Airport Deal Service

<?php
namespace Game\Services;

use Game\Repositories\AirportRepositoryInterface;
use Game\Repositories\AirlineRepositoryInterface;

class AirportDealService
{

    public $fees;

    public function __construct(AirportRepositoryInterface $airportRepository, AirlineRepositoryInterface $airlineRepository)
    {
        $this->airportRepository = $airportRepository;
        $this->airlineRepository = $airlineRepository;
    }

    //Sign a deal with the airport
    public function sign ($airport_id, $airline_id)
    {

        $airline = $this->airlineRepository->getById($airline_id);
        $this->calculate($airport_id);
        $this->airlineRepository->signDeal($airline_id, $airport_id, $this->fees);

        return true;
    }

    //Calculate fees for specific airport
    public function calculate ($airport_id)
    {

        $airport = $this->airportRepository->getById($airport_id);

        $airport_size_factor = pow($airport->role, 3); // 1 to 125

        $this->fees = array('operation_fee' => 500*ceil($airport_size_factor/20), 'weekly_fee' => 3000*ceil($airport_size_factor/10), 'passenger_fee' => 10+floor($airport_size_factor/2));
    }

}