use principaluri instead of userid, allowing to add delegates for rooms and things

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

!fixup add owner_id and proxy_id as db index, since we use it for querying

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

!fixup don't add ACL for each individual proxy, just use calendar-proxy groups

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

!fixup allow delegation of resources / rooms

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

!fixup fix addIndex call in migration

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

!fixup fix remaining constructor calls of Principal

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

!fixup minor fixes and unit tests

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

10 files changed, 360 insertions, 185 deletions

diff --git a/apps/dav/lib/CalDAV/Calendar.php b/apps/dav/lib/CalDAV/Calendar.php
index ae5cb226b0e..38def19af1d 100644
--- a/apps/dav/lib/CalDAV/Calendar.php
+++ b/apps/dav/lib/CalDAV/Calendar.php
@@ -47,9 +47,14 @@ class Calendar extends \Sabre\CalDAV\Calendar implements IShareable {
 	/** @var IConfig */
 	private $config;
 
-	/** @var ProxyMapper */
-	private $proxyMapper;
-
+	/**
+	 * Calendar constructor.
+	 *
+	 * @param BackendInterface $caldavBackend
+	 * @param $calendarInfo
+	 * @param IL10N $l10n
+	 * @param IConfig $config
+	 */
 	public function __construct(BackendInterface $caldavBackend, $calendarInfo, IL10N $l10n, IConfig $config) {
 		parent::__construct($caldavBackend, $calendarInfo);
 
@@ -62,9 +67,6 @@ class Calendar extends \Sabre\CalDAV\Calendar implements IShareable {
 		}
 
 		$this->config = $config;
-
-		// TODO: proper DI
-		$this->proxyMapper = \OC::$server->query(ProxyMapper::class);
 	}
 
 	/**
@@ -126,29 +128,60 @@ class Calendar extends \Sabre\CalDAV\Calendar implements IShareable {
 		return $this->calendarInfo['principaluri'];
 	}
 
+	/**
+	 * @return array
+	 */
 	public function getACL() {
 		$acl =  [
 			[
 				'privilege' => '{DAV:}read',
 				'principal' => $this->getOwner(),
 				'protected' => true,
-			]];
+			],
+			[
+				'privilege' => '{DAV:}read',
+				'principal' => $this->getOwner() . '/calendar-proxy-write',
+				'protected' => true,
+			],
+			[
+				'privilege' => '{DAV:}read',
+				'principal' => $this->getOwner() . '/calendar-proxy-read',
+				'protected' => true,
+			],
+		];
+
 		if ($this->getName() !== BirthdayService::BIRTHDAY_CALENDAR_URI) {
 			$acl[] = [
 				'privilege' => '{DAV:}write',
 				'principal' => $this->getOwner(),
 				'protected' => true,
 			];
+			$acl[] = [
+				'privilege' => '{DAV:}write',
+				'principal' => $this->getOwner() . '/calendar-proxy-write',
+				'protected' => true,
+			];
 		} else {
 			$acl[] = [
 				'privilege' => '{DAV:}write-properties',
 				'principal' => $this->getOwner(),
 				'protected' => true,
 			];
+			$acl[] = [
+				'privilege' => '{DAV:}write-properties',
+				'principal' => $this->getOwner() . '/calendar-proxy-write',
+				'protected' => true,
+			];
 		}
 
+		$acl[] = [
+			'privilege' => '{DAV:}write-properties',
+			'principal' => $this->getOwner() . '/calendar-proxy-read',
+			'protected' => true,
+		];
+
 		if (!$this->isShared()) {
-			return $this->addProxies($acl);
+			return $acl;
 		}
 
 		if ($this->getOwner() !== parent::getOwner()) {
@@ -180,38 +213,16 @@ class Calendar extends \Sabre\CalDAV\Calendar implements IShareable {
 		}
 
