From 44996917c78f2919d31fd4e2fd001a9613347184 Mon Sep 17 00:00:00 2001
From: Mouse Reeve <mousereeve@riseup.net>
Date: Thu, 4 Feb 2021 12:36:39 -0800
Subject: [PATCH] Activitypub model code in more files

---
 bookwyrm/models/activitypub_mixin/__init__.py |   1 +
 .../activitypub_mixin/activitypub_mixin.py    | 330 ++++++++++++++++++
 .../activitypub_mixin/ordered_collection.py   | 115 ++++++
 3 files changed, 446 insertions(+)
 create mode 100644 bookwyrm/models/activitypub_mixin/__init__.py
 create mode 100644 bookwyrm/models/activitypub_mixin/activitypub_mixin.py
 create mode 100644 bookwyrm/models/activitypub_mixin/ordered_collection.py

diff --git a/bookwyrm/models/activitypub_mixin/__init__.py b/bookwyrm/models/activitypub_mixin/__init__.py
new file mode 100644
index 00000000..b6e690fd
--- /dev/null
+++ b/bookwyrm/models/activitypub_mixin/__init__.py
@@ -0,0 +1 @@
+from . import *
diff --git a/bookwyrm/models/activitypub_mixin/activitypub_mixin.py b/bookwyrm/models/activitypub_mixin/activitypub_mixin.py
new file mode 100644
index 00000000..61f042ee
--- /dev/null
+++ b/bookwyrm/models/activitypub_mixin/activitypub_mixin.py
@@ -0,0 +1,330 @@
+''' base model with default fields '''
+from base64 import b64encode
+from functools import reduce
+import json
+import operator
+from uuid import uuid4
+import requests
+
+from Crypto.PublicKey import RSA
+from Crypto.Signature import pkcs1_15
+from Crypto.Hash import SHA256
+from django.apps import apps
+from django.db import models
+from django.db.models import Q
+from django.dispatch import receiver
+from django.utils.http import http_date
+
+
+from bookwyrm import activitypub
+from bookwyrm.settings import USER_AGENT
+from bookwyrm.signatures import make_signature, make_digest
+from bookwyrm.tasks import app
+from .fields import ImageField, ManyToManyField
+
+
+class ActivitypubMixin:
+    ''' add this mixin for models that are AP serializable '''
+    activity_serializer = lambda: {}
+    reverse_unfurl = False
+
+    def __init__(self, *args, **kwargs):
+        ''' collect some info on model fields '''
+        self.image_fields = []
+        self.many_to_many_fields = []
+        self.simple_fields = [] # "simple"
+        for field in self._meta.get_fields():
+            if not hasattr(field, 'field_to_activity'):
+                continue
+
+            if isinstance(field, ImageField):
+                self.image_fields.append(field)
+            elif isinstance(field, ManyToManyField):
+                self.many_to_many_fields.append(field)
+            else:
+                self.simple_fields.append(field)
+
+        self.activity_fields = self.image_fields + \
+                self.many_to_many_fields + self.simple_fields
+
+        self.deserialize_reverse_fields = self.deserialize_reverse_fields \
+                if hasattr(self, 'deserialize_reverse_fields') else []
+        self.serialize_reverse_fields = self.serialize_reverse_fields \
+                if hasattr(self, 'serialize_reverse_fields') else []
+
+        super().__init__(*args, **kwargs)
+
+
+    def delete(self, *args, **kwargs):
+        ''' broadcast suitable delete activities '''
+
+
+    @classmethod
+    def find_existing_by_remote_id(cls, remote_id):
+        ''' look up a remote id in the db '''
+        return cls.find_existing({'id': remote_id})
+
+    @classmethod
+    def find_existing(cls, data):
+        ''' compare data to fields that can be used for deduplation.
+        This always includes remote_id, but can also be unique identifiers
+        like an isbn for an edition '''
+        filters = []
+        for field in cls._meta.get_fields():
+            if not hasattr(field, 'deduplication_field') or \
+                    not field.deduplication_field:
+                continue
+
+            value = data.get(field.get_activitypub_field())
+            if not value:
+                continue
+            filters.append({field.name: value})
+
+        if hasattr(cls, 'origin_id') and 'id' in data:
+            # kinda janky, but this handles special case for books
+            filters.append({'origin_id': data['id']})
+
+        if not filters:
+            # if there are no deduplication fields, it will match the first
+            # item no matter what. this shouldn't happen but just in case.
