import {AsyncCache} from 'utils-decorators';
import * as redis from 'redis';
import {RedisClient} from 'redis';
import {promisify} from 'util';
import * as config from 'config';

export class RedisCache<D> implements AsyncCache<D> {
  delete: (key: string) => Promise<void>;

  private readonly client: RedisClient;
  private readonly clientSet: (key: string, value: string, unit: 'PX', ttl: number) => Promise<void>;
  private readonly clientGet: (key: string) => Promise<string>;

  private readonly cacheConf: CacheConf<D>;

  constructor(cacheConf: CacheConf<D>) {
    this.cacheConf = {
      parse: JSON.parse,
      stringify: JSON.stringify,
      ...cacheConf,
    };
    const redisConf: RedisConf = config.get('redis');

    this.client = redis.createClient({
      host: redisConf.host,
      port: redisConf.port,
      ...(redisConf.password && {password: redisConf.password}),
      prefix: cacheConf.name,
    });

    this.clientGet = promisify(this.client.get).bind(this.client);
    this.clientSet = promisify(this.client.set).bind(this.client);
    this.delete = promisify(this.client.del).bind(this.client);
  }

  async get(key: string): Promise<D> {
    const strVal = await this.clientGet(key);

    return strVal !== null ? this.cacheConf.parse(strVal) : null;
  }

  set(key: string, value: D): Promise<void> {
    return this.clientSet(key, this.cacheConf.stringify(value), 'PX', this.cacheConf.ttl);
  }

  async has(key: string): Promise<boolean> {
    return (await this.get(key)) !== null;
  }
}

interface RedisConf {
  host: string;
  port: number;
  password: string;
}

interface CacheConf<D> {
  name: string;
  ttl: number;
  parse?: (val: string) => D;
  stringify?: (val: D) => string;
}