/* eslint-env browser */

const isFunction = require('lodash/isFunction');
const isObject = require('lodash/isObject');
const isString = require('lodash/isString');
const head = require('lodash/head');
const last = require('lodash/last');

const db = require('../database');
const { deferredToPromise } = require('../deferred_to_promise');


const closeDatabaseConnection = ({ Backbone } = {}) =>
  deferredToPromise(Backbone.sync('closeall'));

exports.runMigrations = async ({ Backbone, database } = {}) => {
  if (!isObject(Backbone) || !isObject(Backbone.Collection) ||
      !isFunction(Backbone.Collection.extend)) {
    throw new TypeError('"Backbone" is required');
  }

  if (!isObject(database) || !isString(database.id) ||
      !Array.isArray(database.migrations)) {
    throw new TypeError('"database" is required');
  }

  const {
    firstVersion: firstMigrationVersion,
    lastVersion: lastMigrationVersion,
  } = getMigrationVersions(database);

  const databaseVersion = await db.getVersion(database.id);
  const isAlreadyUpgraded = databaseVersion >= lastMigrationVersion;

  console.log('Database state', {
    firstMigrationVersion,
    lastMigrationVersion,
    databaseVersion,
    isAlreadyUpgraded,
  });

  if (isAlreadyUpgraded) {
    return;
  }

  const migrationCollection = new (Backbone.Collection.extend({
    database,
    storeName: 'items',
  }))();

  await deferredToPromise(migrationCollection.fetch({ limit: 1 }));
  console.log('Close database connection');
  await closeDatabaseConnection({ Backbone });
};

const getMigrationVersions = (database) => {
  if (!isObject(database) || !Array.isArray(database.migrations)) {
    throw new TypeError('"database" is required');
  }

  const firstMigration = head(database.migrations);
  const lastMigration = last(database.migrations);

  const firstVersion = firstMigration ? parseInt(firstMigration.version, 10) : null;
  const lastVersion = lastMigration ? parseInt(lastMigration.version, 10) : null;

  return { firstVersion, lastVersion };
};