/*

A parking lot can have many slots which has different size.
A slot can occupy at most two vehicles.

Checkin:

 * Find the slot for the vehicle based on size

Checkout:

  * Calculate total fare based on vehicle size and duration

Questions:

  * Design bottom up or top down i.e. Vehicle, Slot or ParkingLot
*/

// Slot details
capacity = [4, 2, 2];
//filled   = [true, false, false];

// Vehicle details
sizes  = [2, 1, 2, 2];
parked = [1, 0, 1, 1];
start  = ['001', nil, '002', '003'];
end    = ['005', nil, '006', '008'];

// slot vehicle relation
vehicleSlot = [0, nil, 0, 1];

function checkin (vehicle) {
  for slot, size in capacity:
    if capacity[slot] >= size[vehicle]:
      start[vehicle]  = currentTimestamp;
      parked[vehicle] = 1;
      capacity[slot] -= size[vehicle];
      return true;
  return 'No slot empty'
}

function checkout (vehicle) {
  if not parked[vehicle]:
    return 'Invalid checkout'
  parked[vehicle] = 0;
  slot = vehicleSlot[vehicle];
  capacity[slot] += size[vehicle];
  end[vehicle] = currentTimestamp;
  return pricingAlgo(vehicle);
}

function pricingAlgo (vehicle) {
  // size * duration
  var duration = (end[vehicle] - start[vehicle]);
  return sizes[vehicle] * duration;
}