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

	this._options = {
		periods: 10,
		startIndex: null,
		endIndex: null,
		sliceOffset: false,
		lazyEvaluation: true,
		maxTickDuration: 10,
	};

	let m = [SetOptionsMixin, ValidateMixin, HandleGeneratorMixin];
	Object.assign(this, ...m);
	this.setOptions(options);
	this._collection = [];
}

SMA.prototype = {

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

	clear() {
		this._collection = [];
	},

	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 = (price, sma) => {
			return { price, sma: NumberUtil.roundTo(sma, 2) };
		}

		if (_.isNull(startIndex)) startIndex = 0;
		if (_.isNull(endIndex)) endIndex = this._collection.length - 1;
		if (startIndex >= endIndex) {
			throw new Error('ERROR: startIndex option must be lower than endIndex');
		}

		let cnt = (endIndex + 1) - (startIndex + 1) - periods + 2;
		if (cnt <= 0) {
			throw new Error('ERROR: Invalid range length');
		}

		let idx = startIndex;
		let endRangeIndex = endIndex - periods + 1;

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

		while (idx <= endRangeIndex) {
			let endPeriodIndex = idx + periods - 1;
			let avg = this._avg(idx, endPeriodIndex);
			let resultItem = convertToResultItem(this._collection[endPeriodIndex], avg);
			results.push(resultItem);
			if (lazyEvaluation) yield resultItem;
			idx++;
		}

		if (!lazyEvaluation) yield results;
	},

	_avg(startIndex, endIndex) {
		let sum = 0;
		let cnt = 0;
		for (let i = startIndex; i <= endIndex; i++) {
			sum += this._collection[i];
			cnt++;
		}
		return (parseFloat(sum) / cnt);
	}
}

export default SMA;