lemmy/server/src/apub/fetcher.rs

use super::*;

// Fetch nodeinfo metadata from a remote instance.
fn _fetch_node_info(domain: &str) -> Result<NodeInfo, Error> {
  let well_known_uri = Url::parse(&format!(
    "{}://{}/.well-known/nodeinfo",
    get_apub_protocol_string(),
    domain
  ))?;
  let well_known = fetch_remote_object::<NodeInfoWellKnown>(&well_known_uri)?;
  Ok(fetch_remote_object::<NodeInfo>(&well_known.links.href)?)
}

/// Fetch any type of ActivityPub object, handling things like HTTP headers, deserialisation,
/// timeouts etc.
pub fn fetch_remote_object<Response>(url: &Url) -> Result<Response, Error>
where
  Response: for<'de> Deserialize<'de>,
{
  if !is_apub_id_valid(&url) {
    return Err(format_err!("Activitypub uri invalid or blocked: {}", url));
  }
  // TODO: this function should return a future
  let timeout = Duration::from_secs(60);
  let text = Request::get(url.as_str())
    .header("Accept", APUB_JSON_CONTENT_TYPE)
    .connect_timeout(timeout)
    .timeout(timeout)
    .body(())?
    .send()?
    .text()?;
  let res: Response = serde_json::from_str(&text)?;
  Ok(res)
}

/// The types of ActivityPub objects that can be fetched directly by searching for their ID.
#[serde(untagged)]
#[derive(serde::Deserialize, Debug)]
pub enum SearchAcceptedObjects {
  Person(Box<PersonExt>),
  Group(Box<GroupExt>),
  Page(Box<Page>),
}

/// Attempt to parse the query as URL, and fetch an ActivityPub object from it.
///
/// Some working examples for use with the docker/federation/ setup:
/// http://lemmy_alpha:8540/c/main
/// http://lemmy_alpha:8540/u/lemmy_alpha
/// http://lemmy_alpha:8540/p/3
pub fn search_by_apub_id(query: &str, conn: &PgConnection) -> Result<SearchResponse, Error> {
  let query_url = Url::parse(&query)?;
  let mut response = SearchResponse {
    type_: SearchType::All.to_string(),
    comments: vec![],
    posts: vec![],
    communities: vec![],
    users: vec![],
  };
  match fetch_remote_object::<SearchAcceptedObjects>(&query_url)? {
    SearchAcceptedObjects::Person(p) => {
      let user_uri = p.base.base.object_props.get_id().unwrap().to_string();
      let user = get_or_fetch_and_upsert_remote_user(&user_uri, &conn)?;
      response.users = vec![UserView::read(conn, user.id)?];
    }
    SearchAcceptedObjects::Group(g) => {
      let community_uri = g.base.base.object_props.get_id().unwrap().to_string();
      let community = get_or_fetch_and_upsert_remote_community(&community_uri, &conn)?;
      // TODO Maybe at some point in the future, fetch all the history of a community
      // fetch_community_outbox(&c, conn)?;
      response.communities = vec![CommunityView::read(conn, community.id, None)?];
    }
    SearchAcceptedObjects::Page(p) => {
      let p = upsert_post(&PostForm::from_apub(&p, conn)?, conn)?;
      response.posts = vec![PostView::read(conn, p.id, None)?];
    }
  }
  Ok(response)
}

/// Check if a remote user exists, create if not found, if its too old update it.Fetch a user, insert/update it in the database and return the user.
pub fn get_or_fetch_and_upsert_remote_user(
  apub_id: &str,
  conn: &PgConnection,
) -> Result<User_, Error> {
  match User_::read_from_actor_id(&conn, &apub_id) {
    Ok(u) => {
      // If its older than a day, re-fetch it
      if !u.local
        && u
          .last_refreshed_at
          .lt(&(naive_now() - chrono::Duration::days(1)))
      {
        debug!("Fetching and updating from remote user: {}", apub_id);
        let person = fetch_remote_object::<PersonExt>(&Url::parse(apub_id)?)?;
        let mut uf = UserForm::from_apub(&person, &conn)?;
        uf.last_refreshed_at = Some(naive_now());
        Ok(User_::update(&conn, u.id, &uf)?)
      } else {
        Ok(u)
      }
    }
    Err(NotFound {}) => {
      debug!("Fetching and creating remote user: {}", apub_id);
      let person = fetch_remote_object::<PersonExt>(&Url::parse(apub_id)?)?;
      let uf = UserForm::from_apub(&person, &conn)?;
      Ok(User_::create(conn, &uf)?)
    }
    Err(e) => Err(Error::from(e)),
  }
}

