package rootstate

import (
	"os"

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

func (d *directory) liveFile(name string, create bool) (*os.File, error) {
	if !component(name) || uint32(os.Geteuid()) != d.owner {
		return nil, os.ErrPermission
	}
	if err := d.check(); err != nil {
		return nil, err
	}
	flags := os.O_RDWR
	if create {
		flags |= os.O_CREATE
	}
	f, err := safefile.OpenFileAt(int(d.file.Fd()), name, flags, 0600)
	if err != nil {
		return nil, err
	}
	if err := trusted(int(f.Fd()), d.owner, unix.S_IFREG); err != nil {
		f.Close()
		return nil, err
	}
	return f, nil
}

func (d *directory) HoldLive(name string) (func(), error) {
	f, err := d.liveFile(name, true)
	if err != nil {
		return nil, err
	}
	lock := unix.Flock_t{Type: unix.F_WRLCK, Whence: 0}
	if err := unix.FcntlFlock(f.Fd(), unix.F_OFD_SETLK, &lock); err != nil {
		f.Close()
		return nil, err
	}
	return func() { _ = f.Close() }, nil
}

func (d *directory) LiveHeld(name string) (bool, error) {
	f, err := d.liveFile(name, false)
	if err != nil {
		return false, err
	}
	defer f.Close()
	lock := unix.Flock_t{Type: unix.F_RDLCK, Whence: 0}
	if err := unix.FcntlFlock(f.Fd(), unix.F_OFD_GETLK, &lock); err != nil {
		return false, err
	}
	return lock.Type == unix.F_WRLCK && lock.Pid == -1, nil
}