const gcd = (...arr) => {
  const _gcd = (x, y) => (!y ? x : gcd(y, x % y));
  return [...arr].reduce((a, b) => _gcd(a, b));
};

gcd(8, 36); // 4
gcd(...[12, 8, 32]); // 4

const jwt = require("jsonwebtoken");

const authToken = (req, res, next) => {
	const token = req.headers["x-auth-token"];

	try {
	req.user = jwt.verify(token, process.env.ACCESS_TOKEN_SECRET);

	next();
	} catch (err) {
	console.log(err.message);
	res.status(401).json({ msg: "Error authenticating token" });
	}
};

module.exports = authToken;

const longestPalindrome = (s) => {
    if(s.length === 1) return s
    
    const odd = longestOddPalindrome(s)
    const even = longestEvenPalindrome(s)
    
    
    if(odd.length >= even.length) return odd
    if(even.length > odd.length) return even
};

const longestOddPalindrome = (s) => {    
    let longest = 0
    let longestSubStr = ""
    
    for(let i = 1; i < s.length; i++) {
        
        let currentLongest = 1
        let currentLongestSubStr = ""
        let left = i - 1
        let right = i + 1
        
        while(left >= 0 && right < s.length) {
            const leftLetter = s[left]
            const rightLetter = s[right]

            left--
            right++

            if(leftLetter === rightLetter) {
                currentLongest += 2
                currentLongestSubStr = s.slice(left+1, right)
            } else break
        }
        
                        
        if(currentLongest > longest) {
            if(currentLongestSubStr) longestSubStr = currentLongestSubStr 
            else longestSubStr = s[i]
            longest = currentLongest
        }
    }
    
    return longestSubStr
}

const longestEvenPalindrome = (s) => {    
    let longest = 0
    let longestSubStr = ""
    
    for(let i = 0; i < s.length - 1; i++) {
        if(s[i] !== s[i+1]) continue;
        
        let currentLongest = 2
        let currentLongestSubStr = ""
        let left = i - 1
        let right = i + 2
        
        while(left >= 0 && right < s.length) {
            const leftLetter = s[left]
            const rightLetter = s[right]

            left--
            right++
            
            if(leftLetter === rightLetter) {
                currentLongest += 2
                currentLongestSubStr = s.slice(left+1, right)
            } else break
        }
                
                
        if(currentLongest > longest) {
            if(currentLongestSubStr) longestSubStr = currentLongestSubStr
            else longestSubStr = s[i] + s[i+1]
    
            longest = currentLongest
        }
    }
    
    return longestSubStr
}
console.log(longestPalindrome("babad"))

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');

// Connection URL
const url = 'mongodb://localhost:27017';

// Database Name
const dbName = 'myproject';

// Use connect method to connect to the server
MongoClient.connect(url, function(err, client) {
  assert.equal(null, err);
  console.log("Connected successfully to server");

  const db = client.db(dbName);

  client.close();
});

class Timer{
	start(){
		this.startTime = Date.now();
	}
	stop(){
		const dt = Date.now() - this.startTime;
		console.log(dt);
		return dt;
	}
	getExecTime(fun, asynchronous){
		return asynchronous ? this.getAsyncExecTime(fun) : this.getSyncExecTime(fun);
	}
	getSyncExecTime(fun){
		this.start();
		fun();
		return this.stop();
	}
	async getAsyncExecTime(fun){
		this.start();
		await fun();
		return this.stop();
	}
	static average(fun, numTimes, asynchronous = false){
		const times = [];
		const promises = [];
		let timer = new Timer();
		if(asynchronous){
			for(let i = 0; i < numTimes; i++){
				timer.getAsyncExecTime(fun);
			}
		}else{
			for(let i = 0; i < numTimes; i++){
				timer.getSyncExecTime(fun);
			}
		}
		return (times => times.reduce(((sum, acc) => sume + acc), 0) / times.length);
	}
	static async timeAsync(fun, numTimes){
		if(numTimes <= 1) return new Timer().getAsyncExecTime(fun);
		const promises = [];
		let timer = new Timer(true);
		for(let i = 0; i < numTimes; i++){
			promises.push(fun().catch((e)=>{}));
		}
		try{
			await Promise.all(promises).catch((e)=>{});
		}catch(e){
			//do absolutely nothing
		}
		return timer.stop();
	}
	constructor(start = false){
		if(start) this.start();
	}
}

const primes = num => {
  let arr = Array.from({ length: num - 1 }).map((x, i) => i + 2),
    sqroot = Math.floor(Math.sqrt(num)),
    numsTillSqroot = Array.from({ length: sqroot - 1 }).map((x, i) => i + 2);
  numsTillSqroot.forEach(x => (arr = arr.filter(y => y % x !== 0 || y === x)));
  return arr;
};

primes(10); // [2, 3, 5, 7]