from typing import Optional from django.db import models from core.ld import canonicalise from core.signatures import HttpSignature from stator.models import State, StateField, StateGraph, StatorModel from users.models.identity import Identity class FollowStates(StateGraph): unrequested = State(try_interval=300) local_requested = State(try_interval=24 * 60 * 60) remote_requested = State(try_interval=24 * 60 * 60) accepted = State(externally_progressed=True) undone_locally = State(try_interval=60 * 60) undone_remotely = State() unrequested.transitions_to(local_requested) unrequested.transitions_to(remote_requested) local_requested.transitions_to(accepted) remote_requested.transitions_to(accepted) accepted.transitions_to(undone_locally) undone_locally.transitions_to(undone_remotely) @classmethod async def handle_unrequested(cls, instance: "Follow"): """ Follows that are unrequested need us to deliver the Follow object to the target server. """ follow = await instance.afetch_full() # Remote follows should not be here if not follow.source.local: return cls.remote_requested # Sign it and send it await HttpSignature.signed_request( uri=follow.target.inbox_uri, body=canonicalise(follow.to_ap()), private_key=follow.source.public_key, key_id=follow.source.public_key_id, ) return cls.local_requested @classmethod async def handle_local_requested(cls, instance: "Follow"): # TODO: Resend follow requests occasionally pass @classmethod async def handle_remote_requested(cls, instance: "Follow"): """ Items in remote_requested need us to send an Accept object to the source server. """ follow = await instance.afetch_full() await HttpSignature.signed_request( uri=follow.source.inbox_uri, body=canonicalise(follow.to_accept_ap()), private_key=follow.target.public_key, key_id=follow.target.public_key_id, ) return cls.accepted @classmethod async def handle_undone_locally(cls, instance: "Follow"): """ Delivers the Undo object to the target server """ follow = await instance.afetch_full() await HttpSignature.signed_request( uri=follow.target.inbox_uri, body=canonicalise(follow.to_undo_ap()), private_key=follow.source.public_key, key_id=follow.source.public_key_id, ) return cls.undone_remotely class Follow(StatorModel): """ When one user (the source) follows other (the target) """ source = models.ForeignKey( "users.Identity", on_delete=models.CASCADE, related_name="outbound_follows", ) target = models.ForeignKey( "users.Identity", on_delete=models.CASCADE, related_name="inbound_follows", ) uri = models.CharField(blank=True, null=True, max_length=500) note = models.TextField(blank=True, null=True) state = StateField(FollowStates) created = models.DateTimeField(auto_now_add=True) updated = models.DateTimeField(auto_now=True) class Meta: unique_together = [("source", "target")] def __str__(self): return f"#{self.id}: {self.source} → {self.target}" ### Alternate fetchers/constructors ### @classmethod def maybe_get(cls, source, target) -> Optional["Follow"]: """ Returns a follow if it exists between source and target """ try: return Follow.objects.get(source=source, target=target) except Follow.DoesNotExist: return None @classmethod def create_local(cls, source, target): """ Creates a Follow from a local Identity to the target (which can be local or remote). """ if not source.local: raise ValueError("You cannot initiate follows from a remote Identity") try: follow = Follow.objects.get(source=source, target=target) except Follow.DoesNotExist: follow = Follow.objects.create(source=source, target=target, uri="") follow.uri = source.actor_uri + f"follow/{follow.pk}/" # TODO: Local follow approvals if target.local: follow.state = FollowStates.accepted follow.save() return follow ### Async helpers ### async def afetch_full(self): """ Returns a version of the object with all relations pre-loaded """ return await Follow.objects.select_related( "source", "source__domain", "target" ).aget(pk=self.pk) ### ActivityPub (outbound) ### def to_ap(self): """ Returns the AP JSON for this object """ return { "type": "Follow", "id": self.uri, "actor": self.source.actor_uri, "object": self.target.actor_uri, } def to_accept_ap(self): """ Returns the AP JSON for this objects' accept. """ return { "type": "Accept", "id": self.uri + "#accept", "actor": self.target.actor_uri, "object": self.to_ap(), } def to_undo_ap(self): """ Returns the AP JSON for this objects' undo. """ return { "type": "Undo", "id": self.uri + "#undo", "actor": self.source.actor_uri, "object": self.to_ap(), } ### ActivityPub (inbound) ### @classmethod def by_ap(cls, data, create=False) -> "Follow": """ Retrieves a Follow instance by its ActivityPub JSON object. Optionally creates one if it's not present. Raises KeyError if it's not found and create is False. """ # Resolve source and target and see if a Follow exists source = Identity.by_actor_uri(data["actor"], create=create) target = Identity.by_actor_uri(data["object"]) follow = cls.maybe_get(source=source, target=target) # If it doesn't exist, create one in the remote_requested state if follow is None: if create: return cls.objects.create( source=source, target=target, uri=data["id"], state=FollowStates.remote_requested, ) else: raise KeyError( f"No follow with source {source} and target {target}", data ) else: return follow @classmethod def handle_request_ap(cls, data): """ Handles an incoming follow request """ follow = cls.by_ap(data, create=True) # Force it into remote_requested so we send an accept follow.transition_perform(FollowStates.remote_requested) @classmethod def handle_accept_ap(cls, data): """ Handles an incoming Follow Accept for one of our follows """ # Ensure the Accept actor is the Follow's object if data["actor"] != data["object"]["object"]: raise ValueError("Accept actor does not match its Follow object", data) # Resolve source and target and see if a Follow exists (it really should) try: follow = cls.by_ap(data["object"]) except KeyError: raise ValueError("No Follow locally for incoming Accept", data) # If the follow was waiting to be accepted, transition it if follow and follow.state in [ FollowStates.unrequested, FollowStates.local_requested, ]: follow.transition_perform(FollowStates.accepted) @classmethod def handle_undo_ap(cls, data): """ Handles an incoming Follow Undo for one of our follows """ # Ensure the Undo actor is the Follow's actor if data["actor"] != data["object"]["actor"]: raise ValueError("Undo actor does not match its Follow object", data) # Resolve source and target and see if a Follow exists (it hopefully does) try: follow = cls.by_ap(data["object"]) except KeyError: raise ValueError("No Follow locally for incoming Undo", data) # Delete the follow follow.delete()