Requirements

Let's refine our logistics system. We previously had a rudimentary system; now, we aim for a more robust and extensible design. The core of any logistics system revolves around managing shipments, tracking their movement, and handling exceptions or issues that arise along the way. A key aspect is integrating different transportation providers (e.g., FedEx, UPS, USPS) without tightly coupling our system to any single provider. This necessitates an abstraction layer. Furthermore, we need a mechanism to efficiently query and filter shipments based on various criteria (status, destination, creation date, etc.). A persistent storage mechanism, even if emulated in-memory, is essential for maintaining shipment data. Exception handling and reporting are crucial for identifying and addressing logistical bottlenecks or errors. Finally, and perhaps most importantly, concurrency must be handled correctly to ensure data integrity when multiple operations are performed simultaneously. # Requirements ## Functional Requirements 1. **Shipment Creation:** * Allow the creation of new shipments with the following attributes: * Unique Shipment ID (automatically generated). * Source Address (including street, city, state, zip code, country). * Destination Address (including street, city, state, zip code, country). * Package Dimensions (length, width, height, weight). * Shipping Date. * Delivery Date Estimate. * Transportation Provider (FedEx, UPS, USPS, etc. - must be extensible). * Shipping Options (e.g., Standard, Express, Overnight; provider-specific options). * The system must validate the source and destination addresses. A simple validation (e.g., checking for empty fields) will suffice for this problem. * The system must calculate the initial delivery date estimate, potentially based on the transportation provider and shipping options selected. 2. **Shipment Tracking:** * Allow retrieval of shipment information by Shipment ID. * Provide the current status of the shipment (e.g., Created, In Transit, Delivered, Delayed, Lost). * Maintain a history of shipment events (e.g., Shipment Created, Package Received, Departed Facility, Arrived at Facility, Out for Delivery, Delivered, Exception). * Each shipment event should include a timestamp and a descriptive message. 3. **Transportation Provider Integration:** * Support multiple transportation providers (FedEx, UPS, USPS, etc.). * Provide a common interface for interacting with different transportation providers. * Allow adding new transportation providers without modifying the core system. * Each provider might have different shipping options, calculation methods, and tracking APIs. 4. **Shipment Filtering and Querying:** * Allow filtering shipments based on various criteria: * Status. * Destination City/State/Zip Code. * Shipping Date Range. * Transportation Provider. * Support pagination for large result sets (return results in batches). 5. **Exception Handling and Reporting:** * Allow marking shipments as "exceptions" (e.g., Delayed, Lost, Damaged). * Record the reason for the exception and any relevant details. * Provide a report of all shipments currently in an exception state. * Support resolving exceptions (e.g., marking a delayed shipment as "Delivered"). 6. **Concurrency:** * Multiple users should be able to create, update, and track shipments concurrently without data corruption or race conditions. ## Non-Functional Requirements 1. **Extensibility:** * The system should be easily extensible to support new transportation providers, shipping options, and filtering criteria. * Adding a new transportation provider should not require modifying existing code. * Consider using design patterns like Strategy and Factory to achieve extensibility. 2. **Modularity:** * The system should be divided into loosely coupled modules with well-defined interfaces. * Changes in one module should have minimal impact on other modules. 3. **Thread Safety:** * The system must be thread-safe to handle concurrent requests. * Protect shared data structures from race conditions using appropriate synchronization mechanisms (e.g., locks, concurrent collections). * Consider the impact of concurrency on performance and choose synchronization mechanisms accordingly. 4. **Testability:** * The system should be designed to be easily testable. * Use dependency injection to facilitate unit testing. * Write comprehensive unit tests to cover all aspects of the system. 5. **Maintainability:** * The code should be well-documented and easy to understand. * Follow SOLID principles to ensure maintainability. * Avoid code duplication. 6. **Performance:** * Shipment retrieval and filtering should be efficient, even with a large number of shipments. * Consider using appropriate data structures and algorithms to optimize performance. ## Core Entities 1. **Shipment:** Represents a single shipment with all its associated information. 2. **Address:** Represents a physical address (source or destination). 3. **Package:** Represents the physical package being shipped, including dimensions and weight. 4. **TransportationProvider:** An interface for interacting with different transportation providers. 5. **ShippingOption:** Represents a specific shipping option offered by a transportation provider. 6. **ShipmentEvent:** Represents an event in the lifecycle of a shipment (e.g., created, in transit, delivered). 7. **ShipmentStatus:** An enumeration representing the current status of a shipment. 8. **ShipmentRepository:** An interface for storing and retrieving shipment data (can be implemented in-memory or using a database). 9. **ShipmentFilter:** An interface for filtering shipments based on various criteria. 10. **ExceptionReport:** Represents a report of shipments currently in exception states.

Design a Logistics System

Requirements

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