Updated thread implementation to work with posts instead of activities

refs [AP-721](https://linear.app/ghost/issue/AP-721/update-getactivitythread-to-work-with-posts-instead-of-activities)

Updated thread implementation to work with posts instead of activities as part
of the posts migration

features/step_definitions/stepdefs.js

@@ -595,8 +595,25 @@ When('we request the outbox', async function () {
 });
 
 When('an authenticated request is made to {string}', async function (path) {
+    let requestPath = path;
+
+    // If this is a request to the /thread/ endpoint, we need to replace the
+    // object name with the object ID as we don't have a way to know the object
+    // ID ahead of time
+    if (path.includes('/thread/')) {
+        const objectName = path.split('/').pop(); // Object name is the last part of the path
+        const object = this.objects[objectName];
+
+        if (object) {
+            requestPath = path.replace(
+                objectName,
+                encodeURIComponent(object.id),
+            );
+        }
+    }
+
     this.response = await fetchActivityPub(
-        `http://fake-ghost-activitypub${path}`,
+        `http://fake-ghost-activitypub${requestPath}`,
         {
             headers: {
                 Accept: 'application/ld+json',
@@ -1624,6 +1641,7 @@ When(
             const activity = await this.response.clone().json();
 
             this.activities[replyName] = activity;
+            this.objects[replyName] = activity.object;
         }
     },
 );
@@ -1717,3 +1735,30 @@ Then(
         }
     },
 );
+
+Then(
+    'post {string} in the thread is {string}',
+    async function (postNumber, objectName) {
+        const responseJson = await this.response.clone().json();
+
+        const object = this.objects[objectName];
+        const post = responseJson.posts[Number(postNumber) - 1];
+
+        assert(post, `Expected to find ${objectName} in thread`);
+
+        assert(
+            post.url === object.id,
+            `Expected ${objectName} to be at position ${postNumber} in thread`,
+        );
+    },
+);
+
+Then('the thread contains {string} posts', async function (string) {
+    const responseJson = await this.response.clone().json();
+
+    assert.equal(
+        responseJson.posts.length,
+        Number(string),
+        `Expected thread to contain ${string} posts, but got ${responseJson.posts.length}`,
+    );
+});

features/thread.feature

@@ -0,0 +1,66 @@
+@only
+Feature: Thread
+  In order to see replies to a post
+  As a user
+  I want to request the thread for a post
+
+  Background:
+    Given an Actor "Person(Alice)"
+    And a "Follow(Us)" Activity "Follow" by "Alice"
+    And "Alice" sends "Follow" to the Inbox
+    And "Follow" is in our Inbox
+    And we follow "Alice"
+    And the request is accepted
+    And a "Accept(Follow(Alice))" Activity "Accept" by "Alice"
+    And "Alice" sends "Accept" to the Inbox
+    And "Accept" is in our Inbox
+    And a "Note" Object "Article" by "Alice"
+    And a "Create(Article)" Activity "Create" by "Alice"
+    And "Alice" sends "Create" to the Inbox
+    And "Create" is in our Inbox
+
+  Scenario: Retrieving the thread for a top level post
+    Given we reply "Reply1" to "Article" with the content
+        """
+        This is a great article!
+        """
+    And "Reply1" is in our Outbox
+    And we reply "Reply2" to "Article" with the content
+        """
+        This is still a great article!
+        """
+    And "Reply2" is in our Outbox
+    And we reply "Reply3" to "Reply1" with the content
+        """
+        This is a great reply!
+        """
+    And "Reply3" is in our Outbox
+    When an authenticated request is made to "/.ghost/activitypub/thread/Article"
+    Then the request is accepted
+    And the thread contains "3" posts
+    And post "1" in the thread is "Article"
+    And post "2" in the thread is "Reply1"
+    And post "3" in the thread is "Reply2"
+
+  Scenario: Retrieving the thread for a reply to a post
+    Given we reply "Reply1" to "Article" with the content
+        """
+        This is a great article!
+        """
+    And "Reply1" is in our Outbox
+    And we reply "Reply2" to "Article" with the content
+        """
+        This is still a great article!
+        """
+    And "Reply2" is in our Outbox
+    And we reply "Reply3" to "Reply1" with the content
+        """
+        This is a great reply!
+        """
+    And "Reply3" is in our Outbox
+    When an authenticated request is made to "/.ghost/activitypub/thread/Reply3"
+    Then the request is accepted
+    And the thread contains "3" posts
+    And post "1" in the thread is "Article"
+    And post "2" in the thread is "Reply1"
+    And post "3" in the thread is "Reply3"

src/app.ts

@@ -99,11 +99,11 @@ import {
     createGetProfileFollowersHandler,
     createGetProfileFollowingHandler,
     createGetProfileHandler,
+    createGetThreadHandler,
     createPostPublishedWebhookHandler,
     createSearchHandler,
     handleCreateNote,
     handleGetActivities,
-    handleGetActivityThread,
     handleGetProfilePosts,
     handleWebhookSiteChanged,
 } from './http/api';
@@ -916,8 +916,8 @@ app.get(
     spanWrapper(handleGetProfilePosts),
 );
 app.get(
-    '/.ghost/activitypub/thread/:object_id',
-    spanWrapper(handleGetActivityThread),
+    '/.ghost/activitypub/thread/:post_ap_id',
+    spanWrapper(createGetThreadHandler(postRepository, accountService)),
 );
 app.get(
     '/.ghost/activitypub/account/:handle',

src/db.ts

@@ -141,32 +141,6 @@ export async function getActivityMetaWithoutJoin(
     return map;
 }
 
