Follow FEP-e232 links when importing post

CHANGELOG.md

@@ -33,6 +33,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Make webfinger response compatible with GNU Social account lookup.
 - Prefer `Group` actor when doing webfinger query on Lemmy server.
 - Fetch missing profiles before doing follower migration.
+- Follow FEP-e232 links when importing post.
 
 ## [1.14.0] - 2023-02-22
 

src/activitypub/fetcher/helpers.rs

@@ -5,7 +5,7 @@ use mitra_config::{Config, Instance};
 
 use crate::activitypub::{
     actors::helpers::{create_remote_profile, update_remote_profile},
-    handlers::create::handle_note,
+    handlers::create::{get_object_links, handle_note},
     identifiers::parse_local_object_id,
     receiver::HandlerError,
     types::Object,
@@ -192,6 +192,7 @@ pub async fn import_post(
         let object_id = match queue.pop() {
             Some(object_id) => {
                 if objects.iter().any(|object| object.id == object_id) {
+                    // Can happen due to redirections
                     log::warn!("loop detected");
                     continue;
                 };
@@ -253,9 +254,9 @@ pub async fn import_post(
             // Fetch parent object on next iteration
             queue.push(object_id.to_owned());
         };
-        if let Some(ref object_id) = object.quote_url {
-            // Fetch quoted object after fetching current thread
-            queue.insert(0, object_id.to_owned());
+        for object_id in get_object_links(&object)? {
+            // Fetch linked objects after fetching current thread
+            queue.insert(0, object_id);
         };
         maybe_object = None;
         objects.push(object);

src/activitypub/handlers/create.rs

@@ -197,6 +197,43 @@ pub async fn get_object_attachments(
     Ok((attachments, unprocessed))
 }
 
+pub fn get_object_links(
+    object: &Object,
+) -> Result<Vec<String>, HandlerError> {
+    let mut links = vec![];
+    if let Some(ref value) = object.tag {
+        let list: Vec<JsonValue> = parse_property_value(value)
+            .map_err(|_| ValidationError("invalid tag property"))?;
+        for tag_value in list {
+            let tag_type = tag_value["type"].as_str().unwrap_or(HASHTAG);
+            if tag_type == LINK {
+                let tag: LinkTag = match serde_json::from_value(tag_value) {
+                    Ok(tag) => tag,
+                    Err(_) => {
+                        log::warn!("invalid link tag");
+                        continue;
+                    },
+                };
+                if tag.media_type != AP_MEDIA_TYPE &&
+                    tag.media_type != AS_MEDIA_TYPE
+                {
+                    // Unknown media type
+                    continue;
+                };
+                if !links.contains(&tag.href) {
+                    links.push(tag.href);
+                };
+            };
+        };
+    };
+    if let Some(ref object_id) = object.quote_url {
+        if !links.contains(object_id) {
+            links.push(object_id.to_owned());
+        };
+    };
+    Ok(links)
+}
+
 pub async fn get_object_tags(
     config: &Config,
     db_client: &impl DatabaseClient,