Tighten disk safety checks

internal/config/config.go

@@ -5,12 +5,17 @@ import (
 	"errors"
 	"os"
 	"path/filepath"
+	"strings"
+
+	"jukebox_maker/internal/disk"
 )
 
 type OverwriteMode string
 type FileSelectMode string
 
 const (
+	DefaultDestFolder = "media"
+
 	OverwriteSkip   OverwriteMode = "skip"
 	OverwriteDelete OverwriteMode = "delete"
 
@@ -30,12 +35,14 @@ type Config struct {
 	OverwriteMode  OverwriteMode  `json:"overwrite_mode"`
 	FileSelectMode FileSelectMode `json:"file_select_mode"`
 	AutoCopy       bool           `json:"auto_copy"`
+	FileReplicaCounts map[string]int      `json:"file_replica_counts,omitempty"`
+	DiskReplicaFiles  map[string][]string `json:"disk_replica_files,omitempty"`
 }
 
 func defaults() Config {
 	return Config{
 		ReserveFreeGB:  2.0,
-		DestFolder:     "media",
+		DestFolder:     DefaultDestFolder,
 		OverwriteMode:  OverwriteSkip,
 		FileSelectMode: SelectNew,
 		AutoCopy:       false,
@@ -55,6 +62,11 @@ func Load(path string) (*Config, error) {
 	if err := json.Unmarshal(data, &cfg); err != nil {
 		return nil, err
 	}
+	if destFolder, err := NormalizeDestFolder(cfg.DestFolder); err == nil {
+		cfg.DestFolder = destFolder
+	} else {
+		cfg.DestFolder = defaults().DestFolder
+	}
 	return &cfg, nil
 }
 
@@ -77,6 +89,9 @@ func (c *Config) Validate() error {
 	if c.ReserveFreeGB < 0 {
 		return errors.New("reserve_free_gb must be >= 0")
 	}
+	if _, err := NormalizeDestFolder(c.DestFolder); err != nil {
+		return err
+	}
 	switch c.OverwriteMode {
 	case OverwriteSkip, OverwriteDelete:
 	default:
@@ -89,3 +104,26 @@ func (c *Config) Validate() error {
 	}
 	return nil
 }
+
+func NormalizeDestFolder(value string) (string, error) {
+	value = strings.TrimSpace(value)
+	if value == "" {
+		return DefaultDestFolder, nil
+	}
+
+	clean := filepath.ToSlash(filepath.Clean(value))
+	clean = strings.TrimPrefix(clean, "./")
+	clean = strings.TrimPrefix(clean, "/")
+
+	switch clean {
+	case "", ".", "..":
+		return "", errors.New("dest_folder must be a subfolder on disk, not the disk root")
+	}
+	if strings.HasPrefix(clean, "../") {
+		return "", errors.New("dest_folder must stay inside the disk")
+	}
+	if clean == disk.MarkerDir || strings.HasPrefix(clean, disk.MarkerDir+"/") {
+		return "", errors.New("dest_folder conflicts with internal disk metadata")
+	}
+	return clean, nil
+}