init comment-service

services/comment-service/comment_service/models/exceptions.py

@@ -0,0 +1,59 @@
+from enum import Enum, auto
+
+from grpc import RpcContext, StatusCode
+
+
+class ServiceErrorCode(Enum):
+    """Error codes used for classifying ServiceExceptions."""
+    INVALID_ARGUMENT = auto()
+    CONFLICT = auto()
+    NOT_FOUND = auto()
+    INVALID_CREDENTIALS = auto()
+    SERVICE_ERROR = auto()
+
+    __RPC_CODE_MAP__ = {
+        INVALID_ARGUMENT: StatusCode.INVALID_ARGUMENT,
+        CONFLICT: StatusCode.ALREADY_EXISTS,
+        NOT_FOUND: StatusCode.NOT_FOUND,
+        INVALID_CREDENTIALS: StatusCode.UNAUTHENTICATED,
+        SERVICE_ERROR: StatusCode.INTERNAL
+    }
+
+    def to_rpc_code(self) -> StatusCode:
+        """Convert a service error code to a gRPC status code.
+
+        Returns:
+            The mapped RPC status code, if found, otherwise gRPC Unknown status code.
+
+        """
+        return self.__class__.__RPC_CODE_MAP__.get(self.value, StatusCode.UNKNOWN)
+
+
+class ServiceException(Exception):
+    """This exception provides an interface to convert service errors 
+    into gRPC errors, which can then be returned to the caller.
+
+    Args:
+        msg (str): Error message.
+        error_code (ServiceErrorCode): Categorisation code for the error.
+    
+    Attributes:
+        msg (str): The error message.
+        error_code (ServiceErrorCode): Categorisation code for the error.
+    
+    """
+
+    def __init__(self, msg: str, error_code: ServiceErrorCode) -> None:
+        super().__init__(msg)
+        self.msg = msg
+        self.error_code = error_code
+
+    def apply_to_rpc(self, context: RpcContext) -> None:
+        """Apply the exception to an RPC context.
+        
+        Args:
+            context (grpc.RpcContext): The context to apply to.
+        
+        """
+        context.set_code(self.error_code.to_rpc_code())
+        context.set_details(self.msg)