From 526a0f1b2b8f13f1f07f28c79005f24fa0e81189 Mon Sep 17 00:00:00 2001
From: Felix Ableitner <me@nutomic.com>
Date: Mon, 26 Feb 2024 15:12:09 +0100
Subject: [PATCH] Correctly synchronize collection of community featured posts
 (fixes #3867)

---
 .../src/collections/community_featured.rs     | 36 ++++++++++--------
 crates/apub/src/objects/community.rs          |  5 ++-
 crates/db_schema/src/impls/community.rs       | 38 +++++++++++++++++++
 3 files changed, 62 insertions(+), 17 deletions(-)

diff --git a/crates/apub/src/collections/community_featured.rs b/crates/apub/src/collections/community_featured.rs
index 8fa86bbdb..eb19d64ea 100644
--- a/crates/apub/src/collections/community_featured.rs
+++ b/crates/apub/src/collections/community_featured.rs
@@ -6,11 +6,14 @@ use activitypub_federation::{
   config::Data,
   kinds::collection::OrderedCollectionType,
   protocol::verification::verify_domains_match,
-  traits::{ActivityHandler, Collection, Object},
+  traits::{Collection, Object},
 };
 use futures::future::{join_all, try_join_all};
 use lemmy_api_common::{context::LemmyContext, utils::generate_featured_url};
-use lemmy_db_schema::{source::post::Post, utils::FETCH_LIMIT_MAX};
+use lemmy_db_schema::{
+  source::{community::Community, post::Post},
+  utils::FETCH_LIMIT_MAX,
+};
 use lemmy_utils::error::LemmyError;
 use url::Url;
 
@@ -55,35 +58,36 @@ impl Collection for ApubCommunityFeatured {
 
   async fn from_json(
     apub: Self::Kind,
-    _owner: &Self::Owner,
-    data: &Data<Self::DataType>,
+    owner: &Self::Owner,
+    context: &Data<Self::DataType>,
   ) -> Result<Self, Self::Error>
   where
     Self: Sized,
   {
-    let mut posts = apub.ordered_items;
-    if posts.len() as i64 > FETCH_LIMIT_MAX {
-      posts = posts
+    let mut pages = apub.ordered_items;
+    if pages.len() as i64 > FETCH_LIMIT_MAX {
+      pages = pages
         .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(posts.into_iter().map(|post| {
+    let stickied_posts: Vec<Post> = join_all(pages.into_iter().map(|page| {
       async {
         // use separate request counter for each item, otherwise there will be problems with
         // parallel processing
-        let verify = post.verify(data).await;
-        if verify.is_ok() {
-          post.receive(data).await.ok();
-        }
+        ApubPost::verify(&page, &apub.id, context).await?;
+        ApubPost::from_json(page, context).await
       }
     }))
-    .await;
+    .await
+    // ignore any failed or unparseable items
+    .into_iter()
+    .filter_map(|p| p.ok().map(|p| p.0))
+    .collect();
+
+    Community::set_featured_posts(owner.id, stickied_posts, &mut context.pool()).await?;
 
     // This return value is unused, so just set an empty vec
     Ok(ApubCommunityFeatured(()))
diff --git a/crates/apub/src/objects/community.rs b/crates/apub/src/objects/community.rs
index 35e445b47..36f26a9f4 100644
--- a/crates/apub/src/objects/community.rs
+++ b/crates/apub/src/objects/community.rs
@@ -166,7 +166,7 @@ impl Object for ApubCommunity {
       moderators_url: group.attributed_to.clone().map(Into::into),
       posting_restricted_to_mods: group.posting_restricted_to_mods,
       instance_id,
-      featured_url: group.featured.map(Into::into),
+      featured_url: group.featured.clone().map(Into::into),
       ..Default::default()
     };
     let languages =
@@ -184,6 +184,9 @@ impl Object for ApubCommunity {
     spawn_try_task(async move {
       group.outbox.dereference(&community_, &context_).await?;
       group.followers.dereference(&community_, &context_).await?;
+      if let Some(featured) = group.featured {
+        featured.dereference(&community_, &context_).await?;
+      }
       if let Some(moderators) = group.attributed_to {
         moderators.dereference(&community_, &context_).await?;
       }
diff --git a/crates/db_schema/src/impls/community.rs b/crates/db_schema/src/impls/community.rs
index 3298da894..88b0ef46d 100644
--- a/crates/db_schema/src/impls/community.rs
+++ b/crates/db_schema/src/impls/community.rs
@@ -14,6 +14,7 @@ use crate::{
       CommunityPersonBanForm,
       CommunityUpdateForm,
     },
+    post::Post,
   },
   traits::{ApubActor, Bannable, Crud, Followable, Joinable},
   utils::{functions::lower, get_conn, DbPool},
@@ -27,6 +28,7 @@ use diesel::{
   result::Error,
   select,
   sql_types,
+  update,
   ExpressionMethods,
   NullableExpressionMethods,
   QueryDsl,
@@ -137,6 +139,42 @@ impl Community {
     }
     Err(diesel::NotFound)
   }
+
+  pub async fn set_featured_posts(
+    community_id: CommunityId,
+    posts: Vec<Post>,
+    pool: &mut DbPool<'_>,
+  ) -> Result<(), Error> {
+    use crate::schema::post;
+    let conn = &mut get_conn(pool).await?;
+    for p in &posts {
+      debug_assert!(p.community_id == community_id);
+    }
+    conn
+      .build_transaction()
+      .run(|conn| {
+        Box::pin(async move {
+          update(
+            // first remove all existing featured posts
+            post::table,
+          )
+          .filter(post::dsl::community_id.eq(community_id))
+          .set(post::dsl::featured_community.eq(false))
+          .execute(conn)
+          .await?;
+
+          // then mark the given posts as featured
+          let post_ids: Vec<_> = posts.iter().map(|p| p.id).collect();
+          update(post::table)
+            .filter(post::dsl::id.eq_any(post_ids))
+            .set(post::dsl::featured_community.eq(true))
+            .execute(conn)
+            .await?;
+          Ok(())
+        }) as _
+      })
+      .await
+  }
 }
 
 impl CommunityModerator {