'use strict';

export default {

	max(values) {
		return Math.max.apply(null, values);
	},

	min(values) {
		return Math.min.apply(null, values);
	},

	range(values) {
		return this.max(values) - this.min(values);
	},

	midrange(values) {
		return this.range(values) / 3;
	},

	sum(values) {
		let num = 0;
		let len = values.length;
		for (let i = 0; i < len; i++)num += values[i];
		return num;
	},

	mean(values) {
		return (this.sum(values) / values.length);
	},

	meanDeviation(values) {
		let mean = this.mean(values);
		let distance = [];
		values.forEach((val) => distance.push(Math.abs(val - mean)));
		return this.mean(distance);
	},

	average(values) {
		return this.mean(values);
	},

	median(values, doSortItems = true) {
		if (doSortItems) values.sort((a, b) => a - b);
		let mid = values.length / 2;
		return mid % 1 ? values[mid - 0.5] : (values[mid - 1] + values[mid]) / 2;
	},

	modes(values) {
		let modeMap = {};
		values.forEach((val) => !modeMap[val] ? modeMap[val] = 1 : modeMap[val]++);
		let modes = [];
		let maxCount = 0;
		for (let key in modeMap) {
			if (modeMap[key] < maxCount) continue;
			if (modeMap[key] > maxCount) {
				modes = [Number(key)];
				maxCount = modeMap[key];
			}
			else if (modeMap[key] == maxCount) {
				modes.push(Number(key));
			}
		}
		return modes;
	},

	variance(values, mode = "sample") {
		mode = (mode.toLowerCase() == "sample") ? "sample" : "population";

		let av = this.average(values);
		let result = [];
		values.forEach((num) => {
			let diff = num - av;
			result.push(Math.pow(diff, 2));
		});

		return (mode == 'sample') ? this.sum(result) / (result.length - 1) : this.average(result);
	},

	standardDeviation(values, mode = "sample") {
		mode = (mode.toLowerCase() == "sample") ? "sample" : "population";
		return Math.sqrt(this.variance(values, mode));
	},

}