Send Undo(Like) activity when post is unfavourited

README.md

@@ -92,6 +92,7 @@ The following activities are supported:
 - Create(Note)
 - Delete(Note)
 - Like(Note)
+- Undo(Like)
 - Announce(Note)
 - Follow(Person)
 - Update(Person)

src/activitypub/activity.rs

@@ -125,7 +125,7 @@ fn create_activity(
     instance_url: &str,
     actor_name: &str,
     activity_type: &str,
-    activity_uuid: Option<Uuid>,
+    internal_activity_id: Option<&Uuid>,
     object: impl Serialize,
     recipients: Vec<String>,
 ) -> Activity {
@@ -135,7 +135,7 @@ fn create_activity(
     );
     let activity_id = get_object_url(
         instance_url,
-        &activity_uuid.unwrap_or(new_uuid()),
+        internal_activity_id.unwrap_or(&new_uuid()),
     );
     Activity {
         context: json!(AP_CONTEXT),
@@ -248,19 +248,39 @@ pub fn create_activity_note(
 pub fn create_activity_like(
     instance_url: &str,
     actor_profile: &DbActorProfile,
-    object_id: &str,
+    note_id: &str,
+    reaction_id: &Uuid,
 ) -> Activity {
     let activity = create_activity(
         instance_url,
         &actor_profile.username,
         LIKE,
-        None,
-        object_id,
+        Some(reaction_id),
+        note_id,
         vec![AP_PUBLIC.to_string()],
     );
     activity
 }
 
+pub fn create_activity_undo_like(
+    instance_url: &str,
+    actor_profile: &DbActorProfile,
+    reaction_id: &Uuid,
+) -> Activity {
+    let object_id = get_object_url(
+        instance_url,
+        reaction_id,
+    );
+    create_activity(
+        instance_url,
+        &actor_profile.username,
+        UNDO,
+        None,
+        object_id,
+        vec![AP_PUBLIC.to_string()],
+    )
+}
+
 pub fn create_activity_announce(
     instance_url: &str,
     actor_profile: &DbActorProfile,
@@ -317,7 +337,7 @@ pub fn create_activity_follow(
         instance_url,
         &actor_profile.username,
         FOLLOW,
-        Some(*follow_request_id),
+        Some(follow_request_id),
         object,
         vec![target_actor_id.to_string()],
     );

src/activitypub/receiver.rs

@@ -24,7 +24,11 @@ use crate::models::profiles::queries::{
     update_profile,
 };
 use crate::models::profiles::types::{DbActorProfile, ProfileUpdateData};
-use crate::models::reactions::queries::create_reaction;
+use crate::models::reactions::queries::{
+    create_reaction,
+    get_reaction_by_activity_id,
+    delete_reaction,
+};
 use crate::models::relationships::queries::{
     follow_request_accepted,
     follow_request_rejected,
@@ -433,6 +437,16 @@ pub async fn receive_activity(
             let target_profile = get_profile_by_acct(db_client, &target_username).await?;
             unfollow(db_client, &source_profile.id, &target_profile.id).await?;
         },
+        (UNDO, _) => {
+            // Undo(Like)
+            let object_id = get_object_id(activity.object)?;
+            let reaction = get_reaction_by_activity_id(db_client, &object_id).await?;
+            delete_reaction(
+                db_client,
+                &reaction.author_id,
+                &reaction.post_id,
+            ).await?;
+        },
         (UPDATE, PERSON) => {
             let actor: Actor = serde_json::from_value(activity.object)
                 .map_err(|_| ValidationError("invalid actor data"))?;

src/mastodon_api/statuses/views.rs

@@ -7,6 +7,7 @@ use uuid::Uuid;
 use crate::activitypub::activity::{
     create_activity_note,
     create_activity_like,
+    create_activity_undo_like,
     create_activity_announce,
     create_activity_delete_note,
 };
@@ -232,20 +233,20 @@ async fn favourite(
     if !can_view_post(Some(&current_user), &post) {
         return Err(HttpError::NotFoundError("post"));
     };
-    let reaction_created = match create_reaction(
+    let maybe_reaction_created = match create_reaction(
         db_client, &current_user.id, &status_id, None,
     ).await {
-        Ok(_) => {
+        Ok(reaction) => {
             post.reaction_count += 1;
-            true
+            Some(reaction)
         },
-        Err(DatabaseError::AlreadyExists(_)) => false, // post already favourited
+        Err(DatabaseError::AlreadyExists(_)) => None, // post already favourited
         Err(other_error) => return Err(other_error.into()),
     };
     get_reposted_posts(db_client, vec![&mut post]).await?;
     get_actions_for_posts(db_client, &current_user.id, vec![&mut post]).await?;
 
