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import type { Algorithm } from "./algorithm.ts";import {  base64url,  convertHexToUint8Array,  HmacSha256,  HmacSha512,  RSA,} from "./deps.ts";
function assertNever(alg: never, message: string): never {  throw new RangeError(message);}
export function convertHexToBase64url(input: string): string {  return base64url.encode(convertHexToUint8Array(input));}
/** * Do a constant time string comparison. Always compare the complete strings * against each other to get a constant time. This method does not short-cut * if the two string's length differs. * CREDIT: https://github.com/Bruce17/safe-compare */function safeCompare(a: string, b: string) {  const strA = String(a);  const lenA = strA.length;  let strB = String(b);  let result = 0;
  if (lenA !== strB.length) {    strB = strA;    result = 1;  }
  for (let i = 0; i < lenA; i++) {    result |= (strA.charCodeAt(i) ^ strB.charCodeAt(i));  }
  return result === 0;}
async function encrypt(  algorithm: Algorithm,  key: string,  message: string,): Promise<string> {  switch (algorithm) {    case "none":      return "";    case "HS256":      return new HmacSha256(key).update(message).toString();    case "HS512":      return new HmacSha512(key).update(message).toString();    case "RS256":      return (        await new RSA(RSA.parseKey(key)).sign(message, { hash: "sha256" })      ).hex();    default:      assertNever(        algorithm,        "no matching crypto algorithm in the header: " + algorithm,      );  }}
export async function create(  algorithm: Algorithm,  key: string,  input: string,): Promise<string> {  return convertHexToBase64url(await encrypt(algorithm, key, input));}
export async function verify({  signature,  key,  algorithm,  signingInput,}: {  signature: string;  key: string;  algorithm: Algorithm;  signingInput: string;}): Promise<boolean> {  switch (algorithm) {    case "none":    case "HS256":    case "HS512": {      return safeCompare(        signature,        (await encrypt(algorithm, key, signingInput)),      );    }    case "RS256": {      return await new RSA(RSA.parseKey(key)).verify(        convertHexToUint8Array(signature),        signingInput,        { hash: "sha256" },      );    }    default:      assertNever(        algorithm,        "no matching crypto algorithm in the header: " + algorithm,      );  }}