package main

import (
	"fmt"
	"syscall"
	"unsafe"

	"github.com/tadvi/winc/w32"
)

// setClipboardText puts s on the Windows clipboard as CF_UNICODETEXT so it
// can be pasted with Ctrl+V. After SetClipboardData succeeds the memory is
// owned by the clipboard, so it must not be freed here.
func setClipboardText(s string) error {
	if !w32.OpenClipboard(0) {
		return fmt.Errorf("OpenClipboard failed")
	}
	defer w32.CloseClipboard()

	if !w32.EmptyClipboard() {
		return fmt.Errorf("EmptyClipboard failed")
	}

	u16, err := syscall.UTF16FromString(s) // includes the terminating NUL
	if err != nil {
		return fmt.Errorf("UTF16 conversion: %w", err)
	}
	h := w32.GlobalAlloc(w32.GMEM_MOVEABLE, uint32(len(u16)*2))
	p := w32.GlobalLock(h)
	copy(unsafe.Slice((*byte)(p), len(u16)*2), unsafe.Slice((*byte)(unsafe.Pointer(&u16[0])), len(u16)*2))
	w32.GlobalUnlock(h)

	if w32.SetClipboardData(w32.CF_UNICODETEXT, h) == 0 {
		return fmt.Errorf("SetClipboardData failed")
	}
	return nil
}