package main

import (
	"bytes"
	"context"
	"errors"
	"io"
	"log"
	"net"
	"net/http"
	"os"
	pathpkg "path"
	"path/filepath"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"time"
	"unicode/utf8"

	"github.com/hirochachacha/go-smb2"
	"github.com/jackc/pgx/v5"
	"golang.org/x/text/encoding/unicode"
	"golang.org/x/text/transform"
)

const (
	backupLogListTailBytes   int64 = 512 * 1024
	backupLogDetailTailBytes int64 = 1024 * 1024
	backupLogMaxFiles              = 200
	backupLogTailLineCount         = 240
	backupSMBTimeout               = 15 * time.Second
)

var errInvalidMilestoneBackupLogName = errors.New("ungueltiger Backup-Protokolldateiname")

type milestoneBackupLogFile struct {
	Name       string                    `json:"name"`
	Size       int64                     `json:"size"`
	ModifiedAt time.Time                 `json:"modifiedAt"`
	Summary    milestoneBackupLogSummary `json:"summary"`
}

type milestoneBackupLogDetail struct {
	milestoneBackupLogFile
	TailLines []string `json:"tailLines"`
}

type milestoneBackupLogSummary struct {
	Status      string                         `json:"status"`
	StartedAt   string                         `json:"startedAt"`
	EndedAt     string                         `json:"endedAt"`
	Duration    string                         `json:"duration"`
	TotalFiles  string                         `json:"totalFiles"`
	CopiedFiles string                         `json:"copiedFiles"`
	FailedCount int                            `json:"failedCount"`
	Rows        []milestoneBackupLogSummaryRow `json:"rows"`
}

type milestoneBackupLogSummaryRow struct {
	Key      string `json:"key"`
	Label    string `json:"label"`
	Total    string `json:"total"`
	Copied   string `json:"copied"`
	Skipped  string `json:"skipped"`
	Mismatch string `json:"mismatch"`
	Failed   string `json:"failed"`
	Extras   string `json:"extras"`
}

type milestoneBackupSettings struct {
	NasHost     string
	NasShare    string
	NasUsername string
	NasPassword string
	LogRootPath string
}

type milestoneBackupFolderRoot struct {
	Label string `json:"label"`
	Path  string `json:"path"`
}

type milestoneBackupFolderItem struct {
	Name        string `json:"name"`
	DisplayName string `json:"displayName,omitempty"`
	Path        string `json:"path"`
	HasChildren bool   `json:"hasChildren"`
}

type milestoneBackupFolderBrowseRequest struct {
	NasHost     string `json:"nasHost"`
	NasShare    string `json:"nasShare"`
	NasUsername string `json:"nasUsername"`
	NasPassword string `json:"nasPassword"`
	Path        string `json:"path"`
}

func (s *Server) handleListMilestoneBackupLogs(w http.ResponseWriter, r *http.Request) {
	settings, err := s.getMilestoneBackupSettings(r.Context())
	if errors.Is(err, pgx.ErrNoRows) {
		writeError(w, http.StatusBadRequest, "Backup-Protokollpfad ist nicht konfiguriert")
		return
	}

	if err != nil {
		log.Printf("Milestone backup log path load failed: %v", err)
		writeError(w, http.StatusInternalServerError, "Backup-Einstellungen konnten nicht geladen werden")
		return
	}

	rootPath := settings.effectiveLogRootPath()
	if strings.TrimSpace(rootPath) == "" {
		writeError(w, http.StatusBadRequest, "Backup-Protokollpfad ist nicht konfiguriert")
		return
	}

	fileName := strings.TrimSpace(r.URL.Query().Get("file"))
	if fileName != "" {
		detail, err := readMilestoneBackupLogDetail(r.Context(), settings, rootPath, fileName)
		if err != nil {
			log.Printf("Milestone backup log detail failed: file=%q error=%v", fileName, err)
			writeMilestoneBackupLogError(w, err)
			return
		}

		writeJSON(w, http.StatusOK, map[string]any{
			"rootPath": rootPath,
			"log":      detail,
		})
		return
	}

	files, err := listMilestoneBackupLogFiles(r.Context(), settings, rootPath)
	if err != nil {
		log.Printf("Milestone backup log list failed: root=%q error=%v", rootPath, err)
		writeMilestoneBackupLogError(w, err)
		return
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"rootPath": rootPath,
		"logs":     files,
	})
}

