[bairy]

A request was made in Service Requests to do this via username instead of userid.
It's not a big change and I was bored so ... happy holidays...


Empty the plugin named "Save private debate data", location: "newthread_post_complete", and put the following in it:

$vbulletin->input->clean_gpc('p', 'tdebates', TYPE_STR);
if($vbulletin->GPC['tdebates'] = trim($vbulletin->GPC['tdebates']))
{
	$tdebatesnames = explode(",", $vbulletin->GPC['tdebates']);
	foreach ($tdebatesnames AS $name)
	{
		$name = $db->escape_string(htmlspecialchars_uni(trim($name)));
		$querywhere .= ",'$name'";
	}
	$querywhere = substr($querywhere, 1);
	
	$tquery = $db->query_read("SELECT userid FROM " . TABLE_PREFIX ."user AS user WHERE username IN ($querywhere)");
	
	while ($row = $db->fetch_array($tquery))
	{
		$tuserids .= "," . $row['userid'];
	}
	$tuserids = substr($tuserids, 1);
	
	$db->query_write("UPDATE " . TABLE_PREFIX . "thread SET debates = '" . $tuserids . "' WHERE threadid = " . $newpost['threadid'] . "");
	
	$db->free_result($tquery);
	unset ($censorwords, $a, $tquery, $querywhere, $tdebatesnames);
}

Empty the plugin named: "thread to debate", location: "threadmanage_action_switch" and put the following in it:

if ($_REQUEST['do'] == 'tdebates')
{
	// only mods with the correct permissions should be able to access this
	if (!can_moderate($threadinfo['forumid'], 'candeleteposts'))
	{
		print_no_permission();
	}
	
	// check if there is a forum password and if so, ensure the user has it set
	verify_forum_password($foruminfo['forumid'], $foruminfo['password']);
	
	// draw navbar
	eval('$navbar = "' . fetch_template('navbar') . '";');
	
	if (trim($threadinfo['debates'] != ''))
	{
		$threadinfo['debates'] = ',' . $threadinfo['debates'];
	}
	$query = $db->query_read("SELECT username FROM " . TABLE_PREFIX . "user AS user WHERE userid IN (0$threadinfo[debates])");
	$threadinfo['debates'] = '';
	while ($row = $db->fetch_array($query))
	{
		$threadinfo['debates'] .= ", " . $row['username'];
	}
	$threadinfo['debates'] = substr($threadinfo['debates'], 2);
	
	// spit out the final HTML if we have got this far
	eval('$HTML = "' . fetch_template('threadadmin_tdebates') . '";');
	eval('print_output("' . fetch_template('THREADADMIN') . '");');
	exit;
}

elseif ($_POST['do'] == 'dotdebates')
{
	$vbulletin->input->clean_gpc('r', 'tdebates', TYPE_STR);
	
	// only mods with the correct permissions should be able to access this
	if (!can_moderate($threadinfo['forumid'], 'candeleteposts'))
	{
		print_no_permission();
	}
	
	// check if there is a forum password and if so, ensure the user has it set
	verify_forum_password($foruminfo['forumid'], $foruminfo['password']);
	
	$vbulletin->GPC['tdebates'] = trim($vbulletin->GPC['tdebates']);
	$tdebatesnames = explode(",", $vbulletin->GPC['tdebates']);
	foreach ($tdebatesnames AS $name)
	{
		$name = $db->escape_string(htmlspecialchars_uni(trim($name)));
		$querywhere .= ",'$name'";
	}
	$querywhere = substr($querywhere, 1);
	
	$tquery = $db->query_read("SELECT userid FROM " . TABLE_PREFIX ."user AS user WHERE username IN ($querywhere)");
	
	while ($row = $db->fetch_array($tquery))
	{
		$tuserids .= "," . $row['userid'];
	}
	$tuserids = substr($tuserids, 1);
	
	$db->free_result($tquery);
	unset ($censorwords, $a, $tquery, $querywhere, $tdebatesnames);
	
	$db->query_write("UPDATE " . TABLE_PREFIX . "thread SET debates = '" . $tuserids . "' WHERE threadid = '" . $threadid . "'");
	$tdebates_phrase = 'Private debate';
	$redirect='redirect_done_dotdebates';
	
	log_moderator_action($threadinfo,'tdebates',$tdebates_phrase);
	$vbulletin->url = 'showthread.php?' . "t=" . $threadid . "";
	eval(print_standard_redirect($redirect, true, true));
	exit;
}

Important: chosen usernames must be seperated by a comma (because some usernames have spaces), so you'll want to change the word "space" to "comma" in the templates:
Debates Templates > tdebates_newthread.
Thread Administration Templates > threadadmin_tdebates

Notes:
= If a non existant username is inputted, it will be ignored. If no valid usernames are inputted, it will not be a private-debate thread.
= I've copied the PM system's way of parsing usernames, therefore special characters and stuff should be accounted for. Or in other words: any valid username should work. However, it's still dependant on how the browser transmits special characters, so it's not 100% guaranteed.
= Any existing private-debate threads that anyone currently has won't be affected by this. Only the input method has been changed, everything else is the same.