Task_Reporter/openspec/changes/archive/2025-11-17-add-realtime-messaging/proposal.md

# Add Realtime Messaging

## Summary
Implement WebSocket-based real-time messaging system for incident rooms, enabling instant communication between team members during production incidents. Messages will be persisted to database for audit trail and report generation.

## Requirements

### Requirement: WebSocket Connection Management
The system SHALL provide WebSocket endpoints for establishing persistent bidirectional connections between clients and server, with automatic reconnection handling and connection state management.

#### Scenario: Establish WebSocket connection
- **WHEN** an authenticated user connects to `ws://localhost:8000/ws/{room_id}`
- **THEN** the system SHALL validate user's room membership
- **AND** establish a WebSocket connection
- **AND** add the connection to the room's active connections pool
- **AND** broadcast a "user joined" event to other room members

#### Scenario: Handle connection authentication
- **WHEN** a WebSocket connection request is made without valid authentication token
- **THEN** the system SHALL reject the connection with status 401
- **AND** close the WebSocket immediately

#### Scenario: Automatic reconnection
- **WHEN** a WebSocket connection is dropped unexpectedly
- **THEN** the client SHALL attempt to reconnect automatically
- **AND** resume from the last received message sequence number
- **AND** request any missed messages during disconnection

### Requirement: Real-time Message Broadcasting
The system SHALL broadcast messages to all active room members in real-time, ensuring message ordering and delivery acknowledgment.

#### Scenario: Send text message
- **WHEN** a room member sends a message via WebSocket:
  ```json
  {
    "type": "message",
    "content": "Equipment temperature rising to 85°C",
    "message_type": "text"
  }
  ```
- **THEN** the system SHALL:
  - Validate user has write permission (OWNER or EDITOR role)
  - Assign a unique message_id and timestamp
  - Store the message in database
  - Broadcast to all active WebSocket connections in the room
  - Return acknowledgment to sender with message_id

#### Scenario: Send system notification
- **WHEN** a system event occurs (user joined, room status changed, etc.)
- **THEN** the system SHALL broadcast a system message:
  ```json
  {
    "type": "system",
    "event": "user_joined",
    "user_id": "john.doe@panjit.com.tw",
    "timestamp": "2025-11-17T10:00:00Z"
  }
  ```
- **AND** all connected clients SHALL display the notification

#### Scenario: Handle message ordering
- **WHEN** multiple messages are sent simultaneously
- **THEN** the system SHALL ensure FIFO ordering using message sequence numbers
- **AND** clients SHALL display messages in the correct order

### Requirement: Message Persistence and History
The system SHALL persist all messages to database for audit trail, report generation, and history retrieval.

#### Scenario: Store message in database
- **WHEN** a message is sent through WebSocket
- **THEN** the system SHALL create a database record with:
  - message_id (UUID)
  - room_id (FK to incident_rooms)
  - sender_id (user email)
  - content (text or JSON for structured messages)
  - message_type (text, image_ref, file_ref, system)
  - created_at timestamp
  - edited_at (nullable for message edits)
  - deleted_at (nullable for soft delete)

#### Scenario: Retrieve message history
- **WHEN** a user joins a room or reconnects
- **THEN** the system SHALL load recent messages via `GET /api/rooms/{room_id}/messages?limit=50&before={timestamp}`
- **AND** return messages in reverse chronological order
- **AND** include pagination metadata for loading more history

#### Scenario: Search messages
- **WHEN** a user searches for messages containing specific keywords
- **THEN** the system SHALL query the database with full-text search
- **AND** return matching messages with highlighted search terms
- **AND** maintain user's access control (only rooms they're members of)

### Requirement: Message Types and Formatting
The system SHALL support various message types including text, image references, file references, and structured data for production incidents.

#### Scenario: Text message with mentions
- **WHEN** a user sends a message with @mentions
  ```json
  {
    "content": "@maintenance_team Please check Line 3 immediately",
    "mentions": ["maintenance_team@panjit.com.tw"]
  }
  ```
- **THEN** the system SHALL parse and store mentions
- **AND** potentially trigger notifications to mentioned users

#### Scenario: Image reference message
- **WHEN** a user uploads an image and sends reference
  ```json
  {
    "type": "message",
    "message_type": "image_ref",
    "content": "Defect found on product",
    "file_id": "550e8400-e29b-41d4-a716-446655440000",
    "file_url": "http://localhost:9000/bucket/room-123/image.jpg"
  }
  ```
- **THEN** the system SHALL store the file reference
- **AND** clients SHALL display image preview inline

#### Scenario: Structured incident data
- **WHEN** reporting specific incident metrics
  ```json
  {
    "type": "message",
    "message_type": "incident_data",
    "content": {
      "temperature": 85,
      "pressure": 120,
      "production_rate": 450,
      "timestamp": "2025-11-17T10:15:00Z"
    }
  }
  ```
- **THEN** the system SHALL store structured data as JSON
- **AND** enable querying/filtering by specific fields later

### Requirement: Connection State Management
The system SHALL track online presence and typing indicators for better collaboration experience.

