Requirements

Let's design an inventory management system for a retail store. This isn't just about tracking how many units of each product we have. We want to build a robust system that supports various inventory tracking strategies, handles stock adjustments, and allows us to easily add new product types and inventory management techniques in the future. The system should be able to handle concurrent requests, ensuring data consistency even when multiple users or processes are updating the inventory simultaneously. Imagine a scenario where a customer buys an item online, and at the same time, an employee is updating the stock count after a new shipment arrives. Our system must be able to manage these concurrent operations without corrupting the data. We also need to consider scenarios where the inventory is spread across multiple locations (stores, warehouses). # Requirements ## Functional Requirements 1. **Product Management:** * Define a product with attributes like SKU, name, description, price, and category. * Support different product types (e.g., physical goods, digital downloads, services) with potentially different attributes. * Allow products to be enabled/disabled (e.g., temporarily unavailable). 2. **Inventory Tracking:** * Track the quantity of each product in each location (store, warehouse). * Support different inventory tracking methods (e.g., FIFO, LIFO, average cost). The default tracking method should be FIFO. * Support batch tracking (e.g., tracking products by lot number or expiration date). * Alert when inventory levels fall below a specified threshold (reorder point). 3. **Inventory Adjustments:** * Record all inventory adjustments (e.g., receiving new stock, sales, returns, damages, write-offs). * Provide reasons for inventory adjustments (e.g., "Received shipment #123", "Damaged during shipping"). * Support adjustment types (e.g., ADD, REMOVE, TRANSFER). * Support adjustments across multiple locations. 4. **Location Management:** * Define locations (stores, warehouses) with attributes like name, address, and contact information. * Support transfer of inventory between locations. 5. **Reporting:** * Generate reports on inventory levels, inventory turnover, and inventory adjustments. * Provide real-time inventory status for specific products and locations. 6. **Concurrency:** * Handle concurrent inventory adjustments from multiple users or processes without data corruption. * Ensure ACID properties (Atomicity, Consistency, Isolation, Durability) for all inventory transactions. ## Non-Functional Requirements 1. **Thread Safety:** The system must be thread-safe to handle concurrent requests. Use appropriate synchronization mechanisms (locks, atomic variables) to prevent race conditions and data corruption. 2. **Extensibility:** The system should be easily extensible to support new product types, inventory tracking methods, and reporting formats. Design the system using interfaces and abstract classes to allow for easy addition of new functionality without modifying existing code. 3. **Modularity:** The system should be modular, with clear separation of concerns between different components (e.g., product management, inventory tracking, reporting). This will make the system easier to understand, maintain, and test. 4. **Testability:** The system should be designed for testability. Use dependency injection and interfaces to allow for easy mocking of dependencies during unit testing. 5. **Maintainability:** The code should be well-documented and easy to understand. Use meaningful variable names, comments, and consistent coding style. 6. **Scalability:** While not a distributed system design, consider how the data structures and algorithms used would scale with a large number of products, locations, and transactions. Focus on efficient data structures and algorithms for searching, updating, and retrieving inventory data. ## Core Entities 1. **Product:** Represents a product in the inventory. Attributes include SKU, name, description, price, category, and product type. The `Product` class should be abstract, with concrete subclasses for different product types (e.g., `PhysicalProduct`, `DigitalProduct`, `Service`). 2. **Inventory:** Represents the quantity of a product at a specific location. It should have methods for adjusting the quantity and retrieving the current quantity. It needs to handle concurrent access to ensure data consistency. 3. **Location:** Represents a physical location (store, warehouse) where inventory is stored. Attributes include name, address, and contact information. 4. **InventoryAdjustment:** Represents an adjustment to the inventory (e.g., receiving stock, sales, returns). Attributes include product, location, quantity, adjustment type, reason, and timestamp. 5. **InventoryTrackingStrategy:** An interface for different inventory tracking methods (e.g., FIFO, LIFO, average cost). Concrete implementations of this interface will handle the actual inventory tracking logic. This is where the Strategy pattern comes in. 6. **ReorderPoint:** Represents the threshold for a product at a location, below which a reorder notification is triggered. It should have attributes like product, location, threshold quantity, and notification method.

Design Inventory System.

Requirements

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