Updated activities endpoint to better support client-side pagination

src/db.ts

@@ -18,25 +18,83 @@ await client.schema.createTableIfNotExists('key_value', function (table) {
     table.datetime('expires').nullable();
 });
 
-// Helper function to get the meta data for a list of activity URIs
+// Helper function to get the meta data for an array of activity URIs
 // from the database. This allows us to fetch information about the activities
 // without having to fetch the full activity object. This is a bit of a hack to
 // support sorting / filtering of the activities and should be replaced when we
 // have a proper db schema
-export async function getActivityMeta(uris: string[]): Promise<Map<string, { id: number, type: string }>> {
+
+type ActivityMeta = {
+    id: number; // Used for sorting
+    activity_type: string; // Used for filtering by activity type
+    object_type: string; // Used for filtering by object type
+    reply_object_url: string; // Used for filtering by isReplyToOwn criteria
+    reply_object_name: string; // Used for filtering by isReplyToOwn criteria
+};
+
+type getActivityMetaQueryResult = {
+    key: string,
+    left_id: number,
+    activity_type: string,
+    object_type: string,
+    reply_object_url: string,
+    reply_object_name: string
+}
+
+export async function getActivityMeta(uris: string[]): Promise<Map<string, ActivityMeta>> {
     const results = await client
-        .select('key', 'id', client.raw('JSON_EXTRACT(value, "$.type") as type'))
-        .from('key_value')
-        .whereIn('key', uris.map(uri => `["${uri}"]`));
+        .select(
+            'left.key',
+            'left.id as left_id',
+            // mongo schmongo...
+            client.raw('JSON_EXTRACT(left.value, "$.type") as activity_type'),
+            client.raw('JSON_EXTRACT(left.value, "$.object.type") as object_type'),
+            client.raw('JSON_EXTRACT(right.value, "$.object.url") as reply_object_url'),
+            client.raw('JSON_EXTRACT(right.value, "$.object.name") as reply_object_name')
+        )
+        .from({ left: 'key_value' })
+        // @ts-ignore: This works as expected but the type definitions complain 🤔
+        .leftJoin(
+            { right: 'key_value' },
+            client.raw('JSON_UNQUOTE(JSON_EXTRACT(right.value, "$.object.id"))'),
+            '=',
+            client.raw('JSON_UNQUOTE(JSON_EXTRACT(left.value, "$.object.inReplyTo"))')
+        )
+        .whereIn('left.key', uris.map(uri => `["${uri}"]`));
 
-    const map = new Map<string, { id: number, type: string }>();
+    const map = new Map<string, ActivityMeta>();
 
-    for (const result of results) {
+    for (const result of results as getActivityMetaQueryResult[]) {
         map.set(result.key.substring(2, result.key.length - 2), {
-            id: result.id,
-            type: result.type,
+            id: result.left_id,
+            activity_type: result.activity_type,
+            object_type: result.object_type,
+            reply_object_url: result.reply_object_url,
+            reply_object_name: result.reply_object_name,
         });
     }
 
     return map;
 }
+
+// Helper function to retrieve a map of replies for an array of activity URIs
+// from the database
+export async function getRepliesMap (uris: string[]): Promise<Map<string, any>> {
+    const map = new Map<string, any>();
+
+    const results = await client
+        .select('value')
+        .from('key_value')
+        .where(client.raw('JSON_EXTRACT(value, "$.object.inReplyTo") IS NOT NULL'))
+        .whereIn('key', uris.map(uri => `["${uri}"]`));
+
+    for (const {value: result} of results) {
+        const replies = map.get(result.object.inReplyTo) ?? [];
+
+        replies.push(result);
+
+        map.set(result.object.inReplyTo, replies);
+    }
+
+    return map;
+}

src/handlers.ts

@@ -18,7 +18,7 @@ import { Buffer } from 'node:buffer';
 import { Context, Next } from 'hono';
 import sanitizeHtml from 'sanitize-html';
 import { v4 as uuidv4 } from 'uuid';
-import { getActivityMeta } from './db';
+import { getActivityMeta, getRepliesMap } from './db';
 import { addToList, removeFromList } from './kv-helpers';
 import { toURL } from './toURL';
 import { ContextData, HonoContextVariables, fedify } from './app';
@@ -489,6 +489,8 @@ async function buildActivity(
     db: KvStore,
     apCtx: APContext<ContextData>,
     liked: string[] = [],
+    repliesMap: Map<string, any> | null = null,
+    expandInReplyTo: boolean = false,
 ): Promise<InboxItem | null> {
     const item = await db.get<InboxItem>([uri]);
 