#### Scenario: Track online users
- **WHEN** users connect/disconnect from a room
- **THEN** the system SHALL maintain a list of online users
- **AND** broadcast presence updates to all room members
- **AND** display online status indicators in UI

#### Scenario: Typing indicators
- **WHEN** a user starts typing a message
- **THEN** the client SHALL send a "typing" event via WebSocket
- **AND** the system SHALL broadcast to other room members
- **AND** automatically clear typing status after 3 seconds of inactivity

#### Scenario: Connection health monitoring
- **WHEN** a WebSocket connection is established
- **THEN** the system SHALL send ping frames every 30 seconds
- **AND** expect pong responses within 10 seconds
- **AND** terminate connection if no response received

### Requirement: Message Operations
The system SHALL support message editing and deletion with proper audit trail and permissions.

#### Scenario: Edit own message
- **WHEN** a user edits their own message within 15 minutes
  ```json
  {
    "type": "edit_message",
    "message_id": "msg-123",
    "content": "Updated: Equipment temperature stabilized at 75°C"
  }
  ```
- **THEN** the system SHALL update the message content
- **AND** set edited_at timestamp
- **AND** broadcast the edit to all connected clients
- **AND** preserve original message in audit log

#### Scenario: Delete message
- **WHEN** a user deletes their own message or admin deletes any message
- **THEN** the system SHALL perform soft delete (set deleted_at)
- **AND** broadcast deletion event to all clients
- **AND** clients SHALL show "message deleted" placeholder
- **AND** preserve message in database for audit

#### Scenario: React to message
- **WHEN** a user adds a reaction emoji to a message
  ```json
  {
    "type": "add_reaction",
    "message_id": "msg-123",
    "emoji": "👍"
  }
  ```
- **THEN** the system SHALL store the reaction
- **AND** broadcast to all connected clients
- **AND** aggregate reaction counts for display

## Scenarios

### Happy Path: Production Incident Communication
1. Equipment failure detected on Line 3
2. Operator creates incident room via REST API
3. Opens WebSocket connection to room
4. Sends initial message: "Conveyor belt stopped, investigating"
5. Maintenance team members join via WebSocket
6. Real-time messages exchanged with status updates
7. Images uploaded and referenced in messages
8. Temperature/pressure data shared as structured messages
9. Issue resolved, final message sent
10. Room status changed to "resolved"
11. All messages available for report generation

### Edge Case: Network Interruption Recovery
1. User actively chatting in incident room
2. Network connection drops for 2 minutes
3. Client automatically attempts reconnection
4. Connection re-established with same room_id
5. Client requests messages since last sequence number
6. Server sends missed messages
7. UI updates seamlessly without user intervention

### Error Case: Unauthorized Message Attempt
1. User with VIEWER role connects to room WebSocket
2. Attempts to send a message
3. Server validates permission based on role
4. Rejects message with error: "Insufficient permissions"
5. WebSocket connection remains active (not terminated)
6. User can still receive messages from others

### Performance Case: High-traffic Incident
1. Major production issue affects multiple lines
2. 20+ team members join incident room
3. Rapid message exchange (100+ messages/minute)
4. System maintains sub-100ms message broadcast latency
5. Database writes queued to prevent blocking
6. All messages preserved in correct order
7. No message loss despite high load

## Technical Considerations

### WebSocket Implementation
- Use FastAPI's native WebSocket support
- Implement connection pooling per room
- Use Redis pub/sub for multi-server scaling (future)
- Graceful shutdown handling to notify clients

### Database Schema
```sql
CREATE TABLE messages (
    message_id VARCHAR(36) PRIMARY KEY,
    room_id VARCHAR(36) NOT NULL REFERENCES incident_rooms(room_id),
    sender_id VARCHAR(255) NOT NULL,
    content TEXT NOT NULL,
    message_type VARCHAR(20) DEFAULT 'text',
    metadata JSONB,
    created_at TIMESTAMP DEFAULT NOW(),
    edited_at TIMESTAMP,
    deleted_at TIMESTAMP,
    sequence_number BIGSERIAL,
    INDEX idx_room_messages (room_id, created_at DESC),
    INDEX idx_message_search (content gin_trgm_ops) -- PostgreSQL full-text
);

CREATE TABLE message_reactions (
    reaction_id SERIAL PRIMARY KEY,
    message_id VARCHAR(36) REFERENCES messages(message_id),
    user_id VARCHAR(255) NOT NULL,
    emoji VARCHAR(10) NOT NULL,
    created_at TIMESTAMP DEFAULT NOW(),
    UNIQUE(message_id, user_id, emoji)
);
```

### Security Considerations
- Validate JWT tokens on WebSocket connection
- Rate limiting per user (max 10 messages/second)
- Message size limit (10KB for text, 100KB for structured data)
- XSS prevention for message content
- SQL injection prevention using parameterized queries

### Performance Requirements
- Message broadcast latency < 100ms for same server
- Support 100+ concurrent connections per room
- Message history query < 200ms for 1000 messages
- Automatic connection cleanup for dropped clients