egg middle for url cache

cache.js

const DEFAULT_TTL = 60 * 1000;
const MIN_10 = 1 * 60 * 1000;
const cacheConfig = {
  '/api/page/index': DEFAULT_TTL,
  '/api/page/miner': DEFAULT_TTL,
  '/api/page/luck': DEFAULT_TTL,
  '/api/page/': DEFAULT_TTL,
  '/api/blocks': DEFAULT_TTL,
  '/api/miner/top10': MIN_10,
  '/api/block/history': MIN_10,
  '/api/pool/difficultyAvg': MIN_10,
  '/api/pool/hashrateAvg': MIN_10,
};

function needCache(key) {
  return cacheConfig[key] || false;
}

/*
 * 接口 cache, 根据 url 前缀设置 cache
 * 开发环境不会启用缓存
 */
module.exports = options => {
  const cachePrefix = 'page:';
  return function* cache(next) {

    if (this.app.config.env !== 'prod' || this.request.query.refresh) {
      yield next;
      return;
    }
    const key = this.request.originalUrl;
    const url = key.indexOf('?') > 0 ? this.request.url.split('?')[0] : key;
    const ttl = needCache(url);
    if (!ttl) {
      yield next;
    } else {
      const data = yield this.app.redis.getAsync(cachePrefix + key);
      if (data) {
        this.logger.info('cached');
        this.set('Cache-Control', `max-age=${ttl / 1000}`);
        this.response.body = data;
        return;
      }

      yield next;
      if (this.status === 200) {
        yield this.app.redis.setAsync(cachePrefix + key, JSON.stringify(this.response.body), 'EX', ttl / 1000);
      }
    }
  };
};