atlas/internal/services/vtl.go

package services

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"

	"gitea.avt.data-center.id/othman.suseno/atlas/internal/models"
)

// DeviceConfig represents parsed device.conf structure
type DeviceConfig struct {
	Libraries []LibraryConfig
	Drives    []DriveConfig
}

// LibraryConfig represents a library from device.conf
type LibraryConfig struct {
	ID      int
	Vendor  string
	Product string
	Serial  string
}

// DriveConfig represents a drive from device.conf
type DriveConfig struct {
	ID        int
	LibraryID int
	SlotID    int
	Vendor    string
	Product   string
	Serial    string
}

// VTLService manages mhvtl (Virtual Tape Library)
type VTLService struct {
	configPath       string // Path to mhvtl config (default: /etc/mhvtl/mhvtl.conf)
	deviceConfigPath string // Path to device config (default: /etc/mhvtl/device.conf)
	storagePath      string // Path to tape storage (default: /opt/mhvtl)
}

// NewVTLService creates a new VTL service
func NewVTLService() *VTLService {
	return &VTLService{
		configPath:       "/etc/mhvtl/mhvtl.conf",
		deviceConfigPath: "/etc/mhvtl/device.conf",
		storagePath:      "/opt/mhvtl",
	}
}

// GetStatus returns the status of mhvtl service
func (s *VTLService) GetStatus() (*models.VTLStatus, error) {
	status := &models.VTLStatus{
		ServiceRunning: false,
		DrivesOnline:   0,
		DrivesTotal:    0,
		TapesTotal:     0,
		TapesAvailable: 0,
	}

	// Check if mhvtl target is active (mhvtl uses mhvtl.target, not mhvtl.service)
	cmd := exec.Command("systemctl", "is-active", "mhvtl.target")
	if err := cmd.Run(); err == nil {
		status.ServiceRunning = true
	} else {
		// Fallback: check if mhvtl-load-modules is active (modules loaded)
		cmd2 := exec.Command("systemctl", "is-active", "mhvtl-load-modules.service")
		if cmd2.Run() == nil {
			// Modules are loaded, service might be running even if target shows inactive
			status.ServiceRunning = true
		}
	}

	// Get drives and tapes info
	drives, err := s.ListDrives()
	if err == nil {
		status.DrivesTotal = len(drives)
		for _, drive := range drives {
			if drive.Status == "online" {
				status.DrivesOnline++
			}
		}
	}

	tapes, err := s.ListTapes()
	if err == nil {
		status.TapesTotal = len(tapes)
		for _, tape := range tapes {
			if tape.Status == "available" {
				status.TapesAvailable++
			}
		}
	}

	return status, nil
}

// ListDrives lists all virtual tape drives from device.conf
func (s *VTLService) ListDrives() ([]models.VTLDrive, error) {
	drives := []models.VTLDrive{}

	// Read from device.conf first (more accurate)
	deviceConfig, err := s.parseDeviceConfig()
	if err == nil && len(deviceConfig.Drives) > 0 {
		// Use drives from device.conf
		for _, driveConfig := range deviceConfig.Drives {
			// Find corresponding device from sysfs
			devicePath := s.findDeviceForDrive(driveConfig.ID)

			// Check if media is loaded
			mediaLoaded, barcode := s.checkMediaLoadedByDriveID(driveConfig.ID)

			drive := models.VTLDrive{
				ID:          driveConfig.ID,
				LibraryID:   driveConfig.LibraryID,
				SlotID:      driveConfig.SlotID,
				Vendor:      driveConfig.Vendor,
				Product:     driveConfig.Product,
				Type:        s.determineDriveType(driveConfig.Product),
				Device:      devicePath,
				Status:      "online",
				MediaLoaded: mediaLoaded,
				Barcode:     barcode,
			}
			drives = append(drives, drive)
		}
		return drives, nil
	}

	// Fallback: Read from /sys/class/scsi_tape/ if device.conf not available
	tapePath := "/sys/class/scsi_tape"
	entries, err := os.ReadDir(tapePath)
	if err != nil {
		return drives, nil
	}

	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}

		deviceName := entry.Name()
		if !strings.HasPrefix(deviceName, "st") && !strings.HasPrefix(deviceName, "nst") {
			continue
		}

		devicePath := fmt.Sprintf("/dev/%s", deviceName)
		vendorPath := fmt.Sprintf("%s/%s/device/vendor", tapePath, deviceName)
		productPath := fmt.Sprintf("%s/%s/device/model", tapePath, deviceName)

		vendor := "Unknown"
		product := "Unknown"
		if vendorBytes, err := os.ReadFile(vendorPath); err == nil {
			vendor = strings.TrimSpace(string(vendorBytes))
		}
		if productBytes, err := os.ReadFile(productPath); err == nil {
			product = strings.TrimSpace(string(productBytes))
		}

		driveID := s.getDriveIDFromDevice(deviceName)
		mediaLoaded, barcode := s.checkMediaLoaded(deviceName)

		// Try to get library ID from device.conf if available
		libraryID := driveID / 10
		slotID := driveID % 10

		// Try to get more accurate info from device.conf
		deviceConfig, err := s.parseDeviceConfig()
		if err == nil {
			for _, driveConfig := range deviceConfig.Drives {
				if driveConfig.ID == driveID {
					libraryID = driveConfig.LibraryID
					slotID = driveConfig.SlotID
					if vendor == "Unknown" {
						vendor = driveConfig.Vendor
					}
					if product == "Unknown" {
						product = driveConfig.Product
					}
					break
				}
			}
		}

		drive := models.VTLDrive{
			ID:          driveID,
			LibraryID:   libraryID,
			SlotID:      slotID,
			Vendor:      vendor,
			Product:     product,
			Type:        s.determineDriveType(product),
			Device:      devicePath,
			Status:      "online",
			MediaLoaded: mediaLoaded,
			Barcode:     barcode,
		}
		drives = append(drives, drive)
	}

	return drives, nil
}

// ListTapes lists all virtual tapes from library_contents and storage directory
func (s *VTLService) ListTapes() ([]models.VTLTape, error) {
	tapes := []models.VTLTape{}

	// Parse device config to get library IDs
	deviceConfig, err := s.parseDeviceConfig()
	if err != nil {
		log.Printf("Warning: failed to parse device.conf: %v", err)
	}

	// Map to track which tapes are in which slots
	slotToBarcode := make(map[string]string) // "libraryID:slotID" -> barcode