 		$acl = $this->caldavBackend->applyShareAcl($this->getResourceId(), $acl);
-		$allowedPrincipals = [$this->getOwner(), parent::getOwner(), 'principals/system/public'];
-		$acl = array_filter($acl, function($rule) use ($allowedPrincipals) {
+		$allowedPrincipals = [
+			$this->getOwner(),
+			$this->getOwner(). '/calendar-proxy-read',
+			$this->getOwner(). '/calendar-proxy-write',
+			parent::getOwner(),
+			'principals/system/public'
+		];
+		return array_filter($acl, function($rule) use ($allowedPrincipals) {
 			return \in_array($rule['principal'], $allowedPrincipals, true);
 		});
-
-		$acl = $this->addProxies($acl);
-
-		return $acl;
-	}
-
-	public function addProxies(array $acl): array {
-		list($prefix, $name) = \Sabre\Uri\split($this->getOwner());
-		$proxies = $this->proxyMapper->getProxiesOf($name);
-
-		foreach ($proxies as $proxy) {
-			if ($proxy->getPermissions() & ProxyMapper::PERMISSION_READ) {
-				$acl[] =  [
-					'privilege' => '{DAV:}read',
-					'principal' => 'principals/users/' . $proxy->getProxyId(),
-					'protected' => true,
-				];
-			}
-			if ($proxy->getPermissions() & ProxyMapper::PERMISSION_WRITE) {
-				$acl[] =  [
-					'privilege' => '{DAV:}write',
-					'principal' => 'principals/users/' . $proxy->getProxyId(),
-					'protected' => true,
-				];
-			}
-		}
-
-		return $acl;
 	}
 
 	public function getChildACL() {
diff --git a/apps/dav/lib/CalDAV/Proxy/ProxyMapper.php b/apps/dav/lib/CalDAV/Proxy/ProxyMapper.php
index 6a569394c4b..8d8adb811b6 100644
--- a/apps/dav/lib/CalDAV/Proxy/ProxyMapper.php
+++ b/apps/dav/lib/CalDAV/Proxy/ProxyMapper.php
@@ -27,17 +27,27 @@ namespace OCA\DAV\CalDAV\Proxy;
 use OCP\AppFramework\Db\QBMapper;
 use OCP\IDBConnection;
 
+/**
+ * Class ProxyMapper
+ *
+ * @package OCA\DAV\CalDAV\Proxy
+ */
 class ProxyMapper extends QBMapper {
 
 	const PERMISSION_READ  = 1;
 	const PERMISSION_WRITE = 2;
 
+	/**
+	 * ProxyMapper constructor.
+	 *
+	 * @param IDBConnection $db
+	 */
 	public function __construct(IDBConnection $db) {
 		parent::__construct($db, 'dav_cal_proxy', Proxy::class);
 	}
 
 	/**
-	 * @param string $proxyId The userId that can act as a proxy for the resulting calendars
+	 * @param string $proxyId The principal uri that can act as a proxy for the resulting calendars
 	 *
 	 * @return Proxy[]
 	 */
@@ -52,7 +62,7 @@ class ProxyMapper extends QBMapper {
 	}
 
 	/**
-	 * @param string $ownerId The userId that has the resulting proxies for their calendars
+	 * @param string $ownerId The principal uri that has the resulting proxies for their calendars
 	 *
 	 * @return Proxy[]
 	 */
diff --git a/apps/dav/lib/CalDAV/ResourceBooking/AbstractPrincipalBackend.php b/apps/dav/lib/CalDAV/ResourceBooking/AbstractPrincipalBackend.php
index aab5fcab8ad..63ed3381d14 100644
--- a/apps/dav/lib/CalDAV/ResourceBooking/AbstractPrincipalBackend.php
+++ b/apps/dav/lib/CalDAV/ResourceBooking/AbstractPrincipalBackend.php
@@ -22,6 +22,8 @@
  */
 namespace OCA\DAV\CalDAV\ResourceBooking;
 
