Implement concurrent order-accept/pickup simulator

Concurrent restaurant order + pickup simulator

Design and implement a thread-safe simulation for a restaurant that:

• Receives incoming orders concurrently (multiple producer threads).
• Prepares orders concurrently (one or more worker/chef threads).
• Allows customers to pick up orders concurrently (multiple consumer threads).

Requirements

1. Each order has:
   • order_id (unique integer)
   • item_name (string)
   • cook_time_ms (positive integer)
2. API / operations to support (names can vary):
   • placeOrder(order_id, item_name, cook_time_ms)
   • startKitchen(num_chefs) (starts background processing)
   • pickupOrder(order_id) blocks until the specified order is ready, then returns it
   • shutdown() stops background threads gracefully
3. Correctness constraints:
   • No order can be picked up before it is cooked.
   • Each order is cooked exactly once and picked up at most once.
   • No deadlocks; avoid busy-waiting.
   • The system should handle N orders with concurrent placement and pickup.

What to discuss/implement

• Your choice of synchronization primitives (mutex/lock, condition variable, semaphore, blocking queue, etc.).
• Data structures used to track order state.
• How you ensure fairness and avoid race conditions.

(You may assume a single process and shared memory; no networking required.)