	// Read library_contents files for each library
	libraryIDs := []int{10, 30} // Default libraries, or get from deviceConfig
	if deviceConfig != nil && len(deviceConfig.Libraries) > 0 {
		libraryIDs = []int{}
		for _, lib := range deviceConfig.Libraries {
			libraryIDs = append(libraryIDs, lib.ID)
		}
	}

	for _, libID := range libraryIDs {
		slotMap, err := s.parseLibraryContents(libID)
		if err == nil {
			for slotID, barcode := range slotMap {
				key := fmt.Sprintf("%d:%d", libID, slotID)
				slotToBarcode[key] = barcode
			}
		}
	}

	// Read tapes from storage directory
	// mhvtl stores tapes directly in /opt/mhvtl/, not in /opt/mhvtl/data/
	tapeStoragePath := s.storagePath
	entries, err := os.ReadDir(tapeStoragePath)
	if err != nil {
		// No tapes directory yet
		log.Printf("Warning: cannot read tape storage directory %s: %v", tapeStoragePath, err)
		return tapes, nil
	}

	// Create a map of barcodes to their slot info
	barcodeToSlot := make(map[string]struct {
		LibraryID int
		SlotID    int
	})
	for key, barcode := range slotToBarcode {
		parts := strings.Split(key, ":")
		if len(parts) == 2 {
			libID, _ := strconv.Atoi(parts[0])
			slotID, _ := strconv.Atoi(parts[1])
			barcodeToSlot[barcode] = struct {
				LibraryID int
				SlotID    int
			}{LibraryID: libID, SlotID: slotID}
		}
	}

	for _, entry := range entries {
		if entry.IsDir() {
			barcode := entry.Name()
			tapePath := filepath.Join(tapeStoragePath, barcode)

			// Get slot info from library_contents
			slotInfo, inSlot := barcodeToSlot[barcode]
			libraryID := 0
			slotID := 0
			if inSlot {
				libraryID = slotInfo.LibraryID
				slotID = slotInfo.SlotID
			} else {
				// If not in library_contents, try to find from device.conf libraries
				// Default to first library if available
				if deviceConfig != nil && len(deviceConfig.Libraries) > 0 {
					libraryID = deviceConfig.Libraries[0].ID
				} else {
					libraryID = 10 // Fallback default
				}
			}

			// Determine tape type from barcode suffix
			tapeType := s.determineTapeTypeFromBarcode(barcode)

			// Get default size based on tape generation
			defaultSize := s.getDefaultTapeSize(tapeType)

			tape := models.VTLTape{
				Barcode:   barcode,
				LibraryID: libraryID,
				SlotID:    slotID,
				DriveID:   -1, // Not loaded (would need to check drive status)
				Type:      tapeType,
				Size:      defaultSize, // Use default size for tape generation
				Used:      0,
				Status:    "available",
			}

			// Get actual used space from tape data file (mhvtl uses "data" file, not "tape")
			tapeFile := filepath.Join(tapePath, "data")
			if info, err := os.Stat(tapeFile); err == nil {
				// Used space is the actual file size
				tape.Used = uint64(info.Size())
			}

			tapes = append(tapes, tape)
		}
	}

	return tapes, nil
}

// CreateTape creates a new virtual tape
// libraryID: Library ID where the tape will be placed
// slotID: Slot ID in the library where the tape will be placed
func (s *VTLService) CreateTape(barcode string, tapeType string, size uint64, libraryID int, slotID int) error {
	// Validate barcode format (must follow LTO standard)
	if err := s.validateLTOBarcode(barcode); err != nil {
		return fmt.Errorf("invalid barcode format: %v", err)
	}

	// Determine tape type from barcode if not provided
	if tapeType == "" {
		tapeType = s.determineTapeTypeFromBarcode(barcode)
	}

	// Use default size based on tape generation if not specified
	if size == 0 {
		size = s.getDefaultTapeSize(tapeType)
	}

	// Validate library ID and slot ID
	if libraryID <= 0 {
		return fmt.Errorf("library ID must be greater than 0")
	}
	if slotID <= 0 {
		return fmt.Errorf("slot ID must be greater than 0")
	}

	// Check if slot is already occupied
	slotMap, err := s.parseLibraryContents(libraryID)
	if err == nil {
		if existingBarcode, occupied := slotMap[slotID]; occupied && existingBarcode != "" && existingBarcode != "-" {
			return fmt.Errorf("slot %d in library %d is already occupied by tape %s", slotID, libraryID, existingBarcode)
		}
	}

	// Check if tape already exists
	tapePath := filepath.Join(s.storagePath, barcode)
	log.Printf("Creating tape: barcode=%s, path=%s, library=%d, slot=%d", barcode, tapePath, libraryID, slotID)

	if _, err := os.Stat(tapePath); err == nil {
		return fmt.Errorf("tape %s already exists at %s", barcode, tapePath)
	}

	// Ensure parent directory exists first
	parentDir := s.storagePath
	log.Printf("Checking parent directory: %s", parentDir)

	// Check if filesystem is read-only and try to remount
	if err := s.ensureWritableFilesystem(parentDir); err != nil {
		log.Printf("Warning: failed to ensure writable filesystem: %v", err)
		// Continue anyway, might still work
	}

	if _, err := os.Stat(parentDir); os.IsNotExist(err) {
		log.Printf("Parent directory does not exist, creating: %s", parentDir)
		// Try to create parent directory
		if err := os.MkdirAll(parentDir, 0755); err != nil {
			log.Printf("Regular mkdir failed for parent %s: %v, trying with sudo", parentDir, err)
			// Try with sudo if regular mkdir fails
			cmd := exec.Command("sudo", "mkdir", "-p", parentDir)
			if output, err := cmd.CombinedOutput(); err != nil {
				outputStr := strings.TrimSpace(string(output))
				return fmt.Errorf("failed to create parent directory %s: %v, output: %s", parentDir, err, outputStr)
			}
			// Set permissions
			cmd = exec.Command("sudo", "chmod", "755", parentDir)
			cmd.Run() // Ignore error for chmod
		}
	} else {
		// Check if we can write to parent directory
		if testFile, err := os.CreateTemp(parentDir, ".write-test-*"); err != nil {
			log.Printf("Warning: cannot write to parent directory %s: %v, attempting remount", parentDir, err)
			// Try to remount as read-write
			if remountErr := s.remountReadWrite(parentDir); remountErr != nil {
				log.Printf("Warning: remount failed: %v", remountErr)
			}
		} else {
			testFile.Close()
			os.Remove(testFile.Name())
			log.Printf("Parent directory is writable: %s", parentDir)
		}
	}

