Merge a simple event kind policy.

mod.ts

@@ -1,5 +1,6 @@
 export { type AntiDuplication, default as antiDuplicationPolicy } from './src/policies/anti-duplication-policy.ts';
 export { default as filterPolicy, type Filter } from './src/policies/filter-policy.ts';
+export { default as kindPolicy } from './src/policies/kind-policy.ts';
 export { default as hellthreadPolicy, type Hellthread } from './src/policies/hellthread-policy.ts';
 export { default as keywordPolicy } from './src/policies/keyword-policy.ts';
 export { default as noopPolicy } from './src/policies/noop-policy.ts';

src/policies/kind-policy.test.ts

@@ -0,0 +1,13 @@
+import { assertEquals } from '../deps.ts';
+import { buildEvent, buildInputMessage } from '../test.ts';
+
+import kindPolicy from './kind-policy.ts';
+
+Deno.test('rejects events by kind', async () => {
+  const msgA = buildInputMessage({ event: buildEvent({ kind: 1 }) });
+  const msgB = buildInputMessage({ event: buildEvent({ kind: 7 }) });
+
+  assertEquals((await kindPolicy(msgA, [7])).action, 'accept');
+  assertEquals((await kindPolicy(msgA, [7])).action, 'accept');
+  assertEquals((await kindPolicy(msgB, [7])).action, 'reject');
+});

src/policies/kind-policy.ts

@@ -0,0 +1,28 @@
+import { KindList, Policy } from '../types.ts';
+
+/**
+ * Reject events by kind.
+ *
+ * @example
+ * ```ts
+ * // Block DMs, likes, and channel messages.
+ * kindPolicy({ kinds: [4, 7, 42] });
+ * ```
+ */
+const kindPolicy: Policy<KindList> = ({ event: { id, kind } }, kinds = []) => {
+  if (kinds.includes(kind)) {
+    return {
+      id,
+      action: 'reject',
+      msg: 'blocked: this event kind is not currently permitted',
+    };
+  }
+
+  return {
+    id,
+    action: 'accept',
+    msg: '',
+  };
+};
+
+export default kindPolicy;

src/types.ts

@@ -54,4 +54,7 @@ type Policy<Opts = unknown> = (msg: InputMessage, opts?: Opts) => Promise<Output
 /** Sync or async iterable of pubkeys, designed for efficiently loading from large files. */
 type IterablePubkeys = Iterable<string> | AsyncIterable<string>;
 
-export type { Event, InputMessage, IterablePubkeys, OutputMessage, Policy };
+/** Syncronous iterable of event kinds. */
+type KindList = number[];
+
+export type { Event, InputMessage, IterablePubkeys, KindList, OutputMessage, Policy };