func (s *Server) handleListMilestoneBackupFolders(w http.ResponseWriter, r *http.Request) {
	settings, err := s.getMilestoneBackupSettings(r.Context())
	if errors.Is(err, pgx.ErrNoRows) {
		writeError(w, http.StatusBadRequest, "Backup-NAS oder Protokollordner ist nicht konfiguriert")
		return
	}

	if err != nil {
		log.Printf("Milestone backup settings load failed: %v", err)
		writeError(w, http.StatusInternalServerError, "Backup-Einstellungen konnten nicht geladen werden")
		return
	}

	rootPath := settings.effectiveBrowseRootPath()
	if rootPath == "" {
		writeError(w, http.StatusBadRequest, "Backup-NAS oder Protokollordner ist nicht konfiguriert")
		return
	}

	requestedPath := strings.TrimSpace(r.URL.Query().Get("path"))
	currentPath := requestedPath
	if currentPath == "" {
		currentPath = rootPath
	}

	folders, err := listMilestoneBackupFolders(r.Context(), settings, rootPath, currentPath)
	if err != nil {
		log.Printf("Milestone backup folder list failed: path=%q error=%v", currentPath, err)
		writeMilestoneBackupLogError(w, err)
		return
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"path": currentPath,
		"roots": []milestoneBackupFolderRoot{
			{Label: "Backup", Path: rootPath},
		},
		"folders": folders,
	})
}

func (s *Server) handleBrowseMilestoneBackupFolders(w http.ResponseWriter, r *http.Request) {
	var input milestoneBackupFolderBrowseRequest

	if err := readJSON(r, &input); err != nil {
		writeError(w, http.StatusBadRequest, "Invalid JSON")
		return
	}

	settings, err := s.getMilestoneBackupBrowseSettings(r.Context(), input)
	if err != nil {
		log.Printf("Milestone backup browse settings load failed: %v", err)
		writeError(w, http.StatusInternalServerError, "Backup-Einstellungen konnten nicht geladen werden")
		return
	}

	if settings.NasHost == "" {
		writeError(w, http.StatusBadRequest, "NAS-IP oder Hostname ist erforderlich")
		return
	}

	browseCtx, cancelBrowse := context.WithTimeout(r.Context(), backupSMBTimeout)
	defer cancelBrowse()

	requestedPath := settings.canonicalDisplayPath(input.Path)
	if settings.NasShare == "" {
		roots, err := listMilestoneBackupShareRoots(browseCtx, settings)
		if err != nil {
			log.Printf("Milestone backup share list failed: host=%q error=%v", settings.NasHost, err)
			writeMilestoneBackupLogError(w, err)
			return
		}

		writeJSON(w, http.StatusOK, map[string]any{
			"path":    settings.uncHostPath(),
			"roots":   roots,
			"folders": []milestoneBackupFolderItem{},
		})
		return
	}

	rootPath := settings.uncRootPath()
	currentPath := requestedPath
	if currentPath == "" {
		currentPath = rootPath
	}

	folders, err := listMilestoneBackupFoldersSMB(browseCtx, settings, rootPath, currentPath)
	if err != nil {
		if errors.Is(err, os.ErrPermission) && normalizeBackupDisplayPath(currentPath) == normalizeBackupDisplayPath(rootPath) {
			writeJSON(w, http.StatusOK, map[string]any{
				"path": currentPath,
				"roots": []milestoneBackupFolderRoot{
					{Label: settings.NasShare, Path: rootPath},
				},
				"folders": []milestoneBackupFolderItem{},
				"warning": "Die NAS-Freigabe wurde gefunden, aber der Ordner kann nicht aufgelistet werden. Prüfe die Leserechte oder trage den Unterordner manuell ein.",
			})
			return
		}

		log.Printf("Milestone backup folder browse failed: path=%q error=%v", currentPath, err)
		writeMilestoneBackupLogError(w, err)
		return
	}

	writeJSON(w, http.StatusOK, map[string]any{
		"path": currentPath,
		"roots": []milestoneBackupFolderRoot{
			{Label: settings.NasShare, Path: rootPath},
		},
		"folders": folders,
	})
}

func (s *Server) getMilestoneBackupBrowseSettings(
	ctx context.Context,
	input milestoneBackupFolderBrowseRequest,
) (milestoneBackupSettings, error) {
	savedSettings, err := s.getMilestoneBackupSettings(ctx)
	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
		return milestoneBackupSettings{}, err
	}

	hasSavedSettings := err == nil
	settings := milestoneBackupSettings{
		NasHost:     normalizeBackupNasHost(input.NasHost),
		NasShare:    normalizeBackupNasShare(input.NasShare),
		NasUsername: strings.TrimSpace(input.NasUsername),
		NasPassword: strings.TrimSpace(input.NasPassword),
		LogRootPath: strings.TrimSpace(input.Path),
	}

