function credentialFromObject()

in packages/auth-compat/src/user_credential.ts [54:139]
74 lines of code
19 McCabe index (conditional complexity)

function credentialFromObject(
  object: FirebaseError | exp.UserCredential
): exp.AuthCredential | null {
  const { _tokenResponse } = (
    object instanceof FirebaseError ? object.customData : object
  ) as exp.TaggedWithTokenResponse;
  if (!_tokenResponse) {
    return null;
  }

  // Handle phone Auth credential responses, as they have a different format
  // from other backend responses (i.e. no providerId). This is also only the
  // case for user credentials (does not work for errors).
  if (!(object instanceof FirebaseError)) {
    if ('temporaryProof' in _tokenResponse && 'phoneNumber' in _tokenResponse) {
      return exp.PhoneAuthProvider.credentialFromResult(object);
    }
  }

  const providerId = _tokenResponse.providerId;

  // Email and password is not supported as there is no situation where the
  // server would return the password to the client.
  if (!providerId || providerId === exp.ProviderId.PASSWORD) {
    return null;
  }

  let provider: Pick<
    typeof exp.OAuthProvider,
    'credentialFromResult' | 'credentialFromError'
  >;
  switch (providerId) {
    case exp.ProviderId.GOOGLE:
      provider = exp.GoogleAuthProvider;
      break;
    case exp.ProviderId.FACEBOOK:
      provider = exp.FacebookAuthProvider;
      break;
    case exp.ProviderId.GITHUB:
      provider = exp.GithubAuthProvider;
      break;
    case exp.ProviderId.TWITTER:
      provider = exp.TwitterAuthProvider;
      break;
    default:
      const {
        oauthIdToken,
        oauthAccessToken,
        oauthTokenSecret,
        pendingToken,
        nonce
      } = _tokenResponse as exp.SignInWithIdpResponse;
      if (
        !oauthAccessToken &&
        !oauthTokenSecret &&
        !oauthIdToken &&
        !pendingToken
      ) {
        return null;
      }
      // TODO(avolkovi): uncomment this and get it working with SAML & OIDC
      if (pendingToken) {
        if (providerId.startsWith('saml.')) {
          return exp.SAMLAuthCredential._create(providerId, pendingToken);
        } else {
          // OIDC and non-default providers excluding Twitter.
          return exp.OAuthCredential._fromParams({
            providerId,
            signInMethod: providerId,
            pendingToken,
            idToken: oauthIdToken,
            accessToken: oauthAccessToken
          });
        }
      }
      return new exp.OAuthProvider(providerId).credential({
        idToken: oauthIdToken,
        accessToken: oauthAccessToken,
        rawNonce: nonce
      });
  }

  return object instanceof FirebaseError
    ? provider.credentialFromError(object)
    : provider.credentialFromResult(object);
}