<?php

declare(strict_types=1);

/**
 * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

namespace OC\Calendar;

use OCA\DAV\CalDAV\CalDavBackend;
use OCP\Calendar\BackendTemporarilyUnavailableException;
use OCP\Calendar\IMetadataProvider;
use OCP\Calendar\Resource\IBackend as IResourceBackend;
use OCP\Calendar\Resource\IManager as IResourceManager;
use OCP\Calendar\Resource\IResource;
use OCP\Calendar\Room\IManager as IRoomManager;
use OCP\Calendar\Room\IRoom;
use OCP\IDBConnection;
use Psr\Container\ContainerInterface;

class ResourcesRoomsUpdater {
	public function __construct(
		private ContainerInterface $container,
		private IDBConnection $dbConnection,
		private CalDavBackend $calDavBackend,
	) {
	}

	/**
	 * Update resource cache from backends
	 */
	public function updateResources(): void {
		$this->updateFromBackend(
			$this->container->get(IResourceManager::class),
			'calendar_resources',
			'calendar_resources_md',
			'resource_id',
			'principals/calendar-resources'
		);
	}

	/**
	 * Update room cache from backends
	 */
	public function updateRooms(): void {
		$this->updateFromBackend(
			$this->container->get(IRoomManager::class),
			'calendar_rooms',
			'calendar_rooms_md',
			'room_id',
			'principals/calendar-rooms'
		);
	}

	/**
	 * Update cache from one specific backend manager, either ResourceManager or RoomManager
	 *
	 * @param IResourceManager|IRoomManager $backendManager
	 */
	private function updateFromBackend($backendManager,
		string $dbTable,
		string $dbTableMetadata,
		string $foreignKey,
		string $principalPrefix): void {
		$backends = $backendManager->getBackends();

		foreach ($backends as $backend) {
			$backendId = $backend->getBackendIdentifier();

			try {
				if ($backend instanceof IResourceBackend) {
					$list = $backend->listAllResources();
				} else {
					$list = $backend->listAllRooms();
				}
			} catch (BackendTemporarilyUnavailableException $ex) {
				continue;
			}

			$cachedList = $this->getAllCachedByBackend($dbTable, $backendId);
			$newIds = array_diff($list, $cachedList);
			$deletedIds = array_diff($cachedList, $list);
			$editedIds = array_intersect($list, $cachedList);

			foreach ($newIds as $newId) {
				try {
					if ($backend instanceof IResourceBackend) {
						$resource = $backend->getResource($newId);
					} else {
						$resource = $backend->getRoom($newId);
					}

					$metadata = [];
					if ($resource instanceof IMetadataProvider) {
						$metadata = $this->getAllMetadataOfBackend($resource);
					}
				} catch (BackendTemporarilyUnavailableException $ex) {
					continue;
				}

				$id = $this->addToCache($dbTable, $backendId, $resource);
				$this->addMetadataToCache($dbTableMetadata, $foreignKey, $id, $metadata);
				// we don't create the calendar here, it is created lazily
				// when an event is actually scheduled with this resource / room
			}

			foreach ($deletedIds as $deletedId) {
				$id = $this->getIdForBackendAndResource($dbTable, $backendId, $deletedId);
				$this->deleteFromCache($dbTable, $id);
				$this->deleteMetadataFromCache($dbTableMetadata, $foreignKey, $id);

				$principalName = implode('-', [$backendId, $deletedId]);
				$this->deleteCalendarDataForResource($principalPrefix, $principalName);
			}

			foreach ($editedIds as $editedId) {
				$id = $this->getIdForBackendAndResource($dbTable, $backendId, $editedId);

				try {
					if ($backend instanceof IResourceBackend) {
						$resource = $backend->getResource($editedId);
					} else {
						$resource = $backend->getRoom($editedId);
					}

					$metadata = [];
					if ($resource instanceof IMetadataProvider) {
						$metadata = $this->getAllMetadataOfBackend($resource);
					}
				} catch (BackendTemporarilyUnavailableException $ex) {
					continue;
				}

