Object-Oriented Delivery Cost Dashboard Service

Goal

Design and implement an object-oriented service to track delivery costs across multiple drivers, support live dashboard totals, and track payment status.

API Requirements

Implement a class (or set of classes) that supports:

1. add_driver(driver_id: integer, usd_hourly_rate: float)
   • Add a driver who is not yet in the system.
2. record_delivery(driver_id: integer, start_time, end_time)
   • Record a completed delivery for an existing driver.
   • Deliveries are entered immediately after completion.
   • No delivery exceeds 3 hours.
   • Time precision must be at least one second.
   • Drivers have individual hourly rates and can run multiple overlapping deliveries; each delivery is paid independently as duration_in_hours × driver_rate.
   • Example: $10.00/hr × 1h30m = $15.00.
3. get_total_cost()
   • Return the aggregated cost of all recorded deliveries across all drivers (suitable for a live dashboard; exact formatting not required).
4. pay_up_to(pay_time: integer, Unix time seconds from epoch)
   • Mark as paid all deliveries that ended at or before pay_time.
5. get_total_cost_unpaid()
   • Return the total cost of all recorded deliveries that have not yet been paid.

Constraints and Assumptions

• Inputs are valid; concurrency and thread-safety are out of scope.
• You may discuss and justify time representation (e.g., Unix seconds, ISO-8601 strings, timezone handling) and any assumptions.
• Demonstrate good OOP practices and share what you would do differently in production.