	// Check if tape directory already exists (should have been caught earlier, but double-check)
	if _, err := os.Stat(tapePath); err == nil {
		// Directory exists, check if it's empty or has files
		entries, _ := os.ReadDir(tapePath)
		if len(entries) > 0 {
			return fmt.Errorf("tape directory %s already exists and is not empty", tapePath)
		}
		// Directory exists but empty, we can use it
	} else {
		// Create tape directory (may need root permissions for /opt/mhvtl)
		// Try without sudo first, if fails, try with sudo
		log.Printf("Attempting to create directory: %s", tapePath)
		if err := os.MkdirAll(tapePath, 0750); err != nil {
			log.Printf("Regular mkdir failed for %s: %v, trying with sudo", tapePath, err)
			// Try with sudo if regular mkdir fails
			cmd := exec.Command("sudo", "mkdir", "-p", tapePath)
			if output, err := cmd.CombinedOutput(); err != nil {
				outputStr := strings.TrimSpace(string(output))
				log.Printf("Sudo mkdir failed for %s: %v, output: %s", tapePath, err, outputStr)
				return fmt.Errorf("failed to create tape directory %s: %v (output: %s)", tapePath, err, outputStr)
			}
			log.Printf("Directory created with sudo: %s", tapePath)
			// Set permissions after creating with sudo
			cmd = exec.Command("sudo", "chmod", "750", tapePath)
			if output, err := cmd.CombinedOutput(); err != nil {
				log.Printf("Warning: failed to set permissions on %s: %v, output: %s", tapePath, err, string(output))
			}
		} else {
			log.Printf("Directory created successfully: %s", tapePath)
		}
	}

	// Create tape data file (mhvtl uses "data" file, not "tape")
	tapeFile := filepath.Join(tapePath, "data")
	file, err := os.Create(tapeFile)
	fileCreated := true
	if err != nil {
		// Try with sudo if regular create fails
		cmd := exec.Command("sudo", "touch", tapeFile)
		if output, err := cmd.CombinedOutput(); err != nil {
			return fmt.Errorf("failed to create tape file %s: %v, output: %s", tapeFile, err, string(output))
		}
		// Set permissions
		cmd = exec.Command("sudo", "chmod", "644", tapeFile)
		cmd.Run() // Ignore error
		file, err = os.OpenFile(tapeFile, os.O_WRONLY, 0644)
		if err != nil {
			return fmt.Errorf("failed to open tape file %s: %v", tapeFile, err)
		}
		fileCreated = false
	}

	// Pre-allocate space if size is specified (do this before closing file)
	if size > 0 {
		if fileCreated {
			// File was created by us, we can truncate it directly
			if err := file.Truncate(int64(size)); err != nil {
				log.Printf("Warning: failed to truncate tape file: %v, trying with sudo", err)
				file.Close()
				// Try with sudo if truncate fails
				cmd := exec.Command("sudo", "truncate", "-s", fmt.Sprintf("%d", size), tapeFile)
				if output, err := cmd.CombinedOutput(); err != nil {
					log.Printf("Warning: failed to pre-allocate tape space: %v, output: %s", err, string(output))
				} else {
					log.Printf("Tape file truncated to %d bytes using sudo", size)
				}
			} else {
				log.Printf("Tape file truncated to %d bytes", size)
			}
		} else {
			// File was created with sudo, use sudo truncate
			file.Close()
			cmd := exec.Command("sudo", "truncate", "-s", fmt.Sprintf("%d", size), tapeFile)
			if output, err := cmd.CombinedOutput(); err != nil {
				log.Printf("Warning: failed to pre-allocate tape space: %v, output: %s", err, string(output))
			} else {
				log.Printf("Tape file truncated to %d bytes using sudo", size)
			}
		}
	}

	if fileCreated {
		file.Close()
	}

	// Create index file (mhvtl also uses "indx" file)
	indxFile := filepath.Join(tapePath, "indx")
	indx, err := os.Create(indxFile)
	if err != nil {
		// Try with sudo if regular create fails
		cmd := exec.Command("sudo", "touch", indxFile)
		if output, err := cmd.CombinedOutput(); err != nil {
			log.Printf("Warning: failed to create index file %s: %v, output: %s", indxFile, err, string(output))
		} else {
			// Set permissions
			cmd = exec.Command("sudo", "chmod", "644", indxFile)
			if output, err := cmd.CombinedOutput(); err != nil {
				log.Printf("Warning: failed to set permissions on %s: %v, output: %s", indxFile, err, string(output))
			}
		}
	} else {
		indx.Close()
	}

	// Add tape to library_contents file
	if err := s.addTapeToLibraryContents(libraryID, slotID, barcode); err != nil {
		// Clean up created directory if library_contents update fails
		os.RemoveAll(tapePath)
		return fmt.Errorf("failed to add tape to library_contents: %v", err)
	}

	// Restart mhvtl service to reflect changes
	if err := s.RestartService(); err != nil {
		log.Printf("Warning: failed to restart mhvtl service after tape creation: %v", err)
		// Continue even if restart fails - tape is created
	}

	log.Printf("Created virtual tape: %s (type: %s, size: %d bytes, library: %d, slot: %d)", barcode, tapeType, size, libraryID, slotID)
	return nil
}

// DeleteTape deletes a virtual tape
func (s *VTLService) DeleteTape(barcode string) error {
	// mhvtl stores tapes directly in /opt/mhvtl/, not in /opt/mhvtl/data/
	tapePath := filepath.Join(s.storagePath, barcode)

	log.Printf("Deleting tape: barcode=%s, path=%s", barcode, tapePath)

	// Check if tape directory exists
	if _, err := os.Stat(tapePath); os.IsNotExist(err) {
		return fmt.Errorf("tape %s does not exist", barcode)
	}

	// Ensure filesystem is writable before delete (same as create)
	parentDir := s.storagePath
	if err := s.ensureWritableFilesystem(parentDir); err != nil {
		log.Printf("Warning: failed to ensure writable filesystem: %v", err)
		// Continue anyway, might still work
	}

	// Find which library and slot this tape is in
	libraryID, slotID := s.findTapeInLibrary(barcode)
	log.Printf("Tape %s found in library %d, slot %d", barcode, libraryID, slotID)

	// Remove the entire tape directory
	// Try without sudo first, if fails, try with sudo
	if err := os.RemoveAll(tapePath); err != nil {
		log.Printf("Regular RemoveAll failed for %s: %v, trying with sudo", tapePath, err)
		// Try with sudo if regular remove fails
		cmd := exec.Command("sudo", "rm", "-rf", tapePath)
		if output, err := cmd.CombinedOutput(); err != nil {
			outputStr := strings.TrimSpace(string(output))
			return fmt.Errorf("failed to delete tape directory %s: %v, output: %s", tapePath, err, outputStr)
		}
		log.Printf("Tape directory deleted with sudo: %s", tapePath)
	} else {
		log.Printf("Tape directory deleted successfully: %s", tapePath)
	}

