code: /*
   * Copyright (c) 2019 the Eclipse Milo Authors
   *
   * This program and the accompanying materials are made
   * available under the terms of the Eclipse Public License 2.0
   * which is available at https://www.eclipse.org/legal/epl-2.0/
   *
   * SPDX-License-Identifier: EPL-2.0
   */
  
  package org.eclipse.milo.opcua.sdk.client.api.identity;
  
  import java.util.List;
  
  import org.eclipse.milo.opcua.stack.core.types.builtin.ByteString;
  import org.eclipse.milo.opcua.stack.core.types.enumerated.UserTokenType;
  import org.eclipse.milo.opcua.stack.core.types.structured.AnonymousIdentityToken;
  import org.eclipse.milo.opcua.stack.core.types.structured.EndpointDescription;
  import org.eclipse.milo.opcua.stack.core.types.structured.SignatureData;
  import org.eclipse.milo.opcua.stack.core.types.structured.UserIdentityToken;
  import org.eclipse.milo.opcua.stack.core.types.structured.UserTokenPolicy;
  
  import static org.eclipse.milo.opcua.stack.core.util.ConversionUtil.l;
  
  /**
   * An {@link IdentityProvider} that will choose the first available anonymous {@link UserTokenPolicy}.
   */
  public class AnonymousProvider implements IdentityProvider {
  
      public static final IdentityProvider INSTANCE = new AnonymousProvider();
  
      @Override
      public SignedIdentityToken getIdentityToken(
          EndpointDescription endpoint,
          ByteString serverNonce) throws Exception {
  
          List<UserTokenPolicy> userIdentityTokens = l(endpoint.getUserIdentityTokens());
  
          return userIdentityTokens.stream()
              .filter(t -> t.getTokenType() == UserTokenType.Anonymous)
              .findFirst()
              .map(policy -> {
                  UserIdentityToken token = new AnonymousIdentityToken(policy.getPolicyId());
  
                  return new SignedIdentityToken(token, new SignatureData(null, null));
              })
              .orElseThrow(() -> new Exception("no anonymous token policy found"));
      }
  
      @Override
      public String toString() {
          return "AnonymousProvider{}";
      }
  
  }
  