Generalize how remote objects and link types may be stored

[Menrath]

Follow up of #1297

Currently most remote objects are only stored as comments. This is fine, as comments are Notes only and there is no other remote comment than replies to original posts.

The Friends plugin (@akirk) stores incoming objects too, probably in it's own way. The Event Bridge does too, again a different implementation.

I suggest to start with introduce a unified way how to mark posts of all post types as "remote with ActivityPub source", e.g. via a unified meta-key that references an actor (ap_actor).

Maybe think of allowing relationships between a comment and a post, replies are mostly Notes, but do they have to be?

[Menrath]

I mention this yesterday in a discussion with @akirk. Maybe a custom post status, e.g. activitypub_remote along with a post_meta _ap_actor, could be proposed and advertised.

[obenland]

@Menrath Is this fixed with the new ap_post post type?

[Menrath]

@obenland I will review it next week!

[Menrath]

@obenland

TL/DR: I guess to answer that question I have to really work with the code hands on and migrate features of the Event Bridge to it, not just read and review!

I guess it is not solved completely, but the recent changes around the inbox/attachments/ap_post etc are huge improvements and are laying a good foundation for a lot of cool applications to come!

I looked into the code, but I think it's easier to give you two example scenarios, than to point out each line of code where a filter/change etc. could be useful at this moment.

1. Event-Bridge like aggregation of events. Following other ActivityPub profiles in order to list their events too. I guess I could hook into the follow table to insert an boolean trigger to activate the behaviour for each followed Actor (not just follow, but also use that Actor as an event source and list their events). When receiving remote ap_actors I need to create an post with the corresponding event post type.

It is complex. I guess I could currently hook and disable the creation of an ap_post and still create an event post. The attachment class and the ap_post class are quite tensely linked, I guess I would have a hard time using it on another post_type than ap_post. In order to give better feedback, I need to really dive into migrating the existing features and make use of your modernisations and really go to the point where there are missing parts, it's hard to tell from an observer point of view. I can start coding so next week.

2. A more simple scenario: You build an ActivityPub reader within WordPress. There you show a timeline which is basically ap_posts. But when receiving an object type that is a more special object type the activity_to_post is maybe not enough. Maybe you want to control this transformation a bit more nuanced.

The transformation from ActivityPub-object to WP_Post (ap_post) is quite static. Maybe a Factory could be useful. I did one in the Event Bridge an just called that process transmogrify not to mix up the two directions.