From 6f80bdf64ebf111e5f5433e58449b06480a8b3ab Mon Sep 17 00:00:00 2001
From: Alexandre <alex.forest1026@gmail.com>
Date: Thu, 29 Apr 2021 17:39:27 +0200
Subject: [PATCH] feat: apiCache class

---
 src/apiCache.ts | 81 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 src/apiCache.ts

diff --git a/src/apiCache.ts b/src/apiCache.ts
new file mode 100644
index 0000000..0091500
--- /dev/null
+++ b/src/apiCache.ts
@@ -0,0 +1,81 @@
+import { brotliCompress, brotliDecompress } from 'zlib';
+import { RedisClient } from 'redis';
+import { promisify } from 'util';
+import { Request } from 'express';
+import { toPairs } from 'lodash';
+import * as flatted from 'flatted';
+import { ERedisFlag, IApiCacheConfiguration } from './types';
+import { defaultConfiguration } from './config';
+
+/**
+ * ApiCache class.
+ */
+export class ApiCache {
+  private readonly redis: RedisClient;
+  private config: IApiCacheConfiguration;
+  public redisSetAsync: (key: string, value: string, flag?: ERedisFlag, expirationInMS?: number) => Promise<unknown>;
+  public redisGetAsync: (key: string) => Promise<string | null>;
+  private readonly compressAsync: (buffer: Buffer) => Promise<Buffer>;
+  private readonly decompressAsync: (buffer: Buffer) => Promise<Buffer>;
+
+  /**
+   * @description Constructor.
+   * @param {RedisClient} redis
+   * @param {IApiCacheConfiguration} config
+   */
+  constructor(redis: RedisClient, config?: IApiCacheConfiguration) {
+    this.redis = redis;
+    this.config = { ...defaultConfiguration, ...config };
+    this.redisSetAsync = promisify(this.redis.set).bind(this.redis);
+    this.redisGetAsync = promisify(this.redis.get).bind(this.redis);
+    this.compressAsync = promisify(brotliCompress);
+    this.decompressAsync = promisify(brotliDecompress);
+  }
+
+  /**
+   * @description Builds the redis key associated with the corresponding request.
+   * @param {Request} req Express request
+   * @private
+   */
+  private buildKey(req: Request): string {
+    const generatedQuery = toPairs(req.query)
+      .map((pair: [string, unknown]) => pair.join(''))
+      .join('');
+
+    return `${this.config.prefix}${req.method}__${req.path.slice(1)}__${generatedQuery}`.toLowerCase();
+  }
+
+  /**
+   * @description Retrieves data from cache.
+   * @param {Request} req Express request to build redis key
+   * @returns {Promise<any>} Cache data
+   */
+  async getCache(req: Request): Promise<unknown> {
+    const rawData: string = (await this.redisGetAsync(this.buildKey(req))) as string;
+
+    if (rawData) {
+      const buffer: Buffer = await this.decompressAsync(Buffer.from(rawData, 'base64'));
+      return flatted.parse(buffer.toString());
+    }
+
+    return;
+  }
+
+  /**
+   * @description Stores data into cache.
+   * @param {Request} req Express request associated with the data
+   * @param {any} data - Data to cache
+   * @param {number} durationInMS Cache expiration in ms
+   * @returns Promise<string>
+   */
+  async setCache(req: Request, data: unknown, durationInMS: number = this.config.expirationInMS): Promise<string> {
+    const compressedData: Buffer = await this.compressAsync(Buffer.from(flatted.stringify(data)));
+
+    return (await this.redisSetAsync(
+      this.buildKey(req),
+      compressedData.toString('base64'),
+      ERedisFlag.EXPIRATION_IN_MS,
+      durationInMS,
+    )) as string;
+  }
+}