+use OCA\DAV\CalDAV\Proxy\ProxyMapper;
+use OCA\DAV\Traits\PrincipalProxyTrait;
 use OCP\IDBConnection;
 use OCP\IGroupManager;
 use OCP\ILogger;
@@ -44,6 +46,9 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 	/** @var ILogger */
 	private $logger;
 
+	/** @var ProxyMapper */
+	private $proxyMapper;
+
 	/** @var string */
 	private $principalPrefix;
 
@@ -72,6 +77,7 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 								IUserSession $userSession,
 								IGroupManager $groupManager,
 								ILogger $logger,
+								ProxyMapper $proxyMapper,
 								string $principalPrefix,
 								string $dbPrefix,
 								string $cuType) {
@@ -79,6 +85,7 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 		$this->userSession = $userSession;
 		$this->groupManager = $groupManager;
 		$this->logger = $logger;
+		$this->proxyMapper = $proxyMapper;
 		$this->principalPrefix = $principalPrefix;
 		$this->dbTableName = 'calendar_' . $dbPrefix . 's';
 		$this->dbMetaDataTableName = $this->dbTableName . '_md';
@@ -86,6 +93,8 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 		$this->cuType = $cuType;
 	}
 
+	use PrincipalProxyTrait;
+
 	/**
 	 * Returns a list of principals based on a prefix.
 	 *
@@ -216,39 +225,6 @@ abstract class AbstractPrincipalBackend implements BackendInterface {
 	}
 
 	/**
-	 * Returns the list of members for a group-principal
-	 *
-	 * @param string $principal
-	 * @return string[]
-	 */
-	public function getGroupMemberSet($principal) {
-		return [];
-	}
-
-	/**
-	 * Returns the list of groups a principal is a member of
-	 *
-	 * @param string $principal
-	 * @return array
-	 */
-	public function getGroupMembership($principal) {
-		return [];
-	}
-
-	/**
-	 * Updates the list of group members for a group principal.
-	 *
-	 * The principals should be passed as a list of uri's.
-	 *
-	 * @param string $principal
-	 * @param string[] $members
-	 * @throws Exception
-	 */
-	public function setGroupMemberSet($principal, array $members) {
-		throw new Exception('Setting members of the group is not supported yet');
-	}
-
-	/**
 	 * @param string $path
 	 * @param PropPatch $propPatch
 	 * @return int
diff --git a/apps/dav/lib/CalDAV/ResourceBooking/ResourcePrincipalBackend.php b/apps/dav/lib/CalDAV/ResourceBooking/ResourcePrincipalBackend.php
index 0f6e6e7b4fd..128e6c21fad 100644
--- a/apps/dav/lib/CalDAV/ResourceBooking/ResourcePrincipalBackend.php
+++ b/apps/dav/lib/CalDAV/ResourceBooking/ResourcePrincipalBackend.php
@@ -22,24 +22,34 @@
  */
 namespace OCA\DAV\CalDAV\ResourceBooking;
 
+use OCA\DAV\CalDAV\Proxy\ProxyMapper;
 use OCP\IDBConnection;
 use OCP\IGroupManager;
 use OCP\ILogger;
 use OCP\IUserSession;
 
+/**
+ * Class ResourcePrincipalBackend
+ *
+ * @package OCA\DAV\CalDAV\ResourceBooking
+ */
 class ResourcePrincipalBackend extends AbstractPrincipalBackend {
 
