VED-821 Refactor get by ID journey in line with cleaner design standards (#868)

Author: dlzhry2nhs

backend/src/controller/__init__.py

@@ -0,0 +1,27 @@
+"""Utility module for interacting with the AWS API Gateway event provided to controllers"""
+from typing import Optional
+
+from aws_lambda_typing.events import APIGatewayProxyEventV1
+
+from controller.constants import SUPPLIER_SYSTEM_HEADER_NAME
+from models.errors import UnauthorizedError
+from utils import dict_utils
+
+
+def get_path_parameter(event: APIGatewayProxyEventV1, param_name: str) -> str:
+    return dict_utils.get_field(
+        event["pathParameters"],
+        param_name,
+        default=""
+    )
+
+
+def get_supplier_system_header(event: APIGatewayProxyEventV1) -> str:
+    """Retrieves the supplier system header from the API Gateway event"""
+    supplier_system: Optional[str] = dict_utils.get_field(dict(event), "headers", SUPPLIER_SYSTEM_HEADER_NAME)
+
+    if supplier_system is None:
+        # SupplierSystem header must be provided for looking up permissions
+        raise UnauthorizedError()
+
+    return supplier_system

backend/src/controller/aws_apig_event_utils.py

@@ -0,0 +1,24 @@
+"""Utility module providing helper functions for dealing with response formats for AWS API Gateway"""
+import json
+from typing import Optional
+
+
+def create_response(
+    status_code: int,
+    body: Optional[dict | str] = None,
+    headers: Optional[dict] = None
+):
+    """Creates response body as per Lambda -> API Gateway proxy integration"""
+    if body is not None:
+        if isinstance(body, dict):
+            body = json.dumps(body)
+        if headers:
+            headers["Content-Type"] = "application/fhir+json"
+        else:
+            headers = {"Content-Type": "application/fhir+json"}
+
+    return {
+        "statusCode": status_code,
+        "headers": headers if headers else {},
+        **({"body": body} if body else {}),
+    }

backend/src/controller/aws_apig_response_utils.py

@@ -0,0 +1,5 @@
+"""FHIR Controller constants"""
+
+
+SUPPLIER_SYSTEM_HEADER_NAME = "SupplierSystem"
+E_TAG_HEADER_NAME = "E-Tag"

backend/src/controller/constants.py

@@ -0,0 +1,42 @@
+"""Module for the global FHIR API exception handler"""
+import functools
+import uuid
+from typing import Callable, Type
+
+from clients import logger
+from constants import GENERIC_SERVER_ERROR_DIAGNOSTICS_MESSAGE
+from controller.aws_apig_response_utils import create_response
+from models.errors import UnauthorizedVaxError, UnauthorizedError, ResourceNotFoundError, create_operation_outcome, \
+    Severity, Code
+
+
+_CUSTOM_EXCEPTION_TO_STATUS_MAP: dict[Type[Exception], int] = {
+    UnauthorizedError: 403,
+    UnauthorizedVaxError: 403,
+    ResourceNotFoundError: 404
+}
+
+
+def fhir_api_exception_handler(function: Callable) -> Callable:
+    """Decorator to handle any expected FHIR API exceptions or unexpected exception and provide a valid response to
+    the client"""
+
+    @functools.wraps(function)
+    def wrapper(*args, **kwargs):
+        try:
+            return function(*args, **kwargs)
+        except tuple(_CUSTOM_EXCEPTION_TO_STATUS_MAP) as exc:
+            status_code = _CUSTOM_EXCEPTION_TO_STATUS_MAP[type(exc)]
+            return create_response(status_code=status_code, body=exc.to_operation_outcome())
+        except Exception:  # pylint: disable = broad-exception-caught
+            logger.exception("Unhandled exception")
+            server_error = create_operation_outcome(
+                resource_id=str(uuid.uuid4()),
+                severity=Severity.error,
+                code=Code.server_error,
+                diagnostics=GENERIC_SERVER_ERROR_DIAGNOSTICS_MESSAGE,
+            )
+            return create_response(500, server_error)
+
+    return wrapper
+

backend/src/controller/fhir_api_exception_handler.py

@@ -1,7 +1,7 @@
 """Function to send the request directly to lambda (or return appropriate diagnostics if this is not possible)"""
 
-from fhir_batch_service import ImmunizationBatchService
-from fhir_batch_repository import ImmunizationBatchRepository
+from service.fhir_batch_service import ImmunizationBatchService
+from repository.fhir_batch_repository import ImmunizationBatchRepository
 
 
 def make_batch_controller():