qus-node-redis-cache/src/string-caching.service.ts

redis cache for nestjs

/*
 * MIT License
 * 
 * Copyright (c) 2025 Quantum Unit Solutions
 * Author: David Meikle
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
import { Injectable, Logger } from '@nestjs/common';
import { RedisClientType, createClient } from 'redis';

@Injectable()
export abstract class StringCachingService {
    protected _client: RedisClientType | null = null;
    protected logger: Logger = new Logger(this.constructor.name);
    protected url: string = process.env.REDIS_SERVER ?? 'redis://localhost:6379';

    constructor(
        protected ttl: number,
        private keyPrefix: string,
        url?: string,
    ) {
        if(url) {
            this.url = url;
        }
        this._client = createClient({ url: this.url });
        this._client.connect().catch(err => this.logger.error('Redis connection error', err));
    }

    protected getClient(): RedisClientType {
        if (!this._client) {
            throw new Error('Redis client not obtained');
        }
        return this._client;
    }

    protected async getFromCache(key: string, fetchData: (...args: any[]) => Promise<string>, ...args: any[]): Promise<string> {
        const client: RedisClientType = this.getClient();
        const prefixedKey = `${this.keyPrefix}${key}`;

        if (await client.exists(prefixedKey)) {
            const cacheResult: string | null = await client.get(prefixedKey);
            if (cacheResult) {
                return cacheResult;
            }
        }

        const result: string = await fetchData(key, ...args);
        await client.setEx(prefixedKey, this.ttl, result);

        return result;
    }

    protected getKeyPrefix(): string {
        return this.keyPrefix;
    }

    async clearCache(key: string): Promise<void> {
        const client: RedisClientType = this.getClient();
        const prefixedKey: string = `${this.keyPrefix}${key}`;
        await client.del(prefixedKey);
    }
}