From 04c7e61fc076e2fa5ddf3d0faf6ebb73f4d52d82 Mon Sep 17 00:00:00 2001
From: Max Isom <hi@maxisom.me>
Date: Thu, 18 Nov 2021 20:55:57 -0500
Subject: Add FileCache model

---
 src/services/key-value-cache.ts | 56 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 src/services/key-value-cache.ts

(limited to 'src/services/key-value-cache.ts')

diff --git a/src/services/key-value-cache.ts b/src/services/key-value-cache.ts
new file mode 100644
index 0000000..7f1164d
--- /dev/null
+++ b/src/services/key-value-cache.ts
@@ -0,0 +1,56 @@
+import {injectable} from 'inversify';
+import {KeyValueCache} from '../models/index.js';
+import debug from '../utils/debug.js';
+
+type Seconds = number;
+
+type Options = {
+  expiresIn: Seconds;
+  key?: string;
+};
+
+const futureTimeToDate = (time: Seconds) => new Date(new Date().getTime() + (time * 1000));
+
+@injectable()
+export default class KeyValueCacheProvider {
+  async wrap<T extends [...any[], Options], F>(func: (...options: any) => Promise<F>, ...options: T): Promise<F> {
+    if (options.length === 0) {
+      throw new Error('Missing cache options');
+    }
+
+    const functionArgs = options.slice(0, options.length - 1);
+
+    const {
+      key = JSON.stringify(functionArgs),
+      expiresIn,
+    } = options[options.length - 1] as Options;
+
+    if (key.length < 4) {
+      throw new Error(`Cache key ${key} is too short.`);
+    }
+
+    const cachedResult = await KeyValueCache.findByPk(key);
+
+    if (cachedResult) {
+      if (new Date() < cachedResult.expiresAt) {
+        debug(`Cache hit: ${key}`);
+        return JSON.parse(cachedResult.value) as F;
+      }
+
+      await cachedResult.destroy();
+    }
+
+    debug(`Cache miss: ${key}`);
+
+    const result = await func(...options as any[]);
+
+    // Save result
+    await KeyValueCache.upsert({
+      key,
+      value: JSON.stringify(result),
+      expiresAt: futureTimeToDate(expiresIn),
+    });
+
+    return result;
+  }
+}
-- 
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