CatsOfMastodonGo/FX_MIGRATION.md

FX Dependency Injection Implementation

This document summarizes the changes made to implement uber-go/fx dependency injection in the CatsOfMastodonBotGo application.

Overview

We've replaced the global variable pattern with proper dependency injection using uber-go/fx. This improves:

• Testability
• Modularity
• Explicit dependency management
• Eliminates fragile initialization order dependencies

Key Changes

1. Added Dependencies

• Added go.uber.org/fx dependency to go.mod
• Added go.uber.org/zap for structured logging

2. Refactored main.go

• Replaced manual initialization with fx application
• Used fx.Provide to register constructors for all components
• Used fx.Invoke to start background tasks and server
• Added proper logger integration

3. Refactored Configuration (config/config.go)

• Removed global Config variable
• Removed Init() function
• Kept Load() function as constructor

4. Refactored Database (database/database.go)

• Removed global Gorm variable
• Function now accepts config as parameter

5. Refactored Services

• PostService: Now accepts database and config as dependencies
• ImgKitHelper: Now accepts config as dependency

6. Refactored Auth

• JwtTokenGenerator: Now accepts config as dependency
• GiteaOAuth2Handler: Now accepts config as dependency

7. Refactored Handlers

• All handlers now use constructor injection
• Dependencies are explicitly declared in constructor signatures
• Removed global instance variables

8. Refactored Server/Router

• Router now receives all handlers through fx dependency injection
• Uses fx.Lifecycle for proper startup/shutdown handling

Benefits Achieved

1. Eliminated Global State: No more global variables causing tight coupling
2. Explicit Dependencies: All dependencies are clearly visible in constructor signatures
3. Automatic Wiring: fx automatically resolves and injects dependencies
4. Improved Testability: Easy to mock dependencies for unit tests
5. Reduced Boilerplate: No need for manual initialization functions
6. Error Detection: Dependency resolution errors caught at startup

Files Modified

• cmd/CatsOfMastodonBotGo/main.go
• go.mod
• go.sum
• internal/auth/jwt.go
• internal/auth/oauth2.go
• internal/config/config.go
• internal/database/database.go
• internal/server/router.go
• internal/services/imgKitHelper.go
• internal/services/postService.go
• internal/web/handlers/adminDash.go
• internal/web/handlers/apiEndpoint.go
• internal/web/handlers/embedCard.go
• internal/web/handlers/oauth.go