/**
 * Given an array of Person objects, returns the root PersonTreeNode (the CEO).
 * @param {Person[]} employees - An array of Person objects representing all the employees of the company.
 * @returns {PersonTreeNode} The CEO of the organization.
 */

function generateTree( employees ) {

  /**
   * @ignore
   * INSTRUCTIONS:
   * 1. ONLY edit this function and nothing else!.
   *
   * 2. Analyze the Person.js and PersonTreeNode.js files.
   *
   * 3. Parse the `employees` array and create a single PersonTreeNode
   *    object representing the CEO (the Person with no `manager`).
   *    All PersonTreeNode object's `directReports` arrays should contain
   *    PersonTreeNode's for their direct reports...creating a tree.
   *
   * 4. Refresh or click the 'Retry Test' button to rerun the test.
   *
   *  Feel free to create any additional functions in this file as needed.
   */

  var ceo = null; // Should be a PersonTreeNode object at the end;

  // YOUR CODE STARTS HERE
  let employeeList = {};

  // used when adding employee to list and converting name to an id
  let mgrNode = {};

  // chain all the things like an adult
  ceo = employees.map((employee) => new PersonTreeNode(employee))

    // add employe node to employee list
    .map((employee) => {
      employeeList[employee.person.id] = employee;
      mgrNode[employee.person.name] = employee;
      return employee;
    })

    // add curret employee to directReports
    .map((employee) => {
      if (employee.person.manager) {
        let mgrId = employee.person.manager.id;
        employeeList[mgrId].directReports.push(employee);
      }
      return employee;
    })

    // find the ceo
    .reduce( ( ceoNode, employee ) => (
      // rule:  cep has no manager(s)
      employee.person.manager === null ? employee : ceoNode ), null );

  // YOUR CODE ENDS HERE

  return ceo;
}