//go:build windows

package spool

import (
	"os"

	"golang.org/x/sys/windows"
)

func acquireInstanceLock(path string) (func() error, error) {
	if err := ensurePrivateFile(path); err != nil {
		return nil, err
	}
	file, err := os.OpenFile(path, os.O_RDWR, 0)
	if err != nil {
		return nil, err
	}
	var overlapped windows.Overlapped
	err = windows.LockFileEx(windows.Handle(file.Fd()), windows.LOCKFILE_EXCLUSIVE_LOCK|windows.LOCKFILE_FAIL_IMMEDIATELY, 0, 1, 0, &overlapped)
	if err != nil {
		_ = file.Close()
		return nil, ErrAlreadyOpen
	}
	return func() error {
		unlockErr := windows.UnlockFileEx(windows.Handle(file.Fd()), 0, 1, 0, &overlapped)
		closeErr := file.Close()
		if unlockErr != nil {
			return unlockErr
		}
		return closeErr
	}, nil
}

func syncDirectory(path string) error {
	value, err := windows.UTF16PtrFromString(path)
	if err != nil {
		return err
	}
	// FlushFileBuffers requires GENERIC_WRITE even when the handle refers to a
	// directory.  Opening it read-only succeeds, then deterministically fails
	// the durability barrier with ERROR_ACCESS_DENIED on Windows.
	handle, err := windows.CreateFile(value, windows.GENERIC_READ|windows.GENERIC_WRITE, windows.FILE_SHARE_READ|windows.FILE_SHARE_WRITE|windows.FILE_SHARE_DELETE, nil, windows.OPEN_EXISTING, windows.FILE_FLAG_BACKUP_SEMANTICS, 0)
	if err != nil {
		return err
	}
	defer windows.CloseHandle(handle)
	return windows.FlushFileBuffers(handle)
}

func replaceIdentityFile(temporaryPath, targetPath string) error {
	from, err := windows.UTF16PtrFromString(temporaryPath)
	if err != nil {
		return err
	}
	to, err := windows.UTF16PtrFromString(targetPath)
	if err != nil {
		return err
	}
	return windows.MoveFileEx(from, to, windows.MOVEFILE_REPLACE_EXISTING|windows.MOVEFILE_WRITE_THROUGH)
}