-export async function getActivityChildren(activity: ActivityJsonLd) {
-    const objectId = activity.object.id;
-
-    const results = await client
-        .select('value')
-        .from('key_value')
-        .where(function () {
-            // If inReplyTo is a string
-            this.where(
-                client.raw(
-                    `JSON_EXTRACT(value, "$.object.inReplyTo") = "${objectId}"`,
-                ),
-            );
-
-            // If inReplyTo is an object
-            this.orWhere(
-                client.raw(
-                    `JSON_EXTRACT(value, "$.object.inReplyTo.id") = "${objectId}"`,
-                ),
-            );
-        })
-        .andWhere(client.raw(`JSON_EXTRACT(value, "$.type") = "Create"`));
-
-    return results.map((result) => result.value);
-}
-
 export async function getActivityChildrenCount(activity: ActivityJsonLd) {
     const objectId = activity.object.id;
 
@@ -210,51 +184,3 @@ export async function getRepostCount(activity: ActivityJsonLd) {
 
     return result[0].count;
 }
-
-export async function getActivityParents(activity: ActivityJsonLd) {
-    const parents: ActivityJsonLd[] = [];
-
-    const getParent = async (objectId: string) => {
-        const result = await client
-            .select('value')
-            .from('key_value')
-            .where(
-                client.raw(
-                    `JSON_EXTRACT(value, "$.object.id") = "${objectId}"`,
-                ),
-            )
-            .andWhere(client.raw(`JSON_EXTRACT(value, "$.type") = "Create"`));
-
-        if (result.length === 1) {
-            const parent = result[0];
-
-            parents.unshift(parent.value);
-
-            // inReplyTo can be a string or an object
-            const inReplyToId =
-                parent.value.object.inReplyTo?.id ??
-                parent.value.object.inReplyTo;
-
-            if (inReplyToId) {
-                await getParent(inReplyToId);
-            }
-        }
-    };
-
-    await getParent(
-        // inReplyTo can be a string or an object
-        activity.object.inReplyTo?.id ?? activity.object.inReplyTo,
-    );
-
-    return parents;
-}
-
-export async function getActivityForObject(objectId: string) {
-    const result = await client
-        .select('value')
-        .from('key_value')
-        .where(client.raw(`JSON_EXTRACT(value, "$.object.id") = "${objectId}"`))
-        .andWhere(client.raw(`JSON_EXTRACT(value, "$.type") = "Create"`));
-
-    return result[0].value;
-}

src/http/api/__snapshots__/thread.json

@@ -0,0 +1,79 @@
+{
+  "posts": [
+    {
+      "attachments": [],
+      "author": {
+        "avatarUrl": "https://example.com/avatars/foobar.png",
+        "handle": "foobar",
+        "id": "https://example.com/users/456",
+        "name": "Foo Bar",
+        "url": "https://example.com/users/456",
+      },
+      "content": "Test Content 1",
+      "excerpt": "Test Excerpt 1",
+      "featureImageUrl": "https://example.com/feature-images/post-1.jpg",
+      "id": "https://example.com/.ghost/activitypub/article/aaa-bbb-ccc",
+      "likeCount": 0,
+      "likedByMe": false,
+      "publishedAt": "2025-02-27T15:40:00.000Z",
+      "readingTimeMinutes": 1,
+      "replyCount": 0,
+      "repostCount": 0,
+      "repostedBy": null,
+      "repostedByMe": false,
+      "title": "Test Post 1",
+      "type": 1,
+      "url": "https://example.com/posts/1",
+    },
+    {
+      "attachments": [],
+      "author": {
+        "avatarUrl": "https://example.com/avatars/foobar.png",
+        "handle": "foobar",
+        "id": "https://example.com/users/456",
+        "name": "Foo Bar",
+        "url": "https://example.com/users/456",
+      },
+      "content": "Test Content 2",
+      "excerpt": "Test Excerpt 2",
+      "featureImageUrl": "https://example.com/feature-images/post-2.jpg",
+      "id": "https://example.com/.ghost/activitypub/article/ddd-eee-fff",
+      "likeCount": 0,
+      "likedByMe": true,
+      "publishedAt": "2025-02-27T15:40:00.000Z",
+      "readingTimeMinutes": 1,
+      "replyCount": 0,
+      "repostCount": 0,
+      "repostedBy": null,
+      "repostedByMe": false,
+      "title": "Test Post 2",
+      "type": 1,
+      "url": "https://example.com/posts/2",
+    },
+    {
+      "attachments": [],
+      "author": {
+        "avatarUrl": "https://example.com/avatars/foobar.png",
+        "handle": "foobar",
+        "id": "https://example.com/users/456",
+        "name": "Foo Bar",
+        "url": "https://example.com/users/456",
+      },
+      "content": "Test Content 3",
+      "excerpt": "Test Excerpt 3",
+      "featureImageUrl": "https://example.com/feature-images/post-3.jpg",
+      "id": "https://example.com/.ghost/activitypub/article/ggg-hhh-iii",
+      "likeCount": 0,
+      "likedByMe": false,
+      "publishedAt": "2025-02-27T15:40:00.000Z",
+      "readingTimeMinutes": 1,
+      "replyCount": 0,
+      "repostCount": 0,
+      "repostedBy": null,
+      "repostedByMe": true,
+      "title": "Test Post 3",
+      "type": 1,
+      "url": "https://example.com/posts/3",
+    },
+  ],
+}