+            return None
+
+        objects = cls.objects
+        if hasattr(objects, 'select_subclasses'):
+            objects = objects.select_subclasses()
+
+        # an OR operation on all the match fields
+        match = objects.filter(
+            reduce(
+                operator.or_, (Q(**f) for f in filters)
+            )
+        )
+        # there OUGHT to be only one match
+        return match.first()
+
+
+    def broadcast(self, activity, sender, software=None):
+        ''' send out an activity '''
+        broadcast_task.delay(
+            sender.id,
+            json.dumps(activity, cls=activitypub.ActivityEncoder),
+            self.get_recipients(software=software)
+        )
+
+
+    def get_recipients(self, software=None):
+        ''' figure out which inbox urls to post to '''
+        # first we have to figure out who should receive this activity
+        privacy = self.privacy if hasattr(self, 'privacy') else 'public'
+        # is this activity owned by a user (statuses, lists, shelves), or is it
+        # general to the instance (like books)
+        user = self.user if hasattr(self, 'user') else None
+        if not user and self.__model__ == 'user':
+            # or maybe the thing itself is a user
+            user = self
+        # find anyone who's tagged in a status, for example
+        mentions = self.mention_users if hasattr(self, 'mention_users') else []
+
+        # we always send activities to explicitly mentioned users' inboxes
+        recipients = [u.inbox for u in mentions or []]
+
+        # unless it's a dm, all the followers should receive the activity
+        if privacy != 'direct':
+            user_model = apps.get_model('bookwyrm.User', require_ready=True)
+            # filter users first by whether they're using the desired software
+            # this lets us send book updates only to other bw servers
+            queryset = user_model.objects.filter(
+                bookwyrm_user=(software == 'bookwyrm')
+            )
+            # if there's a user, we only want to send to the user's followers
+            if user:
+                queryset = queryset.filter(following=user)
+
+            # ideally, we will send to shared inboxes for efficiency
+            shared_inboxes = queryset.filter(
+                shared_inbox__isnull=False
+            ).values_list('shared_inbox', flat=True).distinct()
+            # but not everyone has a shared inbox
+            inboxes = queryset.filter(
+                shared_inboxes__isnull=True
+            ).values_list('inbox', flat=True)
+            recipients += list(shared_inboxes) + list(inboxes)
+        return recipients
+
+
+    def to_activity(self):
+        ''' convert from a model to an activity '''
+        activity = generate_activity(self)
+        return self.activity_serializer(**activity).serialize()
+
+
+    def to_create_activity(self, user, **kwargs):
+        ''' returns the object wrapped in a Create activity '''
+        activity_object = self.to_activity(**kwargs)
+
+        signature = None
+        create_id = self.remote_id + '/activity'
+        if 'content' in activity_object:
+            signer = pkcs1_15.new(RSA.import_key(user.key_pair.private_key))
+            content = activity_object['content']
+            signed_message = signer.sign(SHA256.new(content.encode('utf8')))
+
+            signature = activitypub.Signature(
+                creator='%s#main-key' % user.remote_id,
+                created=activity_object['published'],
+                signatureValue=b64encode(signed_message).decode('utf8')
+            )
+
+        return activitypub.Create(
+            id=create_id,
+            actor=user.remote_id,
+            to=activity_object['to'],
+            cc=activity_object['cc'],
+            object=activity_object,
+            signature=signature,
+        ).serialize()
+
+
+    def to_delete_activity(self, user):
+        ''' notice of deletion '''
+        return activitypub.Delete(
+            id=self.remote_id + '/activity',
+            actor=user.remote_id,
+            to=['%s/followers' % user.remote_id],
+            cc=['https://www.w3.org/ns/activitystreams#Public'],
+            object=self.to_activity(),
+        ).serialize()
+
+
+    def to_update_activity(self, user):
+        ''' wrapper for Updates to an activity '''
+        activity_id = '%s#update/%s' % (self.remote_id, uuid4())
+        return activitypub.Update(
