// curse Javascript's tiny standard library

function id(x) { return x; }

function uncurry(f) {
    return (args => f(...args));
}

function compose(...fs) {
    return fs.reduce((acc, f) => (x => f(acc(x))), id);
}

// oh god, assignment and a loop? >:(
// js doesn't have tail call optimization, unfortunately
function zip(l1, l2) {
    let result = [];
    let minRange = Math.min(l1.length, l2.length);
    for(let i = 0; i < minRange; i++) {
        result.push([l1[i], l2[i]]);
    }
    return result;
}

function sum(lst, acc) {
    return lst.reduce((x, y) => x + y, acc);
}

function fst(tup) {
    return tup[0];
}

function snd(tup) {
    return tup[1];
}

const lowerStr = "abcde"; // shortened for brevity
const upperStr = lowerStr.toUpperCase();
const specialStr = "!@#$%^&*";
const numberStr = "0123456789";

function getCharList(lowercase, uppercase, special, numbers) {
    return compose(uncurry(zip),
        (arr => arr.filter(fst)),
        (arr => arr.map(snd)),
        (arr => sum(arr, [])),
        (s => s.split('')))([[lowercase, uppercase, special, numbers],
                             [lowerStr, upperStr, specialStr, numberStr]])
}

function randomChoice(lst) {
    return lst[Math.floor(Math.random() * lst.length)];
}

function randomPassword(n, lowercase, uppercase, special, numbers) {
    let charList = getCharList(lowercase, uppercase, special, numbers);
    return Array(n).fill(undefined)
                   .map(_ => randomChoice(charList))
                   .join('');
}