	// Remove from library_contents if found
	if libraryID > 0 && slotID > 0 {
		if err := s.removeTapeFromLibraryContents(libraryID, slotID); err != nil {
			log.Printf("Warning: failed to remove tape from library_contents.%d: %v", libraryID, err)
			// Continue even if library_contents update fails
		}
	}

	// Restart mhvtl service to reflect changes
	if err := s.RestartService(); err != nil {
		log.Printf("Warning: failed to restart mhvtl service after tape deletion: %v", err)
		// Continue even if restart fails
	}

	log.Printf("Deleted virtual tape: %s (path: %s, library: %d, slot: %d)", barcode, tapePath, libraryID, slotID)
	return nil
}

// StartService starts the mhvtl service
func (s *VTLService) StartService() error {
	// Check if already active first
	checkCmd := exec.Command("systemctl", "is-active", "mhvtl.target")
	if err := checkCmd.Run(); err == nil {
		log.Printf("mhvtl.target is already active")
		return nil // Already running, no error
	}

	// mhvtl uses mhvtl.target, not mhvtl.service
	// First, ensure modules are loaded
	cmd := exec.Command("systemctl", "start", "mhvtl-load-modules.service")
	if err := cmd.Run(); err != nil {
		// Ignore error if modules are already loaded
		log.Printf("Warning: mhvtl-load-modules start returned: %v (may already be loaded)", err)
	}

	// Start mhvtl.target (this starts all mhvtl services)
	cmd = exec.Command("systemctl", "start", "mhvtl.target")
	output, err := cmd.CombinedOutput()
	if err != nil {
		// Check exit code for better error message
		if exitError, ok := err.(*exec.ExitError); ok {
			exitCode := exitError.ExitCode()
			outputStr := strings.TrimSpace(string(output))
			if outputStr == "" {
				outputStr = "no output"
			}
			log.Printf("mhvtl.target start failed: exit code %d, output: %s", exitCode, outputStr)

			// Provide specific error messages based on exit code
			switch exitCode {
			case 1:
				return fmt.Errorf("failed to start mhvtl service: unit failed to start. Check logs: journalctl -u mhvtl.target -n 50")
			case 5:
				return fmt.Errorf("failed to start mhvtl service: unit not found or permission denied. Ensure mhvtl is installed: apt-get install mhvtl")
			default:
				return fmt.Errorf("failed to start mhvtl service: exit code %d, output: %s", exitCode, outputStr)
			}
		}
		return fmt.Errorf("failed to start mhvtl service: %v", err)
	}

	log.Printf("mhvtl.target started successfully")
	return nil
}

// StopService stops the mhvtl service
func (s *VTLService) StopService() error {
	// Check if already inactive first
	checkCmd := exec.Command("systemctl", "is-active", "mhvtl.target")
	if err := checkCmd.Run(); err != nil {
		log.Printf("mhvtl.target is already inactive")
		return nil // Already stopped, no error
	}

	// Stop mhvtl.target (this stops all mhvtl services)
	cmd := exec.Command("systemctl", "stop", "mhvtl.target")
	output, err := cmd.CombinedOutput()
	if err != nil {
		if exitError, ok := err.(*exec.ExitError); ok {
			exitCode := exitError.ExitCode()
			outputStr := strings.TrimSpace(string(output))
			if outputStr == "" {
				outputStr = "no output"
			}
			log.Printf("mhvtl.target stop failed: exit code %d, output: %s", exitCode, outputStr)
			return fmt.Errorf("failed to stop mhvtl service: exit code %d, output: %s", exitCode, outputStr)
		}
		return fmt.Errorf("failed to stop mhvtl service: %v", err)
	}
	log.Printf("mhvtl.target stopped successfully")
	return nil
}

// RestartService restarts the mhvtl service
func (s *VTLService) RestartService() error {
	// Restart mhvtl.target
	cmd := exec.Command("systemctl", "restart", "mhvtl.target")
	output, err := cmd.CombinedOutput()
	if err != nil {
		if exitError, ok := err.(*exec.ExitError); ok {
			exitCode := exitError.ExitCode()
			outputStr := string(output)
			if outputStr == "" {
				outputStr = "no output"
			}
			log.Printf("mhvtl.target restart failed: exit code %d, output: %s", exitCode, outputStr)

			switch exitCode {
			case 1:
				return fmt.Errorf("failed to restart mhvtl service: unit failed to restart (check logs: journalctl -u mhvtl.target)")
			case 5:
				return fmt.Errorf("failed to restart mhvtl service: unit not found or permission denied")
			default:
				return fmt.Errorf("failed to restart mhvtl service: exit code %d, output: %s", exitCode, outputStr)
			}
		}
		return fmt.Errorf("failed to restart mhvtl service: %v", err)
	}
	log.Printf("mhvtl.target restarted successfully")
	return nil
}

// Helper functions

func (s *VTLService) determineDriveType(product string) string {
	product = strings.ToUpper(product)
	if strings.Contains(product, "LTO-9") || strings.Contains(product, "TD9") {
		return "LTO-9"
	}
	if strings.Contains(product, "LTO-8") || strings.Contains(product, "TD8") {
		return "LTO-8"
	}
	if strings.Contains(product, "LTO-7") || strings.Contains(product, "TD7") {
		return "LTO-7"
	}
	if strings.Contains(product, "LTO-6") || strings.Contains(product, "TD6") {
		return "LTO-6"
	}
	if strings.Contains(product, "LTO-5") || strings.Contains(product, "TD5") {
		return "LTO-5"
	}
	return "Unknown"
}

func (s *VTLService) getDriveIDFromDevice(deviceName string) int {
	// Extract number from device name (e.g., "st0" -> 0, "nst1" -> 1)
	// For now, use a simple mapping
	// In real implementation, this should read from mhvtl config
	if strings.HasPrefix(deviceName, "nst") {
		numStr := strings.TrimPrefix(deviceName, "nst")
		if num, err := strconv.Atoi(numStr); err == nil {
			return num + 10 // Assume library 10
		}
	} else if strings.HasPrefix(deviceName, "st") {
		numStr := strings.TrimPrefix(deviceName, "st")
		if num, err := strconv.Atoi(numStr); err == nil {
			return num + 10 // Assume library 10
		}
	}
	return 0
}

func (s *VTLService) checkMediaLoaded(deviceName string) (bool, string) {
	// Check if tape is loaded by reading from device
	// This is a simplified check - in real implementation, use mt or sg commands
	statusPath := fmt.Sprintf("/sys/class/scsi_tape/%s/device/tape_stat", deviceName)
	if _, err := os.Stat(statusPath); err == nil {
		// Tape device exists, might have media
		// For now, return false - real implementation should check actual status
		return false, ""
	}
	return false, ""
}