	pathHost, pathShare := backupUNCPathHostAndShare(input.Path)
	if settings.NasHost == "" {
		settings.NasHost = pathHost
	}
	if settings.NasShare == "" {
		settings.NasShare = pathShare
	}

	if settings.NasHost == "" && hasSavedSettings {
		settings.NasHost = savedSettings.NasHost
	}

	if settings.NasUsername == "" && hasSavedSettings && settings.NasHost == savedSettings.NasHost {
		settings.NasUsername = savedSettings.NasUsername
	}

	if settings.NasPassword == "" &&
		hasSavedSettings &&
		settings.NasHost == savedSettings.NasHost &&
		settings.NasUsername == savedSettings.NasUsername {
		settings.NasPassword = savedSettings.NasPassword
	}

	return settings, nil
}

func (s *Server) getMilestoneBackupSettings(ctx context.Context) (milestoneBackupSettings, error) {
	var settings milestoneBackupSettings

	err := s.db.QueryRow(
		ctx,
		`
		SELECT
			COALESCE(backup_nas_host, ''),
			COALESCE(backup_nas_share, ''),
			COALESCE(backup_nas_username, ''),
			COALESCE(pgp_sym_decrypt(backup_nas_password_encrypted, $1), ''),
			COALESCE(backup_log_root_path, '')
		FROM milestone_settings
		WHERE id = 1
		LIMIT 1
		`,
		s.milestoneEncryptionKey(),
	).Scan(
		&settings.NasHost,
		&settings.NasShare,
		&settings.NasUsername,
		&settings.NasPassword,
		&settings.LogRootPath,
	)

	settings.NasHost = normalizeBackupNasHost(settings.NasHost)
	settings.NasShare = normalizeBackupNasShare(settings.NasShare)
	settings.NasUsername = strings.TrimSpace(settings.NasUsername)
	settings.NasPassword = strings.TrimSpace(settings.NasPassword)
	settings.LogRootPath = strings.TrimSpace(settings.LogRootPath)

	return settings, err
}

func writeMilestoneBackupLogError(w http.ResponseWriter, err error) {
	if errors.Is(err, os.ErrNotExist) {
		writeError(w, http.StatusNotFound, "Backup-Protokoll wurde nicht gefunden")
		return
	}

	if errors.Is(err, os.ErrPermission) {
		writeError(w, http.StatusForbidden, "Backup-Protokollpfad kann nicht gelesen werden. Prüfe die NAS-Freigabe, den Benutzer und die Leserechte.")
		return
	}

	if errors.Is(err, context.DeadlineExceeded) {
		writeError(w, http.StatusGatewayTimeout, "NAS hat nicht rechtzeitig geantwortet. Prüfe Hostname, Benutzername, Domäne und Netzwerkverbindung.")
		return
	}

	if errors.Is(err, context.Canceled) {
		writeError(w, http.StatusGatewayTimeout, "NAS-Anfrage wurde abgebrochen.")
		return
	}

	if errors.Is(err, errInvalidMilestoneBackupLogName) {
		writeError(w, http.StatusBadRequest, "Backup-Protokolldateiname ist ungültig")
		return
	}

	writeError(w, http.StatusInternalServerError, "Backup-Protokolle konnten nicht geladen werden")
}

func (settings milestoneBackupSettings) hasNAS() bool {
	return settings.NasHost != "" && settings.NasShare != ""
}

func (settings milestoneBackupSettings) uncRootPath() string {
	if !settings.hasNAS() {
		return ""
	}

	return `\\` + settings.NasHost + `\` + settings.NasShare
}

func (settings milestoneBackupSettings) uncHostPath() string {
	if settings.NasHost == "" {
		return ""
	}

	return `\\` + settings.NasHost
}

func (settings milestoneBackupSettings) effectiveBrowseRootPath() string {
	if settings.hasNAS() {
		return settings.uncRootPath()
	}

	return strings.TrimSpace(settings.LogRootPath)
}

func (settings milestoneBackupSettings) effectiveLogRootPath() string {
	if strings.TrimSpace(settings.LogRootPath) != "" {
		return strings.TrimSpace(settings.LogRootPath)
	}

	return settings.effectiveBrowseRootPath()
}

func listMilestoneBackupLogFiles(ctx context.Context, settings milestoneBackupSettings, rootPath string) ([]milestoneBackupLogFile, error) {
	if settings.hasNAS() {
		return listMilestoneBackupLogFilesSMB(ctx, settings, rootPath)
	}

