// Copyright (c) 2020 tickstep.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package cmdliner

import (
	"syscall"
	"unsafe"
)

const (
	std_output_handle = uint32(-11 & 0xFFFFFFFF)
)

var (
	kernel32 = syscall.NewLazyDLL("kernel32.dll")

	procGetStdHandle               = kernel32.NewProc("GetStdHandle")
	procSetConsoleCursorPosition   = kernel32.NewProc("SetConsoleCursorPosition")
	procGetConsoleScreenBufferInfo = kernel32.NewProc("GetConsoleScreenBufferInfo")
	procFillConsoleOutputCharacter = kernel32.NewProc("FillConsoleOutputCharacterW")
)

type (
	coord struct {
		x, y int16
	}
	smallRect struct {
		left, top, right, bottom int16
	}
	consoleScreenBufferInfo struct {
		dwSize              coord
		dwCursorPosition    coord
		wAttributes         int16
		srWindow            smallRect
		dwMaximumWindowSize coord
	}
)

// ClearScreen 清空屏幕
func (pl *CmdLiner) ClearScreen() {
	ClearScreen()
}

// ClearScreen 清空屏幕
func ClearScreen() {
	out, _, _ := procGetStdHandle.Call(uintptr(std_output_handle))
	hOut := syscall.Handle(out)

	var sbi consoleScreenBufferInfo
	procGetConsoleScreenBufferInfo.Call(uintptr(hOut), uintptr(unsafe.Pointer(&sbi)))

	var numWritten uint32
	procFillConsoleOutputCharacter.Call(uintptr(hOut), uintptr(' '),
		uintptr(sbi.dwSize.x)*uintptr(sbi.dwSize.y),
		0,
		uintptr(unsafe.Pointer(&numWritten)))
	procSetConsoleCursorPosition.Call(uintptr(hOut), 0)
}