# Design a Chatbot with Object-Oriented Principles Create an object-oriented design for a chatbot system. Define the responsibilities and relationships needed to manage conversations, participants, messages, delivery, and provider-specific model behavior without coupling every class to one implementation. ### Constraints & Assumptions - Focus on domain and interface design rather than distributed deployment scale. - A conversation contains ordered messages and may receive streamed assistant output. - The design should permit a model provider or storage adapter to be replaced. ### Clarifying Questions to Ask - Can multiple users participate in one conversation? - Must message edits or retries be retained? - Is streaming part of the domain contract or an adapter concern? ```hint Assign ownership Give each object one reason to change and keep infrastructure behind interfaces. ``` ### What a Strong Answer Covers - Core entities, invariants, and object relationships. - Interfaces for generation, storage, delivery, and observability. - Conversation ordering, retries, cancellation, and partial streamed messages. - Extension points and tests that avoid a monolithic manager class. ### Follow-up Questions 1. How would you add tool calls without changing every existing message type? 2. Where would authorization checks belong?