Design a Reseller Inventory Management System

Problem

Design an OOP model for Meesho's reseller inventory system where resellers list products from a shared catalogue and manage their own stock.

Requirements

• addProduct(resellerId, catalogueProductId, price, quantity)
• placeOrder(buyerId, resellerId, productId, qty) → reserves stock
• confirmOrder(orderId) / cancelOrder(orderId)
• getLowStockAlerts(resellerId) — products below threshold

Key classes

Product, CatalogueItem, ResellerListing, Order, InventoryManager

Evaluation criteria

• Separation between catalogue (shared) and reseller listings (owned)
• Optimistic vs pessimistic locking for concurrent stock updates
• Observer pattern for low-stock alerts

Extension

Support bulk order imports from a CSV file.