replicationHandler.js

import axios from 'axios';
import config from '../config';
import moment from 'moment';

class Replication {
  constructor(db, replicationUrl, storageKey, time = 10000) {
    this.db = db;
    this.replicationUrl = replicationUrl;
    this.storageKey = storageKey;

    this.tryReplication = this.tryReplication.bind(this);
    this.stopReplication = this.stopReplication.bind(this);

    this.tryReplication().then(() => {
      this.interval = window.setInterval(this.tryReplication, time);
    });
  }

  stopReplication() {
    window.clearInterval(this.interval);
    window.localStorage.removeItem(this.storageKey);
  }

  async tryReplication() {
    let rawNextChangeDate = localStorage.getItem(this.storageKey);
    let nextChangeDate = moment(rawNextChangeDate).format(
      'YYYY-MM-DDTHH:mm:SSS'
    );
    if (
      !rawNextChangeDate ||
      nextChangeDate < moment(new Date()).format('YYYY-MM-DDTHH:mm:SSS')
    ) {
      try {
        let { data } = await axios.get(this.replicationUrl);
        await this.db.bulkDocs({ docs: data });
        localStorage.setItem(this.storageKey, this.getNextReplicationDate());
      } catch (err) {
        if (err.response) {
        } // else no response received that means the user is offline (or the server is not working)
      }
    }
  }

  getNextReplicationDate() {
    let replicationHour = config.replication_starting_hour; // at 9am every morning the new data is here we have to refetch it
    let date = new Date();
    let nextDate = new Date(
      date.getFullYear(),
      date.getMonth(),
      date.getDate(),
      replicationHour
    );
    if (date.getHours() >= replicationHour) {
      nextDate.setDate(nextDate.getDate() + 1);
    }
    return nextDate;
  }
}

const replicateFromSQL = (db, replicationUrl, storageKey) => {
  return new Replication(db, replicationUrl, storageKey);
};

export default replicateFromSQL;