owtlab-tracking/lib/utils/unique.js

A simple Tracking system

import 'promise-polyfill/src/polyfill';

import md5 from './md5';
import { getFromCache, saveToCache } from './cache-browser';

import configDefault from '../config-default.js';

let uniqueIds = [];

export const isUnique = (customCacheConfig, extendedEventBody) => {
  const configCache = { ...configDefault.cache, ...customCacheConfig.cache };
  const stringifiedEvent = JSON.stringify(extendedEventBody);
  const { hashingMethod } = configCache;
  const hash =
    hashingMethod && hashingMethod.toLowerCase() === 'md5'
      ? md5(stringifiedEvent)
      : stringifiedEvent;
  const expiryTime = configCache.maxAge
    ? Date.now() + configCache.maxAge
    : undefined;
  const item = {
    hash,
    expiryTime,
  };
  if (expiryTime) {
    const now = Date.now();
    uniqueIds = uniqueIds.filter(item => item.expiryTime > now);
  }

  const alreadySentEvent = uniqueIds.find(item => item.hash === hash);
  if (alreadySentEvent) {
    if (
      alreadySentEvent.expiryTime &&
      alreadySentEvent.expiryTime < Date.now()
    ) {
      uniqueIds = uniqueIds.filter(item => item.hash !== hash);
    } else {
      return Promise.resolve(false);
    }
  }
  uniqueIds.push(item);
  if (
    configCache.storage &&
    configCache.storage.toLowerCase() === 'indexeddb'
  ) {
    return getFromCache(hash, configCache).then((alreadySentEvent) => {
      if (alreadySentEvent) {
        return false;
      }
      saveToCache(hash, configCache);
      return true;
    });
  }

  return Promise.resolve(true);
};

export default isUnique;