From 343a507eccc16b27cf2103fd4222d521fb18f092 Mon Sep 17 00:00:00 2001
From: Jesse Wierzbinski <contact@cpluspatch.com>
Date: Wed, 28 May 2025 17:17:03 +0200
Subject: [PATCH] feat(federation): :sparkles: Federate Reactions

---
 classes/database/reaction.ts            | 14 +++++
 classes/database/user.ts                | 72 +++++++++++++++++++++++--
 packages/client/schemas/notification.ts |  1 +
 types/api.ts                            |  3 +-
 4 files changed, 84 insertions(+), 6 deletions(-)

diff --git a/classes/database/reaction.ts b/classes/database/reaction.ts
index a64d372d..e08d73c6 100644
--- a/classes/database/reaction.ts
+++ b/classes/database/reaction.ts
@@ -236,6 +236,20 @@ export class Reaction extends BaseInterface<typeof Reactions, ReactionType> {
         });
     }
 
+    public toVersiaUnreact(): VersiaEntities.Delete {
+        return new VersiaEntities.Delete({
+            type: "Delete",
+            id: crypto.randomUUID(),
+            created_at: new Date().toISOString(),
+            author: User.getUri(
+                this.data.authorId,
+                this.data.author.uri ? new URL(this.data.author.uri) : null,
+            ).href,
+            deleted_type: "pub.versia:reactions/Reaction",
+            deleted: this.getUri(config.http.base_url).href,
+        });
+    }
+
     public static async fromVersia(
         reactionToConvert: VersiaEntities.Reaction,
         author: User,
diff --git a/classes/database/user.ts b/classes/database/user.ts
index 1ab6615d..3486b548 100644
--- a/classes/database/user.ts
+++ b/classes/database/user.ts
@@ -752,7 +752,7 @@ export class User extends BaseInterface<typeof Users, UserWithRelations> {
         }
 
         // Create the reaction
-        await Reaction.insert({
+        const reaction = await Reaction.insert({
             id: randomUUIDv7(),
             authorId: this.id,
             noteId: note.id,
@@ -760,7 +760,29 @@ export class User extends BaseInterface<typeof Users, UserWithRelations> {
             emojiId: emoji instanceof Emoji ? emoji.id : null,
         });
 
-        // TODO: Handle federation and notifications
+        const finalNote = await Note.fromId(note.id, this.id);
+
+        if (!finalNote) {
+            throw new Error("Failed to fetch note after reaction");
+        }
+
+        if (note.author.local) {
+            // Notify the user that their post has been reacted to
+            await note.author.notify("reaction", this, finalNote);
+        }
+
+        if (this.local) {
+            const federatedUsers = await this.federateToFollowers(
+                reaction.toVersia(),
+            );
+
+            if (
+                note.remote &&
+                !federatedUsers.find((u) => u.id === note.author.id)
+            ) {
+                await this.federateToUser(reaction.toVersia(), note.author);
+            }
+        }
     }
 
     /**
@@ -777,11 +799,45 @@ export class User extends BaseInterface<typeof Users, UserWithRelations> {
 
         await reactionToDelete.delete();
 
-        // TODO: Handle federation and notifications
+        if (note.author.local) {
+            // Remove any eventual notifications for this reaction
+            await db
+                .delete(Notifications)
+                .where(
+                    and(
+                        eq(Notifications.accountId, this.id),
+                        eq(Notifications.type, "reaction"),
+                        eq(Notifications.notifiedId, note.data.authorId),
+                        eq(Notifications.noteId, note.id),
+                    ),
+                );
+        }
+
+        if (this.local) {
+            const federatedUsers = await this.federateToFollowers(
+                reactionToDelete.toVersiaUnreact(),
+            );
+
+            if (
+                note.remote &&
+                !federatedUsers.find((u) => u.id === note.author.id)
+            ) {
+                await this.federateToUser(
+                    reactionToDelete.toVersiaUnreact(),
+                    note.author,
+                );
+            }
+        }
     }
 
     public async notify(
-        type: "mention" | "follow_request" | "follow" | "favourite" | "reblog",
+        type:
+            | "mention"
+            | "follow_request"
+            | "follow"
+            | "favourite"
+            | "reblog"
+            | "reaction",
         relatedUser: User,
         note?: Note,
     ): Promise<void> {
@@ -801,7 +857,13 @@ export class User extends BaseInterface<typeof Users, UserWithRelations> {
 
     private async notifyPush(
         notificationId: string,
-        type: "mention" | "follow_request" | "follow" | "favourite" | "reblog",
+        type:
+            | "mention"
+            | "follow_request"
+            | "follow"
+            | "favourite"
+            | "reblog"
+            | "reaction",
         relatedUser: User,
         note?: Note,
     ): Promise<void> {
diff --git a/packages/client/schemas/notification.ts b/packages/client/schemas/notification.ts
index 57541b46..32f9318c 100644
--- a/packages/client/schemas/notification.ts
+++ b/packages/client/schemas/notification.ts
@@ -21,6 +21,7 @@ export const Notification = z
                 "favourite",
                 "poll",
                 "update",
+                "reaction",
                 "admin.sign_up",
                 "admin.report",
                 "severed_relationships",
diff --git a/types/api.ts b/types/api.ts
index 6ca3f549..3e976c69 100644
--- a/types/api.ts
+++ b/types/api.ts
@@ -32,4 +32,5 @@ export type KnownEntity =
     | VersiaEntities.Unfollow
     | VersiaEntities.Delete
     | VersiaEntities.Like
-    | VersiaEntities.Share;
+    | VersiaEntities.Share
+    | VersiaEntities.Reaction;