+            id=activity_id,
+            actor=user.remote_id,
+            to=['https://www.w3.org/ns/activitystreams#Public'],
+            object=self.to_activity()
+        ).serialize()
+
+
+    def to_undo_activity(self, user):
+        ''' undo an action '''
+        return activitypub.Undo(
+            id='%s#undo' % self.remote_id,
+            actor=user.remote_id,
+            object=self.to_activity()
+        ).serialize()
+
+
+
+
+def generate_activity(obj):
+    ''' go through the fields on an object '''
+    activity = {}
+    for field in obj.activity_fields:
+        field.set_activity_from_field(activity, obj)
+
+    if hasattr(obj, 'serialize_reverse_fields'):
+        # for example, editions of a work
+        for model_field_name, activity_field_name, sort_field in \
+                obj.serialize_reverse_fields:
+            related_field = getattr(obj, model_field_name)
+            activity[activity_field_name] = \
+                    unfurl_related_field(related_field, sort_field)
+
+    if not activity.get('id'):
+        activity['id'] = obj.get_remote_id()
+    return activity
+
+
+def unfurl_related_field(related_field, sort_field=None):
+    ''' load reverse lookups (like public key owner or Status attachment '''
+    if hasattr(related_field, 'all'):
+        return [unfurl_related_field(i) for i in related_field.order_by(
+            sort_field).all()]
+    if related_field.reverse_unfurl:
+        return related_field.field_to_activity()
+    return related_field.remote_id
+
+
+@app.task
+def broadcast_task(sender_id, activity, recipients):
+    ''' the celery task for broadcast '''
+    user_model = apps.get_model('bookwyrm.User', require_ready=True)
+    sender = user_model.objects.get(id=sender_id)
+    errors = []
+    for recipient in recipients:
+        try:
+            sign_and_send(sender, activity, recipient)
+        except requests.exceptions.HTTPError as e:
+            errors.append({
+                'error': str(e),
+                'recipient': recipient,
+                'activity': activity,
+            })
+    return errors
+
+
+def sign_and_send(sender, data, destination):
+    ''' crpyto whatever and http junk '''
+    now = http_date()
+
+    if not sender.key_pair.private_key:
+        # this shouldn't happen. it would be bad if it happened.
+        raise ValueError('No private key found for sender')
+
+    digest = make_digest(data)
+
+    response = requests.post(
+        destination,
+        data=data,
+        headers={
+            'Date': now,
+            'Digest': digest,
+            'Signature': make_signature(sender, destination, now, digest),
+            'Content-Type': 'application/activity+json; charset=utf-8',
+            'User-Agent': USER_AGENT,
+        },
+    )
+    if not response.ok:
+        response.raise_for_status()
+    return response
+
+
+@receiver(models.signals.post_save)
+#pylint: disable=unused-argument
+def execute_after_save(sender, instance, created, *args, **kwargs):
+    ''' broadcast when a model instance is created or updated '''
+    # user content like statuses, lists, and shelves, have a "user" field
+    user = instance.user if hasattr(instance, 'user') else None
+    if user and not user.local:
+        # we don't want to broadcast when we save remote activities
+        return
+
+    if created:
+        if not user:
+            # book data and users don't need to broadcast on creation
+            return
+
+        # ordered collection items get "Add"ed
+        if hasattr(instance, 'to_add_activity'):
+            activity = instance.to_add_activity()
+        else:
+            # everything else gets "Create"d
+            activity = instance.to_create_activity(user)
+    else:
+        # now, handle updates
+        if not user:
+            # users don't have associated users, they ARE users
+            if sender.__class__ == 'User':
+                user = instance
+            # book data trakcs last editor
+            elif hasattr(instance, 'last_edited_by'):
+                user = instance.last_edited_by
+        # again, if we don't know the user or they're remote, don't bother
+        if not user or not user.local:
+            return
+        activity = instance.to_update_activity(user)
+
+    if activity and user and user.local:
+        instance.broadcast(activity, user)
diff --git a/bookwyrm/models/activitypub_mixin/ordered_collection.py b/bookwyrm/models/activitypub_mixin/ordered_collection.py
