package wine

import (
	"debug/elf"
	"path/filepath"
	"time"
)

// InstalledVersion reads the selected helper's embedded release without
// executing Wine. Older helpers without the metadata return an empty string.
// This describes the files on disk, which may differ from a running helper.
func InstalledVersion() string {
	helper := helperPath()
	if helper == "" {
		return ""
	}
	// Resolve launcher symlinks before locating its adjacent Winelib sidecar.
	helper, err := filepath.EvalSymlinks(helper)
	if err != nil {
		return ""
	}
	file, err := elf.Open(helper + ".so")
	if err != nil {
		return ""
	}
	defer file.Close()
	section := file.Section(".wine_access.version")
	if section == nil || section.Size != 11 || section.Flags&elf.SHF_COMPRESSED != 0 {
		return ""
	}
	var data [11]byte
	if _, err := section.ReadAt(data[:], 0); err != nil || data[10] != 0 {
		return ""
	}
	release := string(data[:10])
	if _, err := time.Parse("2006.01.02", release); err != nil {
		return ""
	}
	return release
}