'use strict';

import _ from 'underscore';
import NumberUtil from '../utils/number.js';
import ValidateMixin from '../mixin/validate.js';
import SetOptionsMixin from '../mixin/set-options.js';
import HandleGeneratorMixin from '../mixin/handle-generator.js';

/**
 * @param {object} [options]
 * @param {number} [optons.periods=20]
 * @param {number} [options.startIndex]
 * @param {number} [options.endIndex}] 
 * @param {boolean} [options.sliceOffset=false]
 * @param {boolean} [options.lazyEvaluation=true]
 * @param {number} [option.maxTickDuration=10]
 */
function LWMA(options = {}) {
	if (!new.target) throw new Error('ERROR: LWMA() must be called with new');

	this._options = {
		periods: 20,
		startIndex: null,
		endIndex: null,
		sliceOffset: false,
		lazyEvaluation: true,
		maxTickDuration: 10,
	}
	let m = [SetOptionsMixin, ValidateMixin, HandleGeneratorMixin];
	Object.assign(this, ...m);
	this.setOptions(options);
	this._collection = [];
}

LWMA.prototype = {

	setValues(values) {
		if (!Array.isArray(values)) {
			throw new Error('ERROR: values param is not an array');
		}
		this._collection = values;
	},

	calculate() {
		this._validate(this._collection, this._options);
		return this._handleGenerator(this._compute());
	},

	_compute: function* () {
		let results = [];
		let { periods, startIndex, endIndex, sliceOffset, lazyEvaluation } = this._options;

		let convertToResultItem = (lwma, price) => {
			return {
				lwma: NumberUtil.roundTo(lwma, 2),
				price,
			};
		};

		if (_.isNull(startIndex)) startIndex = 0;
		if (_.isNull(endIndex)) endIndex = this._collection.length - 1;

		let endRangeIndex = endIndex - periods + 1;

		if (!sliceOffset) {
			for (let i = startIndex; i < startIndex + periods - 1; i++) {
				let resultItem = convertToResultItem(0, this._collection[i]);
				results.push(resultItem);
				if (lazyEvaluation) yield resultItem;
			}
		}

		let itr_i = 0;
		for (let i = startIndex; i <= endRangeIndex; i++) {
			let sum_vals = 0;
			let sum_weight = 0;
			itr_i++;
			let itr_j = 0;
			let lastIdxInPeriod = 0;
			for (let j = i, len = i + periods; j < len; j++) {
				let n = itr_i + itr_j;
				sum_vals += (this._collection[j] * n);
				sum_weight += n;
				itr_j++;
				lastIdxInPeriod = j;
			}
			let resultItem = convertToResultItem(sum_vals / sum_weight, this._collection[lastIdxInPeriod]);
			results.push(resultItem);
			if (lazyEvaluation) yield resultItem;
		};

		return results;
	},

};

export default LWMA;