	entries, err := os.ReadDir(rootPath)
	if err != nil {
		return nil, err
	}

	files := make([]milestoneBackupLogFile, 0)

	for _, entry := range entries {
		if entry.IsDir() || !strings.EqualFold(filepath.Ext(entry.Name()), ".log") {
			continue
		}

		info, err := entry.Info()
		if err != nil {
			return nil, err
		}

		path := filepath.Join(rootPath, entry.Name())
		text, err := readTextFileTail(path, backupLogListTailBytes)
		if err != nil {
			return nil, err
		}

		files = append(files, milestoneBackupLogFile{
			Name:       entry.Name(),
			Size:       info.Size(),
			ModifiedAt: info.ModTime(),
			Summary:    parseMilestoneBackupLogSummary(text),
		})
	}

	sort.Slice(files, func(left, right int) bool {
		return files[left].ModifiedAt.After(files[right].ModifiedAt)
	})

	if len(files) > backupLogMaxFiles {
		files = files[:backupLogMaxFiles]
	}

	return files, nil
}

func listMilestoneBackupLogFilesSMB(ctx context.Context, settings milestoneBackupSettings, rootPath string) ([]milestoneBackupLogFile, error) {
	share, cleanup, err := openMilestoneBackupSMBShare(ctx, settings)
	if err != nil {
		return nil, err
	}
	defer cleanup()

	relativeRoot, err := settings.relativeSMBPath(rootPath)
	if err != nil {
		return nil, err
	}

	entries, err := share.ReadDir(relativeRoot)
	if err != nil {
		return nil, err
	}

	files := make([]milestoneBackupLogFile, 0)
	for _, entry := range entries {
		if entry.IsDir() || !strings.EqualFold(filepath.Ext(entry.Name()), ".log") {
			continue
		}

		relativeFilePath := joinSMBRelativePath(relativeRoot, entry.Name())
		text, err := readSMBTextFileTail(share, relativeFilePath, backupLogListTailBytes)
		if err != nil {
			return nil, err
		}

		files = append(files, milestoneBackupLogFile{
			Name:       entry.Name(),
			Size:       entry.Size(),
			ModifiedAt: entry.ModTime(),
			Summary:    parseMilestoneBackupLogSummary(text),
		})
	}

	sort.Slice(files, func(left, right int) bool {
		return files[left].ModifiedAt.After(files[right].ModifiedAt)
	})

	if len(files) > backupLogMaxFiles {
		files = files[:backupLogMaxFiles]
	}

	return files, nil
}

func readMilestoneBackupLogDetail(ctx context.Context, settings milestoneBackupSettings, rootPath string, fileName string) (milestoneBackupLogDetail, error) {
	if settings.hasNAS() {
		return readMilestoneBackupLogDetailSMB(ctx, settings, rootPath, fileName)
	}

	path, err := resolveMilestoneBackupLogPath(rootPath, fileName)
	if err != nil {
		return milestoneBackupLogDetail{}, err
	}

	info, err := os.Stat(path)
	if err != nil {
		return milestoneBackupLogDetail{}, err
	}

	if info.IsDir() {
		return milestoneBackupLogDetail{}, os.ErrNotExist
	}

	text, err := readTextFileTail(path, backupLogDetailTailBytes)
	if err != nil {
		return milestoneBackupLogDetail{}, err
	}

	return milestoneBackupLogDetail{
		milestoneBackupLogFile: milestoneBackupLogFile{
			Name:       filepath.Base(path),
			Size:       info.Size(),
			ModifiedAt: info.ModTime(),
			Summary:    parseMilestoneBackupLogSummary(text),
		},
		TailLines: tailNonEmptyLines(text, backupLogTailLineCount),
	}, nil
}

func readMilestoneBackupLogDetailSMB(ctx context.Context, settings milestoneBackupSettings, rootPath string, fileName string) (milestoneBackupLogDetail, error) {
	if err := validateMilestoneBackupLogFileName(fileName); err != nil {
		return milestoneBackupLogDetail{}, err
	}

	share, cleanup, err := openMilestoneBackupSMBShare(ctx, settings)
	if err != nil {
		return milestoneBackupLogDetail{}, err
	}
	defer cleanup()

	relativeRoot, err := settings.relativeSMBPath(rootPath)
	if err != nil {
		return milestoneBackupLogDetail{}, err
	}

	relativeFilePath := joinSMBRelativePath(relativeRoot, fileName)
	info, err := share.Stat(relativeFilePath)
	if err != nil {
		return milestoneBackupLogDetail{}, err
	}

