[feature] Added generic message notification type (shown in dialg box)

README.rst

@@ -527,11 +527,61 @@ value you want but it needs to be unique. For more details read `preventing dupl
 Notification Types
 ------------------
 
-**OpenWISP Notifications** simplifies configuring individual notification by
-using notification types. You can think of a notification type as a template
+**OpenWISP Notifications** allows defining notification types for
+recurring events. Think of a notification type as a template
 for notifications.
 
-These properties can be configured for each notification type:
+``generic_message``
+~~~~~~~~~~~~~~~~~~~
+
+.. figure:: https://raw.githubusercontent.com/openwisp/openwisp-notifications/docs/docs/images/1.1/generic_message.png
+   :target: https://raw.githubusercontent.com/openwisp/openwisp-notifications/docs/docs/images/1.1/generic_message.png
+   :align: center
+
+This module includes a notification type called ``generic_message``.
+
+This notification type is designed to deliver custom messages in the
+user interface for infrequent events or errors that occur during
+background operations and cannot be communicated easily to the user
+in other ways.
+
+These messages may require longer explanations and are therefore
+displayed in a dialog overlay, as shown in the screenshot above.
+This notification type does not send emails.
+
+The following code example demonstrates how to send a notification
+of this type:
+
+.. code-block:: python
+
+    from openwisp_notifications.signals import notify
+    notify.send(
+        type='generic_message',
+        level='error',
+        message='An unexpected error happened!',
+        sender=User.objects.first(),
+        target=User.objects.last(),
+        description="""Lorem Ipsum is simply dummy text
+    of the printing and typesetting industry.
+
+    ### Heading 3
+
+    Lorem Ipsum has been the industry's standard dummy text ever since the 1500s,
+    when an unknown printer took a galley of type and scrambled it to make a
+    type specimen book.
+
+    It has survived not only **five centuries**, but also the leap into
+    electronic typesetting, remaining essentially unchanged.
+
+    It was popularised in the 1960s with the release of Letraset sheets
+    containing Lorem Ipsum passages, and more recently with desktop publishing
+    software like Aldus PageMaker including versions of *Lorem Ipsum*."""
+    )
+
+Properties of Notification Types
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The following properties can be configured for each notification type:
 
 +------------------------+----------------------------------------------------------------+
 | **Property**           | **Description**                                                |
@@ -569,8 +619,15 @@ These properties can be configured for each notification type:
 +------------------------+----------------------------------------------------------------+
 
 
-**Note**: A notification type configuration should contain atleast one of ``message`` or ``message_template``
-settings. If both of them are present, ``message`` is given preference over ``message_template``.
+**Note**: It is recommended that a notification type configuration
+for recurring events contains either the ``message`` or
+``message_template`` properties. If both are present,
+``message`` is given preference over ``message_template``.
+
+If you don't plan on using ``message`` or ``message_template``,
+it may be better to use the existing ``generic_message`` type.
+However, it's advised to do so only if the event being notified
+is infrequent.
 
 **Note**: The callable for ``actor_link``, ``action_object_link`` and ``target_link`` should
 have the following signature:

openwisp_notifications/api/serializers.py

@@ -55,10 +55,13 @@ def data(self):
 
 
 class NotificationListSerializer(NotificationSerializer):
+    description = serializers.CharField(source='rendered_description')
+
     class Meta(NotificationSerializer.Meta):
         fields = [
             'id',
             'message',
+            'description',
             'unread',
             'target_url',
             'email_subject',

openwisp_notifications/base/models.py

@@ -1,4 +1,5 @@
 import logging
+from contextlib import contextmanager
 
 from django.conf import settings
 from django.contrib.contenttypes.fields import GenericForeignKey
@@ -29,6 +30,35 @@
 logger = logging.getLogger(__name__)
 
 
+@contextmanager
+def notification_render_attributes(obj, **attrs):
+    """
+    This context manager sets temporary attributes on
+    the notification object to allowing rendering of
+    notification.
+
+    It can only be used to set aliases of the existing attributes.
+    By default, it will set the following aliases:
+        - actor_link -> actor_url
+        - action_link -> action_url
+        - target_link -> target_url
+    """
+    defaults = {
+        'actor_link': 'actor_url',
+        'action_link': 'action_url',
+        'target_link': 'target_url',
+    }
+    defaults.update(attrs)
+
+    for target_attr, source_attr in defaults.items():
+        setattr(obj, target_attr, getattr(obj, source_attr))
+
+    yield obj
+
+    for attr in defaults.keys():
+        delattr(obj, attr)
+
+
 class AbstractNotification(UUIDModel, BaseNotification):
     CACHE_KEY_PREFIX = 'ow-notifications-'
     type = models.CharField(max_length=30, null=True, choices=NOTIFICATION_CHOICES)
@@ -103,40 +133,44 @@ def target_url(self):
 
     @cached_property
     def message(self):
-        return self.get_message()
+        with notification_render_attributes(self):
+            return self.get_message()
+
+    @cached_property
+    def rendered_description(self):
+        if not self.description:
+            return
+        with notification_render_attributes(self):
+            data = self.data or {}
+            desc = self.description.format(notification=self, **data)
+        return mark_safe(markdown(desc))
 
