timeline-server/timeline-user-service/PREFERENCES_BACKEND_IMPLEMENTATION.md

Preferences Backend Implementation Summary

Overview

Task 19.1 (Create Preferences service and API endpoints) has been successfully implemented. This document summarizes the complete implementation for the Theme Customization backend.

Implementation Status: ✅ COMPLETE

All required components for the Preferences backend have been implemented and are ready for use.

Components Implemented

1. Database Schema ✅

File: timeline-sql/V1.4.0__personal_user_enhancements.sql

The user_preferences table includes:

• id - Primary key
• user_id - Unique user identifier
• Theme settings:
  • theme_mode - light/dark/auto (default: 'auto')
  • color_scheme - Color scheme name (default: 'default')
• Layout settings:
  • gallery_layout - grid/list (default: 'grid')
  • timeline_layout - grid/list (default: 'grid')
  • album_layout - grid/list (default: 'grid')
  • card_size - small/medium/large (default: 'medium')
• Timeline display settings:
  • timeline_display_mode - chronological/grouped/masonry (default: 'chronological')
• create_time - Creation timestamp
• update_time - Last update timestamp

2. Entity Class ✅

File: src/main/java/com/timeline/user/entity/UserPreferences.java

Java entity class with:

• All database fields mapped
• Lombok annotations for getters/setters
• JSON formatting for timestamps

3. Data Access Layer (Mapper) ✅

Files:

• src/main/java/com/timeline/user/dao/PreferencesMapper.java (Interface)
• src/main/resources/com/timeline/user/dao/PreferencesMapper.xml (MyBatis XML)

Mapper methods:

• findByUserId(String userId) - Get user preferences
• insert(UserPreferences) - Create new preferences
• update(UserPreferences) - Update all preferences
• updateTheme(userId, themeMode, colorScheme) - Update theme only
• updateLayout(userId, galleryLayout, timelineLayout, albumLayout, cardSize) - Update layout only
• updateTimelineDisplay(userId, displayMode) - Update timeline display only

4. Service Layer ✅

Files:

• src/main/java/com/timeline/user/service/PreferencesService.java (Interface)
• src/main/java/com/timeline/user/service/impl/PreferencesServiceImpl.java (Implementation)

Service methods:

• getUserPreferences(String userId) - Get preferences, creates default if not exists
• updateThemePreferences(userId, themeMode, colorScheme) - Update theme settings
• updateLayoutPreferences(userId, galleryLayout, timelineLayout, albumLayout, cardSize) - Update layout settings
• updateTimelineDisplayPreferences(userId, displayMode) - Update timeline display
• createDefaultPreferences(String userId) - Create default preferences

Validation logic:

• Theme mode: must be "light", "dark", or "auto"
• Layout: must be "grid" or "list"
• Card size: must be "small", "medium", or "large"
• Display mode: must be "chronological", "grouped", or "masonry"

5. DTO Classes ✅

Files:

• src/main/java/com/timeline/user/dto/UpdateThemeRequest.java
• src/main/java/com/timeline/user/dto/UpdateLayoutRequest.java
• src/main/java/com/timeline/user/dto/UpdateTimelineDisplayRequest.java

All DTOs include:

• Jakarta validation annotations
• Pattern validation for enum-like fields
• Proper error messages in Chinese

6. REST Controller ✅

File: src/main/java/com/timeline/user/controller/PreferencesController.java

API Endpoints:

• GET /api/v1/preferences - Get user preferences
• PUT /api/v1/preferences/theme - Update theme preferences
• PUT /api/v1/preferences/layout - Update layout preferences
• PUT /api/v1/preferences/timeline - Update timeline display preferences

All endpoints:

• Use @RequestHeader("X-User-Id") for user identification
• Include request validation with @Valid
• Return standardized ResponseEntity responses
• Include logging for debugging

7. Unit Tests ✅

File: src/test/java/com/timeline/user/service/PreferencesServiceTest.java

Test coverage includes:

• ✅ Default preferences creation when user has none
• ✅ Theme updates (light, dark, auto)
• ✅ Layout updates (full and partial)
• ✅ Timeline display updates
• ✅ Validation error handling (invalid theme mode, layout, card size, display mode)
• ✅ Default preferences creation

Test approach: Uses Mockito for unit testing without requiring full Spring context

API Specification

GET /api/v1/preferences

Get user preferences (creates default if not exists)

Headers:

• X-User-Id: User identifier (required)

Response (200 OK):

{
  "code": 200,
  "message": "success",
  "data": {
    "id": 1,
    "userId": "user123",
    "themeMode": "auto",
    "colorScheme": "default",
    "galleryLayout": "grid",
    "timelineLayout": "grid",
    "albumLayout": "grid",
    "cardSize": "medium",
    "timelineDisplayMode": "chronological",
    "createTime": "2024-01-01 10:00:00",
    "updateTime": "2024-01-01 10:00:00"
  }
}

PUT /api/v1/preferences/theme

Update theme preferences

Headers:

• X-User-Id: User identifier (required)

Request Body:

{
  "themeMode": "dark",
  "colorScheme": "purple"
}

Validation:

• themeMode: Required, must be "light", "dark", or "auto"
• colorScheme: Optional, must be "default", "blue", "green", "purple", "orange", or "red"

Response (200 OK):

{
  "code": 200,
  "message": "success",
  "data": null
}

PUT /api/v1/preferences/layout

Update layout preferences

Headers:

• X-User-Id: User identifier (required)

Request Body:

{
  "galleryLayout": "list",
  "timelineLayout": "grid",
  "albumLayout": "list",
  "cardSize": "large"
}

Validation:

• All fields optional
• galleryLayout, timelineLayout, albumLayout: must be "grid" or "list"
• cardSize: must be "small", "medium", or "large"

Response (200 OK):

{
  "code": 200,
  "message": "success",
  "data": null
}

PUT /api/v1/preferences/timeline

Update timeline display preferences

Headers:

• X-User-Id: User identifier (required)

Request Body:

{
  "displayMode": "masonry"
}

Validation:

• displayMode: Required, must be "chronological", "grouped", or "masonry"

Response (200 OK):

{
  "code": 200,
  "message": "success",
  "data": null
}

Requirements Validation

Requirement 7.5: Theme preferences persist across sessions ✅

• Preferences are stored in the database
• GET endpoint retrieves persisted preferences
• PUT endpoint updates preferences in database

Requirement 7.6: Theme preferences apply on both web and desktop clients ✅

• Backend API is client-agnostic
• Both web and desktop clients can call the same endpoints
• Preferences are stored per user, not per client

Default Values

When a user has no preferences, the system creates defaults:

• Theme mode: auto (respects system theme)
• Color scheme: default
• Gallery layout: grid
• Timeline layout: grid
• Album layout: grid
• Card size: medium
• Timeline display mode: chronological

Error Handling

The service includes comprehensive validation:

• Invalid theme mode → IllegalArgumentException
• Invalid layout → IllegalArgumentException
• Invalid card size → IllegalArgumentException
• Invalid display mode → IllegalArgumentException

All validation errors are caught by the controller and returned as appropriate HTTP error responses.

Next Steps

Task 19.1 is COMPLETE. The backend implementation is ready for:

1. Frontend integration (Task 20: Theme Customization frontend)
2. Property-based testing (Task 19.2: Optional)
3. Integration testing with the full application stack

Notes

• The implementation follows the existing codebase patterns (similar to ReactionService, CommentService)
• All code includes Chinese and English comments for maintainability
• The service is transactional to ensure data consistency
• Partial updates are supported (e.g., updating only theme without changing layout)