Requirements

Assign parking spots based on vehicle size, allowing motorcycles to park in small spots, cars in medium spots, and trucks in large spots, with the option to park in larger spots if needed.
Issue a ParkingTicket upon vehicle entry, which records the vehicle information, assigned parking spot, and entry timestamp.
Compute the parking fee upon vehicle exit based on the duration of stay and a configurable pricing strategy.
Handle scenarios where the parking lot is full by rejecting entry and displaying a lot-full indicator to the driver.
Support multiple floors in the parking lot, with each floor containing a mix of small, medium, and large parking spots.

extensibility to strategies of finding parking spot using interfaces to adhere to OCP of SOLID principle, eg. 1 strategy class derived from interface could have implementation to find spot based on size, another strategy class could have implementation for custom requirements if they are valid eg. request for larger spot size for a car than the ideal spot size set for the car
extensibility to price calculation strategies, eg. one class could have strategy based on entry time and exit time, with the multiplier of spot size, another price strategy in future could be dynamic based on peek time etc.
handling concurrency conditions and ensuring thread safety in case there are multiple entry gates, and multiple vehicles request for a parking spot at same time using locks