/*
    * ====================================================================
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.hc.client5.http.impl;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  
  import org.apache.hc.client5.http.AuthenticationStrategy;
  import org.apache.hc.client5.http.auth.AuthChallenge;
  import org.apache.hc.client5.http.auth.AuthScheme;
  import org.apache.hc.client5.http.auth.AuthSchemeFactory;
  import org.apache.hc.client5.http.auth.StandardAuthScheme;
  import org.apache.hc.client5.http.auth.ChallengeType;
  import org.apache.hc.client5.http.config.RequestConfig;
  import org.apache.hc.client5.http.protocol.HttpClientContext;
  import org.apache.hc.core5.annotation.Contract;
  import org.apache.hc.core5.annotation.ThreadingBehavior;
  import org.apache.hc.core5.http.config.Lookup;
  import org.apache.hc.core5.http.protocol.HttpContext;
  import org.apache.hc.core5.util.Args;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Default implementation of {@link AuthenticationStrategy}
   *
   * @since 5.0
   */
  @Contract(threading = ThreadingBehavior.STATELESS)
  public class DefaultAuthenticationStrategy implements AuthenticationStrategy {
  
      private static final Logger LOG = LoggerFactory.getLogger(DefaultAuthenticationStrategy.class);
  
      public static final DefaultAuthenticationStrategycationStrategy.html#DefaultAuthenticationStrategy">DefaultAuthenticationStrategy INSTANCE = new DefaultAuthenticationStrategy();
  
      private static final List<String> DEFAULT_SCHEME_PRIORITY =
          Collections.unmodifiableList(Arrays.asList(
                  StandardAuthScheme.SPNEGO,
                  StandardAuthScheme.KERBEROS,
                  StandardAuthScheme.NTLM,
                  StandardAuthScheme.DIGEST,
                  StandardAuthScheme.BASIC));
  
      @Override
      public List<AuthScheme> select(
              final ChallengeType challengeType,
              final Map<String, AuthChallenge> challenges,
              final HttpContext context) {
          Args.notNull(challengeType, "ChallengeType");
          Args.notNull(challenges, "Map of auth challenges");
          Args.notNull(context, "HTTP context");
          final HttpClientContext clientContext = HttpClientContext.adapt(context);
          final String exchangeId = clientContext.getExchangeId();
  
          final List<AuthScheme> options = new ArrayList<>();
          final Lookup<AuthSchemeFactory> registry = clientContext.getAuthSchemeRegistry();
          if (registry == null) {
              if (LOG.isDebugEnabled()) {
                  LOG.debug("{} Auth scheme registry not set in the context", exchangeId);
              }
              return options;
          }
          final RequestConfig config = clientContext.getRequestConfig();
          Collection<String> authPrefs = challengeType == ChallengeType.TARGET ?
                  config.getTargetPreferredAuthSchemes() : config.getProxyPreferredAuthSchemes();
          if (authPrefs == null) {
              authPrefs = DEFAULT_SCHEME_PRIORITY;
          }
          if (LOG.isDebugEnabled()) {
             if (LOG.isDebugEnabled()) {
                 LOG.debug("{} Authentication schemes in the order of preference: {}", exchangeId, authPrefs);
             }
         }
 
         for (final String schemeName: authPrefs) {
             final AuthChallenge challenge = challenges.get(schemeName.toLowerCase(Locale.ROOT));
             if (challenge != null) {
                 final AuthSchemeFactory authSchemeFactory = registry.lookup(schemeName);
                 if (authSchemeFactory == null) {
                     if (LOG.isWarnEnabled()) {
                         LOG.warn("{} Authentication scheme {} not supported", exchangeId, schemeName);
                         // Try again
                     }
                     continue;
                 }
                 final AuthScheme authScheme = authSchemeFactory.create(context);
                 options.add(authScheme);
             } else {
                 if (LOG.isDebugEnabled()) {
                     LOG.debug("{}, Challenge for {} authentication scheme not available", exchangeId, schemeName);
                 }
             }
         }
         return options;
     }
 
 }