// Migrate unsubscriptions collection to new schema

// The console-stamp module must be installed (not included in package.json)

// It requires two environment variables: MONGODB_OLD and MONGODB_NEW

// Due to some big user profiles it needs more RAM than is allowed by default by v8 (arounf 1.7GB).
// Run the script with --max-old-space-size=4096 to allow up to 4GB of RAM
console.log('Starting migrations/api_v3/unsubscriptions.js.');

// IMPORTANT NOTE: this migration was written when we were using version 3 of lodash.
// We've now upgraded to lodash v4 but the code used in this migration has not been
// adapted to work with it. Before this migration is used again any lodash method should
// be checked for compatibility against the v4 changelog and changed if necessary.
// https://github.com/lodash/lodash/wiki/Changelog#v400

require('babel-register');
require('babel-polyfill');

let Bluebird = require('bluebird');
let MongoDB = require('mongodb');
let nconf = require('nconf');
let mongoose = require('mongoose');
let _ = require('lodash');
let uuid = require('uuid');
let consoleStamp = require('console-stamp');

// Add timestamps to console messages
consoleStamp(console);

// Initialize configuration
require('../../website/server/libs/api-v3/setupNconf')();

let MONGODB_OLD = nconf.get('MONGODB_OLD');
let MONGODB_NEW = nconf.get('MONGODB_NEW');

let MongoClient = MongoDB.MongoClient;

mongoose.Promise = Bluebird; // otherwise mongoose models won't work

// Load new models
let EmailUnsubscription = require('../../website/server/models/emailUnsubscription').model;

// To be defined later when MongoClient connects
let mongoDbOldInstance;
let oldUnsubscriptionCollection;

let mongoDbNewInstance;
let newUnsubscriptionCollection;

let BATCH_SIZE = 1000;

let processedUnsubscriptions = 0;

// Only process unsubscriptions that fall in a interval ie -> up to 0000-4000-0000-0000
let AFTER_UNSUBSCRIPTION_ID = nconf.get('AFTER_UNSUBSCRIPTION_ID');
let BEFORE_UNSUBSCRIPTION_ID = nconf.get('BEFORE_UNSUBSCRIPTION_ID');

function processUnsubscriptions (afterId) {
  let processedTasks = 0;
  let lastUnsubscription = null;
  let oldUnsubscriptions;

  let query = {};

  if (BEFORE_UNSUBSCRIPTION_ID) {
    query._id = {$lte: BEFORE_UNSUBSCRIPTION_ID};
  }

  if ((afterId || AFTER_UNSUBSCRIPTION_ID) && !query._id) {
    query._id = {};
  }

  if (afterId) {
    query._id.$gt = afterId;
  } else if (AFTER_UNSUBSCRIPTION_ID) {
    query._id.$gt = AFTER_UNSUBSCRIPTION_ID;
  }

  let batchInsertUnsubscriptions = newUnsubscriptionCollection.initializeUnorderedBulkOp();

  console.log(`Executing unsubscriptions query.\nMatching unsubscriptions after ${afterId ? afterId : AFTER_UNSUBSCRIPTION_ID} and before ${BEFORE_UNSUBSCRIPTION_ID} (included).`);

  return oldUnsubscriptionCollection
    .find(query)
    .sort({_id: 1})
    .limit(BATCH_SIZE)
    .toArray()
    .then(function (oldUnsubscriptionsR) {
      oldUnsubscriptions = oldUnsubscriptionsR;

      console.log(`Processing ${oldUnsubscriptions.length} unsubscriptions. Already processed ${processedUnsubscriptions} unsubscriptions.`);

      if (oldUnsubscriptions.length === BATCH_SIZE) {
        lastUnsubscription = oldUnsubscriptions[oldUnsubscriptions.length - 1]._id;
      }

      oldUnsubscriptions.forEach(function (oldUnsubscription) {
        oldUnsubscription.email = oldUnsubscription.email.toLowerCase();
        let newUnsubscription = new EmailUnsubscription(oldUnsubscription);

        batchInsertUnsubscriptions.insert(newUnsubscription.toObject());
      });

      console.log(`Saving ${oldUnsubscriptions.length} unsubscriptions.`);

      return batchInsertUnsubscriptions.execute();
    })
    .then(function () {
      processedUnsubscriptions += oldUnsubscriptions.length;

      console.log(`Saved ${oldUnsubscriptions.length} unsubscriptions.`);

      if (lastUnsubscription) {
        return processUnsubscriptions(lastUnsubscription);
      } else {
        return console.log('Done!');
      }
    });
}

// Connect to the databases
Bluebird.all([
  MongoClient.connect(MONGODB_OLD),
  MongoClient.connect(MONGODB_NEW),
])
  .then(function (result) {
    let oldInstance = result[0];
    let newInstance = result[1];

    mongoDbOldInstance = oldInstance;
    oldUnsubscriptionCollection = mongoDbOldInstance.collection('emailunsubscriptions');

    mongoDbNewInstance = newInstance;
    newUnsubscriptionCollection = mongoDbNewInstance.collection('emailunsubscriptions');

    console.log(`Connected with MongoClient to ${MONGODB_OLD} and ${MONGODB_NEW}.`);

    return processUnsubscriptions();
  })
  .catch(function (err) {
    console.error(err.stack || err);
  });