Implement attachment backend with a first module for app data file upload

Signed-off-by: Julius Härtl <jus@bitgrid.net>

appinfo/database.xml

@@ -223,7 +223,7 @@
             <field>
                 <name>last_modified</name>
                 <type>integer</type>
-                <default></default>
+                <default/>
                 <length>8</length>
                 <notnull>false</notnull>
                 <unsigned>true</unsigned>
@@ -231,11 +231,17 @@
             <field>
                 <name>created_at</name>
                 <type>integer</type>
-                <default></default>
+                <default/>
                 <length>8</length>
                 <notnull>false</notnull>
                 <unsigned>true</unsigned>
             </field>
+            <field>
+                <name>created_by</name>
+                <type>text</type>
+                <notnull>true</notnull>
+                <length>64</length>
+            </field>
         </declaration>
     </table>
 

appinfo/routes.php

@@ -59,6 +59,12 @@ return [
 		['name' => 'card#assignUser', 'url' => '/cards/{cardId}/assign', 'verb' => 'POST'],
 		['name' => 'card#unassignUser', 'url' => '/cards/{cardId}/assign/{userId}', 'verb' => 'DELETE'],
 
+		['name' => 'attachment#list', 'url' => '/cards/{cardId}/attachments', 'verb' => 'GET'],
+		['name' => 'attachment#display', 'url' => '/cards/{cardId}/attachment/{attachmentId}', 'verb' => 'GET'],
+		['name' => 'attachment#create', 'url' => '/cards/{cardId}/attachment', 'verb' => 'POST'],
+		['name' => 'attachment#update', 'url' => '/cards/{cardId}/attachment/{attachmentId}', 'verb' => 'UPDATE'],
+		['name' => 'attachment#delete', 'url' => '/cards/{cardId}/attachment/{attachmentId}', 'verb' => 'DELETE'],
+
 		// labels
 		['name' => 'label#create', 'url' => '/labels', 'verb' => 'POST'],
 		['name' => 'label#update', 'url' => '/labels/{labelId}', 'verb' => 'PUT'],

lib/Controller/AttachmentController.php

@@ -0,0 +1,71 @@
+<?php
+/**
+ * @copyright Copyright (c) 2018 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @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\Deck\Controller;
+
+
+use OCA\Deck\Service\AttachmentService;
+use OCP\AppFramework\Controller;
+use OCP\IRequest;
+
+class AttachmentController extends Controller {
+
+	/** @var AttachmentService */
+	private $attachmentService;
+
+	public function __construct($appName, IRequest $request, AttachmentService $attachmentService) {
+		parent::__construct($appName, $request);
+		$this->attachmentService = $attachmentService;
+	}
+
+	public function list($cardId) {
+		return $this->attachmentService->getAll($cardId);
+	}
+
+	/**
+	 * @param $cardId
+	 * @param $attachmentId
+	 * @NoCSRFRequired
+	 * @return \OCP\AppFramework\Http\Response
+	 * @throws \OCA\Deck\NotFoundException
+	 */
+	public function display($cardId, $attachmentId) {
+		return $this->attachmentService->display($cardId, $attachmentId);
+	}
+
+	public function create($cardId) {
+		return $this->attachmentService->create(
+			$cardId,
+			$this->request->getParam('type'),
+			$this->request->getParam('data')
+		);
+	}
+
+	public function update($cardId, $attachmentId) {
+		return $this->attachmentService->update($cardId, $attachmentId, $this->request->getParam('data'));
+	}
+
+	public function delete($cardId, $attachmentId) {
+		return $this->attachmentService->delete($cardId, $attachmentId);
+	}
+}

lib/Controller/BoardController.php

@@ -26,12 +26,13 @@ namespace OCA\Deck\Controller;
 use OCA\Deck\Db\Acl;
 use OCA\Deck\Service\BoardService;
 use OCA\Deck\Service\PermissionService;
+use OCP\AppFramework\ApiController;
 use OCP\IRequest;
 use OCP\AppFramework\Controller;
 use OCP\IUserManager;
 use OCP\IGroupManager;
 