	if info.IsDir() {
		return milestoneBackupLogDetail{}, os.ErrNotExist
	}

	text, err := readSMBTextFileTail(share, relativeFilePath, backupLogDetailTailBytes)
	if err != nil {
		return milestoneBackupLogDetail{}, err
	}

	return milestoneBackupLogDetail{
		milestoneBackupLogFile: milestoneBackupLogFile{
			Name:       filepath.Base(fileName),
			Size:       info.Size(),
			ModifiedAt: info.ModTime(),
			Summary:    parseMilestoneBackupLogSummary(text),
		},
		TailLines: tailNonEmptyLines(text, backupLogTailLineCount),
	}, nil
}

func resolveMilestoneBackupLogPath(rootPath string, fileName string) (string, error) {
	if err := validateMilestoneBackupLogFileName(fileName); err != nil {
		return "", err
	}

	cleanName := strings.TrimSpace(fileName)

	return filepath.Join(rootPath, cleanName), nil
}

func validateMilestoneBackupLogFileName(fileName string) error {
	cleanName := strings.TrimSpace(fileName)
	if cleanName == "" ||
		cleanName != filepath.Base(cleanName) ||
		strings.Contains(cleanName, "/") ||
		strings.Contains(cleanName, `\`) ||
		!strings.EqualFold(filepath.Ext(cleanName), ".log") {
		return errInvalidMilestoneBackupLogName
	}

	return nil
}

func readTextFileTail(path string, maxBytes int64) (string, error) {
	file, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer file.Close()

	info, err := file.Stat()
	if err != nil {
		return "", err
	}

	return readTextReadSeekerTail(file, info.Size(), maxBytes)
}

func readSMBTextFileTail(share *smb2.Share, path string, maxBytes int64) (string, error) {
	file, err := share.Open(path)
	if err != nil {
		return "", err
	}
	defer file.Close()

	info, err := file.Stat()
	if err != nil {
		return "", err
	}

	return readTextReadSeekerTail(file, info.Size(), maxBytes)
}

func readTextReadSeekerTail(file interface {
	io.Reader
	io.ReaderAt
	io.Seeker
}, size int64, maxBytes int64) (string, error) {
	start := int64(0)
	if size > maxBytes {
		start = size - maxBytes
	}

	reader := io.NewSectionReader(file, start, size-start)
	data, err := io.ReadAll(reader)
	if err != nil {
		return "", err
	}

	if start > 0 {
		if index := bytes.IndexByte(data, '\n'); index >= 0 && index+1 < len(data) {
			data = data[index+1:]
		}
	}

	return decodeMilestoneBackupLogText(data), nil
}

func listMilestoneBackupFolders(ctx context.Context, settings milestoneBackupSettings, rootPath string, currentPath string) ([]milestoneBackupFolderItem, error) {
	if settings.hasNAS() {
		return listMilestoneBackupFoldersSMB(ctx, settings, rootPath, currentPath)
	}

	return listMilestoneBackupFoldersLocal(rootPath, currentPath)
}

func listMilestoneBackupShareRoots(ctx context.Context, settings milestoneBackupSettings) ([]milestoneBackupFolderRoot, error) {
	session, cleanup, err := openMilestoneBackupSMBSession(ctx, settings)
	if err != nil {
		return nil, err
	}
	defer cleanup()

	shareNames, err := session.ListSharenames()
	if err != nil {
		return nil, err
	}

	roots := make([]milestoneBackupFolderRoot, 0, len(shareNames))
	for _, shareName := range shareNames {
		shareName = normalizeBackupNasShare(shareName)
		if shareName == "" || strings.EqualFold(shareName, "IPC$") {
			continue
		}

		roots = append(roots, milestoneBackupFolderRoot{
			Label: shareName,
			Path:  `\\` + settings.NasHost + `\` + shareName,
		})
	}

	sort.Slice(roots, func(left, right int) bool {
		return strings.ToLower(roots[left].Label) < strings.ToLower(roots[right].Label)
	})

	return roots, nil
}

func listMilestoneBackupFoldersLocal(rootPath string, currentPath string) ([]milestoneBackupFolderItem, error) {
	if !pathIsInsideBackupRoot(rootPath, currentPath) {
		return nil, errInvalidMilestoneBackupLogName
	}

	entries, err := os.ReadDir(currentPath)
	if err != nil {
		return nil, err
	}

	folders := make([]milestoneBackupFolderItem, 0)
	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}

		path := filepath.Join(currentPath, entry.Name())
		folders = append(folders, milestoneBackupFolderItem{
			Name:        entry.Name(),
			DisplayName: entry.Name(),
			Path:        path,
			HasChildren: directoryHasChildFolders(path),
		})
	}

