package backup

import (
	"errors"
	"fmt"
	"io/fs"
	"path/filepath"
	"strings"

	"gitea.dooplex.hu/admin/felhom-controller/internal/settings"
	"gitea.dooplex.hu/admin/felhom-controller/internal/system"
	"gitea.dooplex.hu/admin/felhom-controller/internal/util"
)

// restoreDirError (R-362) turns a failure to create a restore's directory into the truth when the
// cause is a drive that went away. Measured 2026-08-21: the guest-visible bind was unmounted 4 s into
// a scratch restore and the household read „restore dir: mkdir /mnt/felhom-drives/hdd_1/backups:
// permission denied" — a correct refusal that sent the reader after a permissions problem that did
// not exist. The settings flag can lag a detach by seconds, so the drive is also checked directly:
// a drive under the managed parent that is no longer a mount point is gone, whatever the flag says.
// Any other failure keeps its original wording. Pinned by TestR362_DetachedDriveIsNamed.
func (m *Manager) restoreDirError(dir string, err error) error {
	if err == nil {
		return nil
	}
	if !errors.Is(err, fs.ErrPermission) && !errors.Is(err, fs.ErrNotExist) {
		return fmt.Errorf("restore dir: %w", err)
	}
	sp, ok := m.registeredDriveHolding(dir)
	if !ok || !m.driveGone(sp) {
		return fmt.Errorf("restore dir: %w", err)
	}
	name := sp.Label
	if strings.TrimSpace(name) == "" {
		name = sp.Path
	}
	m.logger.Printf("[WARN] [backup] restore dir %s: %v — the drive %s (%s) is not connected; reported as a missing drive (R-362)", dir, err, sp.Path, name)
	return util.MsgError("err.backup.restore_drive_gone", name)
}

// registeredDriveHolding returns the registered storage path that contains dir (longest match).
func (m *Manager) registeredDriveHolding(dir string) (settings.StoragePath, bool) {
	if m == nil || m.settings == nil {
		return settings.StoragePath{}, false
	}
	clean := filepath.Clean(dir)
	var best settings.StoragePath
	found := false
	for _, sp := range m.settings.GetStoragePaths() {
		root := filepath.Clean(sp.Path)
		if root == "" || root == "/" {
			continue
		}
		if clean == root || strings.HasPrefix(clean, root+string(filepath.Separator)) {
			if !found || len(root) > len(filepath.Clean(best.Path)) {
				best, found = sp, true
			}
		}
	}
	return best, found
}

// driveGone: the registry already says disconnected, or the drive lives under the managed parent
// (where every enrolled drive is a bind mount) and is no longer a mount point.
func (m *Manager) driveGone(sp settings.StoragePath) bool {
	if sp.Disconnected {
		return true
	}
	parent := filepath.Clean(settings.NetworkMountRoot) + string(filepath.Separator)
	if !strings.HasPrefix(filepath.Clean(sp.Path)+string(filepath.Separator), parent) {
		return false // a legacy path outside the managed parent: only the flag can say it is gone
	}
	mounted := system.IsMountPoint
	if m.driveMountedFn != nil {
		mounted = m.driveMountedFn
	}
	return !mounted(sp.Path)
}