/// Check if a remote community exists, create if not found, if its too old update it.Fetch a community, insert/update it in the database and return the community.
pub fn get_or_fetch_and_upsert_remote_community(
  apub_id: &str,
  conn: &PgConnection,
) -> Result<Community, Error> {
  match Community::read_from_actor_id(&conn, &apub_id) {
    Ok(c) => {
      // If its older than a day, re-fetch it
      if !c.local
        && c
          .last_refreshed_at
          .lt(&(naive_now() - chrono::Duration::days(1)))
      {
        debug!("Fetching and updating from remote community: {}", apub_id);
        let group = fetch_remote_object::<GroupExt>(&Url::parse(apub_id)?)?;
        let mut cf = CommunityForm::from_apub(&group, conn)?;
        cf.last_refreshed_at = Some(naive_now());
        Ok(Community::update(&conn, c.id, &cf)?)
      } else {
        Ok(c)
      }
    }
    Err(NotFound {}) => {
      debug!("Fetching and creating remote community: {}", apub_id);
      let group = fetch_remote_object::<GroupExt>(&Url::parse(apub_id)?)?;
      let cf = CommunityForm::from_apub(&group, conn)?;
      let community = Community::create(conn, &cf)?;

      // Also add the community moderators too
      let creator_and_moderator_uris = group
        .base
        .base
        .object_props
        .get_many_attributed_to_xsd_any_uris()
        .unwrap();
      let creator_and_moderators = creator_and_moderator_uris
        .map(|c| get_or_fetch_and_upsert_remote_user(&c.to_string(), &conn).unwrap())
        .collect::<Vec<User_>>();

      for mod_ in creator_and_moderators {
        let community_moderator_form = CommunityModeratorForm {
          community_id: community.id,
          user_id: mod_.id,
        };
        CommunityModerator::join(&conn, &community_moderator_form)?;
      }

      Ok(community)
    }
    Err(e) => Err(Error::from(e)),
  }
}

fn upsert_post(post_form: &PostForm, conn: &PgConnection) -> Result<Post, Error> {
  let existing = Post::read_from_apub_id(conn, &post_form.ap_id);
  match existing {
    Err(NotFound {}) => Ok(Post::create(conn, &post_form)?),
    Ok(p) => Ok(Post::update(conn, p.id, &post_form)?),
    Err(e) => Err(Error::from(e)),
  }
}

// TODO It should not be fetching data from a community outbox.
// All posts, comments, comment likes, etc should be posts to our community_inbox
// The only data we should be periodically fetching (if it hasn't been fetched in the last day
// maybe), is community and user actors
// and user actors
// Fetch all posts in the outbox of the given user, and insert them into the database.
// fn fetch_community_outbox(community: &Community, conn: &PgConnection) -> Result<Vec<Post>, Error> {
//   let outbox_url = Url::parse(&community.get_outbox_url())?;
//   let outbox = fetch_remote_object::<OrderedCollection>(&outbox_url)?;
//   let items = outbox.collection_props.get_many_items_base_boxes();

//   Ok(
//     items
//       .unwrap()
//       .map(|obox: &BaseBox| -> Result<PostForm, Error> {
//         let page = obox.clone().to_concrete::<Page>()?;
//         PostForm::from_page(&page, conn)
//       })
//       .map(|pf| upsert_post(&pf?, conn))
//       .collect::<Result<Vec<Post>, Error>>()?,
//   )
// }