feat(cache): add AniwatchAPICache class to implement API caching layer

src/config/cache.ts

@@ -0,0 +1,50 @@
+import { config } from "dotenv";
+import { Redis } from "ioredis";
+
+config();
+
+export class AniwatchAPICache {
+  private _client: Redis | null;
+  public isOptional: boolean = true;
+
+  static DEFAULT_CACHE_EXPIRY_SECONDS = 60 as const;
+  static CACHE_EXPIRY_HEADER_NAME = "X-ANIWATCH-CACHE-EXPIRY" as const;
+
+  constructor() {
+    const redisConnURL = process.env?.ANIWATCH_API_REDIS_CONN_URL;
+    this.isOptional = !Boolean(redisConnURL);
+    this._client = this.isOptional ? null : new Redis(String(redisConnURL));
+  }
+
+  set(key: string | Buffer, value: string | Buffer | number) {
+    if (this.isOptional) return;
+    return this._client?.set(key, value);
+  }
+
+  get(key: string | Buffer) {
+    if (this.isOptional) return;
+    return this._client?.get(key);
+  }
+
+  /**
+   * @param expirySeconds set to 60 by default
+   */
+  async getOrSet<T>(
+    key: string | Buffer,
+    setCB: () => Promise<T>,
+    expirySeconds: number = AniwatchAPICache.DEFAULT_CACHE_EXPIRY_SECONDS
+  ) {
+    const cachedData = this.isOptional
+      ? null
+      : (await this._client?.get(key)) || null;
+    let data = JSON.parse(String(cachedData)) as T;
+
+    if (!data) {
+      data = await setCB();
+      await this._client?.set(key, JSON.stringify(data), "EX", expirySeconds);
+    }
+    return data;
+  }
+}
+
+export const cache = new AniwatchAPICache();