Refactor: Implement uber-go/fx dependency injection

- Replace global variable pattern with proper dependency injection
- Add uber-go/fx for automatic dependency resolution
- Refactor all services and handlers to use constructor injection
- Eliminate fragile initialization order dependencies
- Improve testability and modularity
- Add structured logging with zap

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

internal/services/postService.go

@@ -2,7 +2,6 @@ package services
 
 import (
 	"CatsOfMastodonBotGo/internal/config"
-	"CatsOfMastodonBotGo/internal/database"
 	"CatsOfMastodonBotGo/internal/domain"
 	"context"
 	"encoding/json"
@@ -16,42 +15,41 @@ import (
 )
 
 type PostService struct {
-	db *gorm.DB
+	db  *gorm.DB
+	cfg *config.Config
 }
 
-var PostServiceInstance *PostService
-
 // Constructor
-func InitPostService() {
-	PostServiceInstance = &PostService{db: database.Gorm}
+func NewPostService(db *gorm.DB, cfg *config.Config) *PostService {
+	return &PostService{db: db, cfg: cfg}
 }
 
-func (*PostService) GetPostsFromApi(ctx context.Context, tag string, instance string) (error, []domain.Post) {
+func (ps *PostService) GetPostsFromApi(ctx context.Context, tag string, instance string) ([]domain.Post, error) {
 	var requestUrl = instance + "/api/v1/timelines/tag/" + tag + "?limit=40"
 	req, err := http.NewRequestWithContext(ctx, "GET", requestUrl, nil)
 	if err != nil {
-		return err, nil
+		return nil, err
 	}
 
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
-		return err, nil
+		return nil, err
 	}
 	if resp.StatusCode != 200 || strings.Split(strings.ToLower(resp.Header.Get("Content-Type")), ";")[0] != "application/json" {
-		return fmt.Errorf("Status code:", resp.StatusCode, " Content-Type:", resp.Header.Get("Content-Type")), nil
+		return nil, fmt.Errorf("status code: %d, content-type: %s", resp.StatusCode, resp.Header.Get("Content-Type"))
 	}
 
 	var posts []domain.Post = nil
 	err = json.NewDecoder(resp.Body).Decode(&posts)
 	if err != nil {
-		return err, nil
+		return nil, err
 	}
 	// defer: it basically means "do this later when the function returns"
 	defer resp.Body.Close()
 	if posts == nil {
-		return fmt.Errorf("no posts found for tag %s on instance %s", tag, instance), nil
+		return nil, fmt.Errorf("no posts found for tag %s on instance %s", tag, instance)
 	}
-	return nil, posts
+	return posts, nil
 }
 
 func (ps *PostService) GetExistingPostIds() []string {
@@ -66,7 +64,7 @@ func (ps *PostService) GetExistingAccountIds() []string {
 	return existingAccountIds
 }
 
-func (*PostService) GetNewPosts(existingPostIds []string, posts []domain.Post) []domain.Post {
+func (ps *PostService) GetNewPosts(existingPostIds []string, posts []domain.Post) []domain.Post {
 	var newPosts []domain.Post = nil
 	for _, post := range posts {
 		if !arrayContains(existingPostIds, post.ID) && len(post.Attachments) > 0 && !post.Account.IsBot {
@@ -85,7 +83,7 @@ func (*PostService) GetNewPosts(existingPostIds []string, posts []domain.Post) [
 	return newPosts
 }
 
-func (*PostService) GetNewAccounts(existingAccountIds []string, posts []domain.Post) []domain.Account {
+func (ps *PostService) GetNewAccounts(existingAccountIds []string, posts []domain.Post) []domain.Account {
 	var newAccounts []domain.Account = nil
 	for _, post := range posts {
 		if !arrayContains(existingAccountIds, post.Account.AccId) {
@@ -153,7 +151,7 @@ func (ps *PostService) RejectMedia(mediaId string) bool {
 func (ps *PostService) GetMedia() domain.MediaAttachment {
 	var media domain.MediaAttachment
 	orderExpr := "RANDOM()" // sqlite
-	if config.Config.DBEngine != "sqlite" {
+	if ps.cfg.DBEngine != "sqlite" {
 		orderExpr = "RAND()" // mariadb/mysql
 	}
 	ps.db.Model(&domain.MediaAttachment{}).
@@ -171,4 +169,4 @@ func arrayContains(arr []string, str string) bool {
 		}
 	}
 	return false
-}
+}