				$this->updateCache($dbTable, $id, $resource);

				if ($resource instanceof IMetadataProvider) {
					$cachedMetadata = $this->getAllMetadataOfCache($dbTableMetadata, $foreignKey, $id);
					$this->updateMetadataCache($dbTableMetadata, $foreignKey, $id, $metadata, $cachedMetadata);
				}
			}
		}
	}

	/**
	 * add entry to cache that exists remotely but not yet in cache
	 *
	 * @param string $table
	 * @param string $backendId
	 * @param IResource|IRoom $remote
	 *
	 * @return int Insert id
	 */
	private function addToCache(string $table,
		string $backendId,
		$remote): int {
		$query = $this->dbConnection->getQueryBuilder();
		$query->insert($table)
			->values([
				'backend_id' => $query->createNamedParameter($backendId),
				'resource_id' => $query->createNamedParameter($remote->getId()),
				'email' => $query->createNamedParameter($remote->getEMail()),
				'displayname' => $query->createNamedParameter($remote->getDisplayName()),
				'group_restrictions' => $query->createNamedParameter(
					$this->serializeGroupRestrictions(
						$remote->getGroupRestrictions()
					))
			])
			->executeStatement();
		return $query->getLastInsertId();
	}

	/**
	 * @param string $table
	 * @param string $foreignKey
	 * @param int $foreignId
	 * @param array $metadata
	 */
	private function addMetadataToCache(string $table,
		string $foreignKey,
		int $foreignId,
		array $metadata): void {
		foreach ($metadata as $key => $value) {
			$query = $this->dbConnection->getQueryBuilder();
			$query->insert($table)
				->values([
					$foreignKey => $query->createNamedParameter($foreignId),
					'key' => $query->createNamedParameter($key),
					'value' => $query->createNamedParameter($value),
				])
				->executeStatement();
		}
	}

	/**
	 * delete entry from cache that does not exist anymore remotely
	 *
	 * @param string $table
	 * @param int $id
	 */
	private function deleteFromCache(string $table,
		int $id): void {
		$query = $this->dbConnection->getQueryBuilder();
		$query->delete($table)
			->where($query->expr()->eq('id', $query->createNamedParameter($id)))
			->executeStatement();
	}

	/**
	 * @param string $table
	 * @param string $foreignKey
	 * @param int $id
	 */
	private function deleteMetadataFromCache(string $table,
		string $foreignKey,
		int $id): void {
		$query = $this->dbConnection->getQueryBuilder();
		$query->delete($table)
			->where($query->expr()->eq($foreignKey, $query->createNamedParameter($id)))
			->executeStatement();
	}

	/**
	 * update an existing entry in cache
	 *
	 * @param string $table
	 * @param int $id
	 * @param IResource|IRoom $remote
	 */
	private function updateCache(string $table,
		int $id,
		$remote): void {
		$query = $this->dbConnection->getQueryBuilder();
		$query->update($table)
			->set('email', $query->createNamedParameter($remote->getEMail()))
			->set('displayname', $query->createNamedParameter($remote->getDisplayName()))
			->set('group_restrictions', $query->createNamedParameter(
				$this->serializeGroupRestrictions(
					$remote->getGroupRestrictions()
				)))
			->where($query->expr()->eq('id', $query->createNamedParameter($id)))
			->executeStatement();
	}

	/**
	 * @param string $dbTable
	 * @param string $foreignKey
	 * @param int $id
	 * @param array $metadata
	 * @param array $cachedMetadata
	 */
	private function updateMetadataCache(string $dbTable,
		string $foreignKey,
		int $id,
		array $metadata,
		array $cachedMetadata): void {
		$newMetadata = array_diff_key($metadata, $cachedMetadata);
		$deletedMetadata = array_diff_key($cachedMetadata, $metadata);

		foreach ($newMetadata as $key => $value) {
			$query = $this->dbConnection->getQueryBuilder();
			$query->insert($dbTable)
				->values([
					$foreignKey => $query->createNamedParameter($id),
					'key' => $query->createNamedParameter($key),
					'value' => $query->createNamedParameter($value),
				])
				->executeStatement();
		}

		foreach ($deletedMetadata as $key => $value) {
			$query = $this->dbConnection->getQueryBuilder();
			$query->delete($dbTable)
				->where($query->expr()->eq($foreignKey, $query->createNamedParameter($id)))
				->andWhere($query->expr()->eq('key', $query->createNamedParameter($key)))
				->executeStatement();
		}

