Try to implement federated user deletion (fixes #1284)

lemmy_api/src/user.rs

@@ -13,7 +13,7 @@ use anyhow::Context;
 use bcrypt::verify;
 use captcha::{gen, Difficulty};
 use chrono::Duration;
-use lemmy_apub::ApubObjectType;
+use lemmy_apub::{ActorType, ApubObjectType};
 use lemmy_db::{
   comment::*,
   comment_report::CommentReportView,
@@ -877,6 +877,9 @@ impl Perform for DeleteAccount {
       return Err(APIError::err("password_incorrect").into());
     }
 
+    // Send activity to delete user on federated instances
+    user.send_delete(context).await?;
+
     // Comments
     let user_id = user.id;
     let permadelete = move |conn: &'_ _| Comment::permadelete_for_creator(conn, user_id);

lemmy_apub/src/activities/send/user.rs

@@ -5,13 +5,16 @@ use crate::{
 };
 use activitystreams::{
   activity::{
-    kind::{FollowType, UndoType},
+    kind::{DeleteType, FollowType, UndoType},
+    Delete,
     Follow,
     Undo,
   },
   base::{AnyBase, BaseExt, ExtendsExt},
   object::ObjectExt,
+  public,
 };
+use itertools::Itertools;
 use lemmy_db::{
   community::{Community, CommunityFollower, CommunityFollowerForm},
   user::User_,
@@ -105,8 +108,38 @@ impl ActorType for User_ {
     unimplemented!()
   }
 
-  async fn send_delete(&self, _context: &LemmyContext) -> Result<(), LemmyError> {
-    unimplemented!()
+  /// The user has deleted their account
+  async fn send_delete(&self, context: &LemmyContext) -> Result<(), LemmyError> {
+    let mut delete = Delete::new(self.actor_id()?, self.actor_id()?);
+    delete
+      .set_context(activitystreams::context())
+      .set_id(generate_activity_id(DeleteType::Delete)?)
+      .set_to(public())
+      // TODO: who is `cc`? all the communities the user has posted to? our inbox code can only
+      //       handle activities for one activity. sending separate activities would work, but
+      //       would also create a lot of traffic.
+      .set_many_ccs(vec![self.get_followers_url()?]);
+
+    // TODO: should directly get distinct shared_inboxes from federated communites from db
+    //       (once we store that)
+    let distinct_communities = blocking(context.pool(), move |conn| {
+      Community::distinct_federated_communities(conn)
+    })
+    .await??;
+    let shared_inboxes = distinct_communities
+      .iter()
+      .map(|actor_id| Url::parse(actor_id).ok())
+      .flatten()
+      .map(|url| url.host_str().map(|u| u.to_string()))
+      .flatten()
+      .unique()
+      .map(|c| format!("{}/inbox", c))
+      .collect::<Vec<String>>();
+    // TODO: maybe we should add a separate function `send_activity_multi_dest()`
+    for s in &shared_inboxes {
+      send_activity_single_dest(delete.to_owned(), self, Url::parse(s)?, context).await?;
+    }
+    Ok(())
   }
 
   async fn send_undo_delete(&self, _context: &LemmyContext) -> Result<(), LemmyError> {