 	/**
+	 * ResourcePrincipalBackend constructor.
+	 *
 	 * @param IDBConnection $dbConnection
 	 * @param IUserSession $userSession
 	 * @param IGroupManager $groupManager
 	 * @param ILogger $logger
+	 * @param ProxyMapper $proxyMapper
 	 */
 	public function __construct(IDBConnection $dbConnection,
 								IUserSession $userSession,
 								IGroupManager $groupManager,
-								ILogger $logger) {
+								ILogger $logger,
+								ProxyMapper $proxyMapper) {
 		parent::__construct($dbConnection, $userSession, $groupManager, $logger,
-			'principals/calendar-resources', 'resource', 'RESOURCE');
+			$proxyMapper, 'principals/calendar-resources', 'resource', 'RESOURCE');
 	}
 }
diff --git a/apps/dav/lib/CalDAV/ResourceBooking/RoomPrincipalBackend.php b/apps/dav/lib/CalDAV/ResourceBooking/RoomPrincipalBackend.php
index 68a344aa0ca..3e9e8f68852 100644
--- a/apps/dav/lib/CalDAV/ResourceBooking/RoomPrincipalBackend.php
+++ b/apps/dav/lib/CalDAV/ResourceBooking/RoomPrincipalBackend.php
@@ -22,24 +22,34 @@
  */
 namespace OCA\DAV\CalDAV\ResourceBooking;
 
+use OCA\DAV\CalDAV\Proxy\ProxyMapper;
 use OCP\IDBConnection;
 use OCP\IGroupManager;
 use OCP\ILogger;
 use OCP\IUserSession;
 
+/**
+ * Class RoomPrincipalBackend
+ *
+ * @package OCA\DAV\CalDAV\ResourceBooking
+ */
 class RoomPrincipalBackend extends AbstractPrincipalBackend {
 
 	/**
+	 * RoomPrincipalBackend constructor.
+	 *
 	 * @param IDBConnection $dbConnection
 	 * @param IUserSession $userSession
 	 * @param IGroupManager $groupManager
 	 * @param ILogger $logger
+	 * @param ProxyMapper $proxyMapper
 	 */
 	public function __construct(IDBConnection $dbConnection,
 								IUserSession $userSession,
 								IGroupManager $groupManager,
-								ILogger $logger) {
+								ILogger $logger,
+								ProxyMapper $proxyMapper) {
 		parent::__construct($dbConnection, $userSession, $groupManager, $logger,
-			'principals/calendar-rooms', 'room', 'ROOM');
+			$proxyMapper, 'principals/calendar-rooms', 'room', 'ROOM');
 	}
 }
diff --git a/apps/dav/lib/Command/CreateCalendar.php b/apps/dav/lib/Command/CreateCalendar.php
index 8e3a4abf8cf..a40bf48cc8e 100644
--- a/apps/dav/lib/Command/CreateCalendar.php
+++ b/apps/dav/lib/Command/CreateCalendar.php
@@ -24,6 +24,7 @@
 namespace OCA\DAV\Command;
 
 use OCA\DAV\CalDAV\CalDavBackend;
+use OCA\DAV\CalDAV\Proxy\ProxyMapper;
 use OCA\DAV\Connector\Sabre\Principal;
 use OCP\IDBConnection;
 use OCP\IGroupManager;
@@ -78,8 +79,8 @@ class CreateCalendar extends Command {
 			$this->groupManager,
 			\OC::$server->getShareManager(),
 			\OC::$server->getUserSession(),
-			\OC::$server->getConfig(),
-			\OC::$server->getAppManager()
+			\OC::$server->getAppManager(),
+			\OC::$server->query(ProxyMapper::class)
 		);
 		$random = \OC::$server->getSecureRandom();
 		$logger = \OC::$server->getLogger();
diff --git a/apps/dav/lib/Connector/Sabre/Principal.php b/apps/dav/lib/Connector/Sabre/Principal.php
index cc8e9c7accb..5c61b8371f2 100644
--- a/apps/dav/lib/Connector/Sabre/Principal.php
+++ b/apps/dav/lib/Connector/Sabre/Principal.php
@@ -37,6 +37,7 @@ namespace OCA\DAV\Connector\Sabre;
 use OCA\Circles\Exceptions\CircleDoesNotExistException;
 use OCA\DAV\CalDAV\Proxy\Proxy;
 use OCA\DAV\CalDAV\Proxy\ProxyMapper;
+use OCA\DAV\Traits\PrincipalProxyTrait;
 use OCP\App\IAppManager;
 use OCP\AppFramework\QueryException;
 use OCP\IGroup;
@@ -74,9 +75,21 @@ class Principal implements BackendInterface {
 