-class BoardController extends Controller {
+class BoardController extends ApiController {
 	private $userId;
 	private $boardService;
 	private $userManager;

lib/Db/Attachment.php

@@ -0,0 +1,47 @@
+<?php
+/**
+ * @copyright Copyright (c) 2018 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @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\Deck\Db;
+
+class Attachment extends RelationalEntity {
+
+	protected $cardId;
+	protected $type;
+	protected $data;
+	protected $lastModified;
+	protected $createdAt;
+	protected $createdBy;
+	protected $deletedAt;
+	protected $extendedData = [];
+
+	public function __construct() {
+		$this->addType('id', 'integer');
+		$this->addType('cardId', 'integer');
+		$this->addType('lastModified', 'integer');
+		$this->addType('createdAt', 'integer');
+		$this->addType('deletedAt', 'integer');
+		$this->addResolvable('createdBy');
+		$this->addRelation('extendedData');
+	}
+
+}

lib/Db/AttachmentMapper.php

@@ -0,0 +1,126 @@
+<?php
+/**
+ * @copyright Copyright (c) 2018 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @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\Deck\Db;
+
+use OCP\AppFramework\Db\Entity;
+use OCP\DB\QueryBuilder\IQueryBuilder;
+use OCP\IDBConnection;
+use OCP\IUserManager;
+use PDO;
+
+
+class AttachmentMapper extends DeckMapper implements IPermissionMapper {
+
+	private $cardMapper;
+	private $userManager;
+
+	public function __construct(IDBConnection $db, CardMapper $cardMapper, IUserManager $userManager) {
+		parent::__construct($db, 'deck_attachment', Attachment::class);
+		$this->cardMapper = $cardMapper;
+		$this->userManager = $userManager;
+		$this->qb = $this->db->getQueryBuilder();
+	}
+
+	/**
+	 * @param $id
+	 * @return Entity|Attachment
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
+	public function find($id) {
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('*')
+			->from('deck_attachment')
+			->where($qb->expr()->eq('id', $id));
+
+		$cursor = $qb->execute();
+		$row = $cursor->fetch(PDO::FETCH_ASSOC);
+		$cursor->closeCursor();
+		return $this->mapRowToEntity($row);
+	}
+
+	/**
+	 * Find all attachments for a card
+	 *
+	 * @param $cardId
+	 * @return array
+	 */
+	public function findAll($cardId) {
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('*')
+			->from('deck_attachment')
+			->where($qb->expr()->eq('card_id', $cardId, IQueryBuilder::PARAM_INT));
+
+		$entities = [];
+		$cursor = $qb->execute();
+		while($row = $cursor->fetch()){
+			$entities[] = $this->mapRowToEntity($row);
+		}
+		$cursor->closeCursor();
+		return $entities;
+	}
+
+	/**
+	 * @param Attachment $attachment
+	 * @throws \Exception
+	 */
+	public function mapParticipant(Attachment $attachment) {
+		$userManager = $this->userManager;
+		$attachment->resolveRelation('participant', function() use (&$userManager, &$attachment) {
+			$user = $userManager->get($attachment->getParticipant());
+			if ($user !== null) {
+				return new User($user);
+			}
+			return null;
+		});
+	}
+
+
+	/**
+	 * Check if $userId is owner of Entity with $id
+	 *
+	 * @param $userId string userId
+	 * @param $id int|string unique entity identifier
+	 * @return boolean
+	 */
+	public function isOwner($userId, $id) {
+		// TODO: Implement isOwner() method.
+	}
+
+	/**
+	 * Query boardId for Entity of given $id
+	 *
+	 * @param $id int|string unique entity identifier
+	 * @return int|null id of Board
+	 */
+	public function findBoardId($id) {
+		try {
+			$attachment = $this->find($id);
+		} catch (\Exception $e) {
+			return null;
+		}
+		$this->cardMapper->findBoardId($attachment->getCardId());
+	}
+}

lib/Db/Card.php

@@ -35,6 +35,7 @@ class Card extends RelationalEntity {
 	protected $createdAt;
 	protected $labels;
 	protected $assignedUsers;
+	protected $attachments;
 	protected $owner;
 	protected $order;
 	protected $archived = false;
@@ -58,6 +59,7 @@ class Card extends RelationalEntity {
 		$this->addType('notified', 'boolean');
 		$this->addRelation('labels');
 		$this->addRelation('assignedUsers');
+		$this->addRelation('attachments');
 		$this->addRelation('participants');
 		$this->addResolvable('owner');
 	}

lib/Db/DeckMapper.php

@@ -25,6 +25,13 @@ namespace OCA\Deck\Db;
 
 use OCP\AppFramework\Db\Mapper;
 
+/**
+ * Class DeckMapper
+ *
+ * @package OCA\Deck\Db
+ *
+ * TODO: Move to QBMapper once Nextcloud 14 is a minimum requirement
+ */
 abstract class DeckMapper extends Mapper {
 
