//go:build linux

package host

import (
	"errors"
	"path/filepath"

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

// checkServingArtifactAbsence checks the root-recorded source directory and
// all four source names through one descriptor. Missing parents, links and
// replacement directories are errors, never evidence of absent artifacts.
func checkServingArtifactAbsence(db string, expected servingArtifactDirectory) error {
	dir, err := instancefs.OpenDirBeneath(filepath.Dir(db), ".")
	if err != nil {
		return err
	}
	defer dir.Close()
	var stat unix.Statx_t
	if err = unix.Statx(int(dir.Fd()), "", unix.AT_EMPTY_PATH|unix.AT_SYMLINK_NOFOLLOW, unix.STATX_BASIC_STATS|unix.STATX_MNT_ID, &stat); err != nil {
		return err
	}
	if stat.Mask&unix.STATX_MNT_ID == 0 || unix.Mkdev(stat.Dev_major, stat.Dev_minor) != expected.Device || stat.Ino != expected.Inode || stat.Mnt_id != expected.Mount {
		return hostbox.ErrChanged
	}
	for _, suffix := range []string{"", ".gen", "-wal", "-shm"} {
		var item unix.Stat_t
		err = unix.Fstatat(int(dir.Fd()), filepath.Base(db)+suffix, &item, unix.AT_SYMLINK_NOFOLLOW)
		if err == nil {
			return hostbox.ErrChanged
		}
		if !errors.Is(err, unix.ENOENT) {
			return err
		}
	}
	return nil
}

func servingAgentDirectory(db string) (servingArtifactDirectory, error) {
	dir, err := instancefs.OpenDirBeneath(filepath.Dir(db), ".")
	if err != nil {
		return servingArtifactDirectory{}, err
	}
	defer dir.Close()
	return servingParkDirID(dir)
}