 	/** @var bool */
 	private $hasCircles;
+
 	/** @var ProxyMapper */
 	private $proxyMapper;
 
+	/**
+	 * Principal constructor.
+	 *
+	 * @param IUserManager $userManager
+	 * @param IGroupManager $groupManager
+	 * @param IShareManager $shareManager
+	 * @param IUserSession $userSession
+	 * @param IAppManager $appManager
+	 * @param ProxyMapper $proxyMapper
+	 * @param string $principalPrefix
+	 */
 	public function __construct(IUserManager $userManager,
 								IGroupManager $groupManager,
 								IShareManager $shareManager,
@@ -94,6 +107,10 @@ class Principal implements BackendInterface {
 		$this->proxyMapper = $proxyMapper;
 	}
 
+	use PrincipalProxyTrait {
+		getGroupMembership as protected traitGetGroupMembership;
+	}
+
 	/**
 	 * Returns a list of principals based on a prefix.
 	 *
@@ -162,23 +179,6 @@ class Principal implements BackendInterface {
 	}
 
 	/**
-	 * Returns the list of members for a group-principal
-	 *
-	 * @param string $principal
-	 * @return string[]
-	 * @throws Exception
-	 */
-	public function getGroupMemberSet($principal) {
-		// TODO: for now the group principal has only one member, the user itself
-		$principal = $this->getPrincipalByPath($principal);
-		if (!$principal) {
-			throw new Exception('Principal not found');
-		}
-
-		return [$principal['uri']];
-	}
-
-	/**
 	 * Returns the list of groups a principal is a member of
 	 *
 	 * @param string $principal
@@ -189,99 +189,30 @@ class Principal implements BackendInterface {
 	public function getGroupMembership($principal, $needGroups = false) {
 		list($prefix, $name) = \Sabre\Uri\split($principal);
 
-		if ($prefix === $this->principalPrefix) {
-			$user = $this->userManager->get($name);
-			if (!$user) {
-				throw new Exception('Principal not found');
-			}
-
-			if ($this->hasGroups || $needGroups) {
-				$groups = $this->groupManager->getUserGroups($user);
-				$groups = array_map(function($group) {
-					/** @var IGroup $group */
-					return 'principals/groups/' . urlencode($group->getGID());
-				}, $groups);
-
-				$proxies = $this->proxyMapper->getProxiesFor($user->getUID());
-				foreach ($proxies as $proxy) {
-					if ($proxy->getPermissions() & ProxyMapper::PERMISSION_READ) {
-						$groups[] = 'principals/users/' . $proxy->getOwnerId() . '/calendar-proxy-read';
-					}
-
-					if ($proxy->getPermissions() & ProxyMapper::PERMISSION_WRITE) {
-						$groups[] = 'principals/users/' . $proxy->getOwnerId() . '/calendar-proxy-write';
-					}
-				}
-
-				return $groups;
-			}
-		}
-		return [];
-	}
-
-	/**
-	 * Updates the list of group members for a group principal.
-	 *
-	 * The principals should be passed as a list of uri's.
-	 *
-	 * @param string $principal
-	 * @param string[] $members
-	 * @throws Exception
-	 */
-	public function setGroupMemberSet($principal, array $members) {
-		list($prefix, $target) = \Sabre\Uri\split($principal);
-
-		if ($target !== 'calendar-proxy-write' && $target !== 'calendar-proxy-read') {
-			throw new Exception('Setting members of the group is not supported yet');
+		if ($prefix !== $this->principalPrefix) {
+			return [];
 		}
 
-		$permission = ProxyMapper::PERMISSION_READ;
-		if ($target === 'calendar-proxy-write') {
-			$permission |= ProxyMapper::PERMISSION_WRITE;
+		$user = $this->userManager->get($name);
+		if (!$user) {
+			throw new Exception('Principal not found');
 		}
 