 	/**

lib/InvalidAttachmentType.php

@@ -0,0 +1,37 @@
+<?php
+/**
+ * @copyright Copyright (c) 2018 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @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\Deck;
+
+
+class InvalidAttachmentType extends \Exception {
+
+	/**
+	 * InvalidAttachmentType constructor.
+	 */
+	public function __construct($type) {
+
+		parent::__construct('No matching IAttachmentService implementation found for type ' . $type);
+
+	}
+}

lib/Service/AttachmentService.php

@@ -0,0 +1,197 @@
+<?php
+/**
+ * @copyright Copyright (c) 2018 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @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\Deck\Service;
+
+
+use OCA\Deck\AppInfo\Application;
+use OCA\Deck\Db\Acl;
+use OCA\Deck\Db\Attachment;
+use OCA\Deck\Db\AttachmentMapper;
+use OCA\Deck\Db\CardMapper;
+use OCA\Deck\InvalidAttachmentType;
+use OCA\Deck\NotFoundException;
+use OCP\AppFramework\Http\Response;
+
+class AttachmentService {
+
+	private $attachmentMapper;
+	private $cardMapper;
+	private $permissionService;
+	private $userId;
+
+	/** @var IAttachmentService[] */
+	private $services = [];
+	private $application;
+
+	/**
+	 * AttachmentService constructor.
+	 *
+	 * @param AttachmentMapper $attachmentMapper
+	 * @param CardMapper $cardMapper
+	 * @param PermissionService $permissionService
+	 * @param $userId
+	 * @throws \OCP\AppFramework\QueryException
+	 */
+	public function __construct(AttachmentMapper $attachmentMapper, CardMapper $cardMapper, PermissionService $permissionService, Application $application, $userId) {
+		$this->attachmentMapper = $attachmentMapper;
+		$this->cardMapper = $cardMapper;
+		$this->permissionService = $permissionService;
+		$this->userId = $userId;
+		$this->application = $application;
+
+		// Register shipped attachment services
+		// TODO: move this to a plugin based approach once we have different types of attachments
+		$this->registerAttachmentService('deck_file', FileService::class);
+	}
+
+	/**
+	 * @param string $type
+	 * @param string $class
+	 * @throws \OCP\AppFramework\QueryException
+	 */
+	public function registerAttachmentService($type, $class) {
+		$this->services[$type] = $this->application->getContainer()->query($class);
+	}
+
+	/**
+	 * @param string $type
+	 * @return IAttachmentService
+	 * @throws InvalidAttachmentType
+	 */
+	public function getService($type) {
+		if (isset($this->services[$type])) {
+			return $this->services[$type];
+		}
+		throw new InvalidAttachmentType($type);
+	}
+
+	/**
+	 * @param $cardId
+	 * @return array
+	 * @throws \OCA\Deck\NoPermissionException
+	 */
+	public function findAll($cardId) {
+		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_READ);
+
+		$attachments = $this->attachmentMapper->findAll($cardId);
+		foreach ($attachments as &$attachment) {
+			try {
+				$service = $this->getService($attachment->getType());
+				$service->extendData($attachment);
+			} catch (InvalidAttachmentType $e) {
+				// Ingore invalid attachment types when extending the data
+			}
+		}
+		return $attachments;
+	}
+
+	public function create($cardId, $type, $data) {
+		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_EDIT);
+
+		$attachment = new Attachment();
+		$attachment->setCardId($cardId);
+		$attachment->setType($type);
+		$attachment->setData($data);
+		$attachment->setCreatedBy($this->userId);
+		$attachment->setLastModified(time());
+		$attachment->setCreatedAt(time());
+
+		try {
+			$service = $this->getService($attachment->getType());
+			$service->create($attachment);
+		} catch (InvalidAttachmentType $e) {
+			// just store the data
+		}
+		$attachment = $this->attachmentMapper->insert($attachment);
+
+		// extend data so the frontend can use it properly after creating
+		try {
+			$service = $this->getService($attachment->getType());
+			$service->extendData($attachment);
+		} catch (InvalidAttachmentType $e) {
+			// just store the data
+		}
+		return $attachment;
+	}
+
+
+	/**
+	 * Display the attachment
+	 *
+	 * @param $cardId
+	 * @param $attachmentId
+	 * @return Response
+	 * @throws NotFoundException
+	 */
+	public function display($cardId, $attachmentId) {
+		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_READ);
+
+		$attachment = $this->attachmentMapper->find($attachmentId);
+
+		try {
+			$service = $this->getService($attachment->getType());
+			return $service->display($attachment);
+		} catch (InvalidAttachmentType $e) {
+			throw new NotFoundException();
+		}
+	}
+
+	/**
+	 * Update an attachment with custom data
+	 *
+	 * @param $cardId
+	 * @param $attachmentId
+	 * @param $request
+	 * @return mixed
+	 * @throws \OCA\Deck\NoPermissionException
+	 * @throws \OCP\AppFramework\Db\DoesNotExistException
+	 * @throws \OCP\AppFramework\Db\MultipleObjectsReturnedException
+	 */
+	public function update($cardId, $attachmentId, $data) {
+		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_EDIT);
+		$attachment = $this->attachmentMapper->find($attachmentId);
+		$attachment->setData($data);
+		try {
+			$service = $this->getService($attachment->getType());
+			$service->update($attachment);
+		} catch (InvalidAttachmentType $e) {
+			// just update without further action
+		}
+		return $attachment;
+	}
+
+	public function delete($cardId, $attachmentId) {
+		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_EDIT);
+
+		$attachment = $this->attachmentMapper->find($attachmentId);
+		try {
+			$service = $this->getService($attachment->getType());
+			$service->delete($attachment);
+		} catch (InvalidAttachmentType $e) {
+			// just delete without further action
+		}
+		$this->attachmentMapper->delete($attachment);
+		return $attachment;
+	}
+}

