// Vacillate [ vas-uh-leyt ]:

// utilities defined below

const vacillate = (...args) => {
  const ideas = unique(args);

  if (ideas.length <= 1) {
    throw new Error('must have more than 1 idea to vacillate');
  }

  const vacillations = Math.ceil(Math.random() * 10) + 5;
  const iterator = generateRandomPairs(ideas, templates);

  let iterations = 1;
  for (const [idea, template] of iterator) {
    switch (iterations) {
      case 1:
        console.log(idea)
        break;
      case vacillations:
        console.log(`${idea}! (vacillated ${vacillations} times)`);
        return idea;
      default:
        console.log(template(idea));
        break;
    }
    iterations++;
  }
};

const unique = arr => [...new Set(arr)];

const shuffle = arr => arr
  .map(a => [Math.random(), a])
  .sort((a, b) => a[0] - b[0])
  .map(a => a[1]);

/**
 * Return shuffled array making sure no values are repeated
 * (important for vacillating!)
 */
const noRepeatNext = (arr) => {
  const shuffled = shuffle(arr);
  return arr[arr.length - 1] === shuffled[0]
    ? [...shuffled.slice(1), shuffled[0]]
    : shuffled;
};

const getNext = (arr, i) =>
  i === arr.length - 1
    ? [noRepeatNext(arr), 0]
    : [arr, i + 1];

function *generateRandomPairs(a, b) {
  let aIndex = a.length - 1;
  let bIndex = b.length - 1;

  while (true) {
    [a, aIndex] = getNext(a, aIndex);
    [b, bIndex] = getNext(b, bIndex);

    yield [
      a[aIndex],
      b[bIndex],
    ];
  }
}

const templates = [
  idea => `Just kidding: ${idea}`,
  idea => `No wait: ${idea}`,
  idea => `Actually: ${idea}`,
  idea => `What I really meant was: ${idea}`,
];

const result = vacillate(
  'do work',
  'eat lunch',
  'play video games'
);
// result will be one of
//   'do work', 'eat lunch', or 'play video games'!
//   It will also be clear that the function vacillated...

> JSVOW.vacillate('eat', 'pray', 'love');
// see what happens!
> const lunch = JSVOW.vacillate('pizza', 'mexican', 'burgers');
// make a decision on lunch!

const sleep = ms => new Promise(
  resolve => setTimeout(resolve, ms)
);
// and then in the function:
for (const [idea, template] of iterator) {
  await sleep(100);
  switch (iterations) {
  // ...

import vacillate from 'vacillate';

vacillate('React', 'Ember', 'Svelte', 'Vue');