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// Copyright 2023-latest the httpland authors. All rights reserved. MIT license.// This module is browser compatible.
import { isString, RepresentationHeader, stringifyETag } from "./deps.ts";import type { ComputeETag } from "./types.ts";
/** Response with `ETag` header field. * @param response Response * @param calculate Function to calculate ETag values. */export async function withEtag(  response: Response,  calculate: ComputeETag,): Promise<Response> {  if (    !response.ok ||    !response.body ||    response.bodyUsed ||    response.headers.has(RepresentationHeader.ETag)  ) return response;
  const etagLike = await calculate(response.clone());  const etag = isString(etagLike) ? etagLike : stringifyETag(etagLike);  const res = response.clone();
  res.headers.set(RepresentationHeader.ETag, etag);
  return res;}