lib/Service/CardService.php

@@ -41,19 +41,22 @@ class CardService {
 	private $boardService;
 	private $assignedUsersMapper;
 
-	public function __construct(CardMapper $cardMapper, StackMapper $stackMapper, PermissionService $permissionService, BoardService $boardService, AssignedUsersMapper $assignedUsersMapper) {
+	public function __construct(CardMapper $cardMapper, StackMapper $stackMapper, PermissionService $permissionService, BoardService $boardService, AssignedUsersMapper $assignedUsersMapper, AttachmentService $attachmentService) {
 		$this->cardMapper = $cardMapper;
 		$this->stackMapper = $stackMapper;
 		$this->permissionService = $permissionService;
 		$this->boardService = $boardService;
 		$this->assignedUsersMapper = $assignedUsersMapper;
+		$this->attachmentService = $attachmentService;
 	}
 
 	public function find($cardId) {
 		$this->permissionService->checkPermission($this->cardMapper, $cardId, Acl::PERMISSION_READ);
 		$card = $this->cardMapper->find($cardId);
 		$assignedUsers = $this->assignedUsersMapper->find($card->getId());
+		$attachments = $this->attachmentService->findAll($cardId);
 		$card->setAssignedUsers($assignedUsers);
+		$card->setAttachments($attachments);
 		return $card;
 	}
 

