From 539804215665d141f526014042e6f924bab779b2 Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Wed, 27 Dec 2023 22:49:35 -0600
Subject: [PATCH] Add memorelay module

---
 src/db/memorelay.ts | 27 +++++++++++++++++++++++++++
 src/filter.ts       | 18 +++++++++++++++---
 2 files changed, 42 insertions(+), 3 deletions(-)
 create mode 100644 src/db/memorelay.ts

diff --git a/src/db/memorelay.ts b/src/db/memorelay.ts
new file mode 100644
index 00000000..a6dc2d97
--- /dev/null
+++ b/src/db/memorelay.ts
@@ -0,0 +1,27 @@
+import { Debug, type Event, type Filter, LRUCache } from '@/deps.ts';
+import { getFilterId, type GetFiltersOpts, isMicrofilter } from '@/filter.ts';
+
+const debug = Debug('ditto:memorelay');
+const events = new LRUCache<string, Event>({ max: 1000 });
+
+/** Get events from memory. */
+function getFilters<K extends number>(filters: Filter<K>[], opts: GetFiltersOpts = {}): Promise<Event<K>[]> {
+  if (opts.signal?.aborted) return Promise.resolve([]);
+  if (!filters.length) return Promise.resolve([]);
+  debug('REQ', JSON.stringify(filters));
+
+  const results: Event<K>[] = [];
+
+  for (const filter of filters) {
+    if (isMicrofilter(filter)) {
+      const event = events.get(getFilterId(filter));
+      if (event) {
+        results.push(event as Event<K>);
+      }
+    }
+  }
+
+  return Promise.resolve(results);
+}
+
+export { getFilters };
diff --git a/src/filter.ts b/src/filter.ts
index 7178e2d7..f562a828 100644
--- a/src/filter.ts
+++ b/src/filter.ts
@@ -1,7 +1,7 @@
 import { Conf } from '@/config.ts';
-import { type Event, type Filter, matchFilters, stringifyStable } from '@/deps.ts';
-
-import type { EventData } from '@/types.ts';
+import { type Event, type Filter, matchFilters, stringifyStable, z } from '@/deps.ts';
+import { nostrIdSchema } from '@/schemas/nostr.ts';
+import { type EventData } from '@/types.ts';
 
 /** Additional properties that may be added by Ditto to events. */
 type Relation = 'author' | 'author_stats' | 'event_stats';
@@ -70,11 +70,23 @@ function eventToMicroFilter(event: Event): MicroFilter {
   }
 }
 
+/** Microfilter schema. */
+const microFilterSchema = z.union([
+  z.object({ ids: z.tuple([nostrIdSchema]) }).strict(),
+  z.object({ kinds: z.tuple([z.literal(0)]), authors: z.tuple([nostrIdSchema]) }).strict(),
+]);
+
+/** Checks whether the filter is a microfilter. */
+function isMicrofilter(filter: Filter): filter is MicroFilter {
+  return microFilterSchema.safeParse(filter).success;
+}
+
 export {
   type DittoFilter,
   eventToMicroFilter,
   getFilterId,
   type GetFiltersOpts,
+  isMicrofilter,
   matchDittoFilters,
   type MicroFilter,
   type Relation,