From c92a96d1fa723fdacc3056c4a22ff87ac1066bdd Mon Sep 17 00:00:00 2001
From: takker99 <37929109+takker99@users.noreply.github.com>
Date: Wed, 22 May 2024 10:39:56 +0900
Subject: [PATCH] feat(REST API): Get cached time of `Response`

---
 rest/getCachedAt.ts | 12 ++++++++++++
 rest/mod.ts         |  1 +
 2 files changed, 13 insertions(+)
 create mode 100644 rest/getCachedAt.ts

diff --git a/rest/getCachedAt.ts b/rest/getCachedAt.ts
new file mode 100644
index 0000000..0dd5dbf
--- /dev/null
+++ b/rest/getCachedAt.ts
@@ -0,0 +1,12 @@
+/** ServiceWorkerにcacheされた日時を得る
+ *
+ * cacheされたResponseでなければ`undefined`を返す
+ *
+ * @param res Response to check the chached date
+ * @return cached date (as UNIX timestamp) or `undefined`
+ */
+export const getCachedAt = (res: Response): number | undefined => {
+  const cachedAt = res.headers.get("x-serviceworker-cached");
+  if (!cachedAt) return;
+  return parseInt(cachedAt);
+};
diff --git a/rest/mod.ts b/rest/mod.ts
index 610f070..916fa9a 100644
--- a/rest/mod.ts
+++ b/rest/mod.ts
@@ -16,3 +16,4 @@ export * from "./error.ts";
 export * from "./getCodeBlocks.ts";
 export * from "./getCodeBlock.ts";
 export * from "./uploadToGCS.ts";
+export * from "./getCachedAt.ts";