<?php

declare(strict_types=1);
/**
 * @copyright Copyright (c) 2019 Arthur Schiwon <blizzz@arthur-schiwon.de>
 *
 * @author Arthur Schiwon <blizzz@arthur-schiwon.de>
 *
 * @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 <http://www.gnu.org/licenses/>.
 *
 */

namespace OCA\Talk\Flow;

use OCA\Talk\Chat\ChatManager;
use OCA\Talk\Exceptions\ParticipantNotFoundException;
use OCA\Talk\Exceptions\RoomNotFoundException;
use OCA\Talk\Manager as TalkManager;
use OCA\Talk\Participant;
use OCA\Talk\Room;
use OCP\EventDispatcher\Event;
use OCP\EventDispatcher\IEventDispatcher;
use OCP\IL10N;
use OCP\IURLGenerator;
use OCP\IUser;
use OCP\IUserSession;
use OCP\Util;
use OCP\WorkflowEngine\EntityContext\IDisplayText;
use OCP\WorkflowEngine\EntityContext\IUrl;
use OCP\WorkflowEngine\IEntity;
use OCP\WorkflowEngine\IManager as FlowManager;
use OCP\WorkflowEngine\IOperation;
use OCP\WorkflowEngine\IRuleMatcher;
use Symfony\Component\EventDispatcher\GenericEvent;
use UnexpectedValueException;

class Operation implements IOperation {

	/** @var int[] */
	public const MESSAGE_MODES = [
		'NO_MENTION' => 1,
		'SELF_MENTION' => 2,
		'ROOM_MENTION' => 3,
	];

	/** @var IL10N */
	private $l;
	/** @var IURLGenerator */
	private $urlGenerator;
	/** @var TalkManager */
	private $talkManager;
	/** @var IUserSession */
	private $session;
	/** @var ChatManager */
	private $chatManager;

	public function __construct(
		IL10N $l,
		IURLGenerator $urlGenerator,
		TalkManager $talkManager,
		IUserSession $session,
		ChatManager $chatManager
	) {
		$this->l = $l;
		$this->urlGenerator = $urlGenerator;
		$this->talkManager = $talkManager;
		$this->session = $session;
		$this->chatManager = $chatManager;
	}

	public static function register(IEventDispatcher $dispatcher): void {
		$dispatcher->addListener(FlowManager::EVENT_NAME_REG_OPERATION, function (GenericEvent $event) {
			$operation = \OC::$server->query(Operation::class);
			$event->getSubject()->registerOperation($operation);
			Util::addScript('spreed', 'flow');
		});
	}

	public function getDisplayName(): string {
		return $this->l->t('Write to conversation');
	}

	public function getDescription(): string {
		return $this->l->t('Writes event information into a conversation of your choice');
	}

	public function getIcon(): string {
		return $this->urlGenerator->imagePath('spreed', 'app.svg');
	}

	public function isAvailableForScope(int $scope): bool {
		return $scope === FlowManager::SCOPE_USER;
	}

	/**
	 * Validates whether a configured workflow rule is valid. If it is not,
	 * an `\UnexpectedValueException` is supposed to be thrown.
	 *
	 * @throws UnexpectedValueException
	 * @since 9.1
	 */
	public function validateOperation(string $name, array $checks, string $operation): void {
		list($mode, $token) = $this->parseOperationConfig($operation);
		$this->validateOperationConfig($mode, $token, $this->getUser()->getUID());
	}

	public function onEvent(string $eventName, Event $event, IRuleMatcher $ruleMatcher): void {
		$flows = $ruleMatcher->getFlows(false);
		foreach ($flows as $flow) {
			try {
				list($mode, $token) = $this->parseOperationConfig($flow['operation']);
				$uid = $flow['scope_actor_id'];
				$this->validateOperationConfig($mode, $token, $uid);

				$entity = $ruleMatcher->getEntity();

				$message = $this->prepareText($entity, $eventName);
				if ($message === '') {
					continue;
				}

				$room = $this->getRoom($token, $uid);
				$participant = $this->getParticipant($uid, $room);
				$this->chatManager->sendMessage(
					$room,
					$participant,
					'bots',
					$participant->getUser(),
					$this->prepareMention($mode, $participant) . $message,
					new \DateTime(),
					null,
					''
				);
			} catch (UnexpectedValueException $e) {
				continue;
			} catch (ParticipantNotFoundException $e) {
				continue;
			} catch (RoomNotFoundException $e) {
				continue;
			}
		}
	}

	protected function prepareText(IEntity $entity, string $eventName) {
		$message = $eventName;
		if ($entity instanceof IDisplayText) {
			$message = trim($entity->getDisplayText(3));
		}
		if ($entity instanceof IUrl && $message !== '') {
			$message .= ' ' . $entity->getUrl();
		}
		return $message;
	}

	/**
	 * returns a mention including a trailing whitespace, or an empty string
	 */
	protected function prepareMention(int $mode, Participant $participant): string {
		switch ($mode) {
			case self::MESSAGE_MODES['ROOM_MENTION']:
				return '@all ';
			case self::MESSAGE_MODES['SELF_MENTION']:
				$hasWhitespace = strpos($participant->getUser(), ' ') !== false;
				$enclosure = $hasWhitespace ? '"' : '';
				return '@' . $enclosure . $participant->getUser() . $enclosure . ' ';
			case self::MESSAGE_MODES['NO_MENTION']:
			default:
				return '';
		}
	}

	protected function parseOperationConfig(string $raw): array {
		/**
		 * We expect $operation be a json string, containing
		 * 	't' => string, the room token
		 *  'm' => int > 0, see self::MESSAGE_MODES
		 *
		 * setting up room mentions are only permitted to moderators
		 */

		$opConfig = \json_decode($raw, true);
		if (!is_array($opConfig) || empty($opConfig)) {
			throw new UnexpectedValueException('Cannot decode operation details');
		}

		$mode = (int)($opConfig['m'] ?? 0);
		$token = trim((string)($opConfig['t'] ?? ''));

		return [$mode, $token];
	}

	protected function validateOperationConfig(int $mode, string $token, string $uid): void {
		if (!in_array($mode, self::MESSAGE_MODES)) {
			throw new UnexpectedValueException('Invalid mode');
		}

		if (empty($token)) {
			throw new UnexpectedValueException('Invalid token');
		}

		try {
			$room = $this->getRoom($token, $uid);
		} catch (RoomNotFoundException $e) {
			throw new UnexpectedValueException('Room not found', $e->getCode(), $e);
		}

		if ($mode === self::MESSAGE_MODES['ROOM_MENTION']) {
			try {
				$participant = $this->getParticipant($uid, $room);
				if (!$participant->hasModeratorPermissions(false)) {
					throw new UnexpectedValueException('Not allowed to mention room');
				}
			} catch (ParticipantNotFoundException $e) {
				throw new UnexpectedValueException('Participant not found', $e->getCode(), $e);
			}
		}
	}

	/**
	 * @throws UnexpectedValueException
	 */
	protected function getUser(): IUser {
		$user = $this->session->getUser();
		if ($user === null) {
			throw new UnexpectedValueException('User not logged in');
		}
		return $user;
	}

	/**
	 * @throws RoomNotFoundException
	 */
	protected function getRoom(string $token, string $uid): Room {
		return $this->talkManager->getRoomForParticipantByToken($token, $uid);
	}

	/**
	 * @throws ParticipantNotFoundException
	 */
	protected function getParticipant(string $uid, Room $room): Participant {
		return $room->getParticipant($uid);
	}
}