-		list($prefix, $owner) = \Sabre\Uri\split($prefix);
-		$proxies = $this->proxyMapper->getProxiesOf($owner);
+		$groups = [];
 
-		foreach ($members as $member) {
-			list($prefix, $name) = \Sabre\Uri\split($member);
-
-			if ($prefix !== $this->principalPrefix) {
-				throw new Exception('Invalid member group prefix: ' . $prefix);
-			}
-
-			$user = $this->userManager->get($name);
-			if ($user === null) {
-				throw new Exception('Invalid member: ' . $name);
-			}
-
-			$found = false;
-			foreach ($proxies as $proxy) {
-				if ($proxy->getProxyId() === $user->getUID()) {
-					$found = true;
-					$proxy->setPermissions($proxy->getPermissions() | $permission);
-					$this->proxyMapper->update($proxy);
-
-					$proxies = array_filter($proxies, function(Proxy $p) use ($proxy) {
-						return $p->getId() !== $proxy->getId();
-					});
-					break;
-				}
-			}
-
-			if ($found === false) {
-				$proxy = new Proxy();
-				$proxy->setOwnerId($owner);
-				$proxy->setProxyId($user->getUID());
-				$proxy->setPermissions($permission);
-				$this->proxyMapper->insert($proxy);
+		if ($this->hasGroups || $needGroups) {
+			$userGroups = $this->groupManager->getUserGroups($user);
+			foreach($userGroups as $userGroup) {
+				$groups[] = 'principals/groups/' . urlencode($userGroup->getGID());
 			}
 		}
 
-		// Delete all remaining proxies
-		foreach ($proxies as $proxy) {
-			$this->proxyMapper->delete($proxy);
-		}
+		$groups = array_unique(array_merge(
+			$groups,
+			$this->traitGetGroupMembership($principal, $needGroups)
+		));
+
+		return $groups;
 	}
 
 	/**
@@ -552,5 +483,4 @@ class Principal implements BackendInterface {
 
 		return [];
 	}
-
 }
diff --git a/apps/dav/lib/Migration/Version1011Date20190806104428.php b/apps/dav/lib/Migration/Version1011Date20190806104428.php
index 4c237b591ec..c144e62bcde 100644
--- a/apps/dav/lib/Migration/Version1011Date20190806104428.php
+++ b/apps/dav/lib/Migration/Version1011Date20190806104428.php
@@ -47,6 +47,8 @@ class Version1011Date20190806104428 extends SimpleMigrationStep {
 
 		$table->setPrimaryKey(['id']);
 		$table->addUniqueIndex(['owner_id', 'proxy_id', 'permissions'], 'dav_cal_proxy_uidx');
+		$table->addIndex(['owner_id'], 'dav_cal_proxy_ioid');
+		$table->addIndex(['proxy_id'], 'dav_cal_proxy_ipid');
 
 		return $schema;
 	}
diff --git a/apps/dav/lib/RootCollection.php b/apps/dav/lib/RootCollection.php
index 12b870932b3..ed8297783d7 100644
--- a/apps/dav/lib/RootCollection.php
+++ b/apps/dav/lib/RootCollection.php
@@ -54,17 +54,19 @@ class RootCollection extends SimpleCollection {
 		$shareManager = \OC::$server->getShareManager();
 		$db = \OC::$server->getDatabaseConnection();
 		$dispatcher = \OC::$server->getEventDispatcher();
+		$proxyMapper = \OC::$server->query(ProxyMapper::class);
+
 		$userPrincipalBackend = new Principal(
 			$userManager,
 			$groupManager,
 			$shareManager,
 			\OC::$server->getUserSession(),
 			\OC::$server->getAppManager(),
-			\OC::$server->query(ProxyMapper::class)
+			$proxyMapper
 		);
 		$groupPrincipalBackend = new GroupPrincipalBackend($groupManager, $userSession, $shareManager, $l10n);
-		$calendarResourcePrincipalBackend = new ResourcePrincipalBackend($db, $userSession, $groupManager, $logger);
-		$calendarRoomPrincipalBackend = new RoomPrincipalBackend($db, $userSession, $groupManager, $logger);
+		$calendarResourcePrincipalBackend = new ResourcePrincipalBackend($db, $userSession, $groupManager, $logger, $proxyMapper);
+		$calendarRoomPrincipalBackend = new RoomPrincipalBackend($db, $userSession, $groupManager, $logger, $proxyMapper);
 		// as soon as debug mode is enabled we allow listing of principals
 		$disableListing = !$config->getSystemValue('debug', false);
 