@@ -559,6 +561,38 @@ async function buildActivity(
         }
     }
 
+    // If a replies map has been provided, the item is not a string, and the
+    // item has an id, we should nest any replies recursively (which involves
+    // calling this function again for each reply)
+    if (repliesMap && typeof item.object !== 'string' && item.object.id) {
+        item.object.replies = [];
+
+        const replies = repliesMap.get(item.object.id);
+
+        if (replies) {
+            const builtReplies = [];
+
+            for (const reply of replies) {
+                const builtReply = await buildActivity(reply.id, db, apCtx, liked, repliesMap);
+
+                if (builtReply) {
+                    builtReplies.push(builtReply);
+                }
+            }
+
+            item.object.replies = builtReplies;
+        }
+    }
+
+    // Expand the inReplyTo object if it is a string and we are expanding inReplyTo
+    if (expandInReplyTo && typeof item.object !== 'string' && item.object.inReplyTo) {
+        const replyObject = await db.get([item.object.inReplyTo]);
+
+        if (replyObject) {
+            item.object.inReplyTo = replyObject;
+        }
+    }
+
     // Return the built item
     return item;
 }
@@ -622,15 +656,56 @@ export async function getActivities(
     const globaldb = ctx.get('globaldb');
     const apCtx = fedify.createContext(ctx.req.raw as Request, {db, globaldb});
 
-    // Parse cursor and limit from query parameters
+    // -------------------------------------------------------------------------
+    // Process query parameters
+    // -------------------------------------------------------------------------
+
+    // Parse "cursor" and "limit" from query parameters
+    // These are used to paginate the results
+    // ?cursor=<string>
+    // ?limit=<number>
     const queryCursor = ctx.req.query('cursor')
     const cursor = queryCursor ? Buffer.from(queryCursor, 'base64url').toString('utf-8') : null;
     const limit = Number.parseInt(ctx.req.query('limit') || DEFAULT_LIMIT.toString(), 10);
 
-    // Parse includeOwn from query parameters
+    // Parse "includeOwn" from query parameters
     // This is used to include the user's own activities in the results
+    // ?includeOwn=<boolean>
     const includeOwn = ctx.req.query('includeOwn') === 'true';
 
+    // Parse "includeReplies" from query parameters
+    // This is used to include nested replies in the results
+    // ?includeReplies=<boolean>
+    const includeReplies = ctx.req.query('includeReplies') === 'true';
+
+    // Parse "filter" from query parameters
+    // This is used to filter the activities by various criteria
+    // ?filter={type: ['<activityType>', '<activityType>:<objectType>', '<activityType>:<objectType>:<criteria>']}
+    const queryFilters = ctx.req.query('filter') || '[]';
+    const filters = JSON.parse(decodeURI(queryFilters))
+
+    const typeFilters = (filters.type || []).map((filter: string) => {
+        const [activityType, objectType = null, criteria = null] = filter.split(':');
+
+        return {
+            activity: activityType,
+            object: objectType,
+            criteria,
+        }
+    });
+
+    console.log('Request query =', ctx.req.query());
+    console.log('Processed query params =', JSON.stringify({
+        cursor,
+        limit,
+        includeOwn,
+        typeFilters,
+    }, null, 2));
+
+    // -------------------------------------------------------------------------
+    // Fetch required data from the database
+    // -------------------------------------------------------------------------
+
     // Fetch the liked object refs from the database:
     //   - Data is structured as an array of strings
     //   - Each string is a URI to an object in the database
@@ -654,26 +729,75 @@ export async function getActivities(
         outboxRefs = await db.get<string[]>(['outbox']) || [];
     }
 
