add middleware

http-api/middlewares/audit_log_middleware.py

@@ -0,0 +1,95 @@
+from aws_lambda_powertools.event_handler.api_gateway import (
+    APIGatewayHttpResolver,
+    Response,
+)
+from aws_lambda_powertools.event_handler.middlewares import (
+    BaseMiddlewareHandler,
+    NextMiddleware,
+)
+from aws_lambda_powertools.shared.functions import (
+    extract_event_from_common_models,
+)
+from layercake.dateutils import now, ttl
+from layercake.dynamodb import (
+    ComposeKey,
+    DynamoDBCollection,
+    KeyPair,
+)
+from layercake.funcs import pick
+
+from .authorizer_middleware import User
+
+YEAR_DAYS = 365
+LOG_RETENTION_DAYS = YEAR_DAYS * 2
+
+
+class AuditLogMiddleware(BaseMiddlewareHandler):
+    """This middleware logs audit details for successful requests, storing user,
+    action, and IP info with a specified retention period.
+
+    Parameters
+    ----------
+    action : str
+        The identifier for the audit log action.
+    collect : DynamoDBCollection
+        The collection instance used to persist the audit log data.
+    audit_attrs : tuple of str, optional
+        A tuple of attribute names to extract from the response body for logging.
+        These represent the specific fields to include in the audit log.
+    retention_days : int or None, optional
+        The number of days the log is retained on the server.
+        If None, no time-to-live (TTL) will be applied.
+    """
+
+    def __init__(
+        self,
+        action: str,
+        /,
+        collect: DynamoDBCollection,
+        audit_attrs: tuple[str, ...] = (),
+        retention_days: int | None = LOG_RETENTION_DAYS,
+    ) -> None:
+        self.action = action
+        self.collect = collect
+        self.audit_attrs = audit_attrs
+        self.retention_days = retention_days
+
+    def handler(
+        self,
+        app: APIGatewayHttpResolver,
+        next_middleware: NextMiddleware,
+    ) -> Response:
+        user: User | None = app.context.get('user')
+        req_context = app.current_event.request_context
+        ip_addr = req_context.http.source_ip
+        response = next_middleware(app)
+
+        # Successful response
+        # https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status#successful_responses
+        if 200 <= response.status_code < 300 and user:
+            now_ = now()
+            data = (
+                pick(self.audit_attrs, extract_event_from_common_models(response.body))
+                if response.is_json()
+                else None
+            )
+            retention_days = (
+                ttl(start_dt=now_, days=self.retention_days)
+                if self.retention_days
+                else None
+            )
+
+            self.collect.put_item(
+                key=KeyPair(
+                    # Post-migration: remove `delimiter` and update prefix from `log` to `logs`
+                    # in ComposeKey.
+                    pk=ComposeKey(user.id, prefix='log', delimiter=':'),
+                    sk=now_.isoformat(),
+                ),
+                action=self.action,
+                data=data,
+                ip=ip_addr,
+                ttl=retention_days,
+            )
+
+        return response