	sort.Slice(folders, func(left, right int) bool {
		return strings.ToLower(folders[left].Name) < strings.ToLower(folders[right].Name)
	})

	return folders, nil
}

func listMilestoneBackupFoldersSMB(ctx context.Context, settings milestoneBackupSettings, rootPath string, currentPath string) ([]milestoneBackupFolderItem, error) {
	if !pathIsInsideBackupRoot(rootPath, currentPath) {
		return nil, errInvalidMilestoneBackupLogName
	}

	share, cleanup, err := openMilestoneBackupSMBShare(ctx, settings)
	if err != nil {
		return nil, err
	}
	defer cleanup()

	relativeCurrentPath, err := settings.relativeSMBPath(currentPath)
	if err != nil {
		return nil, err
	}

	entries, err := share.ReadDir(relativeCurrentPath)
	if err != nil {
		return nil, err
	}

	folders := make([]milestoneBackupFolderItem, 0)
	for _, entry := range entries {
		if !entry.IsDir() {
			continue
		}

		relativePath := joinSMBRelativePath(relativeCurrentPath, entry.Name())
		folders = append(folders, milestoneBackupFolderItem{
			Name:        entry.Name(),
			DisplayName: entry.Name(),
			Path:        settings.uncPathFromRelative(relativePath),
			HasChildren: smbDirectoryHasChildFolders(share, relativePath),
		})
	}

	sort.Slice(folders, func(left, right int) bool {
		return strings.ToLower(folders[left].Name) < strings.ToLower(folders[right].Name)
	})

	return folders, nil
}

func pathIsInsideBackupRoot(rootPath string, currentPath string) bool {
	root := normalizeBackupDisplayPath(rootPath)
	current := normalizeBackupDisplayPath(currentPath)

	return root != "" && (current == root || strings.HasPrefix(current, root+`\`))
}

func normalizeBackupDisplayPath(value string) string {
	value = strings.TrimSpace(value)
	value = strings.ReplaceAll(value, "/", `\`)
	value = strings.TrimRight(value, `\`)

	if strings.HasPrefix(value, `\\`) {
		value = `\\` + strings.TrimPrefix(value, `\\`)
	}

	return strings.ToLower(value)
}

func (settings milestoneBackupSettings) canonicalDisplayPath(value string) string {
	value = strings.TrimSpace(value)
	value = strings.ReplaceAll(value, "/", `\`)
	value = strings.TrimRight(value, `\`)

	if value == "" {
		return ""
	}

	if strings.HasPrefix(value, `\\`) {
		return `\\` + strings.TrimPrefix(value, `\\`)
	}

	host := strings.TrimSpace(settings.NasHost)
	if host != "" && strings.HasPrefix(strings.ToLower(value), strings.ToLower(host)+`\`) {
		return `\\` + value
	}

	return value
}

func directoryHasChildFolders(path string) bool {
	entries, err := os.ReadDir(path)
	if err != nil {
		return false
	}

	for _, entry := range entries {
		if entry.IsDir() {
			return true
		}
	}

	return false
}

func smbDirectoryHasChildFolders(share *smb2.Share, path string) bool {
	entries, err := share.ReadDir(path)
	if err != nil {
		return false
	}

	for _, entry := range entries {
		if entry.IsDir() {
			return true
		}
	}

	return false
}

func openMilestoneBackupSMBSession(ctx context.Context, settings milestoneBackupSettings) (*smb2.Session, func(), error) {
	dialer := net.Dialer{Timeout: 10 * time.Second}
	conn, err := dialer.DialContext(ctx, "tcp", net.JoinHostPort(settings.NasHost, "445"))
	if err != nil {
		return nil, func() {}, err
	}

	domain, username := splitBackupNasUsername(settings.NasUsername)
	smbDialer := smb2.Dialer{
		Initiator: &smb2.NTLMInitiator{
			User:     username,
			Password: settings.NasPassword,
			Domain:   domain,
		},
	}

	session, err := smbDialer.DialContext(ctx, conn)
	if err != nil {
		conn.Close()
		return nil, func() {}, err
	}

	cleanup := func() {
		session.Logoff()
		conn.Close()
	}

	return session, cleanup, nil
}

func openMilestoneBackupSMBShare(ctx context.Context, settings milestoneBackupSettings) (*smb2.Share, func(), error) {
	session, cleanupSession, err := openMilestoneBackupSMBSession(ctx, settings)
	if err != nil {
		return nil, func() {}, err
	}

