const REDIS_URI = process.env.REDIS_URI || 'redis://127.0.0.1:6379';
const redisClient = redis.createClient({ url: REDIS_URI });

const CACHE_EXPIRE_SECONDS = 4 * 60 * 60; // 4 hours;

export async function getArticleViews(articleId: string): Promise<number> {
  return new Promise((resolve) => {
    redisClient.get(articleId, async (_, views) => {
      if (views) {
        resolve(Number(views));
      } else {
        const manager = await getManager();

        const articleViewRecord = await manager.findOne(ArticleView, { ArticleId: articleId });

        if (articleViewRecord) {
          redisClient.set(articleId, articleViewRecord.views.toString());
          redisClient.expire(articleId, CACHE_EXPIRE_SECONDS);

          resolve(articleViewRecord.views);
        } else {
          redisClient.set(articleId, '0');
          redisClient.expire(articleId, CACHE_EXPIRE_SECONDS);

          resolve(0);
        }
      }
    });
  });
}

import { Kafka, logLevel } from 'kafkajs';

const KAFKA_CLIENT_ID = process.env.KAFKA_CLIENT_ID || 'wealth-usage-listener';
const KAFKA_BROKER_URI = process.env.KAFKA_BROKER_URI || 'localhost:7092';
const KAFKA_ARTICLE_VIEW_TOPIC = process.env.KAFKA_ARTICLE_VIEW_TOPIC || 'wealth-article-views';

const kafka = new Kafka({
  logLevel: logLevel.INFO,
  brokers: [KAFKA_BROKER_URI],
  clientId: KAFKA_CLIENT_ID,
});

const initQueue: QueueRecord[] = [];

export default async function init() {
  if (isInitialing || isConnected) {
    return;
  }

  debugKafkaProducer('Connecting Producer...');

  isInitialing = true;

  producer.on('producer.connect', () => {
    initQueue.map((record) => async () => {
      await producer.send({
        topic: KAFKA_ARTICLE_VIEW_TOPIC,
        messages: [
          {
            key: 'id',
            value: record.articleId,
            ...(record.memberId ? {
              headers: {
                memberId: record.memberId,
              },
            } : {}),
          },
        ],
      });
    }).reduce((prev, next) => prev.then(next), Promise.resolve());
  });

  await producer.connect();

  isConnected = true;
}

export async function recordArticleView(
  articleId: string,
  memberId?: string | undefined,
): Promise<void> {
  redisClient.get(articleId, (_, views) => {
    if (views) {
      redisClient.set(articleId, (Number(views) + 1).toString());
    } else {
      redisClient.set(articleId, '1');
    }

    redisClient.expire(articleId, CACHE_EXPIRE_SECONDS);
  });

  if (!isConnected) {
    debugKafkaProducer('Kafka Producer is not connected.');

    initQueue.push({ articleId, memberId });

    if (!isInitialing) {
      init();
    }

    return;
  }

  await producer.send({
    topic: KAFKA_ARTICLE_VIEW_TOPIC,
    messages: [
      {
        key: 'id',
        value: articleId,
        ...(memberId ? {
          headers: {
            memberId,
          },
        } : {}),
      },
    ],
  });
}

const KAFKA_CONSUMER_GROUP_ID = process.env.KAFKA_CONSUMER_GROUP_ID || 'wealth-consumer';
const KAFKA_ARTICLE_VIEW_TOPIC = process.env.KAFKA_ARTICLE_VIEW_TOPIC || 'wealth-article-views';
const ARTICLE_VIEW_UPDATE_FEQ_IN_MS = Number(process.env.ARTICLE_VIEW_UPDATE_FEQ_IN_MS || '30000'); // 30 sec

const consumer = kafka.consumer({ groupId: KAFKA_CONSUMER_GROUP_ID });

export default async function run() {
  await consumer.subscribe({ topic: KAFKA_ARTICLE_VIEW_TOPIC });
  
  let lastSync = Date.now();

  await consumer.run({
    eachMessage: async ({ topic, message }) => {
      const articleId = message.value!.toString();

      if (topic === KAFKA_ARTICLE_VIEW_TOPIC && message?.key?.toString() === 'id') {
        const manager = await getManager();

        const log = manager.create(ArticleViewLog, {
          ArticleId: articleId,
          MemberId: message.headers?.memberId?.toString() ?? undefined,
        });

        await manager.save(log);
      }

      if (ARTICLE_VIEW_UPDATE_FEQ_IN_MS
        && (Date.now() - lastSync) > ARTICLE_VIEW_UPDATE_FEQ_IN_MS) {
        const manager = await getManager();

        const count = await manager.count(ArticleViewLog, { ArticleId: articleId });

        const viewRecord = await manager.findOne(ArticleView, articleId);

        if (viewRecord) {
          viewRecord.views = count;
          viewRecord.updatedAt = new Date();

          await manager.save(viewRecord);
        } else {
          const newRecord = manager.create(ArticleView, {
            ArticleId: articleId,
            views: count,
          });

          await manager.save(newRecord);
        }

        lastSync = Date.now();

        debugKafkaConsumer(`Article ${articleId} updated views to ${count}`);
      }
    },
  });
}

import debug from 'debug';
import Koa from 'koa';
import { createConnection } from 'typeorm';
import { getArticleViews } from './worker';

const debugServer = debug('Wealth:UsageListenerServer');
const USAGE_LISTENER_PORT = Number(process.env.USAGE_LISTENER_PORT || '6068');

const app = new Koa();

app.use(async (ctx) => {
  const articleId = ctx.url.replace(/^\//, '');

  ctx.body = await getArticleViews(articleId);
});

createConnection().then(() => {
  app.listen(USAGE_LISTENER_PORT, () => {
    debugServer(`Usage Listener Server listen on ${USAGE_LISTENER_PORT}`);
  });
});