//go:build windows

package main

import (
	"runtime"
	"syscall"
	"time"
	"unsafe"

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

var (
	procIsClipboardFormatAvailable = windows.NewLazySystemDLL("user32.dll").NewProc("IsClipboardFormatAvailable")
	procOpenClipboard              = windows.NewLazySystemDLL("user32.dll").NewProc("OpenClipboard")
	procCloseClipboard             = windows.NewLazySystemDLL("user32.dll").NewProc("CloseClipboard")
	procGetClipboardData           = windows.NewLazySystemDLL("user32.dll").NewProc("GetClipboardData")
	procDragQueryFileW             = windows.NewLazySystemDLL("shell32.dll").NewProc("DragQueryFileW")
)

// cfHDrop 剪贴板文件列表格式（资源管理器复制文件/文件夹），Win32 稳定 ABI 值
const cfHDrop = 15

// ReadClipboardFiles 读取系统剪贴板中的文件/文件夹路径列表。
// 剪贴板为文本/截图等非文件内容时返回空列表，前端据此回落图片粘贴等原有链路。
func (a *App) ReadClipboardFiles() ([]string, error) {
	// OpenClipboard 与 CloseClipboard 必须同线程，否则剪贴板死锁
	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	if r, _, _ := procIsClipboardFormatAvailable.Call(cfHDrop); r == 0 {
		return nil, nil
	}

	// 剪贴板是全局互斥资源，短重试避开其他进程的瞬时占用
	opened := false
	for i := 0; i < 20; i++ {
		if r, _, _ := procOpenClipboard.Call(0); r != 0 {
			opened = true
			break
		}
		time.Sleep(10 * time.Millisecond)
	}
	if !opened {
		return nil, syscall.EBUSY
	}
	defer procCloseClipboard.Call()

	h, _, _ := procGetClipboardData.Call(cfHDrop)
	if h == 0 {
		return nil, nil
	}

	count, _, _ := procDragQueryFileW.Call(h, 0xFFFFFFFF, 0, 0)
	if count == 0 {
		return nil, nil
	}

	paths := make([]string, 0, count)
	for i := uintptr(0); i < count; i++ {
		n, _, _ := procDragQueryFileW.Call(h, i, 0, 0)
		if n == 0 {
			continue
		}
		buf := make([]uint16, n+1)
		procDragQueryFileW.Call(h, i, uintptr(unsafe.Pointer(&buf[0])), n+1)
		paths = append(paths, syscall.UTF16ToString(buf))
	}
	return paths, nil
}