// ListMediaChangers lists all virtual media changers from device.conf
func (s *VTLService) ListMediaChangers() ([]models.VTLMediaChanger, error) {
	changers := []models.VTLMediaChanger{}

	// Parse device.conf to get libraries
	deviceConfig, err := s.parseDeviceConfig()
	if err == nil && len(deviceConfig.Libraries) > 0 {
		// Count drives per library
		drivesPerLibrary := make(map[int]int)
		for _, drive := range deviceConfig.Drives {
			drivesPerLibrary[drive.LibraryID]++
		}

		// Count slots per library from library_contents
		slotsPerLibrary := make(map[int]int)
		for _, lib := range deviceConfig.Libraries {
			slotMap, err := s.parseLibraryContents(lib.ID)
			if err == nil {
				slotsPerLibrary[lib.ID] = len(slotMap)
			} else {
				slotsPerLibrary[lib.ID] = 10 // Default
			}
		}

		// Find device path for each library
		for _, lib := range deviceConfig.Libraries {
			devicePath := s.findMediaChangerDevice(lib.ID)

			changer := models.VTLMediaChanger{
				ID:        lib.ID,
				LibraryID: lib.ID,
				Device:    devicePath,
				Status:    "online",
				Slots:     slotsPerLibrary[lib.ID],
				Drives:    drivesPerLibrary[lib.ID],
			}
			changers = append(changers, changer)
		}
		return changers, nil
	}

	// Fallback: Read from /sys/class/scsi_generic/
	sgPath := "/sys/class/scsi_generic"
	entries, err := os.ReadDir(sgPath)
	if err != nil {
		return changers, nil
	}

	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}

		deviceName := entry.Name()
		devicePath := fmt.Sprintf("/dev/%s", deviceName)

		vendorPath := fmt.Sprintf("%s/%s/device/vendor", sgPath, deviceName)
		productPath := fmt.Sprintf("%s/%s/device/model", sgPath, deviceName)

		vendor := "Unknown"
		product := "Unknown"
		if vendorBytes, err := os.ReadFile(vendorPath); err == nil {
			vendor = strings.TrimSpace(string(vendorBytes))
		}
		if productBytes, err := os.ReadFile(productPath); err == nil {
			product = strings.TrimSpace(string(productBytes))
		}

		// Check if it's a media changer (STK L700 or L80)
		if strings.Contains(strings.ToUpper(vendor), "STK") ||
			strings.Contains(strings.ToUpper(product), "L700") ||
			strings.Contains(strings.ToUpper(product), "L80") {
			// Try to determine library ID from device
			libraryID := 10
			if strings.Contains(strings.ToUpper(product), "L80") {
				libraryID = 30
			}

			// Count slots and drives for this library
			slotMap, _ := s.parseLibraryContents(libraryID)
			slots := len(slotMap)
			if slots == 0 {
				slots = 10 // Default
			}

			// Count drives from device.conf
			deviceConfig, _ := s.parseDeviceConfig()
			drives := 0
			if deviceConfig != nil {
				for _, drive := range deviceConfig.Drives {
					if drive.LibraryID == libraryID {
						drives++
					}
				}
			}
			if drives == 0 {
				drives = 4 // Default
			}

			changer := models.VTLMediaChanger{
				ID:        libraryID,
				LibraryID: libraryID,
				Device:    devicePath,
				Status:    "online",
				Slots:     slots,
				Drives:    drives,
			}
			changers = append(changers, changer)
		}
	}

	return changers, nil
}

// LoadTape loads a tape into a drive using mtx (media changer command)
func (s *VTLService) LoadTape(driveID int, barcode string) error {
	// Find the media changer device
	changers, err := s.ListMediaChangers()
	if err != nil || len(changers) == 0 {
		return fmt.Errorf("no media changer found")
	}

	changer := changers[0]

	// Find the slot containing this tape
	// In real implementation, this would query the media changer for slot info
	// For now, we'll use a simplified approach
	slotID := 1 // Default slot

	// Use mtx command to load tape: mtx -f /dev/sg0 load <slot> <drive>
	// Drive mapping: drive 0 = element 0, drive 1 = element 1, etc.
	// Slot mapping: slots start from element 256
	mtxCmd := exec.Command("mtx", "-f", changer.Device, "load", fmt.Sprintf("%d", slotID), fmt.Sprintf("%d", driveID))
	if err := mtxCmd.Run(); err != nil {
		// If mtx is not available, log and return error
		log.Printf("mtx command failed (may not be installed): %v", err)
		return fmt.Errorf("failed to load tape: mtx command failed (is mtx installed?)")
	}

	log.Printf("Loaded tape %s into drive %d", barcode, driveID)
	return nil
}

// EjectTape ejects a tape from a drive
func (s *VTLService) EjectTape(driveID int) error {
	// Find the media changer device
	changers, err := s.ListMediaChangers()
	if err != nil || len(changers) == 0 {
		return fmt.Errorf("no media changer found")
	}

	changer := changers[0]

	// Use mtx command to unload tape: mtx -f /dev/sg0 unload <slot> <drive>
	mtxCmd := exec.Command("mtx", "-f", changer.Device, "unload", "1", fmt.Sprintf("%d", driveID))
	if err := mtxCmd.Run(); err != nil {
		// If mtx is not available, log and return error
		log.Printf("mtx command failed (may not be installed): %v", err)
		return fmt.Errorf("failed to eject tape: mtx command failed (is mtx installed?)")
	}

	log.Printf("Ejected tape from drive %d", driveID)
	return nil
}

// GetMediaChangerStatus returns detailed status of the media changer
func (s *VTLService) GetMediaChangerStatus() (*models.VTLMediaChanger, error) {
	changers, err := s.ListMediaChangers()
	if err != nil {
		return nil, err
	}

	if len(changers) == 0 {
		return nil, fmt.Errorf("no media changer found")
	}

	return &changers[0], nil
}

// parseDeviceConfig parses /etc/mhvtl/device.conf
func (s *VTLService) parseDeviceConfig() (*DeviceConfig, error) {
	config := &DeviceConfig{
		Libraries: []LibraryConfig{},
		Drives:    []DriveConfig{},
	}

	file, err := os.Open(s.deviceConfigPath)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	var currentLibraryID int
	var currentDrive *DriveConfig

	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}

		// Parse Library line: "Library: 10 CHANNEL: 00 TARGET: 00 LUN: 00"
		if strings.HasPrefix(line, "Library:") {
			parts := strings.Fields(line)
			if len(parts) >= 2 {
				libID, _ := strconv.Atoi(parts[1])
				currentLibraryID = libID
				// Create new library entry
				config.Libraries = append(config.Libraries, LibraryConfig{
					ID: libID,
				})
			}
			continue
		}

