fix: create reusable default profile pictures (#406)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/job/file_cleanup_job.go

@@ -0,0 +1,78 @@
+package job
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/go-co-op/gocron/v2"
+	"github.com/pocket-id/pocket-id/backend/internal/common"
+	"github.com/pocket-id/pocket-id/backend/internal/model"
+	"gorm.io/gorm"
+)
+
+func RegisterFileCleanupJobs(db *gorm.DB) {
+	scheduler, err := gocron.NewScheduler()
+	if err != nil {
+		log.Fatalf("Failed to create a new scheduler: %s", err)
+	}
+
+	jobs := &FileCleanupJobs{db: db}
+
+	registerJob(scheduler, "ClearUnusedDefaultProfilePictures", "0 2 * * 0", jobs.clearUnusedDefaultProfilePictures)
+
+	scheduler.Start()
+}
+
+type FileCleanupJobs struct {
+	db *gorm.DB
+}
+
+// ClearUnusedDefaultProfilePictures deletes default profile pictures that don't match any user's initials
+func (j *FileCleanupJobs) clearUnusedDefaultProfilePictures() error {
+	var users []model.User
+	if err := j.db.Find(&users).Error; err != nil {
+		return fmt.Errorf("failed to fetch users: %w", err)
+	}
+
+	// Create a map to track which initials are in use
+	initialsInUse := make(map[string]bool)
+	for _, user := range users {
+		initialsInUse[user.Initials()] = true
+	}
+
+	defaultPicturesDir := common.EnvConfig.UploadPath + "/profile-pictures/defaults"
+	if _, err := os.Stat(defaultPicturesDir); os.IsNotExist(err) {
+		return nil
+	}
+
+	files, err := os.ReadDir(defaultPicturesDir)
+	if err != nil {
+		return fmt.Errorf("failed to read default profile pictures directory: %w", err)
+	}
+
+	filesDeleted := 0
+	for _, file := range files {
+		if file.IsDir() {
+			continue // Skip directories
+		}
+
+		filename := file.Name()
+		initials := strings.TrimSuffix(filename, ".png")
+
+		// If these initials aren't used by any user, delete the file
+		if !initialsInUse[initials] {
+			filePath := filepath.Join(defaultPicturesDir, filename)
+			if err := os.Remove(filePath); err != nil {
+				log.Printf("Failed to delete unused default profile picture %s: %v", filePath, err)
+			} else {
+				filesDeleted++
+			}
+		}
+	}
+
+	log.Printf("Deleted %d unused default profile pictures", filesDeleted)
+	return nil
+}