index.js

let lifts = [];
let q = [];
let input_floors = document.getElementById('input-floors');
let input_lifts = document.getElementById('input-lifts');
let no_of_floors;
let no_of_lifts;
let intervalId;
let tempInterval;

let form = document.getElementById('form');
form.addEventListener('click', function (e) {
  e.preventDefault();
});

function createLifts(n) {
  lifts = [];
  for (let i = 1; i <= n; i++) {
    let lift = document.createElement('div');
    lift.className = 'lift';
    lift.id = 'l' + i;
    let left_door = document.createElement('div');
    let right_door = document.createElement('div');
    left_door.classList.add('lift__door', 'lift__door-left');
    right_door.classList.add('lift__door', 'lift__door-right');
    left_door.id = 'ld' + i;
    right_door.id = 'rd' + i;
    lift.style.left = `${10 + 10 * i}%`;
    lift.appendChild(left_door);
    lift.appendChild(right_door);
    let liftObj = {
      id: i,
      lift: lift,
      currentFloor: 1,
      moving: false,
    };
    lifts.push(liftObj);
  }
}

function createFloor(floor_number) {
  let container = document.getElementById('container');

  let new_div = document.createElement('div');
  new_div.className = 'floor';
  new_div.id = 'floor' + floor_number;

  let new_up_btn = document.createElement('button');
  let up_text = document.createTextNode('U');
  // up_text.src = "./img/up-arrow-icon.png";
  let new_down_btn = document.createElement('button');
  let down_text = document.createTextNode('D');
  // down_text.src = "./img/down-arrow-icon.png";
  let new_br = document.createElement('br');
  let new_hr = document.createElement('hr');
  let new_span = document.createElement('span');
  let new_floor_text = document.createTextNode(floor_number);
  new_span.appendChild(new_floor_text);
  new_span.className = 'floor__number';
  new_hr.className = 'hr';
  new_hr.id = 'hr' + floor_number;
  new_up_btn.classList.add('control-btn', 'control-btn--up');
  new_down_btn.classList.add('control-btn', 'control-btn--down');
  // up_text.classList.add("arrow-icon");
  // down_text.classList.add("arrow-icon");

  new_up_btn.appendChild(up_text);
  new_up_btn.id = 'up' + floor_number;
  new_down_btn.appendChild(down_text);
  new_down_btn.id = 'down' + floor_number;

  new_div.appendChild(new_up_btn);
  new_div.appendChild(new_br);
  new_div.appendChild(new_down_btn);
  new_div.appendChild(new_span);
  new_div.appendChild(new_hr);

  container.insertBefore(new_div, container.childNodes[0]);
}

function closeDoor(e) {
  let target_id = e.target.id;
  let lift_no = target_id[target_id.length - 1];
  let left_door = document.getElementById('ld' + lift_no);
  let right_door = document.getElementById('rd' + lift_no);
  right_door.removeEventListener('webkitTransitionEnd', closeDoor);
  left_door.style.transform = `translateX(0)`;
  right_door.style.transform = `translateX(0)`;
  left_door.style.transition = `all 2.5s ease-out`;
  right_door.style.transition = `all 2.5s ease-out`;
  setTimeout(() => {
    stop_lift(lift_no);
  }, 2500);
}

function stop_lift(lift_no) {
  for (lft of lifts) {
    if (lft.id == lift_no) {
      lft.moving = false;
    }
  }
}

function doorAnimation(e) {
  let target_id = e.target.id;
  // NOTE :- BAD ASSUMPTION , MAX LIFTS = 9
  let lift_no = target_id[target_id.length - 1];
  let lift = document.getElementById('l' + lift_no);
  lift.removeEventListener('webkitTransitionEnd', doorAnimation);
  let left_door = document.getElementById('ld' + lift_no);
  let right_door = document.getElementById('rd' + lift_no);
  left_door.removeEventListener('webkitTransitionEnd', doorAnimation);
  right_door.removeEventListener('webkitTransitionEnd', doorAnimation);
  right_door.addEventListener('webkitTransitionEnd', closeDoor);
  left_door.style.transform = `translateX(-100%)`;
  right_door.style.transform = `translateX(100%)`;
  left_door.style.transition = `all 2.5s ease-out`;
  right_door.style.transition = `all 2.5s ease-out`;
}

function scheduledLift(floor) {
  let selected_lift;
  let min_distance = Infinity;

  for (lift of lifts) {
    if (!lift.moving && Math.abs(floor - lift.currentFloor) < min_distance) {
      min_distance = Math.abs(floor - lift.currentFloor);
      selected_lift = lift;
    }
  }
  return selected_lift;
}

function moveLift(lift, to) {
  let distance = -1 * (to - 1) * 100;
  let lift_no = lift.id;
  let from = lift.currentFloor;
  lift.currentFloor = to;
  lift.moving = true;
  let lft = lift.lift;
  lft.addEventListener('webkitTransitionEnd', doorAnimation);
  lft.style.transform = `translateY(${distance}%)`;
  let time = 2 * Math.abs(from - to);
  if (time === 0) {
    let e = {};
    e.target = {};
    e.target.id = `l${lift_no}`;
    doorAnimation(e);
  }
  lft.style.transitionDuration = `${time}s`;
  console.log(
    `Lift Number: ${lift_no} \n Floor: \n From: ${from} To: ${to} \n Time: ${time} sec`,
  );
}

function save_click(e) {
  let clicked_on = e.target.id;
  let n;
  if (clicked_on.startsWith('up'))
    n = Number(clicked_on.substring(2, clicked_on.length));
  else if (clicked_on.startsWith('down'))
    n = Number(clicked_on.substring(4, clicked_on.length));
  q.push(n);
}

function getButtons() {
  let up_btn_list = document.getElementsByClassName('control-btn--up');
  let down_btn_list = document.getElementsByClassName('control-btn--down');
  for (up_btn of up_btn_list) {
    up_btn.addEventListener('click', save_click);
  }
  for (down_btn of down_btn_list) {
    down_btn.addEventListener('click', save_click);
  }
}

function make_lifts() {
  no_of_lifts = input_lifts.value;

  createLifts(no_of_lifts);

  for (lft of lifts) {
    let lift = lft.lift;
    lift.style.transform = null;
    lift.style.transitionDuration = null;
  }
}

function make_floors() {
  container.innerHTML = '';
  no_of_floors = input_floors.value;

  for (let i = 1; i <= no_of_floors; i++) {
    createFloor(i);
  }
}

function place_lifts() {
  let first_floor = document.getElementById('floor1');
  for (let i = lifts.length - 1; i >= 0; i--) {
    first_floor.insertBefore(
      lifts[i].lift,
      first_floor.childNodes[first_floor.childNodes.length - 1],
    );
  }
}

function check_for_scheduling() {
  if (q.length === 0) return;
  floor = q.shift();
  let lift = scheduledLift(floor);
  if (!lift) {
    q.unshift(floor);
    return;
  }
  moveLift(lift, floor);
}

function start() {
  clearInterval(intervalId);
  q = [];
  lifts = [];

  if (input_floors.value > 15) {
    alert('FLOORS CAN BE NO MORE THAN 15');
    return;
  } else if (input_lifts.value > 5) {
    alert("LIFTS CAN'T BE MORE THAN 5");
    return;
  } else {
    make_floors();
    make_lifts();
  }

  place_lifts();
  // set up buttons to listen for click event
  getButtons();
  intervalId = setInterval(check_for_scheduling, 100);
}

let input_btn = document.getElementById('input-btn');
input_btn.addEventListener('click', start);