refactor(plugin-sdk): unify channel dedupe primitives

src/infra/dedupe.ts

@@ -2,6 +2,7 @@ import { pruneMapToMaxSize } from "./map-size.js";
 
 export type DedupeCache = {
   check: (key: string | undefined | null, now?: number) => boolean;
+  peek: (key: string | undefined | null, now?: number) => boolean;
   clear: () => void;
   size: () => number;
 };
@@ -37,20 +38,39 @@ export function createDedupeCache(options: DedupeCacheOptions): DedupeCache {
     pruneMapToMaxSize(cache, maxSize);
   };
 
+  const hasUnexpired = (key: string, now: number, touchOnRead: boolean): boolean => {
+    const existing = cache.get(key);
+    if (existing === undefined) {
+      return false;
+    }
+    if (ttlMs > 0 && now - existing >= ttlMs) {
+      cache.delete(key);
+      return false;
+    }
+    if (touchOnRead) {
+      touch(key, now);
+    }
+    return true;
+  };
+
   return {
     check: (key, now = Date.now()) => {
       if (!key) {
         return false;
       }
-      const existing = cache.get(key);
-      if (existing !== undefined && (ttlMs <= 0 || now - existing < ttlMs)) {
-        touch(key, now);
+      if (hasUnexpired(key, now, true)) {
         return true;
       }
       touch(key, now);
       prune(now);
       return false;
     },
+    peek: (key, now = Date.now()) => {
+      if (!key) {
+        return false;
+      }
+      return hasUnexpired(key, now, false);
+    },
     clear: () => {
       cache.clear();
     },

src/infra/infra-store.test.ts

@@ -227,5 +227,13 @@ describe("infra store", () => {
       expect(cache.check("c", 200)).toBe(false);
       expect(cache.size()).toBe(2);
     });
+
+    it("supports non-mutating existence checks via peek()", () => {
+      const cache = createDedupeCache({ ttlMs: 1000, maxSize: 10 });
+      expect(cache.peek("a", 100)).toBe(false);
+      expect(cache.check("a", 100)).toBe(false);
+      expect(cache.peek("a", 200)).toBe(true);
+      expect(cache.peek("a", 1201)).toBe(false);
+    });
   });
 });