// element.children => HTMLCollection
// element.className => string

/**
* @function getByClassName
* @param {Element} root – The root of the DOM tree
* @param {string} className
* @return {Array<Element>} nodes – All the nodes in the tree which include the target className in their classes.
*/
function getByClassName(root, className) {
	// todo
}

const { JSDOM } = require("jsdom");
const { document } = new JSDOM(`
  <div class='a' id="root">
    <div class='b' id='b-1'>
      <div class='a' id='a-2'>
        <div class='d' id='d-1'></div>
      </div>
      <div class='c' id='c-1'>
        <div class='a' id='a-3'>
          <div class='d' id='d-2'></div>
        </div>
      </div>
    </div>
  </div>
`).window;
const getIds = (elements=[]) => Array.from(elements).map(x => x.id);
const root = document.getElementById('root');
console.log('actual:  ', getIds(getByClassName(root, 'a')));
console.log('expected:' , `[ 'root', 'a-2', 'a-3' ]`);

const { document: document2 } = new JSDOM(`
<div class=”a" id=”a-1”>
  <div class=”b" id=”b-1”>
    <div class=”c" id=”c-1”/>
    <div class=”c" id=”c-2”/>
  </div>
  <div class=”c" id=”c-3”/>
</div>
`).window;

function getByClassnameHierarchy(root, classNames) {
	// todo
}
 
const root2 = document2.getElementById('root2');

console.log('actual: ', getIds(getByClassnameHierarchy(root2, 'a>b')));
console.log(`a>b expected:` , `['b-1']`, '\n');

// order matters!:
console.log('actual: ', getIds(getByClassnameHierarchy(root2, 'b>a')));
console.log(`b>a expected:` , `[]`, '\n');

// must be direct descendants:
console.log('actual: ', getIds(getByClassnameHierarchy(root2, 'a>c')));
console.log(`a>c expected:` , `[c-3]`, '\n');

// the number of classes in the string doesn't matter:
console.log('actual: ', getIds(getByClassnameHierarchy(root2, 'a>b>c')));
console.log(`a>b>c expected:` , `['c-1', 'c-2']`, '\n');

console.log('actual: ', getIds(getByClassnameHierarchy(root2, 'b>c')));
console.log(`b>c expected:` , `['c-1', 'c-2']`, '\n');

console.log('actual: ', getIds(getByClassnameHierarchy(root2, 'c')));
console.log(`c expected:` , `['c-1', 'c-2', 'c-3']`, '\n');