//go:build windows

// ============================================================================
// timesync_windows.go — 系统时间同步（Windows 平台）
//
// 启用 SeSystemtimePrivilege 特权后用 SetLocalTime 校准系统时间；
// 直接调用 syscall 声明 user32/kernel32 函数，不引入额外依赖。
// ============================================================================
package main

import (
	"fmt"
	"syscall"
	"time"
	"unsafe"
)

// systemTime Windows SYSTEMTIME 结构
type systemTime struct {
	Year, Month, DayOfWeek, Day, Hour, Minute, Second, Milliseconds uint16
}

type luid struct {
	LowPart  uint32
	HighPart int32
}

type luidAndAttributes struct {
	Luid       luid
	Attributes uint32
}

type tokenPrivileges struct {
	PrivilegeCount uint32
	Privileges     [1]luidAndAttributes
}

// enablePrivilege 启用当前进程的指定特权（SeSystemtimePrivilege 默认禁用，
// 必须先 AdjustTokenPrivileges 启用，否则 SetLocalTime 会失败）
func enablePrivilege(name string) error {
	const (
		tokenQuery            = 0x0008
		tokenAdjustPrivileges = 0x0020
		sePrivilegeEnabled    = 0x00000002
		errNotAllAssigned     = syscall.Errno(1300) // ERROR_NOT_ALL_ASSIGNED
	)

	advapi32 := syscall.NewLazyDLL("advapi32.dll")
	procOpenProcessToken := advapi32.NewProc("OpenProcessToken")
	procLookupPrivilegeValue := advapi32.NewProc("LookupPrivilegeValueW")
	procAdjustTokenPrivileges := advapi32.NewProc("AdjustTokenPrivileges")

	currentProc, _ := syscall.GetCurrentProcess()
	var token syscall.Handle
	ret, _, err := procOpenProcessToken.Call(
		uintptr(currentProc),
		tokenQuery|tokenAdjustPrivileges,
		uintptr(unsafe.Pointer(&token)),
	)
	if ret == 0 {
		return fmt.Errorf("OpenProcessToken: %v", err)
	}
	defer syscall.CloseHandle(token)

	var luidVal luid
	namePtr, _ := syscall.UTF16PtrFromString(name)
	ret, _, err = procLookupPrivilegeValue.Call(
		0,
		uintptr(unsafe.Pointer(namePtr)),
		uintptr(unsafe.Pointer(&luidVal)),
	)
	if ret == 0 {
		return fmt.Errorf("LookupPrivilegeValue(%s): %v", name, err)
	}

	tp := tokenPrivileges{
		PrivilegeCount: 1,
		Privileges: [1]luidAndAttributes{
			{Luid: luidVal, Attributes: sePrivilegeEnabled},
		},
	}
	ret, _, err = procAdjustTokenPrivileges.Call(
		uintptr(token), 0,
		uintptr(unsafe.Pointer(&tp)), 0, 0, 0,
	)
	if ret == 0 {
		return fmt.Errorf("AdjustTokenPrivileges: %v", err)
	}
	if err == errNotAllAssigned {
		return fmt.Errorf("进程不具备特权 %s（需以管理员身份运行）", name)
	}
	return nil
}

// setLocalTime 按系统当前时区设置本地时间（需管理员权限）
func setLocalTime(t time.Time) error {
	if err := enablePrivilege("SeSystemtimePrivilege"); err != nil {
		return err
	}

	st := systemTime{
		Year:         uint16(t.Year()),
		Month:        uint16(t.Month()),
		DayOfWeek:    uint16(t.Weekday()),
		Day:          uint16(t.Day()),
		Hour:         uint16(t.Hour()),
		Minute:       uint16(t.Minute()),
		Second:       uint16(t.Second()),
		Milliseconds: uint16(t.Nanosecond() / 1e6),
	}
	ret, _, err := syscall.NewLazyDLL("kernel32.dll").NewProc("SetLocalTime").
		Call(uintptr(unsafe.Pointer(&st)))
	if ret == 0 {
		return fmt.Errorf("SetLocalTime: %v", err)
	}
	return nil
}