new file mode 100644
index 00000000..e755e522
--- /dev/null
+++ b/bookwyrm/models/activitypub_mixin/ordered_collection.py
@@ -0,0 +1,115 @@
+''' lists of objects '''
+from django.core.paginator import Paginator
+
+from bookwyrm import activitypub
+from bookwyrm.settings import PAGE_LENGTH
+from . import ActivitypubMixin, generate_activity
+
+
+class OrderedCollectionPageMixin(ActivitypubMixin):
+    ''' just the paginator utilities, so you don't HAVE to
+        override ActivitypubMixin's to_activity (ie, for outbox '''
+    @property
+    def collection_remote_id(self):
+        ''' this can be overriden if there's a special remote id, ie outbox '''
+        return self.remote_id
+
+
+    def to_ordered_collection(self, queryset, \
+            remote_id=None, page=False, collection_only=False, **kwargs):
+        ''' an ordered collection of whatevers '''
+        if not queryset.ordered:
+            raise RuntimeError('queryset must be ordered')
+
+        remote_id = remote_id or self.remote_id
+        if page:
+            return to_ordered_collection_page(
+                queryset, remote_id, **kwargs)
+
+        if collection_only or not hasattr(self, 'activity_serializer'):
+            serializer = activitypub.OrderedCollection
+            activity = {}
+        else:
+            serializer = self.activity_serializer
+            # a dict from the model fields
+            activity = generate_activity(self)
+
+        if remote_id:
+            activity['id'] = remote_id
+
+        paginated = Paginator(queryset, PAGE_LENGTH)
+        # add computed fields specific to orderd collections
+        activity['totalItems'] = paginated.count
+        activity['first'] = '%s?page=1' % remote_id
+        activity['last'] = '%s?page=%d' % (remote_id, paginated.num_pages)
+
+        return serializer(**activity).serialize()
+
+
+# pylint: disable=unused-argument
+def to_ordered_collection_page(
+        queryset, remote_id, id_only=False, page=1, **kwargs):
+    ''' serialize and pagiante a queryset '''
+    paginated = Paginator(queryset, PAGE_LENGTH)
+
+    activity_page = paginated.page(page)
+    if id_only:
+        items = [s.remote_id for s in activity_page.object_list]
+    else:
+        items = [s.to_activity() for s in activity_page.object_list]
+
+    prev_page = next_page = None
+    if activity_page.has_next():
+        next_page = '%s?page=%d' % (remote_id, activity_page.next_page_number())
+    if activity_page.has_previous():
+        prev_page = '%s?page=%d' % \
+                (remote_id, activity_page.previous_page_number())
+    return activitypub.OrderedCollectionPage(
+        id='%s?page=%s' % (remote_id, page),
+        partOf=remote_id,
+        orderedItems=items,
+        next=next_page,
+        prev=prev_page
+    ).serialize()
+
+
+class OrderedCollectionMixin(OrderedCollectionPageMixin):
+    ''' extends activitypub models to work as ordered collections '''
+    @property
+    def collection_queryset(self):
+        ''' usually an ordered collection model aggregates a different model '''
+        raise NotImplementedError('Model must define collection_queryset')
+
+    activity_serializer = activitypub.OrderedCollection
+
+    def to_activity(self, **kwargs):
+        ''' an ordered collection of the specified model queryset  '''
+        return self.to_ordered_collection(self.collection_queryset, **kwargs)
+
+
+class CollectionItemMixin(ActivitypubMixin):
+    ''' for items that are part of an (Ordered)Collection '''
+    activity_serializer = activitypub.Add
+    object_field = collection_field = None
+
+    def to_add_activity(self):
+        ''' AP for shelving a book'''
+        object_field = getattr(self, self.object_field)
+        collection_field = getattr(self, self.collection_field)
+        return activitypub.Add(
+            id='%s#add' % self.remote_id,
+            actor=self.user.remote_id,
+            object=object_field.to_activity(),
+            target=collection_field.remote_id
+        ).serialize()
+
+    def to_remove_activity(self):
+        ''' AP for un-shelving a book'''
+        object_field = getattr(self, self.object_field)
+        collection_field = getattr(self, self.collection_field)
+        return activitypub.Remove(
+            id='%s#remove' % self.remote_id,
+            actor=self.user.remote_id,
+            object=object_field.to_activity(),
+            target=collection_field.remote_id
+        ).serialize()