extra --> relations, move it back to a filter option

src/db/events.ts

@@ -144,6 +144,30 @@ function getFilterQuery(filter: DittoFilter): EventQuery {
       : query.leftJoin('users', 'users.pubkey', 'events.pubkey').where('users.pubkey', 'is', null) as typeof query;
   }
 
+  if (filter.relations?.includes('author')) {
+    query = query
+      .leftJoin(
+        (eb) =>
+          eb
+            .selectFrom('events')
+            .selectAll()
+            .where('kind', '=', 0)
+            .orderBy('created_at', 'desc')
+            .groupBy('pubkey')
+            .as('authors'),
+        (join) => join.onRef('authors.pubkey', '=', 'events.pubkey'),
+      )
+      .select([
+        'authors.id as author_id',
+        'authors.kind as author_kind',
+        'authors.pubkey as author_pubkey',
+        'authors.content as author_content',
+        'authors.tags as author_tags',
+        'authors.created_at as author_created_at',
+        'authors.sig as author_sig',
+      ]) as typeof query;
+  }
+
   if (filter.search) {
     query = query
       .innerJoin('events_fts', 'events_fts.id', 'events.id')
@@ -172,30 +196,6 @@ async function getFilters<K extends number>(
   if (!filters.length) return Promise.resolve([]);
   let query = getFiltersQuery(filters);
 
-  if (opts.extra?.includes('author')) {
-    query = query
-      .leftJoin(
-        (eb) =>
-          eb
-            .selectFrom('events')
-            .selectAll()
-            .where('kind', '=', 0)
-            .orderBy('created_at', 'desc')
-            .groupBy('pubkey')
-            .as('authors'),
-        (join) => join.onRef('authors.pubkey', '=', 'events.pubkey'),
-      )
-      .select([
-        'authors.id as author_id',
-        'authors.kind as author_kind',
-        'authors.pubkey as author_pubkey',
-        'authors.content as author_content',
-        'authors.tags as author_tags',
-        'authors.created_at as author_created_at',
-        'authors.sig as author_sig',
-      ]) as typeof query;
-  }
-
   if (typeof opts.limit === 'number') {
     query = query.limit(opts.limit);
   }

src/filter.ts

@@ -3,22 +3,23 @@ import { type Event, type Filter, matchFilters } from '@/deps.ts';
 
 import type { EventData } from '@/types.ts';
 
+/** Additional properties that may be added by Ditto to events. */
+type Relation = 'author';
+
 /** Custom filter interface that extends Nostr filters with extra options for Ditto. */
 interface DittoFilter<K extends number = number> extends Filter<K> {
+  /** Whether the event was authored by a local user. */
   local?: boolean;
+  /** Additional fields to add to the returned event. */
+  relations?: Relation[];
 }
 
-/** Additional properties that may be added by Ditto to events. */
-type Extra = 'author';
-
 /** Additional options to apply to the whole subscription. */
 interface GetFiltersOpts {
   /** How long to wait (in milliseconds) until aborting the request. */
   timeout?: number;
   /** Event limit for the whole subscription. */
   limit?: number;
-  /** Whether to include a corresponding kind 0 event in the `authors` key of each event. */
-  extra?: Extra[];
 }
 
 function matchDittoFilter(filter: DittoFilter, event: Event, data: EventData): boolean {