fix: handle no gateway priority configured case

app/services/handlers/abstract_handler.py

@@ -4,7 +4,10 @@
 
 from app.commons.logging.types import AsyncLoggerContextCreator, LogRecord
 from app.constants import HTTPStatusCodes
-from app.services.handlers.gateway_priority import PriorityGatewaySelection
+from app.services.handlers.gateway_priority import (
+    NoGatewayPriorityConfigured,
+    PriorityGatewaySelection,
+)
 from app.services.handlers.notifier import Notifier
 
 logger = logging.getLogger()
@@ -81,10 +84,22 @@ async def notify(cls, to, message, **kwargs):
         # If log_info is not present use log_id as `-1``
         log_info = kwargs.pop("log_info", LogRecord(log_id="-1"))
         provider, response = None, None
-        for n_attempts in range(cls.ENABLED_GATEWAYS_COUNT):
-            gateway = cls.select_gateway(
-                n_attempts, cls._get_priority_logic_data(to, **kwargs)
+        if not cls.ENABLED_GATEWAYS_COUNT:
+            logger.error(
+                "No gateways enabled for channel %s; cannot send notification.",
+                cls.CHANNEL,
             )
+            return provider, response
+        for n_attempts in range(cls.ENABLED_GATEWAYS_COUNT):
+            try:
+                gateway = cls.select_gateway(
+                    n_attempts, cls._get_priority_logic_data(to, **kwargs)
+                )
+            except NoGatewayPriorityConfigured as exc:
+                logger.error(
+                    "Skipping send for channel %s: %s", cls.CHANNEL, exc,
+                )
+                return provider, response
             provider = cls.PROVIDERS[gateway]
             response = await provider.send_notification(to, message, **kwargs)
             async with cls.logger as log:

app/services/handlers/gateway_priority.py

@@ -1,5 +1,12 @@
+import logging
 from abc import ABC, abstractmethod
 
+logger = logging.getLogger(__name__)
+
+
+class NoGatewayPriorityConfigured(Exception):
+    """Raised when a channel has no gateway priority configured."""
+
 
 class PriorityGatewaySelection(ABC):
     """
@@ -39,15 +46,30 @@ def select_gateway(cls, n_attempts: int, request_data: dict) -> str:
 
         """
         priority_logic_expression = cls.get_priority_logic()
-        current_priority = cls.get_default_priority()
+        default_priority = cls.get_default_priority() or []
+        current_priority = list(default_priority)
         if priority_logic_expression:
             # execute the priority logic to get the priority order of gateways
             try:
                 # Never delete the 'data' declaration below. It is used in the eval statement.
                 data = request_data
                 current_priority = eval(priority_logic_expression)
-            except Exception:
-                # Log the exception and fallback to default priority order
-                pass
-        total_gateways = min(len(cls.get_default_priority()), len(current_priority))
+            except Exception as exc:
+                logger.warning(
+                    "Priority logic evaluation failed for channel %s; falling back to default priority. Error: %s",
+                    cls.__name__,
+                    exc,
+                )
+                current_priority = list(default_priority)
+
+        if not current_priority or not default_priority:
+            logger.error(
+                "No gateway priority configured for channel %s; cannot select a gateway.",
+                cls.__name__,
+            )
+            raise NoGatewayPriorityConfigured(
+                f"No gateway priority configured for channel {cls.__name__}"
+            )
+
+        total_gateways = min(len(default_priority), len(current_priority))
         return current_priority[n_attempts % total_gateways]