My adventure in implementing #ActivityPub:

With the support of #ChatGPT I roughly understand how the protocol works and have a working implementation for at least #WebFinger and a json-LD conforming profile page.

There are some gaps in the structures, e.g. I can lookup my own user profile, @andreas@pramari.de, from microblog.pub, but not from mastodon.social yet. Obviously following does not yet work, although I have the data structures in place to store followers by profile.

Next up is the implementation of a mechanism to follow.

Today in #ActivityPub. Progress with the Inbox for my future actor on the #fediverse The server should now be able to receive events in the Inbox. With that, it does already differentiate over the activity type as defined for Server to Server Interaction. Today, it does take the actor, the activity if 'Follow' and create a following relationship later on. That will come handy once we start publishing to all Followers. It does roughly look like this:

class InboxView(View):
    @method_decorator(csrf_exempt)
    def dispatch(self, *args, **kwargs):
        return super().dispatch(*args, **kwargs)

    def post(self, request, *args, **kwargs):
        try:
            # Assuming the request payload is a valid JSON activity
            body = request.body.decode('utf-8')
            activity = json.loads(body)  # Deserialize the JSON payload
        except ValueError:
            return JsonResponse({'error': 'Invalid JSON'}, status=400)


        # Process the incoming activity
        # Save the activity to the database, perform necessary actions, etc.
        from .models import Activity

        activity_type = activity.get('type')
        activity_actor = activity.get('actor')
        activity_object = activity.get('object', {})
        object_type = activity_object.get("type")
        object_content = activity_object.get("content")

        match(activity_type):
            case 'Follow':
                # Store the follower in the database
                follower_profile, created = Profile.objects.get_or_create(
                    username=activity_actor
                )
                if created:
                    follower_profile.save()
                profile_to_follow = Profile.objects.get(username=request.user.username)
                follower_profile.following.add(profile_to_follow)

                # Optionally, you can send a response indicating the success of the follow request
                response = {
                    "type": "Follow",
                    "actor": request.build_absolute_uri(
                        reverse(
                            "profile",
                            args=[request.user.username]
                        )
                    ),
                    "object": request.build_absolute_uri(
                        reverse(
                            "profile",
                            args=[activity_actor]
                        )
                    ),
                    "id": "unique-id-for-the-response",
                }

                return JsonResponse(response)
            case 'Create':
                # Save the Follow activity to the database
                pass
 
            case _:
                logger.error("Activity Actor: {}".format(activity_actor))
                logger.error("Activity Object: {}".format(activity_object))
                print(activity)
                follow_activity = Activity(
                    actor=activity_actor,
                    verb=f'Unkown: {activity_type}',
                    object=activity_object
                )
                follow_activity.save()
                return JsonResponse({"error": "Invalid activity type"}, status=400)

        # Return a success response
        return JsonResponse({'status': 'success'})

With that, @andreas@pramari.de comes a bit closer.

Further advancements with @andreas@pramari.de: Yakshaving. Google Cloud SDK outdated. And Python on the development machine outdated, too.

@andreas

Did you learn about host-meta?

And that it should be called before you call WebFinger?

@reiver@mastodon.social kind of. I am implementing the server component that clients are calling.

/.well-known/host-meta is currently implemented as a static file.

What do I have to pay attention to in this flow?

@andreas

If you are implementing a server, then you will likely have to contact other servers.

(For example, to do a remote-follow.)

You should request host-meta on the remote-server first, to see where WebFinger is. And not just assume it is at the /.well-known/ path.

@reiver@mastodon.social Appreciate the pointer. I'm not there yet, but will consider when implementing the follow function. Right now I'm only over the 'being followed' part.