     @property
     def email_message(self):
-        return self.get_message(email_message=True)
+        with notification_render_attributes(self, target_link='redirect_view_url'):
+            return self.get_message()
 
-    def get_message(self, email_message=False):
-        if self.type:
-            # setting links in notification object for message rendering
-            self.actor_link = self.actor_url
-            self.action_link = self.action_url
-            self.target_link = (
-                self.target_url if not email_message else self.redirect_view_url
-            )
-            try:
-                config = get_notification_configuration(self.type)
-                data = self.data or {}
-                if 'message' in config:
-                    md_text = config['message'].format(notification=self, **data)
-                else:
-                    md_text = render_to_string(
-                        config['message_template'], context=dict(notification=self)
-                    ).strip()
-            except (AttributeError, KeyError, NotificationRenderException) as exception:
-                self._invalid_notification(
-                    self.pk,
-                    exception,
-                    'Error encountered in rendering notification message',
-                )
-            # clean up
-            self.actor_link = self.action_link = self.target_link = None
-            return mark_safe(markdown(md_text))
-        else:
+    def get_message(self):
+        if not self.type:
             return self.description
+        try:
+            config = get_notification_configuration(self.type)
+            data = self.data or {}
+            if 'message' in data:
+                md_text = data['message'].format(notification=self, **data)
+            elif 'message' in config:
+                md_text = config['message'].format(notification=self, **data)
+            else:
+                md_text = render_to_string(
+                    config['message_template'], context=dict(notification=self, **data)
+                ).strip()
+        except (AttributeError, KeyError, NotificationRenderException) as exception:
+            self._invalid_notification(
+                self.pk,
+                exception,
+                'Error encountered in rendering notification message',
+            )
+        return mark_safe(markdown(md_text))
 
     @cached_property
     def email_subject(self):

openwisp_notifications/handlers.py

@@ -57,8 +57,8 @@ def notify_handler(**kwargs):
     except NotificationRenderException as error:
         logger.error(f'Error encountered while creating notification: {error}')
         return
-    level = notification_template.get(
-        'level', kwargs.pop('level', Notification.LEVELS.info)
+    level = kwargs.pop(
+        'level', notification_template.get('level', Notification.LEVELS.info)
     )
     verb = notification_template.get('verb', kwargs.pop('verb', None))
     user_app_name = User._meta.app_label
@@ -195,22 +195,22 @@ def send_email_notification(sender, instance, created, **kwargs):
         # Do not send email if notification is malformed.
         return
     url = instance.data.get('url', '') if instance.data else None
-    description = instance.message
+    body_text = instance.email_message
     if url:
         target_url = url
     elif instance.target:
         target_url = instance.redirect_view_url
     else:
         target_url = None
     if target_url:
-        description += _('\n\nFor more information see %(target_url)s.') % {
+        body_text += _('\n\nFor more information see %(target_url)s.') % {
             'target_url': target_url
         }
 
     send_email(
-        subject,
-        description,
-        instance.message,
+        subject=subject,
+        body_text=body_text,
+        body_html=instance.email_message,
         recipients=[instance.recipient.email],
         extra_context={
             'call_to_action_url': target_url,

openwisp_notifications/static/openwisp-notifications/css/notifications.css

@@ -257,6 +257,7 @@
 .ow-notification-level-text {
   padding: 0px 6px;
   text-transform: uppercase;
+  font-weight: bold;
 }
 .ow-notification-elem .icon,
 .ow-notification-toast .icon {
@@ -300,6 +301,66 @@
 }
 .ow-notification-elem:last-child .ow-notification-inner { border-bottom: none }
 
+/* Generic notification dialog */
+.ow-overlay-notification {
+  background-color: rgba(0, 0, 0, 0.6);
+  display: flex;
+  justify-content: center;
+  align-items: center;
+  transition: opacity 0.3s;
+}
+.ow-dialog-notification {
+  position: relative;
+  background-color: white;
+  padding: 20px;
+  padding-top: 20px;
+  border-radius: 10px;
+  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
+  width: 90%;
+  max-width: 500px;
+  text-align: left;
+}
+.ow-dialog-notification .ow-notification-date {
+  padding-right: 15px;
+}
+.ow-dialog-notification .button {
+  margin-right: 10px;
+}
+.ow-dialog-notification-level-wrapper {
+  display: flex;
+  justify-content: space-between;
+}
+.ow-dialog-notification .icon {
+  min-height: 15;
+  min-width: 15px;
+  background-repeat: no-repeat;
+}
+.ow-dialog-close-x {
+  cursor: pointer;
+  font-size: 1.75em;
+  position: absolute;
+  display: block;
+  font-weight: bold;
+  top: 3px;
+  right: 10px;
+}
+.ow-dialog-close-x:hover {
+  color: #df5d43;
+}
+.ow-message-title {
+  color: #333;
+  margin-bottom: 10px;
+}
+.ow-message-title a {
+  color: #df5d43;
+}
+.ow-message-title a:hover {
+  text-decoration: underline;
+}
+.ow-dialog-buttons {
+  line-height: 3em;
+}
+
 @media screen and (max-width: 600px) {
   .ow-notification-dropdown {
     width: 98%;