'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=14]
 * @param {number} [options.startIndex]
 * @param {number} [options.endIndex}] 
 * @param {boolean} [options.sliceOffset=false]
 * @param {boolean} [options.lazyEvaluation=true]
 * @param {number} [option.maxTickDuration=10]
 */
function ROC(options = {}) {
	if (!new.target) throw new Error('ERROR: ROC() must be called with new');

	this._options = {
		periods: 14,
		startIndex: null,
		endIndex: null,
		sliceOffset: false,
		lazyEvaluation: true,
		maxTickDuration: 10,
	};
	let m = [SetOptionsMixin, ValidateMixin, HandleGeneratorMixin];
	Object.assign(this, ...m);
	this.setOptions(options);
	this._collection = [];
}

ROC.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 { startIndex, endIndex, periods, lazyEvaluation, sliceOffset } = this._options;

		if (!NumberUtil.isNumeric(startIndex)) startIndex = 0;
		if (!NumberUtil.isNumeric(endIndex)) endIndex = this._collection.length - 1;

		let resultItem = null;

		for (let i = startIndex; i <= endIndex; i++) {
			let currentPrice = this._collection[i];
			if (i <= startIndex + periods - 1) {
				if (!sliceOffset) {
					resultItem = { roc: 0, price: currentPrice };
					results.push(resultItem);
					if (lazyEvaluation) yield resultItem;
				}
				continue;
			}
			let prevPrice = this._collection[i - periods];
			let roc = ((currentPrice - prevPrice) / prevPrice) * 100;
			resultItem = { roc: NumberUtil.roundTo(roc, 2), price: currentPrice };
			results.push(resultItem);
			if (lazyEvaluation) yield resultItem;
		};

		return results;
	},
}

export default ROC;