Design a Chat / Messaging Component

Problem

Design the object model for in-meeting chat: messages, channels, participants, and delivery state.

Requirements

• send/receive messages in a meeting
• 1:1 and group messages
• delivery/read state
• message history

What evaluators look for

• Clean classes: Message, Channel, Participant, ChatService
• State machine for delivery
• Thread safety

Extension

Add reactions and typing indicators.