		// Parse Library attributes (only if we're not parsing a drive)
		if currentDrive == nil && currentLibraryID > 0 {
			if strings.HasPrefix(line, "Vendor identification:") {
				if len(config.Libraries) > 0 {
					idx := len(config.Libraries) - 1
					config.Libraries[idx].Vendor = strings.TrimSpace(strings.TrimPrefix(line, "Vendor identification:"))
				}
				continue
			}
			if strings.HasPrefix(line, "Product identification:") {
				if len(config.Libraries) > 0 {
					idx := len(config.Libraries) - 1
					config.Libraries[idx].Product = strings.TrimSpace(strings.TrimPrefix(line, "Product identification:"))
				}
				continue
			}
			if strings.HasPrefix(line, "Unit serial number:") {
				if len(config.Libraries) > 0 {
					idx := len(config.Libraries) - 1
					config.Libraries[idx].Serial = strings.TrimSpace(strings.TrimPrefix(line, "Unit serial number:"))
				}
				continue
			}
		}

		// Parse Drive line: "Drive: 11 CHANNEL: 00 TARGET: 01 LUN: 00"
		if strings.HasPrefix(line, "Drive:") {
			parts := strings.Fields(line)
			if len(parts) >= 2 {
				driveID, _ := strconv.Atoi(parts[1])
				currentDrive = &DriveConfig{
					ID:        driveID,
					LibraryID: currentLibraryID,
				}
				config.Drives = append(config.Drives, *currentDrive)
			}
			continue
		}

		// Reset currentDrive when we encounter a new Library or other section
		if strings.HasPrefix(line, "Library:") {
			currentDrive = nil
		}

		// Parse Drive attributes
		if currentDrive != nil && len(config.Drives) > 0 {
			idx := len(config.Drives) - 1
			if strings.HasPrefix(line, "Library ID:") {
				parts := strings.Fields(line)
				if len(parts) >= 3 {
					libID, _ := strconv.Atoi(parts[2])
					config.Drives[idx].LibraryID = libID
				}
			}
			if strings.HasPrefix(line, "Slot:") {
				parts := strings.Fields(line)
				if len(parts) >= 2 {
					slotID, _ := strconv.Atoi(parts[1])
					config.Drives[idx].SlotID = slotID
				}
			}
			if strings.HasPrefix(line, "Vendor identification:") {
				config.Drives[idx].Vendor = strings.TrimSpace(strings.TrimPrefix(line, "Vendor identification:"))
			}
			if strings.HasPrefix(line, "Product identification:") {
				config.Drives[idx].Product = strings.TrimSpace(strings.TrimPrefix(line, "Product identification:"))
			}
			if strings.HasPrefix(line, "Unit serial number:") {
				config.Drives[idx].Serial = strings.TrimSpace(strings.TrimPrefix(line, "Unit serial number:"))
			}
		}
	}

	return config, scanner.Err()
}

// parseLibraryContents parses library_contents.X file
func (s *VTLService) parseLibraryContents(libraryID int) (map[int]string, error) {
	// Map slot ID to barcode
	slotMap := make(map[int]string)

	contentsPath := fmt.Sprintf("/etc/mhvtl/library_contents.%d", libraryID)
	file, err := os.Open(contentsPath)
	if err != nil {
		return slotMap, err
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)
	// Match "Slot 1: E01001L8" or "Slot 10: E01010L8" or "Slot 1: -" or "Slot 1:" format
	slotRegex := regexp.MustCompile(`^Slot\s+(\d+):\s*(.*)$`)

	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}

		matches := slotRegex.FindStringSubmatch(line)
		if len(matches) >= 2 {
			slotID, err := strconv.Atoi(matches[1])
			if err != nil {
				continue
			}
			// matches[2] is the barcode (or empty, or "-")
			barcode := strings.TrimSpace(matches[2])
			// Only add to map if barcode exists and is not empty or "-"
			if barcode != "" && barcode != "-" {
				slotMap[slotID] = barcode
			}
		}
	}

	return slotMap, scanner.Err()
}

// findDeviceForDrive finds device path for a drive ID
func (s *VTLService) findDeviceForDrive(driveID int) string {
	// Try to find device in /sys/class/scsi_tape/
	tapePath := "/sys/class/scsi_tape"
	entries, err := os.ReadDir(tapePath)
	if err != nil {
		return fmt.Sprintf("/dev/st%d", driveID%10) // Fallback
	}

	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}
		deviceName := entry.Name()
		if !strings.HasPrefix(deviceName, "st") && !strings.HasPrefix(deviceName, "nst") {
			continue
		}

		// Check if this device matches the drive ID
		// This is a simplified check - in real implementation, we'd need to map device to drive ID
		deviceID := s.getDriveIDFromDevice(deviceName)
		if deviceID == driveID {
			return fmt.Sprintf("/dev/%s", deviceName)
		}
	}

	return fmt.Sprintf("/dev/st%d", driveID%10) // Fallback
}

// checkMediaLoadedByDriveID checks if media is loaded in a drive by drive ID
func (s *VTLService) checkMediaLoadedByDriveID(driveID int) (bool, string) {
	devicePath := s.findDeviceForDrive(driveID)
	deviceName := filepath.Base(devicePath)
	return s.checkMediaLoaded(deviceName)
}

// findMediaChangerDevice finds device path for a media changer/library
func (s *VTLService) findMediaChangerDevice(libraryID int) string {
	// Try to find in /sys/class/scsi_generic/
	sgPath := "/sys/class/scsi_generic"
	entries, err := os.ReadDir(sgPath)
	if err != nil {
		return fmt.Sprintf("/dev/sg%d", libraryID%10) // Fallback
	}

	// Map library ID to device based on target in device.conf
	// Library 10 -> TARGET: 00 -> usually sg0
	// Library 30 -> TARGET: 08 -> usually sg1 or sg2
	deviceIndex := 0
	if libraryID == 30 {
		deviceIndex = 1
	}

	// Get all sg devices sorted
	sgDevices := []string{}
	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}
		deviceName := entry.Name()
		if strings.HasPrefix(deviceName, "sg") {
			sgDevices = append(sgDevices, deviceName)
		}
	}

	// Try to find matching device by checking vendor/product
	for _, deviceName := range sgDevices {
		devicePath := fmt.Sprintf("/dev/%s", deviceName)
		vendorPath := fmt.Sprintf("%s/%s/device/vendor", sgPath, deviceName)
		productPath := fmt.Sprintf("%s/%s/device/model", sgPath, deviceName)

		vendor := ""
		product := ""
		if vendorBytes, err := os.ReadFile(vendorPath); err == nil {
			vendor = strings.TrimSpace(string(vendorBytes))
		}
		if productBytes, err := os.ReadFile(productPath); err == nil {
			product = strings.TrimSpace(string(productBytes))
		}

