package snapshot

import (
	"os"
	"syscall"
	"time"
)

// fileCTime returns the file creation time (birth time) on macOS.
//
// On macOS/Darwin, "ctime" refers to the file's birth time (when the file
// was first created on disk). This is stored in the Birthtimespec field of
// the syscall.Stat_t structure.
//
// This differs from Linux where "ctime" means inode change time (the last
// time file metadata was modified). See ctime_linux.go for details.
//
// If the underlying stat information is unavailable (e.g. when using a
// virtual filesystem like afero.MemMapFs), this falls back to mtime.
func fileCTime(info os.FileInfo) time.Time {
	stat, ok := info.Sys().(*syscall.Stat_t)
	if !ok {
		return info.ModTime()
	}
	return time.Unix(stat.Birthtimespec.Sec, stat.Birthtimespec.Nsec).UTC()
}