//go:build windows
// +build windows

package staros

import (
	"b612.me/win32api"
	"golang.org/x/sys/windows"
	"os"
	"syscall"
	"time"
)

type FileLock struct {
	filepath string
	handle   win32api.HANDLE
	locked   bool
}

func GetFileCreationTime(fileinfo os.FileInfo) time.Time {
	if fileinfo == nil {
		return time.Time{}
	}
	if data, ok := fileinfo.Sys().(*syscall.Win32FileAttributeData); ok && data != nil {
		return time.Unix(0, data.CreationTime.Nanoseconds())
	}
	return time.Time{}
}

func GetFileAccessTime(fileinfo os.FileInfo) time.Time {
	if fileinfo == nil {
		return time.Time{}
	}
	if data, ok := fileinfo.Sys().(*syscall.Win32FileAttributeData); ok && data != nil {
		return time.Unix(0, data.LastAccessTime.Nanoseconds())
	}
	return time.Time{}
}

func SetFileTimes(file *os.File, info os.FileInfo) {
	_ = SetFileTimesE(file, info)
}

func SetFileTimesbyTime(file *os.File) {
	_ = SetFileTimesbyTimeE(file)
}

func SetFileTimesE(file *os.File, info os.FileInfo) error {
	if file == nil {
		return errNilFile
	}
	if info == nil {
		return errNilFileInfo
	}
	data, ok := info.Sys().(*syscall.Win32FileAttributeData)
	if !ok || data == nil {
		return errUnsupportedFileInfo
	}
	ctime := time.Unix(0, data.CreationTime.Nanoseconds())
	atime := time.Unix(0, data.LastAccessTime.Nanoseconds())
	mtime := info.ModTime()
	return setFileTimes(file.Name(), ctime, atime, mtime)
}

func SetFileTimesByTimeE(file *os.File) error {
	return SetFileTimesbyTimeE(file)
}

func SetFileTimesbyTimeE(file *os.File) error {
	if file == nil {
		return errNilFile
	}
	now := time.Now()
	return setFileTimes(file.Name(), now, now, now)
}

func setFileTimes(path string, ctime, atime, mtime time.Time) error {
	path16, err := windows.UTF16PtrFromString(path)
	if err != nil {
		return err
	}
	handle, err := windows.CreateFile(
		path16,
		windows.FILE_WRITE_ATTRIBUTES,
		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)

	ctimeFt := windows.NsecToFiletime(ctime.UnixNano())
	atimeFt := windows.NsecToFiletime(atime.UnixNano())
	mtimeFt := windows.NsecToFiletime(mtime.UnixNano())
	return windows.SetFileTime(handle, &ctimeFt, &atimeFt, &mtimeFt)

}

func (f *FileLock) openFileForLock() error {
	name, err := syscall.UTF16PtrFromString(f.filepath)
	if err != nil {
		return err
	}
	handle, err := syscall.CreateFile(
		name,
		syscall.GENERIC_READ,
		syscall.FILE_SHARE_READ,
		nil,
		syscall.OPEN_ALWAYS,
		syscall.FILE_FLAG_OVERLAPPED|0x00000080,
		0)
	if err != nil {
		return err
	}
	f.handle = win32api.HANDLE(handle)
	return nil
}

func (f *FileLock) lockForTimeout(timeout time.Duration, lockType win32api.DWORD) error {
	if f.locked {
		return ERR_ALREADY_LOCKED
	}
	var err error
	if err = f.openFileForLock(); err != nil {
		return err
	}
	event, err := win32api.CreateEventW(nil, true, false, nil)
	if err != nil {
		_ = f.closeHandle()
		return err
	}
	myEvent := &syscall.Overlapped{HEvent: syscall.Handle(event)}
	defer syscall.CloseHandle(myEvent.HEvent)
	_, err = win32api.LockFileEx(f.handle, lockType, 0, 1, 0, myEvent)
	if err == nil {
		f.locked = true
		return nil
	}
	if err != syscall.ERROR_IO_PENDING {
		_ = f.closeHandle()
		return err
	}
	millis := uint32(syscall.INFINITE)
	if timeout >= 0 {
		millis = uint32(timeout.Nanoseconds() / 1000000)
	}
	s, err := syscall.WaitForSingleObject(myEvent.HEvent, millis)
	switch s {
	case syscall.WAIT_OBJECT_0:
		// success!
		f.locked = true
		return nil
	case syscall.WAIT_TIMEOUT:
		_ = f.closeHandle()
		return ERR_TIMEOUT
	default:
		_ = f.closeHandle()
		return err
	}
}

func (f *FileLock) Lock(Exclusive bool) error {
	var lockType win32api.DWORD
	if Exclusive {
		lockType = win32api.LOCKFILE_EXCLUSIVE_LOCK
	} else {
		lockType = 0
	}
	return f.lockForTimeout(-1, lockType)
}

func (f *FileLock) LockWithTimeout(tm time.Duration, Exclusive bool) error {
	var lockType win32api.DWORD
	if Exclusive {
		lockType = win32api.LOCKFILE_EXCLUSIVE_LOCK
	} else {
		lockType = 0
	}
	return f.lockForTimeout(tm, lockType)
}

func (f *FileLock) LockNoBlocking(Exclusive bool) error {
	var lockType win32api.DWORD
	if Exclusive {
		lockType = win32api.LOCKFILE_EXCLUSIVE_LOCK
	} else {
		lockType = 0
	}
	return f.lockForTimeout(0, lockType|win32api.LOCKFILE_FAIL_IMMEDIATELY)
}

func (f *FileLock) Unlock() error {
	if f == nil || !f.locked {
		return errFileLockNotLocked
	}
	if err := f.closeHandle(); err != nil {
		return err
	}
	f.locked = false
	return nil
}

func (f *FileLock) closeHandle() error {
	if f == nil || f.handle == 0 {
		return nil
	}
	err := syscall.Close(syscall.Handle(f.handle))
	if err != nil {
		return err
	}
	f.handle = 0
	return nil
}