Subscriptions and notifications for namespaces, tasks and lists (#786)

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/786
Co-authored-by: konrad <konrad@kola-entertainments.de>
Co-committed-by: konrad <konrad@kola-entertainments.de>

pkg/models/subscription_rights.go

@@ -0,0 +1,66 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-2021 Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public Licensee 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 Licensee for more details.
+//
+// You should have received a copy of the GNU Affero General Public Licensee
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package models
+
+import (
+	"code.vikunja.io/web"
+	"xorm.io/xorm"
+)
+
+// CanCreate checks if a user can subscribe to an entity
+func (sb *Subscription) CanCreate(s *xorm.Session, a web.Auth) (can bool, err error) {
+	if _, is := a.(*LinkSharing); is {
+		return false, &ErrGenericForbidden{}
+	}
+
+	sb.EntityType = getEntityTypeFromString(sb.Entity)
+
+	switch sb.EntityType {
+	case SubscriptionEntityNamespace:
+		n := &Namespace{ID: sb.EntityID}
+		can, _, err = n.CanRead(s, a)
+	case SubscriptionEntityList:
+		l := &List{ID: sb.EntityID}
+		can, _, err = l.CanRead(s, a)
+	case SubscriptionEntityTask:
+		t := &Task{ID: sb.EntityID}
+		can, _, err = t.CanRead(s, a)
+	default:
+		return false, &ErrUnknownSubscriptionEntityType{EntityType: sb.EntityType}
+	}
+
+	return
+}
+
+// CanDelete checks if a user can delete a subscription
+func (sb *Subscription) CanDelete(s *xorm.Session, a web.Auth) (can bool, err error) {
+	if _, is := a.(*LinkSharing); is {
+		return false, &ErrGenericForbidden{}
+	}
+
+	sb.EntityType = getEntityTypeFromString(sb.Entity)
+
+	realSb := &Subscription{}
+	exists, err := s.
+		Where("entity_id = ? AND entity_type = ? AND user_id = ?", sb.EntityID, sb.EntityType, a.GetID()).
+		Get(realSb)
+	if err != nil {
+		return false, err
+	}
+
+	return exists, nil
+}