moviewyrm/bookwyrm/activitypub/base_activity.py

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""" basics for an activitypub serializer """
from dataclasses import dataclass, fields, MISSING
from json import JSONEncoder
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from django.apps import apps
from django.db import IntegrityError, transaction
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from bookwyrm.connectors import ConnectorException, get_data
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from bookwyrm.tasks import app
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class ActivitySerializerError(ValueError):
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""" routine problems serializing activitypub json """
class ActivityEncoder(JSONEncoder):
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""" used to convert an Activity object into json """
def default(self, o):
return o.__dict__
@dataclass
class Link:
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""" for tagging a book in a status """
href: str
name: str
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type: str = "Link"
@dataclass
class Mention(Link):
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""" a subtype of Link for mentioning an actor """
type: str = "Mention"
@dataclass
class Signature:
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""" public key block """
creator: str
created: str
signatureValue: str
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type: str = "RsaSignature2017"
def naive_parse(activity_objects, activity_json, serializer=None):
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""" this navigates circular import issues """
if not serializer:
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if activity_json.get("publicKeyPem"):
# ugh
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activity_json["type"] = "PublicKey"
activity_type = activity_json.get("type")
try:
serializer = activity_objects[activity_type]
except KeyError as e:
# we know this exists and that we can't handle it
if activity_type in ["Question"]:
return None
raise ActivitySerializerError(e)
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return serializer(activity_objects=activity_objects, **activity_json)
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@dataclass(init=False)
class ActivityObject:
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""" actor activitypub json """
id: str
type: str
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def __init__(self, activity_objects=None, **kwargs):
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"""this lets you pass in an object with fields that aren't in the
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dataclass, which it ignores. Any field in the dataclass is required or
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has a default value"""
for field in fields(self):
try:
value = kwargs[field.name]
if value in (None, MISSING, {}):
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raise KeyError()
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try:
is_subclass = issubclass(field.type, ActivityObject)
except TypeError:
is_subclass = False
# serialize a model obj
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if hasattr(value, "to_activity"):
value = value.to_activity()
# parse a dict into the appropriate activity
elif is_subclass and isinstance(value, dict):
if activity_objects:
value = naive_parse(activity_objects, value)
else:
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value = naive_parse(
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activity_objects, value, serializer=field.type
)
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except KeyError:
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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)
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def to_model(self, model=None, instance=None, allow_create=True, save=True):
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""" convert from an activity to a model instance """
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model = model or get_model_from_type(self.type)
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# only reject statuses if we're potentially creating them
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if (
allow_create
and hasattr(model, "ignore_activity")
and model.ignore_activity(self)
):
return None
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# check for an existing instance
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instance = instance or model.find_existing(self.serialize())
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if not instance and not allow_create:
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# so that we don't create when we want to delete or update
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return None
instance = instance or model()
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for field in instance.simple_fields:
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try:
field.set_field_from_activity(instance, self)
except AttributeError as e:
raise ActivitySerializerError(e)
# image fields have to be set after other fields because they can save
# too early and jank up users
for field in instance.image_fields:
field.set_field_from_activity(instance, self, save=save)
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if not save:
return instance
with transaction.atomic():
# we can't set many to many and reverse fields on an unsaved object
try:
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try:
instance.save(broadcast=False)
except TypeError:
instance.save()
except IntegrityError as e:
raise ActivitySerializerError(e)
# add many to many fields, which have to be set post-save
for field in instance.many_to_many_fields:
# mention books/users, for example
field.set_field_from_activity(instance, self)
# reversed relationships in the models
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for (
model_field_name,
activity_field_name,
) in instance.deserialize_reverse_fields:
# attachments on Status, for example
values = getattr(self, activity_field_name)
if values is None or values is MISSING:
continue
model_field = getattr(model, model_field_name)
# creating a Work, model_field is 'editions'
# creating a User, model field is 'key_pair'
related_model = model_field.field.model
related_field_name = model_field.field.name
for item in values:
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set_related_field.delay(
related_model.__name__,
instance.__class__.__name__,
related_field_name,
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instance.remote_id,
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item,
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)
return instance
def serialize(self):
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""" convert to dictionary with context attr """
data = self.__dict__.copy()
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# recursively serialize
for (k, v) in data.items():
try:
if issubclass(type(v), ActivityObject):
data[k] = v.serialize()
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except TypeError:
pass
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data = {k: v for (k, v) in data.items() if v is not None}
data["@context"] = "https://www.w3.org/ns/activitystreams"
return data
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@app.task
@transaction.atomic
def set_related_field(
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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)
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with transaction.atomic():
if isinstance(data, str):
existing = model.find_existing_by_remote_id(data)
if existing:
data = existing.to_activity()
else:
data = get_data(data)
activity = model.activity_serializer(**data)
# 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:
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raise ValueError("Invalid related remote id: %s" % related_remote_id)
# set the origin's remote id on the activity so it will be there when
# the model instance is created
# edition.parentWork = instance, for example
model_field = getattr(model, related_field_name)
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if hasattr(model_field, "activitypub_field"):
setattr(
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activity, getattr(model_field, "activitypub_field"), instance.remote_id
)
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item = activity.to_model()
# if the related field isn't serialized (attachments on Status), then
# we have to set it post-creation
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if not hasattr(model_field, "activitypub_field"):
setattr(item, related_field_name, instance)
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item.save()
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def get_model_from_type(activity_type):
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""" given the activity, what type of model """
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models = apps.get_models()
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model = [
m
for m in models
if hasattr(m, "activity_serializer")
and hasattr(m.activity_serializer, "type")
and m.activity_serializer.type == activity_type
]
if not model:
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raise ActivitySerializerError(
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'No model found for activity type "%s"' % activity_type
)
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return model[0]
def resolve_remote_id(
remote_id, model=None, refresh=False, save=True, get_activity=False
):
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""" take a remote_id and return an instance, creating if necessary """
if model: # a bonus check we can do if we already know the model
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result = model.find_existing_by_remote_id(remote_id)
if result and not refresh:
return result if not get_activity else result.to_activity_dataclass()
# load the data and create the object
try:
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data = get_data(remote_id)
except ConnectorException:
raise ActivitySerializerError(
"Could not connect to host for remote_id in: %s" % (remote_id)
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)
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# determine the model implicitly, if not provided
# or if it's a model with subclasses like Status, check again
if not model or hasattr(model.objects, "select_subclasses"):
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model = get_model_from_type(data.get("type"))
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# check for existing items with shared unique identifiers
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result = model.find_existing(data)
if result and not refresh:
return result if not get_activity else result.to_activity_dataclass()
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item = model.activity_serializer(**data)
if get_activity:
return item
# if we're refreshing, "result" will be set and we'll update it
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return item.to_model(model=model, instance=result, save=save)