Notify users who have starred a part when that part's stock quantity falls below the minimum quanitity/threshold through email.

InvenTree/InvenTree/tasks.py

@@ -11,6 +11,7 @@ from django.utils import timezone
 
 from django.core.exceptions import AppRegistryNotReady
 from django.db.utils import OperationalError, ProgrammingError
+from django.template.loader import render_to_string
 
 
 logger = logging.getLogger("inventree")
@@ -52,7 +53,7 @@ def schedule_task(taskname, **kwargs):
         pass
 
 
-def offload_task(taskname, force_sync=False, *args, **kwargs):
+def offload_task(taskname, *args, force_sync=False, **kwargs):
     """
         Create an AsyncTask if workers are running.
         This is different to a 'scheduled' task,
@@ -290,7 +291,7 @@ def update_exchange_rates():
     Rate.objects.filter(backend="InvenTreeExchange").exclude(currency__in=currency_codes()).delete()
 
 
-def send_email(subject, body, recipients, from_email=None):
+def send_email(subject, body, recipients, from_email=None, html_message=None):
     """
     Send an email with the specified subject and body,
     to the specified recipients list.
@@ -306,4 +307,35 @@ def send_email(subject, body, recipients, from_email=None):
         from_email,
         recipients,
         fail_silently=False,
+        html_message=html_message
     )
+
+
+def notify_low_stock(stock_item):
+    """
+    Notify users who have starred a part when its stock quantity falls below the minimum threshold
+    """
+
+    from allauth.account.models import EmailAddress
+    starred_users = EmailAddress.objects.filter(user__starred_parts__part=stock_item.part)
+
+    if len(starred_users) > 0:
+        logger.info(f"Notify users regarding low stock of {stock_item.part.name}")
+        body = f'Hi, {stock_item.part.name} is low on stock. Kindly do the needful.'
+        context = {
+            'part_name': stock_item.part.name,
+            # Part url can be used to open the page of part in application from the email.
+            # It can be facilitated when the application base url is accessible programmatically.
+            # 'part_url': f'{application_base_url}/part/{stock_item.part.id}',
+
+            'message': body,
+
+            # quantity is in decimal field datatype. Since the same datatype is used in models,
+            # it is not converted to number/integer,
+            'part_quantity': stock_item.quantity,
+            'minimum_quantity': stock_item.part.minimum_stock
+        }
+        subject = f'Attention! {stock_item.part.name} is low on stock'
+        html_message = render_to_string('stock/low_stock_notification.html', context)
+        recipients = starred_users.values_list('email', flat=True)
+        send_email(subject, body, recipients, html_message=html_message)

InvenTree/stock/models.py

@@ -17,7 +17,7 @@ from django.db.models import Sum, Q
 from django.db.models.functions import Coalesce
 from django.core.validators import MinValueValidator
 from django.contrib.auth.models import User
-from django.db.models.signals import pre_delete
+from django.db.models.signals import pre_delete, post_save
 from django.dispatch import receiver
 
 from markdownx.models import MarkdownxField
@@ -36,6 +36,7 @@ import label.models
 from InvenTree.status_codes import StockStatus, StockHistoryCode
 from InvenTree.models import InvenTreeTree, InvenTreeAttachment
 from InvenTree.fields import InvenTreeModelMoneyField, InvenTreeURLField
+from InvenTree import tasks as inventree_tasks
 
 from users.models import Owner
 
@@ -1651,6 +1652,17 @@ def before_delete_stock_item(sender, instance, using, **kwargs):
         child.save()
 
 
+@receiver(post_save, sender=StockItem)
+def after_save_stock_item(sender, instance: StockItem, **kwargs):
+    """
+    Check if the stock quantity has fallen below the minimum threshold of part. If yes, notify the users who have
+    starred the part
+    """
+
+    if instance.quantity <= instance.part.minimum_stock:
+        inventree_tasks.notify_low_stock(instance)
+
+
 class StockItemAttachment(InvenTreeAttachment):
     """
     Model for storing file attachments against a StockItem object.

InvenTree/stock/templates/stock/low_stock_notification.html

@@ -0,0 +1,27 @@
+<p>{{ message }}</p>
+
+<table style="border-collapse:collapse; width: 80%;margin-left: 10%; font-size: 1rem">
+
+    <tr style="background: aliceblue; height: 4rem;">
+        <th colspan="3" style="padding-bottom: 1rem; font-size: 1.5rem; color:rgb(210,0, 0)">Part low on stock</th>
+    </tr>
+
+    <tr style="height: 3rem; border-bottom: 1px solid">
+        <th>Part Name</th>
+        <th>Available Quantity</th>
+        <th>Minimum Quantity</th>
+    </tr>
+
+    <tr style="height: 3rem">
+        <td style="text-align: center">{{ part_name }}</td>
+        <td style="text-align: center">{{ part_quantity }}</td>
+        <td style="text-align: center">{{ minimum_quantity }}</td>
+    </tr>
+
+    <tr style="background-color: aliceblue;height: 4rem;">
+        <td colspan="3" style="padding-top:1rem; text-align: center">You are receiving this mail because you have starred the part {{ part_name }} in
+            Inventree application</td>
+    </tr>
+
+</table>
+