'use strict';

const { EachSeries } = require('./eachSeries');
const { setSeries } = require('./internal/collection');

class GroupBySeries extends EachSeries {
  constructor(collection, iterator) {
    super(collection, iterator, set);
    this._result = {};
  }
}

module.exports = { groupBySeries, GroupBySeries };

function set(collection) {
  setSeries.call(this, collection);
  this._callResolve = this._keys === undefined ? callResolveArray : callResolveObject;
  return this;
}

function callResolveArray(key, index) {
  if (this._result[key]) {
    this._result[key].push(this._coll[index]);
  } else {
    this._result[key] = [this._coll[index]];
  }
  if (--this._rest === 0) {
    this._promise._resolve(this._result);
  } else {
    this._iterate();
  }
}

function callResolveObject(key, index) {
  if (this._result[key]) {
    this._result[key].push(this._coll[this._keys[index]]);
  } else {
    this._result[key] = [this._coll[this._keys[index]]];
  }
  if (--this._rest === 0) {
    this._promise._resolve(this._result);
  } else {
    this._iterate();
  }
}

/**
 * @param {Array|Object} collection
 * @param {Function} iterator
 * @return {Aigle} Returns an Aigle instance
 * @example
 * const order = [];
 * const collection = [1, 4, 2];
 * const iterator = (num, index) => {
 *   return Aigle.delay(num * 10)
 *     .then(() => {
 *       order.push(num);
 *       return num % 2;
 *     });
 * };
 * Aigle.groupBySeries(collection, iterator)
 *   .then(object => {
 *     console.log(object); // { '0': [4, 2], '1': [1] };
 *     console.log(order); // [1, 4, 2];
 *   });
 *
 * @example
 * const order = [];
 * const collection = { a: 1, b: 4, c: 2 };
 * const iterator = (num, key) => {
 *   return Aigle.delay(num * 10)
 *     .then(() => {
 *       order.push(num);
 *       return num % 2;
 *     });
 * };
 * Aigle.groupBySeries(collection, iterator)
 *   .then(object => {
 *     console.log(object); // { '0': [4, 2], '1': [1] };
 *     console.log(order); // [1, 4, 2];
 *   });
 */
function groupBySeries(collection, iterator) {
  return new GroupBySeries(collection, iterator)._execute();
}