chore: add flexibleChecksumsInterceptorMiddleware to populate input[r…

…equestValidationModeMember]

packages/middleware-flexible-checksums/src/configuration.ts

@@ -9,7 +9,7 @@ import {
   StreamHasher,
 } from "@smithy/types";
 
-import { RequestChecksumCalculation } from "./constants";
+import { RequestChecksumCalculation, ResponseChecksumValidation } from "./constants";
 
 export interface PreviouslyResolved {
   /**
@@ -39,6 +39,11 @@ export interface PreviouslyResolved {
    */
   requestChecksumCalculation: Provider<RequestChecksumCalculation>;
 
+  /**
+   * Determines when a checksum will be calculated for response payloads
+   */
+  responseChecksumValidation: Provider<ResponseChecksumValidation>;
+
   /**
    * A constructor for a class implementing the {@link Hash} interface that computes SHA1 hashes.
    * @internal

packages/middleware-flexible-checksums/src/flexibleChecksumsInterceptorMiddleware.ts

@@ -0,0 +1,62 @@
+import {
+  HandlerExecutionContext,
+  MetadataBearer,
+  RelativeMiddlewareOptions,
+  SerializeHandler,
+  SerializeHandlerArguments,
+  SerializeHandlerOutput,
+  SerializeMiddleware,
+} from "@smithy/types";
+
+import { PreviouslyResolved } from "./configuration";
+import { ResponseChecksumValidation } from "./constants";
+
+export interface FlexibleChecksumsInterceptorMiddlewareConfig {
+  /**
+   * Defines a top-level operation input member used to opt-in to best-effort validation
+   * of a checksum returned in the HTTP response of the operation.
+   */
+  requestValidationModeMember?: string;
+}
+
+/**
+ * @internal
+ */
+export const flexibleChecksumsInterceptorMiddlewareOptions: RelativeMiddlewareOptions = {
+  name: "flexibleChecksumsInterceptorMiddleware",
+  toMiddleware: "serializerMiddleware",
+  relation: "before",
+  tags: ["BODY_CHECKSUM"],
+  override: true,
+};
+
+/**
+ * @internal
+ *
+ * The interceptor counterpart to the flexibleChecksumsMiddleware.
+ */
+export const flexibleChecksumsInterceptorMiddleware =
+  (
+    config: PreviouslyResolved,
+    middlewareConfig: FlexibleChecksumsInterceptorMiddlewareConfig
+  ): SerializeMiddleware<any, any> =>
+  <Output extends MetadataBearer>(
+    next: SerializeHandler<any, Output>,
+    context: HandlerExecutionContext
+  ): SerializeHandler<any, Output> =>
+  async (args: SerializeHandlerArguments<any>): Promise<SerializeHandlerOutput<Output>> => {
+    const input = args.input;
+    const { requestValidationModeMember } = middlewareConfig;
+    const responseChecksumValidation = await config.responseChecksumValidation();
+
+    const isResponseChecksumValidationNeeded =
+      requestValidationModeMember &&
+      (input[requestValidationModeMember] === "ENABLED" ||
+        responseChecksumValidation === ResponseChecksumValidation.WHEN_SUPPORTED);
+
+    if (isResponseChecksumValidationNeeded) {
+      input[requestValidationModeMember] = "ENABLED";
+    }
+
+    return next(args);
+  };

packages/middleware-flexible-checksums/src/getFlexibleChecksumsPlugin.ts

@@ -1,6 +1,10 @@
 import { Pluggable } from "@smithy/types";
 
 import { PreviouslyResolved } from "./configuration";
+import {
+  flexibleChecksumsInterceptorMiddleware,
+  flexibleChecksumsInterceptorMiddlewareOptions,
+} from "./flexibleChecksumsInterceptorMiddleware";
 import {
   flexibleChecksumsMiddleware,
   flexibleChecksumsMiddlewareOptions,
@@ -22,6 +26,10 @@ export const getFlexibleChecksumsPlugin = (
 ): Pluggable<any, any> => ({
   applyToStack: (clientStack) => {
     clientStack.add(flexibleChecksumsMiddleware(config, middlewareConfig), flexibleChecksumsMiddlewareOptions);
+    clientStack.addRelativeTo(
+      flexibleChecksumsInterceptorMiddleware(config, middlewareConfig),
+      flexibleChecksumsInterceptorMiddlewareOptions
+    );
     clientStack.addRelativeTo(
       flexibleChecksumsResponseMiddleware(config, middlewareConfig),
       flexibleChecksumsResponseMiddlewareOptions