# realtime-messaging Specification

## ADDED Requirements

### Requirement: Message Sender Display Name

The system SHALL include the sender's display name in message responses and broadcasts, enabling the UI to show user-friendly names instead of email addresses.

#### Scenario: Message response includes display name
- **WHEN** a message is retrieved via REST API or WebSocket
- **THEN** the response SHALL include `sender_display_name` field
- **AND** the display name SHALL be obtained by joining with the `tr_users` table
- **AND** if the sender does not exist in `tr_users`, the field SHALL fallback to `sender_id`

#### Scenario: WebSocket broadcast includes display name
- **WHEN** a new message is broadcast via WebSocket
- **THEN** the broadcast SHALL include `sender_display_name` field
- **AND** the value SHALL be the sender's display name from `tr_users` table

#### Scenario: Historical messages include display name
- **WHEN** a client requests message history via `GET /api/rooms/{room_id}/messages`
- **THEN** each message in the response SHALL include `sender_display_name`
- **AND** messages from unknown users SHALL show their `sender_id` as fallback

### Requirement: GMT+8 Timezone Display

The frontend SHALL display all timestamps in GMT+8 (Asia/Taipei) timezone for consistent user experience across all browsers.

#### Scenario: Message timestamp in GMT+8
- **WHEN** a message is displayed in the chat room
- **THEN** the timestamp SHALL be formatted in GMT+8 timezone
- **AND** use format "HH:mm" for today's messages
- **AND** use format "MM/DD HH:mm" for older messages

#### Scenario: Room list timestamps in GMT+8
- **WHEN** the room list is displayed
- **THEN** the "last updated" time SHALL be formatted in GMT+8 timezone