		// Check if it's a media changer (STK L700 or L80)
		if strings.Contains(strings.ToUpper(vendor), "STK") ||
			strings.Contains(strings.ToUpper(product), "L700") ||
			strings.Contains(strings.ToUpper(product), "L80") {
			// For library 10, prefer L700; for library 30, prefer L80
			if libraryID == 10 && strings.Contains(strings.ToUpper(product), "L700") {
				return devicePath
			}
			if libraryID == 30 && strings.Contains(strings.ToUpper(product), "L80") {
				return devicePath
			}
			// If we haven't found a specific match yet, use this one
			if deviceIndex < len(sgDevices) && deviceName == sgDevices[deviceIndex] {
				return devicePath
			}
		}
	}

	// Fallback: use device index
	if deviceIndex < len(sgDevices) {
		return fmt.Sprintf("/dev/%s", sgDevices[deviceIndex])
	}
	return fmt.Sprintf("/dev/sg%d", deviceIndex)
}

// validateLTOBarcode validates that barcode follows LTO standard format
// LTO barcodes typically end with L1-L9, LW, LT, LU, LV
func (s *VTLService) validateLTOBarcode(barcode string) error {
	barcode = strings.ToUpper(strings.TrimSpace(barcode))

	if barcode == "" {
		return fmt.Errorf("barcode cannot be empty")
	}

	// Check minimum length (at least 3 characters, e.g., "E01L5")
	if len(barcode) < 3 {
		return fmt.Errorf("barcode too short (minimum 3 characters)")
	}

	// Check suffix (last 2 characters must be valid LTO suffix)
	if len(barcode) < 2 {
		return fmt.Errorf("barcode must end with valid LTO suffix (L1-L9, LW, LT, LU, LV)")
	}

	suffix := barcode[len(barcode)-2:]
	validSuffixes := []string{"L1", "L2", "L3", "L4", "L5", "L6", "L7", "L8", "L9", "LW", "LT", "LU", "LV"}

	valid := false
	for _, vs := range validSuffixes {
		if suffix == vs {
			valid = true
			break
		}
	}

	if !valid {
		return fmt.Errorf("barcode must end with valid LTO suffix (L1-L9, LW, LT, LU, LV), got: %s", suffix)
	}

	return nil
}

// determineTapeTypeFromBarcode determines tape type from barcode suffix
func (s *VTLService) determineTapeTypeFromBarcode(barcode string) string {
	barcode = strings.ToUpper(barcode)

	// Check suffix (last 2 characters)
	if len(barcode) >= 2 {
		suffix := barcode[len(barcode)-2:]
		switch suffix {
		case "L1":
			return "LTO-1"
		case "L2":
			return "LTO-2"
		case "L3":
			return "LTO-3"
		case "L4":
			return "LTO-4"
		case "L5":
			return "LTO-5"
		case "L6":
			return "LTO-6"
		case "L7":
			return "LTO-7"
		case "L8":
			return "LTO-8"
		case "L9":
			return "LTO-9"
		case "LW":
			return "LTO-6 WORM"
		case "LT":
			return "LTO-3 WORM"
		case "LU":
			return "LTO-4 WORM"
		case "LV":
			return "LTO-5 WORM"
		}
	}

	return "LTO-5" // Default
}

// getDefaultTapeSize returns default size in bytes for LTO generation
func (s *VTLService) getDefaultTapeSize(tapeType string) uint64 {
	tapeType = strings.ToUpper(tapeType)

	// LTO capacities (compressed, in bytes)
	// LTO-1: 200 GB = 200 * 1024^3 bytes
	// LTO-2: 400 GB = 400 * 1024^3 bytes
	// LTO-3: 800 GB = 800 * 1024^3 bytes
	// LTO-4: 1.6 TB = 1600 * 1024^3 bytes
	// LTO-5: 3.0 TB = 3000 * 1024^3 bytes
	// LTO-6: 6.25 TB = 6250 * 1024^3 bytes
	// LTO-7: 15 TB = 15000 * 1024^3 bytes
	// LTO-8: 30 TB = 30000 * 1024^3 bytes
	// LTO-9: 45 TB = 45000 * 1024^3 bytes

	switch {
	case strings.Contains(tapeType, "LTO-9"):
		return 45 * 1024 * 1024 * 1024 * 1024 // 45 TB
	case strings.Contains(tapeType, "LTO-8"):
		return 30 * 1024 * 1024 * 1024 * 1024 // 30 TB
	case strings.Contains(tapeType, "LTO-7"):
		return 15 * 1024 * 1024 * 1024 * 1024 // 15 TB
	case strings.Contains(tapeType, "LTO-6"):
		return 6250 * 1024 * 1024 * 1024 // 6.25 TB
	case strings.Contains(tapeType, "LTO-5"):
		return 3000 * 1024 * 1024 * 1024 // 3 TB
	case strings.Contains(tapeType, "LTO-4"):
		return 1600 * 1024 * 1024 * 1024 // 1.6 TB
	case strings.Contains(tapeType, "LTO-3"):
		return 800 * 1024 * 1024 * 1024 // 800 GB
	case strings.Contains(tapeType, "LTO-2"):
		return 400 * 1024 * 1024 * 1024 // 400 GB
	case strings.Contains(tapeType, "LTO-1"):
		return 200 * 1024 * 1024 * 1024 // 200 GB
	default:
		return 3000 * 1024 * 1024 * 1024 // Default: 3 TB (LTO-5)
	}
}

// findTapeInLibrary finds which library and slot a tape is in
func (s *VTLService) findTapeInLibrary(barcode string) (libraryID int, slotID int) {
	// Check all known libraries
	libraryIDs := []int{10, 30}

	// Also try to get from device.conf
	deviceConfig, err := s.parseDeviceConfig()
	if err == nil && len(deviceConfig.Libraries) > 0 {
		libraryIDs = []int{}
		for _, lib := range deviceConfig.Libraries {
			libraryIDs = append(libraryIDs, lib.ID)
		}
	}

	for _, libID := range libraryIDs {
		slotMap, err := s.parseLibraryContents(libID)
		if err == nil {
			for sid, bc := range slotMap {
				if bc == barcode {
					return libID, sid
				}
			}
		}
	}

	return 0, 0
}

// removeTapeFromLibraryContents removes a tape from library_contents file
func (s *VTLService) removeTapeFromLibraryContents(libraryID int, slotID int) error {
	contentsPath := fmt.Sprintf("/etc/mhvtl/library_contents.%d", libraryID)

	// Read the file
	file, err := os.OpenFile(contentsPath, os.O_RDWR, 0644)
	if err != nil {
		return fmt.Errorf("failed to open library_contents file: %v", err)
	}
	defer file.Close()

