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import { ClientConfig, Credentials } from "../mod.ts";import { kdf } from "./aws_signature_v4.ts";import { Doc, date } from "../util.ts";
/** Service name. */const SERVICE: string = "dynamodb";
/** Cache for credentialScope and expensive signature key. */export function createCache(conf: ClientConfig): Doc {  return {    _credentialScope: "",    _signingKey: null,    _accessKeyId: "",    _sessionToken: "",    async refresh(): Promise<void> {      const dateStamp: string = date.format(new Date(), "dateStamp");
      let credentials: Credentials;
      if (typeof conf.credentials === "function") {        credentials = await conf.credentials();      } else {        credentials = conf.credentials!;      }
      this._signingKey = kdf(        credentials.secretAccessKey,        dateStamp,        conf.region!,        SERVICE,      ) as Uint8Array;
      this._credentialScope =        `${dateStamp}/${conf.region}/${SERVICE}/aws4_request`;      this._accessKeyId = credentials.accessKeyId;      this._sessionToken = credentials.sessionToken;    },    get signingKey(): Uint8Array {      return this._signingKey;    },    get credentialScope(): string {      return this._credentialScope;    },    get accessKeyId(): string {      return this._accessKeyId;    },    get sessionToken(): string {      return this._sessionToken;    },  };}