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import { decode as base64url } from './base64url.ts'import { decoder } from '../lib/buffer_utils.ts'import isObject from '../lib/is_object.ts'import type { JWSHeaderParameters, JWEHeaderParameters } from '../types.d.ts'
export type ProtectedHeaderParameters = JWSHeaderParameters & JWEHeaderParameters
/** * Decodes the Protected Header of a JWE/JWS/JWT token utilizing any JOSE serialization. * * @param token JWE/JWS/JWT token in any JOSE serialization. */export function decodeProtectedHeader(token: string | object) {  let protectedB64u!: unknown
  if (typeof token === 'string') {    const parts = token.split('.')    if (parts.length === 3 || parts.length === 5) {      ;[protectedB64u] = parts    }  } else if (typeof token === 'object' && token) {    if ('protected' in token) {      protectedB64u = token.protected    } else {      throw new TypeError('Token does not contain a Protected Header')    }  }
  try {    if (typeof protectedB64u !== 'string' || !protectedB64u) {      throw new Error()    }    const result = JSON.parse(decoder.decode(base64url(protectedB64u!)))    if (!isObject(result)) {      throw new Error()    }    return <ProtectedHeaderParameters>result  } catch {    throw new TypeError('Invalid Token or Protected Header formatting')  }}