moviewyrm/bookwyrm/activitypub/base_activity.py
2021-09-17 21:39:18 -07:00

306 lines
11 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 IntegrityError, transaction
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
# pylint: disable=invalid-name
class Signature:
"""public key block"""
creator: str
created: str
signatureValue: str
type: str = "RsaSignature2017"
def naive_parse(activity_objects, activity_json, serializer=None):
"""this navigates circular import issues by looking up models' serializers"""
if not serializer:
if activity_json.get("publicKeyPem"):
# ugh
activity_json["type"] = "PublicKey"
activity_type = activity_json.get("type")
try:
serializer = activity_objects[activity_type]
except KeyError as err:
# we know this exists and that we can't handle it
if activity_type in ["Question"]:
return None
raise ActivitySerializerError(err)
return serializer(activity_objects=activity_objects, **activity_json)
@dataclass(init=False)
class ActivityObject:
"""actor activitypub json"""
id: str
type: str
def __init__(self, activity_objects=None, **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]
if value in (None, MISSING, {}):
raise KeyError()
try:
is_subclass = issubclass(field.type, ActivityObject)
except TypeError:
is_subclass = False
# serialize a model obj
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:
value = naive_parse(
activity_objects, value, serializer=field.type
)
except KeyError:
if field.default == MISSING and field.default_factory == MISSING:
raise ActivitySerializerError(
f"Missing required field: {field.name}"
)
value = field.default
setattr(self, field.name, value)
# pylint: disable=too-many-locals,too-many-branches,too-many-arguments
def to_model(
self, model=None, instance=None, allow_create=True, save=True, overwrite=True
):
"""convert from an activity to a model instance"""
model = model or get_model_from_type(self.type)
# only reject statuses if we're potentially creating them
if (
allow_create
and hasattr(model, "ignore_activity")
and model.ignore_activity(self)
):
return None
# check for an existing instance
instance = instance or model.find_existing(self.serialize())
if not instance and not allow_create:
# so that we don't create when we want to delete or update
return None
instance = instance or model()
# keep track of what we've changed
update_fields = []
# sets field on the model using the activity value
for field in instance.simple_fields:
try:
changed = field.set_field_from_activity(
instance, self, overwrite=overwrite
)
if changed:
update_fields.append(field.name)
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:
changed = field.set_field_from_activity(
instance, self, save=save, overwrite=overwrite
)
if changed:
update_fields.append(field.name)
if not save:
return instance
with transaction.atomic():
# can't force an update on fields unless the object already exists in the db
if not instance.id:
update_fields = None
# we can't set many to many and reverse fields on an unsaved object
try:
try:
instance.save(broadcast=False, update_fields=update_fields)
except TypeError:
instance.save(update_fields=update_fields)
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
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:
set_related_field.delay(
related_model.__name__,
instance.__class__.__name__,
related_field_name,
instance.remote_id,
item,
)
return instance
def serialize(self):
"""convert to dictionary with context attr"""
data = self.__dict__.copy()
# recursively serialize
for (k, v) in data.items():
try:
if issubclass(type(v), ActivityObject):
data[k] = v.serialize()
except TypeError:
pass
data = {k: v for (k, v) in data.items() if v is not None}
data["@context"] = "https://www.w3.org/ns/activitystreams"
return data
@app.task(queue="medium_priority")
@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(f"bookwyrm.{model_name}", require_ready=True)
origin_model = apps.get_model(f"bookwyrm.{origin_model_name}", require_ready=True)
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:
raise ValueError(f"Invalid related remote id: {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)
if hasattr(model_field, "activitypub_field"):
setattr(
activity, getattr(model_field, "activitypub_field"), instance.remote_id
)
item = activity.to_model()
# if the related field isn't serialized (attachments on Status), then
# we have to set it post-creation
if not hasattr(model_field, "activitypub_field"):
setattr(item, related_field_name, instance)
item.save()
def get_model_from_type(activity_type):
"""given the activity, what type of model"""
models = apps.get_models()
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:
raise ActivitySerializerError(
f'No model found for activity type "{activity_type}"'
)
return model[0]
def resolve_remote_id(
remote_id, model=None, refresh=False, save=True, get_activity=False
):
"""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
if isinstance(model, str):
model = apps.get_model(f"bookwyrm.{model}", require_ready=True)
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:
data = get_data(remote_id)
except ConnectorException:
raise ActivitySerializerError(
f"Could not connect to host for remote_id: {remote_id}"
)
# 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"):
model = get_model_from_type(data.get("type"))
# check for existing items with shared unique identifiers
result = model.find_existing(data)
if result and not refresh:
return result if not get_activity else result.to_activity_dataclass()
item = model.activity_serializer(**data)
if get_activity:
return item
# if we're refreshing, "result" will be set and we'll update it
return item.to_model(model=model, instance=result, save=save)