feat: [FC-0047] add functionality to send push notifications

edx_ace/ace.py

@@ -19,12 +19,18 @@
     )
     ace.send(msg)
 """
+import logging
+
+from django.template import TemplateDoesNotExist
+
 from edx_ace import delivery, policy, presentation
 from edx_ace.channel import get_channel_for_message
 from edx_ace.errors import ChannelError, UnsupportedChannelError
 
+log = logging.getLogger(__name__)
+
 
-def send(msg):
+def send(msg, limit_to_channels=None):
     """
     Send a message to a recipient.
 
@@ -37,19 +43,32 @@ def send(msg):
 
     Args:
         msg (Message): The message to send.
+        limit_to_channels (list of ChannelType, optional): If provided, only send the message over the specified
+            channels. If not provided, the message will be sent over all channels that the policies allow.
     """
     msg.report_basics()
 
     channels_for_message = policy.channels_for(msg)
 
     for channel_type in channels_for_message:
+        if limit_to_channels and channel_type not in limit_to_channels:
+            log.info('Skipping channel %s', channel_type)
+
         try:
             channel = get_channel_for_message(channel_type, msg)
         except UnsupportedChannelError:
             continue
 
         try:
             rendered_message = presentation.render(channel, msg)
+        except TemplateDoesNotExist as error:
+            msg.report(
+                'template_error',
+                'Unable to send message because template not found\n' + str(error)
+            )
+            continue
+
+        try:
             delivery.deliver(channel, rendered_message, msg)
         except ChannelError as error:
             msg.report(

edx_ace/channel/__init__.py

@@ -78,6 +78,7 @@ class ChannelMap:
     """
     A class that represents a channel map, usually as described in Django settings and `setup.py` files.
     """
+
     def __init__(self, channels_list):
         """
         Initialize a ChannelMap.
@@ -170,27 +171,29 @@ def get_channel_for_message(channel_type, message):
         Channel: The selected channel object.
     """
     channels_map = channels()
+    channel_names = []
 
     if channel_type == ChannelType.EMAIL:
         if message.options.get('transactional'):
             channel_names = [settings.ACE_CHANNEL_TRANSACTIONAL_EMAIL, settings.ACE_CHANNEL_DEFAULT_EMAIL]
         else:
             channel_names = [settings.ACE_CHANNEL_DEFAULT_EMAIL]
 
-        try:
-            possible_channels = [
-                channels_map.get_channel_by_name(channel_type, channel_name)
-                for channel_name in channel_names
-            ]
-        except KeyError:
-            return channels_map.get_default_channel(channel_type)
-
-        # First see if any channel specifically demands to deliver this message
-        for channel in possible_channels:
-            if channel.overrides_delivery_for_message(message):
-                return channel
-
-        # Else the normal path: use the preferred channel for this message type
-        return possible_channels[0]
-
-    return channels_map.get_default_channel(channel_type)
+    if channel_type == ChannelType.PUSH:
+        channel_names = [settings.ACE_CHANNEL_DEFAULT_PUSH]
+
+    try:
+        possible_channels = [
+            channels_map.get_channel_by_name(channel_type, channel_name)
+            for channel_name in channel_names
+        ]
+    except KeyError:
+        return channels_map.get_default_channel(channel_type)
+
+    # First see if any channel specifically demands to deliver this message
+    for channel in possible_channels:
+        if channel.overrides_delivery_for_message(message):
+            return channel
+
+    # Else the normal path: use the preferred channel for this message type
+    return possible_channels[0] if possible_channels else channels_map.get_default_channel(channel_type)