-    if reaction_created {
+    if let Some(reaction) = maybe_reaction_created {
         let maybe_remote_actor = post.author.remote_actor()
             .map_err(|_| HttpError::InternalError)?;
         if let Some(remote_actor) = maybe_remote_actor {
@@ -255,6 +256,7 @@ async fn favourite(
                 &config.instance_url(),
                 &current_user.profile,
                 object_id,
+                &reaction.id,
             );
             deliver_activity(&config, &current_user, activity, vec![remote_actor]);
         }
@@ -277,13 +279,33 @@ async fn unfavourite(
     if !can_view_post(Some(&current_user), &post) {
         return Err(HttpError::NotFoundError("post"));
     };
-    match delete_reaction(db_client, &current_user.id, &status_id).await {
-        Ok(_) => post.reaction_count -= 1,
-        Err(DatabaseError::NotFound(_)) => (), // post not favourited
+    let maybe_reaction_deleted = match delete_reaction(
+        db_client, &current_user.id, &status_id,
+    ).await {
+        Ok(reaction_id) => {
+            post.reaction_count -= 1;
+            Some(reaction_id)
+        },
+        Err(DatabaseError::NotFound(_)) => None, // post not favourited
         Err(other_error) => return Err(other_error.into()),
-    }
+    };
     get_reposted_posts(db_client, vec![&mut post]).await?;
     get_actions_for_posts(db_client, &current_user.id, vec![&mut post]).await?;
+
+    if let Some(reaction_id) = maybe_reaction_deleted {
+        let maybe_remote_actor = post.author.remote_actor()
+            .map_err(|_| HttpError::InternalError)?;
+        if let Some(remote_actor) = maybe_remote_actor {
+            // Federate
+            let activity = create_activity_undo_like(
+                &config.instance_url(),
+                &current_user.profile,
+                &reaction_id,
+            );
+            deliver_activity(&config, &current_user, activity, vec![remote_actor]);
+        };
+    };
+
     let status = Status::from_post(post, &config.instance_url());
     Ok(HttpResponse::Ok().json(status))
 }

src/models/reactions/queries.rs

@@ -42,25 +42,42 @@ pub async fn create_reaction(
     Ok(reaction)
 }
 
+pub async fn get_reaction_by_activity_id(
+    db_client: &impl GenericClient,
+    activity_id: &str,
+) -> Result<DbReaction, DatabaseError> {
+    let maybe_row = db_client.query_opt(
+        "
+        SELECT post_reaction
+        FROM post_reaction
+        WHERE activity_id = $1
+        ",
+        &[&activity_id],
+    ).await?;
+    let row = maybe_row.ok_or(DatabaseError::NotFound("reaction"))?;
+    let reaction = row.try_get("post_reaction")?;
+    Ok(reaction)
+}
+
 pub async fn delete_reaction(
     db_client: &mut impl GenericClient,
     author_id: &Uuid,
     post_id: &Uuid,
-) -> Result<(), DatabaseError> {
+) -> Result<Uuid, DatabaseError> {
     let transaction = db_client.transaction().await?;
-    let deleted_count = transaction.execute(
+    let maybe_row = transaction.query_opt(
         "
         DELETE FROM post_reaction
         WHERE author_id = $1 AND post_id = $2
+        RETURNING post_reaction.id
         ",
         &[&author_id, &post_id],
     ).await?;
-    if deleted_count == 0 {
-        return Err(DatabaseError::NotFound("reaction"));
-    }
+    let row = maybe_row.ok_or(DatabaseError::NotFound("reaction"))?;
+    let reaction_id = row.try_get("id")?;
     update_reaction_count(&transaction, post_id, -1).await?;
     transaction.commit().await?;
-    Ok(())
+    Ok(reaction_id)
 }
 
 /// Finds favourites among given posts and returns their IDs