lib/Service/FileService.php

@@ -0,0 +1,152 @@
+<?php
+/**
+ * @copyright Copyright (c) 2018 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @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\Deck\Service;
+
+
+use OCA\Deck\Db\Attachment;
+use OCP\AppFramework\Http\FileDisplayResponse;
+use OCP\Files\IAppData;
+use OCP\Files\NotFoundException;
+use OCP\Files\NotPermittedException;
+use OCP\Files\SimpleFS\ISimpleFile;
+use OCP\Files\SimpleFS\ISimpleFolder;
+use OCP\IL10N;
+use OCP\IRequest;
+
+
+class FileService implements IAttachmentService {
+
+	private $l10n;
+	private $appData;
+	private $request;
+
+	public function __construct(
+		IL10N $l10n,
+		IAppData $appData,
+		IRequest $request
+	) {
+		$this->l10n = $l10n;
+		$this->appData = $appData;
+		$this->request = $request;
+	}
+
+	/**
+	 * @param Attachment $attachment
+	 * @return ISimpleFile
+	 * @throws NotFoundException
+	 * @throws NotPermittedException
+	 */
+	private function getFileForAttachment(Attachment $attachment) {
+		return $this->getFolder($attachment)
+			->getFile($attachment->getData());
+	}
+
+	/**
+	 * @param Attachment $attachment
+	 * @return ISimpleFolder
+	 * @throws NotPermittedException
+	 */
+	private function getFolder(Attachment $attachment) {
+		$folderName = 'file-card-' . (int)$attachment->getCardId();
+		try {
+			$folder = $this->appData->getFolder($folderName);
+		} catch (NotFoundException $e) {
+			$folder = $this->appData->newFolder($folderName);
+		}
+		return $folder;
+	}
+
+	public function extendData(Attachment $attachment) {
+		try {
+			$file = $this->getFileForAttachment($attachment);
+		} catch (NotFoundException $e) {
+			// TODO: log error
+			return $attachment;
+		} catch (NotPermittedException $e) {
+			return $attachment;
+		}
+		$attachment->setExtendedData([
+			'filesize' => $file->getSize(),
+			'mimetype' => $file->getMimeType(),
+			'info' => pathinfo($file->getName())
+		]);
+		return $attachment;
+	}
+
+	public function create(Attachment $attachment) {
+		$file = $this->request->getUploadedFile('file');
+		$cardId = $attachment->getCardId();
+		$error = null;
+		$phpFileUploadErrors = [
+			UPLOAD_ERR_OK => $this->l10n->t('The file was uploaded'),
+			UPLOAD_ERR_INI_SIZE => $this->l10n->t('The uploaded file exceeds the upload_max_filesize directive in php.ini'),
+			UPLOAD_ERR_FORM_SIZE => $this->l10n->t('The uploaded file exceeds the MAX_FILE_SIZE directive that was specified in the HTML form'),
+			UPLOAD_ERR_PARTIAL => $this->l10n->t('The file was only partially uploaded'),
+			UPLOAD_ERR_NO_FILE => $this->l10n->t('No file was uploaded'),
+			UPLOAD_ERR_NO_TMP_DIR => $this->l10n->t('Missing a temporary folder'),
+			UPLOAD_ERR_CANT_WRITE => $this->l10n->t('Could not write file to disk'),
+			UPLOAD_ERR_EXTENSION => $this->l10n->t('A PHP extension stopped the file upload'),
+		];
+
+		if (empty($file)) {
+			$error = $this->l10n->t('No file uploaded');
+		}
+		if (!empty($file) && array_key_exists('error', $file) && $file['error'] !== UPLOAD_ERR_OK) {
+			$error = $phpFileUploadErrors[$file['error']];
+		}
+		if ($error !== null) {
+			throw new \RuntimeException($error);
+		}
+
+		$folder = $this->getFolder($attachment);
+		$fileName = $file['name'];
+		if ($folder->fileExists($fileName)) {
+			throw new \Exception('File already exists.');
+		}
+		$target = $folder->newFile($fileName);
+		$target->putContent(file_get_contents($file['tmp_name'], 'r'));
+
+		$attachment->setData($fileName);
+	}
+
+	public function update(Attachment $attachment) {
+		$file = $this->getFileForAttachment($attachment);
+
+	}
+
+	public function delete(Attachment $attachment) {
+		try {
+			$file = $this->getFileForAttachment($attachment);
+			$file->delete();
+		} catch (NotFoundException $e) {
+		}
+	}
+
+	public function display(Attachment $attachment) {
+		$file = $this->getFileForAttachment($attachment);
+		$response = new FileDisplayResponse($file);
+		$response->addHeader('Content-Type', $file->getMimeType());
+		return $response;
+	}
+}

lib/Service/IAttachmentService.php

@@ -0,0 +1,84 @@
+<?php
+/**
+ * @copyright Copyright (c) 2018 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @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\Deck\Service;
+
+
+use OCA\Deck\Db\Attachment;
+use OCP\AppFramework\Http\Response;
+
+/**
+ * Interface IAttachmentService
+ *
+ * Implement this interface to extend the default attachment behaviour
+ * This interface allows to extend/reduce the data stored with an attachment,
+ * as well as rendering a custom output per attachment type
+ *
+ */
+interface IAttachmentService {
+
+	/**
+	 * Add extended data to the returned data of an attachment
+	 *
+	 * @param Attachment $attachment
+	 * @return mixed
+	 */
+	public function extendData(Attachment $attachment);
+
+	/**
+	 * Display the attachment
+	 *
+	 * TODO: Move to IAttachmentDisplayService for better separation
+	 *
+	 * @param Attachment $attachment
+	 * @return Response
+	 */
+	public function display(Attachment $attachment);
+
+	/**
+	 * Create a new attachment
+	 *
+	 * This method will be called before inserting the attachment entry in the database
+	 *
+	 * @param Attachment $attachment
+	 */
+	public function create(Attachment $attachment);
+
+	/**
+	 * Update an attachment with custom data
+	 *
+	 * This method will be called before updating the attachment entry in the database
+	 *
+	 * @param Attachment $attachment
+	 */
+	public function update(Attachment $attachment);
+
+	/**
+	 * Delete an attachment
+	 *
+	 * This method will be called before removing the attachment entry from the database
+	 *
+	 * @param Attachment $attachment
+	 */
+	public function delete(Attachment $attachment);
+}