		$existingKeys = array_keys(array_intersect_key($metadata, $cachedMetadata));
		foreach ($existingKeys as $existingKey) {
			if ($metadata[$existingKey] !== $cachedMetadata[$existingKey]) {
				$query = $this->dbConnection->getQueryBuilder();
				$query->update($dbTable)
					->set('value', $query->createNamedParameter($metadata[$existingKey]))
					->where($query->expr()->eq($foreignKey, $query->createNamedParameter($id)))
					->andWhere($query->expr()->eq('key', $query->createNamedParameter($existingKey)))
					->executeStatement();
			}
		}
	}

	/**
	 * serialize array of group restrictions to store them in database
	 *
	 * @param array $groups
	 *
	 * @return string
	 */
	private function serializeGroupRestrictions(array $groups): string {
		return \json_encode($groups, JSON_THROW_ON_ERROR);
	}

	/**
	 * Gets all metadata of a backend
	 *
	 * @param IResource|IRoom $resource
	 *
	 * @return array
	 */
	private function getAllMetadataOfBackend($resource): array {
		if (!($resource instanceof IMetadataProvider)) {
			return [];
		}

		$keys = $resource->getAllAvailableMetadataKeys();
		$metadata = [];
		foreach ($keys as $key) {
			$metadata[$key] = $resource->getMetadataForKey($key);
		}

		return $metadata;
	}

	/**
	 * @param string $table
	 * @param string $foreignKey
	 * @param int $id
	 *
	 * @return array
	 */
	private function getAllMetadataOfCache(string $table,
		string $foreignKey,
		int $id): array {
		$query = $this->dbConnection->getQueryBuilder();
		$query->select(['key', 'value'])
			->from($table)
			->where($query->expr()->eq($foreignKey, $query->createNamedParameter($id)));
		$result = $query->executeQuery();
		$rows = $result->fetchAll();
		$result->closeCursor();

		$metadata = [];
		foreach ($rows as $row) {
			$metadata[$row['key']] = $row['value'];
		}

		return $metadata;
	}

	/**
	 * Gets all cached rooms / resources by backend
	 *
	 * @param $tableName
	 * @param $backendId
	 *
	 * @return array
	 */
	private function getAllCachedByBackend(string $tableName,
		string $backendId): array {
		$query = $this->dbConnection->getQueryBuilder();
		$query->select('resource_id')
			->from($tableName)
			->where($query->expr()->eq('backend_id', $query->createNamedParameter($backendId)));
		$result = $query->executeQuery();
		$rows = $result->fetchAll();
		$result->closeCursor();

		return array_map(function ($row): string {
			return $row['resource_id'];
		}, $rows);
	}

	/**
	 * @param $principalPrefix
	 * @param $principalUri
	 */
	private function deleteCalendarDataForResource(string $principalPrefix,
		string $principalUri): void {
		$calendar = $this->calDavBackend->getCalendarByUri(
			implode('/', [$principalPrefix, $principalUri]),
			CalDavBackend::RESOURCE_BOOKING_CALENDAR_URI);

		if ($calendar !== null) {
			$this->calDavBackend->deleteCalendar(
				$calendar['id'],
				true // Because this wasn't deleted by a user
			);
		}
	}

	/**
	 * @param $table
	 * @param $backendId
	 * @param $resourceId
	 *
	 * @return int
	 */
	private function getIdForBackendAndResource(string $table,
		string $backendId,
		string $resourceId): int {
		$query = $this->dbConnection->getQueryBuilder();
		$query->select('id')
			->from($table)
			->where($query->expr()->eq('backend_id', $query->createNamedParameter($backendId)))
			->andWhere($query->expr()->eq('resource_id', $query->createNamedParameter($resourceId)));
		$result = $query->executeQuery();

		$id = (int)$result->fetchOne();
		$result->closeCursor();
		return $id;
	}
}