const utils = require('../libs/utils');
const path = require('path');
const MongoClient = require('mongoose').mongo.MongoClient;
const appConfig = require('../config/app');
const SyncSeq = require('./sync-seq');
const { format } = require('date-fns');

const dbs = ['coloring_ol'];  // 需要同步的数据库, 主数据库（即syncevent表所在的库）放在第一个

/**
 * sync from remote
 */
async function run() {
  let delay = 30 * 1000; // sync freq
  let localDBHash = {};
  let remoteDBHash = {};
  const localClient = await new MongoClient(appConfig.mongodbUrl).connect();
  const remoteClient = await new MongoClient(appConfig.syncUrl).connect();
  for (let db of dbs) {
    localDBHash[db] = localClient.db(db);
    remoteDBHash[db] = remoteClient.db(db);
  }
  console.log('Connect to remote mongodb ' + appConfig.syncUrl + ' success!');

  // 读取远程syncevent表
  const synceventTB = remoteDBHash[dbs[0]].collection('syncevents');
  // get current local slave sync seq (use mongoose)
  let seq = -1;
  let seqDoc = await SyncSeq.findOne();
  if (seqDoc) seq = seqDoc.seq;
  else seqDoc = new SyncSeq({});

  let count, localtb, remotetb, localdoc, remotedoc;
  setTimeout(async function cycleRun() {
    try {
      let eventDocs = await synceventTB.find({ _id: { $gt: seq } }).limit(200).toArray() || [];
      count = 0;
      for (let i = 0; i < eventDocs.length; i++) {
        let eventDoc = eventDocs[i];
        console.log(eventDoc);
        if (eventDoc.tb == 'identitycounters') continue;  // skip
        // 只同步特定的几张表： arts， daily-arts， users， albums， translates
        if (eventDoc.tb != 'arts'
          && eventDoc.tb != 'daily-arts'
          && eventDoc.tb != 'users'
          && eventDoc.tb != 'albums'
          && eventDoc.tb != 'translates') {
          continue;
        }

        if (!eventDoc.db) eventDoc.db = dbs[0];
        // 对应的表
        remotetb = remoteDBHash[eventDoc.db] ? remoteDBHash[eventDoc.db].collection(eventDoc.tb) : null;
        localtb = localDBHash[eventDoc.db] ? localDBHash[eventDoc.db].collection(eventDoc.tb) : null;
        if (!remotetb || !localtb) {
          console.warn('unkown sync database: ' + eventDoc.db + ', will skip');
          continue;
        }

        if (eventDoc.op == 'remove') {
          await localtb.deleteOne({ _id: eventDoc.rid });
          console.log("sync remove : " + eventDoc.tb + " " + eventDoc.rid);
        } else if (eventDoc.op == 'save') {
          remotedoc = await remotetb.findOne({ _id: eventDoc.rid });
          localdoc = await localtb.findOne({ _id: eventDoc.rid });
          if (!remotedoc) {
            console.log("remote doc not found, may be deleted, skip: " + eventDoc.tb + " " + eventDoc.rid);
          } else if (!localdoc) {
            console.log("sync add :" + eventDoc.tb + " " + eventDoc.rid);
            try {
              await localtb.insertOne(remotedoc);
            } catch (e) {
              console.error(e);
            }
          } else {
            console.log("sync update :" + eventDoc.tb + " " + eventDoc.rid);
            // 删除desc和title字段，避免覆盖
            delete remotedoc.desc;
            await localtb.replaceOne({ _id: eventDoc.rid }, remotedoc);
          }
        }

        seq = eventDoc._id;
        seqDoc.seq = seq;
        await seqDoc.save();
        count++;
      }

      console.log(`${format(new Date(), 'yyyy-MM-dd HH:mm')} sync event length: ${eventDocs.length}, precessed: ${count}`);

    } catch (err) {
      console.error(err);
    }

    if (count > 0) setTimeout(cycleRun, 0);
    // else setTimeout(run, delay);

  }, 0);

}


module.exports = {
  run
}


if (require.main == module) {
  run().catch(console.error);
}