<?php
/**
 * @copyright Copyright (C) 2010-2022, the Friendica project
 *
 * @license GNU AGPL version 3 or any later version
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 */

use Friendica\App;
use Friendica\Core\Logger;
use Friendica\Core\Session;
use Friendica\Core\System;
use Friendica\Database\DBA;
use Friendica\DI;
use Friendica\Model\Contact;
use Friendica\Model\Profile;
use Friendica\Util\Strings;

function redir_init(App $a) {
	if (!Session::isAuthenticated()) {
		throw new \Friendica\Network\HTTPException\ForbiddenException(DI::l10n()->t('Access denied.'));
	}

	$url = $_GET['url'] ?? '';

	if (DI::args()->getArgc() > 1 && intval(DI::args()->getArgv()[1])) {
		$cid = intval(DI::args()->getArgv()[1]);
	} else {
		$cid = 0;
	}

	// Try magic auth before the legacy stuff
	redir_magic($a, $cid, $url);

	if (empty($cid)) {
		throw new \Friendica\Network\HTTPException\BadRequestException(DI::l10n()->t('Bad Request.'));
	}

	$fields = ['id', 'uid', 'nurl', 'url', 'addr', 'name'];
	$contact = DBA::selectFirst('contact', $fields, ['id' => $cid, 'uid' => [0, local_user()]]);
	if (!DBA::isResult($contact)) {
		throw new \Friendica\Network\HTTPException\NotFoundException(DI::l10n()->t('Contact not found.'));
	}

	$contact_url = $contact['url'];

	if (!empty($a->getContactId()) && $a->getContactId() == $cid) {
		// Local user is already authenticated.
		redir_check_url($contact_url, $url);
		$a->redirect($url ?: $contact_url);
	}

	if ($contact['uid'] == 0 && local_user()) {
		// Let's have a look if there is an established connection
		// between the public contact we have found and the local user.
		$contact = DBA::selectFirst('contact', $fields, ['nurl' => $contact['nurl'], 'uid' => local_user()]);

		if (DBA::isResult($contact)) {
			$cid = $contact['id'];
		}

		if (!empty($a->getContactId()) && $a->getContactId() == $cid) {
			// Local user is already authenticated.
			redir_check_url($contact_url, $url);
			$target_url = $url ?: $contact_url;
			Logger::info($contact['name'] . " is already authenticated. Redirecting to " . $target_url);
			$a->redirect($target_url);
		}
	}

	if (remote_user()) {
		$host = substr(DI::baseUrl()->getUrlPath() . (DI::baseUrl()->getUrlPath() ? '/' . DI::baseUrl()->getUrlPath() : ''), strpos(DI::baseUrl()->getUrlPath(), '://') + 3);
		$remotehost = substr($contact['addr'], strpos($contact['addr'], '@') + 1);

		// On a local instance we have to check if the local user has already authenticated
		// with the local contact. Otherwise the local user would ask the local contact
		// for authentification everytime he/she is visiting a profile page of the local
		// contact.
		if (($host == $remotehost) && (Session::getRemoteContactID(Session::get('visitor_visiting')) == Session::get('visitor_id'))) {
			// Remote user is already authenticated.
			redir_check_url($contact_url, $url);
			$target_url = $url ?: $contact_url;
			Logger::info($contact['name'] . " is already authenticated. Redirecting to " . $target_url);
			$a->redirect($target_url);
		}
	}

	if (empty($url)) {
		throw new \Friendica\Network\HTTPException\BadRequestException(DI::l10n()->t('Bad Request.'));
	}

	// If we don't have a connected contact, redirect with
	// the 'zrl' parameter.
	$my_profile = Profile::getMyURL();

	if (!empty($my_profile) && !Strings::compareLink($my_profile, $url)) {
		$separator = strpos($url, '?') ? '&' : '?';

		$url .= $separator . 'zrl=' . urlencode($my_profile);
	}

	Logger::info('redirecting to ' . $url);
	$a->redirect($url);
}

function redir_magic($a, $cid, $url)
{
	$visitor = Profile::getMyURL();
	if (!empty($visitor)) {
		Logger::info('Got my url', ['visitor' => $visitor]);
	}

	$contact = DBA::selectFirst('contact', ['url'], ['id' => $cid]);
	if (!DBA::isResult($contact)) {
		Logger::info('Contact not found', ['id' => $cid]);
		throw new \Friendica\Network\HTTPException\NotFoundException(DI::l10n()->t('Contact not found.'));
	} else {
		$contact_url = $contact['url'];
		redir_check_url($contact_url, $url);
		$target_url = $url ?: $contact_url;
	}

	$basepath = Contact::getBasepath($contact_url);

	// We don't use magic auth when there is no visitor, we are on the same system or we visit our own stuff
	if (empty($visitor) || Strings::compareLink($basepath, DI::baseUrl()) || Strings::compareLink($contact_url, $visitor)) {
		Logger::info('Redirecting without magic', ['target' => $target_url, 'visitor' => $visitor, 'contact' => $contact_url]);
		DI::app()->redirect($target_url);
	}

	// Test for magic auth on the target system
	$serverret = DI::httpClient()->get($basepath . '/magic');
	if ($serverret->isSuccess()) {
		$separator = strpos($target_url, '?') ? '&' : '?';
		$target_url .= $separator . 'zrl=' . urlencode($visitor) . '&addr=' . urlencode($contact_url);

		Logger::info('Redirecting with magic', ['target' => $target_url, 'visitor' => $visitor, 'contact' => $contact_url]);
		System::externalRedirect($target_url);
	} else {
		Logger::info('No magic for contact', ['contact' => $contact_url]);
	}
}

function redir_check_url(string $contact_url, string $url)
{
	if (empty($contact_url) || empty($url)) {
		return;
	}

	$url_host = parse_url($url, PHP_URL_HOST);
	if (empty($url_host)) {
		$url_host = parse_url(DI::baseUrl(), PHP_URL_HOST);
	}

	$contact_url_host = parse_url($contact_url, PHP_URL_HOST);

	if ($url_host == $contact_url_host) {
		return;
	}

	Logger::error('URL check host mismatch', ['contact' => $contact_url, 'url' => $url]);
	throw new \Friendica\Network\HTTPException\ForbiddenException(DI::l10n()->t('Access denied.'));
}