diff --git a/apps/dav/lib/Traits/PrincipalProxyTrait.php b/apps/dav/lib/Traits/PrincipalProxyTrait.php
new file mode 100644
index 00000000000..5e16d3a2f83
--- /dev/null
+++ b/apps/dav/lib/Traits/PrincipalProxyTrait.php
@@ -0,0 +1,223 @@
+<?php
+/**
+ * @copyright 2019, Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @author Georg Ehrke <oc.list@georgehrke.com>
+ *
+ * @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\DAV\Traits;
+
+use OCA\DAV\CalDAV\Proxy\Proxy;
+use OCA\DAV\CalDAV\Proxy\ProxyMapper;
+use Sabre\DAV\Exception;
+
+/**
+ * Trait PrincipalTrait
+ *
+ * @package OCA\DAV\Traits
+ */
+trait PrincipalProxyTrait {
+
+	/**
+	 * Returns the list of members for a group-principal
+	 *
+	 * @param string $principal
+	 * @return string[]
+	 * @throws Exception
+	 */
+	public function getGroupMemberSet($principal) {
+		$members = [];
+
+		if ($this->isProxyPrincipal($principal)) {
+			$realPrincipal = $this->getPrincipalUriFromProxyPrincipal($principal);
+			$principalArray = $this->getPrincipalByPath($realPrincipal);
+			if (!$principalArray) {
+				throw new Exception('Principal not found');
+			}
+
+			$proxies = $this->proxyMapper->getProxiesOf($principalArray['uri']);
+			foreach ($proxies as $proxy) {
+				if ($this->isReadProxyPrincipal($principal) && $proxy->getPermissions() === ProxyMapper::PERMISSION_READ) {
+					$members[] = $proxy->getProxyId();
+				}
+
+				if ($this->isWriteProxyPrincipal($principal) && $proxy->getPermissions() === (ProxyMapper::PERMISSION_READ | ProxyMapper::PERMISSION_WRITE)) {
+					$members[] = $proxy->getProxyId();
+				}
+			}
+		}
+
+		return $members;
+	}
+
+	/**
+	 * Returns the list of groups a principal is a member of
+	 *
+	 * @param string $principal
+	 * @param bool $needGroups
+	 * @return array
+	 * @throws Exception
+	 */
+	public function getGroupMembership($principal, $needGroups = false) {
+		list($prefix, $name) = \Sabre\Uri\split($principal);
+
+		if ($prefix !== $this->principalPrefix) {
+			return [];
+		}
+
+		$principalArray = $this->getPrincipalByPath($principal);
+		if (!$principalArray) {
+			throw new Exception('Principal not found');
+		}
+
+		$groups = [];
+		$proxies = $this->proxyMapper->getProxiesFor($principal);
+		foreach ($proxies as $proxy) {
+			if ($proxy->getPermissions() === ProxyMapper::PERMISSION_READ) {
+				$groups[] = $proxy->getOwnerId() . '/calendar-proxy-read';
+			}
+
+			if ($proxy->getPermissions() === (ProxyMapper::PERMISSION_READ | ProxyMapper::PERMISSION_WRITE)) {
+				$groups[] = $proxy->getOwnerId() . '/calendar-proxy-write';
+			}
+		}
+
+		return $groups;
+	}
+
+	/**
+	 * Updates the list of group members for a group principal.
+	 *
+	 * The principals should be passed as a list of uri's.
+	 *
+	 * @param string $principal
+	 * @param string[] $members
+	 * @throws Exception
+	 */
+	public function setGroupMemberSet($principal, array $members) {
+		list($principalUri, $target) = \Sabre\Uri\split($principal);
+
+		if ($target !== 'calendar-proxy-write' && $target !== 'calendar-proxy-read') {
