//go:build linux

package host

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/carlosframework/platform/internal/hostbox"
	"golang.org/x/sys/unix"
)

// Resolve the filesystem's kernel device, then its containing disk if it is a
// partition. Only an EBS NVMe controller serial supplies independent identity;
// filesystem UUIDs and loop backing files cannot distinguish snapshot clones.
func servingParkVolume(device uint64) string {
	return servingParkVolumeAt("/sys", device)
}

func servingParkVolumeAt(sys string, device uint64) string {
	path, err := filepath.EvalSymlinks(filepath.Join(sys, "dev", "block", fmt.Sprintf("%d:%d", unix.Major(device), unix.Minor(device))))
	if err != nil {
		return ""
	}
	if _, err := os.Stat(filepath.Join(path, "partition")); err == nil {
		path = filepath.Dir(path)
	} else if !os.IsNotExist(err) {
		return ""
	}
	raw, err := os.ReadFile(filepath.Join(path, "device", "serial"))
	if err != nil {
		return ""
	}
	serial := strings.TrimSpace(string(raw))
	if !strings.HasPrefix(serial, "vol") {
		return ""
	}
	id := strings.TrimPrefix(strings.TrimPrefix(serial, "vol"), "-")
	if len(id) != 8 && len(id) != 17 {
		return ""
	}
	for _, c := range id {
		if !(c >= '0' && c <= '9' || c >= 'a' && c <= 'f') {
			return ""
		}
	}
	return "vol" + id
}

// A reboot binding grants recovery but never supplies missing volume evidence.
// Check again at deletion so a subsequent reboot or remount cannot borrow it.
func (f *servingParkFS) checkReapVolume(r *servingParkRecord) error {
	b, err := servingParkReadBinding(f.state, "retirement-"+r.Authorization.ID)
	if err != nil {
		return err
	}
	if b == nil {
		return nil
	}
	if f.volume == nil || b.Volume == "" || b.Volume != r.Source.Volume || f.volume(r.Source.Parent.Device) != r.Source.Volume {
		return hostbox.ErrChanged
	}
	return f.checkBoot(b.BootID)
}