	share, err := session.Mount(settings.NasShare)
	if err != nil {
		cleanupSession()
		return nil, func() {}, err
	}
	share = share.WithContext(ctx)

	cleanup := func() {
		share.Umount()
		cleanupSession()
	}

	return share, cleanup, nil
}

func splitBackupNasUsername(value string) (string, string) {
	value = strings.TrimSpace(value)
	if value == "" {
		return "", ""
	}

	if index := strings.Index(value, `\`); index > 0 {
		return value[:index], value[index+1:]
	}

	if index := strings.Index(value, `/`); index > 0 {
		return value[:index], value[index+1:]
	}

	return "", value
}

func backupUNCPathHostAndShare(value string) (string, string) {
	value = strings.TrimSpace(value)
	value = strings.ReplaceAll(value, "/", `\`)
	value = strings.TrimPrefix(value, `\\`)
	value = strings.Trim(value, `\`)

	parts := strings.Split(value, `\`)
	if len(parts) < 2 {
		return normalizeBackupNasHost(value), ""
	}

	return normalizeBackupNasHost(parts[0]), normalizeBackupNasShare(parts[1])
}

func (settings milestoneBackupSettings) relativeSMBPath(displayPath string) (string, error) {
	base := normalizeBackupDisplayPath(settings.uncRootPath())
	current := normalizeBackupDisplayPath(displayPath)

	if current == "" || current == base {
		return ".", nil
	}

	if !strings.HasPrefix(current, base+`\`) {
		return "", errInvalidMilestoneBackupLogName
	}

	relativePath := strings.TrimPrefix(current, base+`\`)
	relativePath = strings.ReplaceAll(relativePath, `\`, "/")
	relativePath = pathpkg.Clean(relativePath)

	if relativePath == "." || relativePath == "/" {
		return ".", nil
	}

	if relativePath == ".." || strings.HasPrefix(relativePath, "../") {
		return "", errInvalidMilestoneBackupLogName
	}

	return relativePath, nil
}

func (settings milestoneBackupSettings) uncPathFromRelative(relativePath string) string {
	cleanRelativePath := strings.TrimSpace(relativePath)
	cleanRelativePath = strings.Trim(cleanRelativePath, `/\`)
	cleanRelativePath = strings.ReplaceAll(cleanRelativePath, "/", `\`)

	if cleanRelativePath == "" || cleanRelativePath == "." {
		return settings.uncRootPath()
	}

	return strings.TrimRight(settings.uncRootPath(), `\`) + `\` + cleanRelativePath
}

func joinSMBRelativePath(basePath string, childName string) string {
	basePath = strings.TrimSpace(basePath)
	childName = strings.Trim(childName, `/\`)

	if basePath == "" || basePath == "." {
		return childName
	}

	return strings.TrimRight(basePath, `/\`) + "/" + childName
}

func decodeMilestoneBackupLogText(data []byte) string {
	if len(data) >= 2 {
		if data[0] == 0xff && data[1] == 0xfe {
			return decodeUTF16(data, unicode.LittleEndian)
		}

		if data[0] == 0xfe && data[1] == 0xff {
			return decodeUTF16(data, unicode.BigEndian)
		}
	}

	if looksLikeUTF16LE(data) {
		return decodeUTF16(data, unicode.LittleEndian)
	}

	if looksLikeUTF16BE(data) {
		return decodeUTF16(data, unicode.BigEndian)
	}

	if utf8.Valid(data) {
		return string(data)
	}

	return string(bytes.ToValidUTF8(data, []byte("?")))
}

func decodeUTF16(data []byte, endianness unicode.Endianness) string {
	decoder := unicode.UTF16(endianness, unicode.UseBOM).NewDecoder()
	decoded, _, err := transform.Bytes(decoder, data)
	if err != nil {
		return string(bytes.ToValidUTF8(data, []byte("?")))
	}

	return string(decoded)
}

func looksLikeUTF16LE(data []byte) bool {
	return countZeroBytesAtParity(data, 1) > len(data)/8
}

func looksLikeUTF16BE(data []byte) bool {
	return countZeroBytesAtParity(data, 0) > len(data)/8
}

func countZeroBytesAtParity(data []byte, parity int) int {
	count := 0
	limit := len(data)
	if limit > 4096 {
		limit = 4096
	}

	for index := parity; index < limit; index += 2 {
		if data[index] == 0 {
			count++
		}
	}