+			throw new Exception('Setting members of the group is not supported yet');
+		}
+
+		$masterPrincipalArray = $this->getPrincipalByPath($principalUri);
+		if (!$masterPrincipalArray) {
+			throw new Exception('Principal not found');
+		}
+
+		$permission = ProxyMapper::PERMISSION_READ;
+		if ($target === 'calendar-proxy-write') {
+			$permission |= ProxyMapper::PERMISSION_WRITE;
+		}
+
+		list($prefix, $owner) = \Sabre\Uri\split($principalUri);
+		$proxies = $this->proxyMapper->getProxiesOf($principalUri);
+
+		foreach ($members as $member) {
+			list($prefix, $name) = \Sabre\Uri\split($member);
+
+			if ($prefix !== $this->principalPrefix) {
+				throw new Exception('Invalid member group prefix: ' . $prefix);
+			}
+
+			$principalArray = $this->getPrincipalByPath($member);
+			if (!$principalArray) {
+				throw new Exception('Principal not found');
+			}
+
+			$found = false;
+			foreach ($proxies as $proxy) {
+				if ($proxy->getProxyId() === $member) {
+					$found = true;
+					$proxy->setPermissions($proxy->getPermissions() | $permission);
+					$this->proxyMapper->update($proxy);
+
+					$proxies = array_filter($proxies, function(Proxy $p) use ($proxy) {
+						return $p->getId() !== $proxy->getId();
+					});
+					break;
+				}
+			}
+
+			if ($found === false) {
+				$proxy = new Proxy();
+				$proxy->setOwnerId($principalUri);
+				$proxy->setProxyId($member);
+				$proxy->setPermissions($permission);
+				$this->proxyMapper->insert($proxy);
+			}
+		}
+
+		// Delete all remaining proxies
+		foreach ($proxies as $proxy) {
+			// Write and Read Proxies have individual requests,
+			// so only delete proxies of this permission
+			if ($proxy->getPermissions() === $permission) {
+				$this->proxyMapper->delete($proxy);
+			}
+		}
+	}
+
+	/**
+	 * @param string $principalUri
+	 * @return bool
+	 */
+	private function isProxyPrincipal(string $principalUri):bool {
+		list($realPrincipalUri, $proxy) = \Sabre\Uri\split($principalUri);
+		list($prefix, $userId) = \Sabre\Uri\split($realPrincipalUri);
+
+		if (!isset($prefix) || !isset($userId)) {
+			return false;
+		}
+		if ($prefix !== $this->principalPrefix) {
+			return false;
+		}
+
+		return $proxy === 'calendar-proxy-read'
+			|| $proxy === 'calendar-proxy-write';
+
+	}
+
+	/**
+	 * @param string $principalUri
+	 * @return bool
+	 */
+	private function isReadProxyPrincipal(string $principalUri):bool {
+		list(, $proxy) = \Sabre\Uri\split($principalUri);
+		return $proxy === 'calendar-proxy-read';
+	}
+
+	/**
+	 * @param string $principalUri
+	 * @return bool
+	 */
+	private function isWriteProxyPrincipal(string $principalUri):bool {
+		list(, $proxy) = \Sabre\Uri\split($principalUri);
+		return $proxy === 'calendar-proxy-write';
+	}
+
+	/**
+	 * @param string $principalUri
+	 * @return string
+	 */
+	private function getPrincipalUriFromProxyPrincipal(string $principalUri):string {
+		list($realPrincipalUri, ) = \Sabre\Uri\split($principalUri);
+		return $realPrincipalUri;
+	}
+}