Adds handler preparation step

packages/nextjs-cache-handler/src/handlers/cache-handler.ts

@@ -649,6 +649,30 @@ export class CacheHandler implements NextCacheHandler {
         "Successfully created CacheHandler configuration.",
       );
     }
+
+    const prepareResults = await Promise.allSettled(
+      handlersList.map((handler) => handler.prepare?.()),
+    );
+
+    if (CacheHandler.#debug) {
+      prepareResults.forEach((result, index) => {
+        if (result.status === "rejected") {
+          console.warn(
+            "[CacheHandler] [handler: %s] [method: %s] %s",
+            handlersList[index]?.name ?? `unknown-${index}`,
+            "prepare",
+            `Error: ${result.reason}`,
+          );
+        } else if (result.status === "fulfilled" && result.value !== undefined) {
+          console.info(
+            "[CacheHandler] [handler: %s] [method: %s] %s",
+            handlersList[index]?.name ?? `unknown-${index}`,
+            "prepare",
+            "Successfully completed preparation tasks.",
+          );
+        }
+      });
+    }
   }
 
   /**

packages/nextjs-cache-handler/src/handlers/cache-handler.types.ts

@@ -173,6 +173,15 @@ export type Handler = {
    * @returns A Promise that resolves when the cache entry has been successfully deleted.
    */
   delete?: (key: string) => Promise<void>;
+
+  /**
+   * Prepares the handler for use, such as cleaning up expired entries or stale resources.
+   * This method is optional and will be automatically called by the `CacheHandler` class after handlers are configured.
+   * Handlers can use this to perform one-time setup tasks, remove stale entries, or prepare internal state.
+   *
+   * @returns A Promise that resolves when the preparation tasks have been completed.
+   */
+  prepare?: () => Promise<void>;
 };
 /**
  * Represents the parameters for Time-to-Live (TTL) configuration.

packages/nextjs-cache-handler/src/handlers/composite.ts

@@ -50,5 +50,9 @@ export default function createHandler({
     async delete(key) {
       await Promise.all(handlers.map((handler) => handler.delete?.(key)));
     },
+
+    async prepare() {
+      await Promise.all(handlers.map((handler) => handler.prepare?.()));
+    },
   };
 }

packages/nextjs-cache-handler/src/handlers/redis-strings.ts

@@ -333,5 +333,8 @@ export default function createHandler({
           .hDel(keyPrefix + sharedTagsTtlKey, key),
       ]);
     },
+    async prepare() {
+      await revalidateSharedKeys();
+    },
   };
 }