lemmy/crates/apub/src/collections/community_outbox.rs

use crate::{
  activity_lists::AnnouncableActivities,
  objects::{community::ApubCommunity, post::ApubPost},
  protocol::{
    activities::{
      community::announce::AnnounceActivity,
      create_or_update::page::CreateOrUpdatePage,
      CreateOrUpdateType,
    },
    collections::group_outbox::GroupOutbox,
  },
};
use activitypub_federation::{
  config::Data,
  kinds::collection::OrderedCollectionType,
  protocol::verification::verify_domains_match,
  traits::{ActivityHandler, Collection},
};
use futures::future::join_all;
use lemmy_api_common::{context::LemmyContext, utils::generate_outbox_url};
use lemmy_db_schema::{
  source::{person::Person, post::Post},
  traits::Crud,
  utils::FETCH_LIMIT_MAX,
};
use lemmy_utils::error::LemmyError;
use url::Url;

#[derive(Clone, Debug)]
pub(crate) struct ApubCommunityOutbox(());

#[async_trait::async_trait]
impl Collection for ApubCommunityOutbox {
  type Owner = ApubCommunity;
  type DataType = LemmyContext;
  type Kind = GroupOutbox;
  type Error = LemmyError;

  #[tracing::instrument(skip_all)]
  async fn read_local(
    owner: &Self::Owner,
    data: &Data<Self::DataType>,
  ) -> Result<Self::Kind, LemmyError> {
    let post_list: Vec<ApubPost> = Post::list_for_community(&mut data.pool(), owner.id)
      .await?
      .into_iter()
      .map(Into::into)
      .collect();
    let mut ordered_items = vec![];
    for post in post_list {
      let person = Person::read(&mut data.pool(), post.creator_id)
        .await?
        .into();
      let create =
        CreateOrUpdatePage::new(post, &person, owner, CreateOrUpdateType::Create, data).await?;
      let announcable = AnnouncableActivities::CreateOrUpdatePost(create);
      let announce = AnnounceActivity::new(announcable.try_into()?, owner, data)?;
      ordered_items.push(announce);
    }

    Ok(GroupOutbox {
      r#type: OrderedCollectionType::OrderedCollection,
      id: generate_outbox_url(&owner.actor_id)?.into(),
      total_items: ordered_items.len() as i32,
      ordered_items,
    })
  }

  #[tracing::instrument(skip_all)]
  async fn verify(
    group_outbox: &GroupOutbox,
    expected_domain: &Url,
    _data: &Data<Self::DataType>,
  ) -> Result<(), LemmyError> {
    verify_domains_match(expected_domain, &group_outbox.id)?;
    Ok(())
  }

  #[tracing::instrument(skip_all)]
  async fn from_json(
    apub: Self::Kind,
    _owner: &Self::Owner,
    data: &Data<Self::DataType>,
  ) -> Result<Self, LemmyError> {
    let mut outbox_activities = apub.ordered_items;
    if outbox_activities.len() as i64 > FETCH_LIMIT_MAX {
      outbox_activities = outbox_activities
        .get(0..(FETCH_LIMIT_MAX as usize))
        .unwrap_or_default()
        .to_vec();
    }

    // We intentionally ignore errors here. This is because the outbox might contain posts from old
    // Lemmy versions, or from other software which we cant parse. In that case, we simply skip the
    // item and only parse the ones that work.
    // process items in parallel, to avoid long delay from fetch_site_metadata() and other processing
    join_all(outbox_activities.into_iter().map(|activity| {
      async {
        // Receiving announce requires at least one local community follower for anti spam purposes.
        // This won't be the case for newly fetched communities, so we extract the inner activity
        // and handle it directly to bypass this check.
        let inner = activity.object.object(data).await.map(TryInto::try_into);
        if let Ok(Ok(AnnouncableActivities::CreateOrUpdatePost(inner))) = inner {
          let verify = inner.verify(data).await;
          if verify.is_ok() {
            inner.receive(data).await.ok();
          }
        }
      }
    }))
    .await;

    // This return value is unused, so just set an empty vec
    Ok(ApubCommunityOutbox(()))
  }
}