# 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