edx_ace/channel/push_notification.py

@@ -0,0 +1,110 @@
+"""
+Channel for sending push notifications.
+"""
+import logging
+import re
+
+from firebase_admin.messaging import APNSConfig, APNSPayload, Aps, ApsAlert
+from push_notifications.gcm import dict_to_fcm_message, send_message
+from push_notifications.models import GCMDevice
+
+from django.conf import settings
+
+from edx_ace.channel import Channel, ChannelType
+from edx_ace.errors import FatalChannelDeliveryError
+from edx_ace.message import Message
+from edx_ace.renderers import RenderedPushNotification
+
+LOG = logging.getLogger(__name__)
+APNS_DEFAULT_PRIORITY = '5'
+APNS_DEFAULT_PUSH_TYPE = 'alert'
+
+
+class PushNotificationChannel(Channel):
+    """
+    A channel for sending push notifications.
+    """
+
+    channel_type = ChannelType.PUSH
+
+    @classmethod
+    def enabled(cls):
+        """
+        Returns true if the push notification settings are configured.
+        """
+        return bool(getattr(settings, 'PUSH_NOTIFICATIONS_SETTINGS', None))
+
+    def deliver(self, message: Message, rendered_message: RenderedPushNotification) -> None:
+        """
+        Transmit a rendered message to a recipient.
+
+        Args:
+            message: The message to transmit.
+            rendered_message: The rendered content of the message that has been personalized
+                for this particular recipient.
+        """
+        device_tokens = self.get_user_device_tokens(message.recipient.lms_user_id)
+        if not device_tokens:
+            LOG.info(
+                'Recipient with ID %s has no push token. Skipping push notification.',
+                message.recipient.lms_user_id
+            )
+            return
+
+        for token in device_tokens:
+            self.send_message(message, token, rendered_message)
+
+    def send_message(self, message: Message, token: str, rendered_message: RenderedPushNotification) -> None:
+        """
+        Send a push notification to a device by token.
+        """
+        notification_data = {
+            'title': self.compress_spaces(rendered_message.title),
+            'body': self.compress_spaces(rendered_message.body),
+            'notification_key': token,
+            **message.context.get('push_notification_extra_context', {}),
+        }
+        message = dict_to_fcm_message(notification_data)
+        # Note: By default dict_to_fcm_message does not support APNS configuration,
+        #   only Android configuration, so we need to collect and set it manually.
+        apns_config = self.collect_apns_config(notification_data)
+        message.apns = apns_config
+        try:
+            send_message(token, message, settings.FCM_APP_NAME)
+        except Exception as e:
+            LOG.exception('Failed to send push notification to %s', token)
+            raise FatalChannelDeliveryError(f'Failed to send push notification to {token}') from e
+
+    @staticmethod
+    def collect_apns_config(notification_data: dict) -> APNSConfig:
+        """
+        Collect APNS configuration with payload for the push notification.
+
+        This APNSConfig must be set to notifications for Firebase to send push notifications to iOS devices.
+        Notification has default priority and visibility settings, described in Apple's documentation.
+        (https://developer.apple.com/documentation/usernotifications/sending-notification-requests-to-apns)
+        """
+        apns_alert = ApsAlert(title=notification_data['title'], body=notification_data['body'])
+        aps = Aps(alert=apns_alert, sound='default')
+        return APNSConfig(
+            headers={'apns-priority': APNS_DEFAULT_PRIORITY, 'apns-push-type': APNS_DEFAULT_PUSH_TYPE},
+            payload=APNSPayload(aps)
+        )
+
+    @staticmethod
+    def get_user_device_tokens(user_id: int) -> list:
+        """
+        Get the device tokens for a user.
+        """
+        return list(GCMDevice.objects.filter(
+            user_id=user_id,
+            cloud_message_type='FCM',
+            active=True,
+        ).values_list('registration_id', flat=True))
+
+    @staticmethod
+    def compress_spaces(html_str: str) -> str:
+        """
+        Compress spaces and remove newlines to make it easier to author templates.
+        """
+        return re.sub('\\s+', ' ', html_str, re.UNICODE).strip()

edx_ace/presentation.py

@@ -9,6 +9,7 @@
 
 RENDERERS = {
     ChannelType.EMAIL: renderers.EmailRenderer(),
+    ChannelType.PUSH: renderers.PushNotificationRenderer(),
 }
 
 

edx_ace/push_notifications/views/__init__.py

@@ -0,0 +1 @@
+from push_notifications.api.rest_framework import GCMDeviceViewSet

edx_ace/renderers.py

@@ -81,3 +81,21 @@ class EmailRenderer(AbstractRenderer):
     A renderer for :attr:`.ChannelType.EMAIL` channels.
     """
     rendered_message_cls = RenderedEmail
+
+
+@attr.s
+class RenderedPushNotification:
+    """
+    Encapsulates all values needed to send a :class:`.Message`
+    over an :attr:`.ChannelType.PUSH`.
+    """
+
+    title = attr.ib()
+    body = attr.ib()
+
+
+class PushNotificationRenderer(AbstractRenderer):
+    """
+    A renderer for :attr:`.ChannelType.PUSH` channels.
+    """
+    rendered_message_cls = RenderedPushNotification

edx_ace/tests/channel/test_channel_helpers.py

@@ -39,6 +39,7 @@ def setUp(self):
         },
         ACE_CHANNEL_DEFAULT_EMAIL='braze_email',
         ACE_CHANNEL_TRANSACTIONAL_EMAIL='file_email',
+        ACE_CHANNEL_DEFAULT_PUSH='push_notification',
     )
     def test_get_channel_for_message(self):
         channel_map = ChannelMap([