<?php

declare(strict_types=1);

/**
 * @author Matthias Rella <mrella@pisys.eu>
 *
 * Mail
 *
 * This code is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * 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, version 3,
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */

namespace OCA\Mail\Service;

use OCA\Mail\Service\Group\ContactsGroupService;
use OCA\Mail\Service\Group\IGroupService;
use OCA\Mail\Service\Group\NextcloudGroupService;
use OCA\Mail\Exception\ServiceException;

class GroupsIntegration {

	/**
	 * The services to get groups from
	 *
	 * @var IGroupService[]
	 */
	private $groupServices = [];

	public function __construct(ContactsGroupService $contactsGroupService, NextcloudGroupService $nextcloudGroupService) {
		$this->groupServices = [
			$contactsGroupService,
			$nextcloudGroupService,
		];
	}

	/**
	 * Extracts all matching contacts with email address and name
	 *
	 * @param string $term
	 * @return array
	 */
	public function getMatchingGroups(string $term): array {
		$receivers = [];
		foreach ($this->groupServices as $gs) {
			$result = $gs->search($term);
			foreach ($result as $g) {
				$gid = $this->servicePrefix($gs) . $g['id'];
				$receivers[] = [
					'id' => $gid,
					'label' => $g['name'] . " (" . $gs->getNamespace() . ")",
					'email' => $gid,
					'photo' => null,
				];
			}
		}

		return $receivers;
	}

	/**
	 * Returns the prefix for the group service.
	 *
	 * @param IGroupService $gs
	 * @return string
	 */
	public function servicePrefix(IGroupService $gs): string {
		if (empty($gs->getNamespace())) {
			throw new ServiceException('GroupService has no namespace');
		}
		return strtolower($gs->getNamespace()) . ":";
	}

	/**
	 * Expands a string of group names to its members email addresses.
	 *
	 * @param string $recipients
	 *
	 * @return null|string
	 */
	public function expand(string $recipients): ?string {
		return array_reduce($this->groupServices,
			function ($carry, $service) {
				return preg_replace_callback(
					'/' . preg_quote($this->servicePrefix($service)) . '([^,]+)(,?)/',
					function ($matches) use ($service) {
						if (empty($matches[1])) {
							return '';
						}
						$members = $service->getUsers($matches[1]);
						if (empty($members)) {
							throw new ServiceException($matches[1] . " ({$service->getNamespace()}) has no members");
						}
						$addresses = [];
						foreach ($members as $m) {
							if (!empty($m['email'])) {
								$addresses[] = $m['email'];
							}
						}
						return implode(',', $addresses)
							. (!empty($matches[2]) && !empty($addresses) ? ',' : '');
					}, $carry);
			}, $recipients);
	}
}