	// Read all lines
	var lines []string
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		lines = append(lines, scanner.Text())
	}
	if err := scanner.Err(); err != nil {
		return fmt.Errorf("failed to read library_contents file: %v", err)
	}

	// Find and clear the slot line (set to empty, don't remove the line)
	slotPattern := fmt.Sprintf("Slot %d:", slotID)
	updated := false
	var newLines []string
	for _, line := range lines {
		trimmed := strings.TrimSpace(line)
		if strings.HasPrefix(trimmed, slotPattern) {
			// Clear the slot by setting it to empty (format: "Slot X:" without "-")
			// Preserve original indentation
			indent := ""
			for i, char := range line {
				if char != ' ' && char != '\t' {
					indent = line[:i]
					break
				}
			}
			newLines = append(newLines, fmt.Sprintf("%sSlot %d:", indent, slotID))
			updated = true
		} else {
			newLines = append(newLines, line)
		}
	}

	if !updated {
		log.Printf("Slot %d not found in library_contents.%d", slotID, libraryID)
		return nil // Not an error if slot not found
	}

	// Write back to file
	if err := file.Truncate(0); err != nil {
		return fmt.Errorf("failed to truncate file: %v", err)
	}
	if _, err := file.Seek(0, 0); err != nil {
		return fmt.Errorf("failed to seek file: %v", err)
	}

	writer := bufio.NewWriter(file)
	for _, line := range newLines {
		if _, err := writer.WriteString(line + "\n"); err != nil {
			return fmt.Errorf("failed to write line: %v", err)
		}
	}
	if err := writer.Flush(); err != nil {
		return fmt.Errorf("failed to flush file: %v", err)
	}

	log.Printf("Removed slot %d from library_contents.%d", slotID, libraryID)
	return nil
}

// addTapeToLibraryContents adds a tape to library_contents file
func (s *VTLService) addTapeToLibraryContents(libraryID int, slotID int, barcode string) error {
	contentsPath := fmt.Sprintf("/etc/mhvtl/library_contents.%d", libraryID)

	// Read the file
	file, err := os.OpenFile(contentsPath, os.O_RDWR, 0644)
	if err != nil {
		return fmt.Errorf("failed to open library_contents file: %v", err)
	}
	defer file.Close()

	// Read all lines
	var lines []string
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		lines = append(lines, scanner.Text())
	}
	if err := scanner.Err(); err != nil {
		return fmt.Errorf("failed to read library_contents file: %v", err)
	}

	// Find and update the slot line
	slotPattern := fmt.Sprintf("Slot %d:", slotID)
	updated := false
	var newLines []string
	slotRegex := regexp.MustCompile(`^Slot\s+(\d+):\s*(.+)$`)

	for _, line := range lines {
		trimmed := strings.TrimSpace(line)
		if strings.HasPrefix(trimmed, slotPattern) {
			// Update the slot with barcode
			// Preserve original indentation
			indent := ""
			for i, char := range line {
				if char != ' ' && char != '\t' {
					indent = line[:i]
					break
				}
			}
			newLines = append(newLines, fmt.Sprintf("%sSlot %d: %s", indent, slotID, barcode))
			updated = true
		} else {
			newLines = append(newLines, line)
		}
	}

	// If slot not found, add it at the end
	if !updated {
		// Find the highest slot number to determine where to add
		maxSlot := 0
		for _, line := range lines {
			trimmed := strings.TrimSpace(line)
			matches := slotRegex.FindStringSubmatch(trimmed)
			if len(matches) == 3 {
				if sid, err := strconv.Atoi(matches[1]); err == nil && sid > maxSlot {
					maxSlot = sid
				}
			}
		}

		// Add new slot line
		newLines = append(newLines, fmt.Sprintf("Slot %d: %s", slotID, barcode))
		updated = true
	}

	if !updated {
		return fmt.Errorf("failed to update slot %d in library_contents.%d", slotID, libraryID)
	}

	// Write back to file
	if err := file.Truncate(0); err != nil {
		return fmt.Errorf("failed to truncate file: %v", err)
	}
	if _, err := file.Seek(0, 0); err != nil {
		return fmt.Errorf("failed to seek file: %v", err)
	}

	writer := bufio.NewWriter(file)
	for _, line := range newLines {
		if _, err := writer.WriteString(line + "\n"); err != nil {
			return fmt.Errorf("failed to write line: %v", err)
		}
	}
	if err := writer.Flush(); err != nil {
		return fmt.Errorf("failed to flush file: %v", err)
	}

	log.Printf("Added tape %s to slot %d in library_contents.%d", barcode, slotID, libraryID)
	return nil
}

// ensureWritableFilesystem checks if filesystem is writable and remounts if needed
func (s *VTLService) ensureWritableFilesystem(path string) error {
	// Try to create a test file to check if writable
	testFile := filepath.Join(path, ".write-test-check")
	if file, err := os.Create(testFile); err == nil {
		file.Close()
		os.Remove(testFile)
		return nil // Already writable
	}

	// Filesystem might be read-only, try to remount
	log.Printf("Filesystem appears read-only, attempting remount for %s", path)
	return s.remountReadWrite(path)
}

// remountReadWrite attempts to remount the filesystem containing the path as read-write
func (s *VTLService) remountReadWrite(path string) error {
	// Find the mount point for the path
	// Try /opt first, then /, then use findmnt
	var mountPoint string

	// Check if path is under /opt
	if strings.HasPrefix(path, "/opt") {
		mountPoint = "/opt"
	} else {
		mountPoint = "/"
	}

	// Try to remount with sudo
	log.Printf("Attempting to remount %s as read-write", mountPoint)
	cmd := exec.Command("sudo", "mount", "-o", "remount,rw", mountPoint)
	if output, err := cmd.CombinedOutput(); err != nil {
		outputStr := strings.TrimSpace(string(output))
		log.Printf("Remount failed for %s: %v, output: %s", mountPoint, err, outputStr)

		// Try alternative: remount root
		if mountPoint != "/" {
			log.Printf("Trying to remount root filesystem")
			cmd = exec.Command("sudo", "mount", "-o", "remount,rw", "/")
			if output, err := cmd.CombinedOutput(); err != nil {
				outputStr = strings.TrimSpace(string(output))
				return fmt.Errorf("failed to remount filesystem: %v, output: %s", err, outputStr)
			}
			log.Printf("Root filesystem remounted as read-write")
			return nil
		}
		return fmt.Errorf("failed to remount %s: %v, output: %s", mountPoint, err, outputStr)
	}

	log.Printf("Filesystem %s remounted as read-write", mountPoint)
	return nil
}