feat(snapshot): NIP-09-filter

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

snapshot/src/core/nip09-filter.ts

@@ -0,0 +1,22 @@
+import type { SignedEvent } from './types.ts'
+
+export function filterDeleted(
+  events: SignedEvent[],
+  deletions: SignedEvent[],
+  authorPubkey: string,
+): SignedEvent[] {
+  const deletedCoords = new Set<string>()
+  for (const del of deletions) {
+    if (del.kind !== 5) continue
+    if (del.pubkey !== authorPubkey) continue
+    for (const tag of del.tags) {
+      if (tag[0] === 'a' && tag[1]) deletedCoords.add(tag[1])
+    }
+  }
+  return events.filter((ev) => {
+    const d = ev.tags.find((t) => t[0] === 'd')?.[1]
+    if (!d) return true
+    const coord = `${ev.kind}:${ev.pubkey}:${d}`
+    return !deletedCoords.has(coord)
+  })
+}

snapshot/tests/nip09-filter.test.ts

@@ -0,0 +1,30 @@
+import { assertEquals } from '@std/assert'
+import { filterDeleted } from '../src/core/nip09-filter.ts'
+import type { SignedEvent } from '../src/core/types.ts'
+
+function post(d: string, id: string): SignedEvent {
+  return { id, pubkey: 'P', created_at: 1, kind: 30023, sig: 's', content: '', tags: [['d', d]] }
+}
+function deletion(coords: string[]): SignedEvent {
+  return {
+    id: 'del', pubkey: 'P', created_at: 2, kind: 5, sig: 's', content: '',
+    tags: coords.map((c) => ['a', c]),
+  }
+}
+
+Deno.test('filterDeleted entfernt events deren coord in einem kind:5 referenziert ist', () => {
+  const out = filterDeleted(
+    [post('alive', 'a'), post('dead', 'b')],
+    [deletion(['30023:P:dead'])],
+    'P',
+  )
+  assertEquals(out.map((e) => e.id), ['a'])
+})
+
+Deno.test('filterDeleted ignoriert kind:5 fremder pubkeys', () => {
+  const fremde: SignedEvent = {
+    ...deletion(['30023:P:alive']), pubkey: 'OTHER',
+  }
+  const out = filterDeleted([post('alive', 'a')], [fremde], 'P')
+  assertEquals(out.length, 1)
+})