feat: implement initial GoDump backup service with management web UI and MySQL support

backup/retention.go

@@ -0,0 +1,60 @@
+package backup
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"time"
+
+	"godump/config"
+	"godump/logger"
+)
+
+func enforceRetention(cfg config.InstanceConfig) (int, error) {
+	if cfg.RetentionDays <= 0 {
+		return 0, nil
+	}
+
+	cutoff := time.Now().AddDate(0, 0, -cfg.RetentionDays)
+	deletedCount := 0
+
+	err := filepath.WalkDir(cfg.BackupDir, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			if os.IsNotExist(err) {
+				return nil
+			}
+			return err
+		}
+
+		if d.IsDir() {
+			return nil
+		}
+
+		info, err := d.Info()
+		if err != nil {
+			return err
+		}
+
+		if info.ModTime().Before(cutoff) {
+			ageDays := int(time.Since(info.ModTime()).Hours() / 24)
+			if err := os.Remove(path); err != nil {
+				logger.Error(cfg.Name, "Failed to delete old backup %s: %v", path, err)
+			} else {
+				logger.Info(cfg.Name, "Deleted old backup %s (age: %d days)", path, ageDays)
+				deletedCount++
+			}
+		}
+
+		return nil
+	})
+
+	if err != nil {
+		if os.IsNotExist(err) {
+			return 0, nil
+		}
+		return deletedCount, fmt.Errorf("error walking backup directory: %w", err)
+	}
+
+	return deletedCount, nil
+}