// SPDX-License-Identifier: LGPL-2.1-only
// Copyright (C) 2026 Liberux Labs, S. L. <info@liberux.net>

//! The system clipboard as `CF_UNICODETEXT`, whose lines Windows ends with CR LF.

use windows_sys::Win32::Foundation::{ GlobalFree, HWND };
use windows_sys::Win32::System::DataExchange::{ CloseClipboard, EmptyClipboard, GetClipboardData, OpenClipboard, SetClipboardData };
use windows_sys::Win32::System::Memory::{ GlobalAlloc, GlobalLock, GlobalSize, GlobalUnlock, GMEM_MOVEABLE };
use windows_sys::Win32::System::Ole::CF_UNICODETEXT;

/// Offer `text` to other applications as the clipboard.
pub( super ) fn set( hwnd: HWND, text: &str )
{
	let wide: Vec<u16> = text.replace( "\r\n", "\n" ).replace( '\n', "\r\n" ).encode_utf16().chain( std::iter::once( 0 ) ).collect();
	// SAFETY: the clipboard is opened and closed here; the memory handed to it is a movable global block of the text's size, which the clipboard owns once `SetClipboardData` succeeds.
	unsafe
	{
		if OpenClipboard( hwnd ) == 0 { return; }
		EmptyClipboard();
		let memory = GlobalAlloc( GMEM_MOVEABLE, wide.len() * 2 );
		if !memory.is_null()
		{
			let target = GlobalLock( memory ).cast::<u16>();
			if target.is_null()
			{
				GlobalFree( memory );
			} else {
				std::ptr::copy_nonoverlapping( wide.as_ptr(), target, wide.len() );
				GlobalUnlock( memory );
				if SetClipboardData( CF_UNICODETEXT as u32, memory ).is_null() { GlobalFree( memory ); }
			}
		}
		CloseClipboard();
	}
}

/// The clipboard's text; `None` when it holds none or another application has it open.
pub( super ) fn text( hwnd: HWND ) -> Option<String>
{
	// SAFETY: the clipboard is opened and closed here; its block is read only while locked, up to its size or its terminating NUL.
	unsafe
	{
		if OpenClipboard( hwnd ) == 0 { return None; }
		let text = read();
		CloseClipboard();
		text
	}
}

unsafe fn read() -> Option<String>
{
	let memory = unsafe { GetClipboardData( CF_UNICODETEXT as u32 ) };
	if memory.is_null() { return None; }
	let units = unsafe { GlobalSize( memory ) } / 2;
	let start = unsafe { GlobalLock( memory ) }.cast::<u16>().cast_const();
	if start.is_null() { return None; }
	let all  = unsafe { std::slice::from_raw_parts( start, units ) };
	let len  = all.iter().position( |&u| u == 0 ).unwrap_or( units );
	let text = String::from_utf16_lossy( &all[ ..len ] );
	unsafe { GlobalUnlock( memory ); }
	Some( text.replace( "\r\n", "\n" ) )
}