to many fields, which have to be set post-save
for (model_key, values) in many_to_many_fields.items():
# mention books/users, for example
getattr(instance, model_key).set(values)
if not save or not hasattr(model, 'deserialize_reverse_fields'):
return instance
# reversed relationships in the models
for (model_field_name, activity_field_name) in \
model.deserialize_reverse_fields:
# attachments on Status, for example
values = getattr(self, activity_field_name)
if values is None or values is MISSING:
continue
try:
# this is for one to many
related_model = getattr(model, model_field_name).field.model
except AttributeError:
# it's a one to one or foreign key
related_model = getattr(model, model_field_name)\
.related.related_model
values = [values]
for item in values:
set_related_field.delay(
related_model.__name__,
instance.__class__.__name__,
instance.__class__.__name__.lower(),
instance.remote_id,
item
)
return instance
def serialize(self):
''' convert to dictionary with context attr '''
data = self.__dict__
data['@context'] = 'https://www.w3.org/ns/activitystreams'
return data
@app.task
@transaction.atomic
def set_related_field(
model_name, origin_model_name,
related_field_name, related_remote_id, data):
''' load reverse related fields (editions, attachments) without blocking '''
model = apps.get_model('bookwyrm.%s' % model_name, require_ready=True)
origin_model = apps.get_model(
'bookwyrm.%s' % origin_model_name,
require_ready=True
)
if isinstance(data, str):
item = resolve_remote_id(model, data, save=False)
else:
# look for a match based on all the available data
item = model.find_existing(data)
if not item:
# create a new model instance
item = model.activity_serializer(**data)
item = item.to_model(model, save=False)
# this must exist because it's the object that triggered this function
instance = origin_model.find_existing_by_remote_id(related_remote_id)
if not instance:
raise ValueError('Invalid related remote id: %s' % related_remote_id)
# edition.parent_work = instance, for example
setattr(item, related_field_name, instance)
item.save()
def resolve_remote_id(model, remote_id, refresh=False, save=True):
''' take a remote_id and return an instance, creating if necessary '''
result = model.find_existing_by_remote_id(remote_id)
if result and not refresh:
return result
# load the data and create the object
try:
data = get_data(remote_id)
except (ConnectorException, ConnectionError):
raise ActivitySerializerError(
'Could not connect to host for remote_id in %s model: %s' % \
(model.__name__, remote_id))
# check for existing items with shared unique identifiers
if not result:
result = model.find_existing(data)
if result and not refresh:
return result
item = model.activity_serializer(**data)
# if we're refreshing, "result" will be set and we'll update it
return item.to_model(model, instance=result, save=save)