private AuthenticationSequence(User user, AuthenticationMethod completed)
{
User = user;
remaining = new HashSet <AuthenticationMethod>(
user.AuthenticationMethods);
if (!remaining.Remove(completed))
{
throw new ArgumentException("Cannot start authentication sequence "
+ "with an authentication method the user doesn't have");
}
NextAuthenticationMethod = remaining.First();
}
/// <summary>
/// Begin an authentication sequence using the given authentication method.
/// </summary>
/// <param name="authenticationMethod">
/// The authentication method presented. Can be a <see cref="Card"/> or a
/// <see cref="BluetoothDevice"/>.
/// </param>
/// <returns>
/// An <see cref="AuthenticationSequence"/> if there exists a user with the
/// given authentication method, or <c>null</c> otherwise.
/// </returns>
public static AuthenticationSequence Start(
AuthenticationMethod authenticationMethod)
{
long?nullableUserId = Backend.GetUserIdForAuthenticationMethod(
authenticationMethod ?? throw new ArgumentNullException(
"authenticationMethod"));
if (nullableUserId is long userId)
{
return(new AuthenticationSequence(
new User(userId), authenticationMethod));
}
return(null);
}
/// <summary>
/// Continue the authentication sequence with this authentication method.
/// </summary>
/// <returns>
/// <c>true</c> if the authentication method was accepted, or <c>false</c>
/// otherwise.
/// </returns>
/// <remarks>
/// If this method returns <c>true</c>, do not assume that the user has been
/// successfully authenticated. Instead, check
/// <see cref="AuthenticationSequence.NextAuthenticationMethod"/>, which is
/// <c>null</c> if authentication is successful or otherwise indicates the
/// next authentication method the user must present.
/// </remarks>
public bool Continue(
AuthenticationMethod authenticationMethod)
{
if (!remaining.Remove(authenticationMethod
?? throw new ArgumentNullException("authenticationMethod")))
{
return(false);
}
if (remaining.Count == 0)
{
NextAuthenticationMethod = null;
return(true);
}
NextAuthenticationMethod = remaining.First();
return(true);
}