-    // To be able to return a sorted / filtered "feed" of activities, we need to
+    // To be able to return a sorted / filtered list of activities, we need to
     // fetch some additional meta data about the referenced activities. Doing this
     // upfront allows us to sort, filter and paginate the activities before
     // building them for the response which saves us from having to perform
     // unnecessary database lookups for referenced activities that will not be
-    // included in the response. If we can't find the meta data in the database
-    // for an activity, we skip it as this is unexpected
+    // included in the response
     let activityRefs = [...inboxRefs, ...outboxRefs];
     const activityMeta = await getActivityMeta(activityRefs);
 
+    // If we can't find the meta data in the database for an activity, we skip
+    // it as this is unexpected
     activityRefs = activityRefs.filter(ref => activityMeta.has(ref));
 
-    // Sort the activity refs by the id of the activity (newest first)
+    // -------------------------------------------------------------------------
+    // Apply filtering and sorting
+    // -------------------------------------------------------------------------
+
+    // Filter the activity refs by any provided type filters
+    if (typeFilters.length > 0) {
+        activityRefs = activityRefs.filter(ref => {
+            const activity = activityMeta.get(ref)!;
+
+            return typeFilters.some((filter: { activity: string; object: string | null, criteria: string | null }) => {
+                // ?filter={type: ['<activityType>']}
+                if (filter.activity && activity.activity_type !== filter.activity) {
+                    return false;
+                }
+
+                // ?filter={type: ['<activityType>:<objectType>']}
+                if (filter.object && activity.object_type !== filter.object) {
+                    return false;
+                }
+
+                // ?filter={type: ['<activityType>:<objectType>:isReplyToOwn,<siteHost>']}
+                if (filter.criteria && filter.criteria.startsWith('isReplyToOwn,')) {
+                    // If the activity does not have a reply object url or name,
+                    // we can't determine if it's a reply to an own object so
+                    // we skip it
+                    if (!activity.reply_object_url || !activity.reply_object_name) {
+                        return false;
+                    }
+
+                    // Verify that the reply is to an object created by the user by
+                    // checking that the hostname associated with the reply object
+                    // is the same as the hostname of the site. This is not a bullet
+                    // proof check, but it's a good enough for now (i think 😅)
+                    const [_, siteHost] = filter.criteria.split(',');
+                    const { hostname: replyHost } = new URL(activity.reply_object_url);
+
+                    return siteHost === replyHost;
+                }
+
+                return true;
+            });
+        });
+    }
+
+    // Sort the activity refs by the id of the activity (newest first).
     // We are using the id to sort because currently not all activity types have
     // a timestamp. The id property is a unique auto incremented number at the
     // database level
     activityRefs.sort((a, b) => {
         return activityMeta.get(b)!.id - activityMeta.get(a)!.id;
     });
 
+    // -------------------------------------------------------------------------
+    // Paginate
+    // -------------------------------------------------------------------------
+
     // Find the starting index based on the cursor
     const startIndex = cursor ? activityRefs.findIndex(ref => ref === cursor) + 1 : 0;
 
@@ -685,12 +809,22 @@ export async function getActivities(
         ? Buffer.from(paginatedRefs[paginatedRefs.length - 1]).toString('base64url')
         : null;
 
-    // Build the activities for the response
+    // -------------------------------------------------------------------------
+    // Build the activities and return the response
+    // -------------------------------------------------------------------------
+
     const activities = [];
 
+    // If we need to include replies, fetch the replies map based on the paginated
+    // activity refs, which will be utilised when building the activities
+    const repliesMap = includeReplies
+        ? await getRepliesMap(paginatedRefs)
+        : null;
+
+    // Build the activities
     for (const ref of paginatedRefs) {
         try {
-            const builtActivity = await buildActivity(ref, globaldb, apCtx, likedRefs);
+            const builtActivity = await buildActivity(ref, globaldb, apCtx, likedRefs, repliesMap, true);
 
             if (builtActivity) {
                 activities.push(builtActivity);
@@ -700,7 +834,7 @@ export async function getActivities(
         }
     }
 
-    // Return the built activities and the next cursor
+    // Return the response
     return new Response(JSON.stringify({
         items: activities,
         nextCursor,