From 17589843da22e7a75f7ad6a3d49ec2bfbd0d4a06 Mon Sep 17 00:00:00 2001
From: syuilo <Syuilotan@yahoo.co.jp>
Date: Sat, 26 Mar 2022 19:09:57 +0900
Subject: perf(server): use cached user info in getUserFromApId

---
 packages/backend/src/misc/cache.ts | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

(limited to 'packages/backend/src/misc/cache.ts')

diff --git a/packages/backend/src/misc/cache.ts b/packages/backend/src/misc/cache.ts
index 9ce5c3e8b0..01bbe98a85 100644
--- a/packages/backend/src/misc/cache.ts
+++ b/packages/backend/src/misc/cache.ts
@@ -48,7 +48,32 @@ export class Cache<T> {
 
 		// Cache MISS
 		const value = await fetcher();
-		this.set(key, value);
+		return value;
+	}
+
+	/**
+	 * キャッシュがあればそれを返し、無ければfetcherを呼び出して結果をキャッシュ&返します
+	 * optional: キャッシュが存在してもvalidatorでfalseを返すとキャッシュ無効扱いにします
+	 */
+	public async fetchMaybe(key: string | null, fetcher: () => Promise<T | undefined>, validator?: (cachedValue: T) => boolean): Promise<T | undefined> {
+		const cachedValue = this.get(key);
+		if (cachedValue !== undefined) {
+			if (validator) {
+				if (validator(cachedValue)) {
+					// Cache HIT
+					return cachedValue;
+				}
+			} else {
+				// Cache HIT
+				return cachedValue;
+			}
+		}
+
+		// Cache MISS
+		const value = await fetcher();
+		if (value !== undefined) {
+			this.set(key, value);
+		}
 		return value;
 	}
 }
-- 
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