	return count
}

var backupLogSummaryLinePattern = regexp.MustCompile(`^\s*([^:]{1,48})\s*:\s*(.+?)\s*$`)
var multiSpacePattern = regexp.MustCompile(`\s{2,}`)
var leadingIntegerPattern = regexp.MustCompile(`^\D*([0-9][0-9.,]*)`)

func parseMilestoneBackupLogSummary(text string) milestoneBackupLogSummary {
	summary := milestoneBackupLogSummary{
		Status: "unknown",
		Rows:   []milestoneBackupLogSummaryRow{},
	}

	lines := strings.Split(strings.ReplaceAll(text, "\r\n", "\n"), "\n")
	startIndex := len(lines) - 600
	if startIndex < 0 {
		startIndex = 0
	}

	for _, line := range lines[startIndex:] {
		trimmedLine := strings.TrimSpace(line)
		if trimmedLine == "" {
			continue
		}

		lowerLine := strings.ToLower(trimmedLine)
		if strings.Contains(lowerLine, "started") || strings.Contains(lowerLine, "gestartet") {
			if value := valueAfterColon(trimmedLine); value != "" {
				summary.StartedAt = value
			}
		}

		if strings.Contains(lowerLine, "ended") || strings.Contains(lowerLine, "beendet") {
			if value := valueAfterColon(trimmedLine); value != "" {
				summary.EndedAt = value
			}
		}

		matches := backupLogSummaryLinePattern.FindStringSubmatch(line)
		if len(matches) != 3 {
			continue
		}

		key, label := normalizeBackupLogSummaryLabel(matches[1])
		if key == "" {
			continue
		}

		cells := parseBackupLogSummaryCells(matches[2])
		if len(cells) < 6 {
			continue
		}

		row := milestoneBackupLogSummaryRow{
			Key:      key,
			Label:    label,
			Total:    cells[0],
			Copied:   cells[1],
			Skipped:  cells[2],
			Mismatch: cells[3],
			Failed:   cells[4],
			Extras:   cells[5],
		}
		summary.Rows = append(summary.Rows, row)

		if key == "files" {
			summary.TotalFiles = row.Total
			summary.CopiedFiles = row.Copied
			summary.FailedCount += parseBackupLogInteger(row.Failed)
		}

		if key == "dirs" {
			summary.FailedCount += parseBackupLogInteger(row.Failed)
		}

		if key == "times" {
			summary.Duration = row.Total
		}
	}

	if summary.FailedCount > 0 {
		summary.Status = "failed"
	} else if len(summary.Rows) > 0 {
		summary.Status = "success"
	}

	return summary
}

func valueAfterColon(value string) string {
	index := strings.Index(value, ":")
	if index < 0 || index+1 >= len(value) {
		return ""
	}

	return strings.TrimSpace(value[index+1:])
}

func normalizeBackupLogSummaryLabel(value string) (string, string) {
	normalized := strings.ToLower(strings.TrimSpace(value))
	normalized = strings.Trim(normalized, ".")

	switch normalized {
	case "dirs", "directories", "verzeichnisse", "ordner":
		return "dirs", "Verzeichnisse"
	case "files", "dateien":
		return "files", "Dateien"
	case "bytes", "byte":
		return "bytes", "Bytes"
	case "times", "zeiten", "time":
		return "times", "Dauer"
	}

	return "", ""
}

func parseBackupLogSummaryCells(value string) []string {
	cells := multiSpacePattern.Split(strings.TrimSpace(value), -1)
	if len(cells) >= 6 {
		return cells[:6]
	}

	fields := strings.Fields(value)
	if len(fields) >= 6 {
		return fields[:6]
	}

	return cells
}

func parseBackupLogInteger(value string) int {
	match := leadingIntegerPattern.FindStringSubmatch(strings.TrimSpace(value))
	if len(match) != 2 {
		return 0
	}

	cleanValue := strings.NewReplacer(".", "", ",", "", " ", "").Replace(match[1])
	number, err := strconv.Atoi(cleanValue)
	if err != nil {
		return 0
	}

	return number
}

func tailNonEmptyLines(text string, maxLines int) []string {
	lines := strings.Split(strings.ReplaceAll(text, "\r\n", "\n"), "\n")
	cleanLines := make([]string, 0, len(lines))

	for _, line := range lines {
		cleanLines = append(cleanLines, strings.TrimRight(line, "\r"))
	}

	for len(cleanLines) > 0 && strings.TrimSpace(cleanLines[len(cleanLines)-1]) == "" {
		cleanLines = cleanLines[:len(cleanLines)-1]
	}

	if len(cleanLines) > maxLines {
		cleanLines = cleanLines[len(cleanLines)-maxLines:]
	}

	return cleanLines
}