/*
    * 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.
   */
  package org.apache.logging.log4j.audit.rest;
  
  import java.io.IOException;
  import java.util.Map;
  
  import org.apache.logging.log4j.ThreadContext;
  import org.apache.logging.log4j.audit.request.RequestContextMapping;
  import org.apache.logging.log4j.audit.request.RequestContextMappings;
  import org.springframework.http.HttpHeaders;
  import org.springframework.http.HttpRequest;
  import org.springframework.http.client.ClientHttpRequestExecution;
  import org.springframework.http.client.ClientHttpRequestInterceptor;
  import org.springframework.http.client.ClientHttpResponse;
  
  /**
   * Creates a List of Headers containing the keys and values in the RequestContext that have a mapping indicating
   * they should be propogated to the service being called.
   *
   * This class is designed to be used by Spring as part of the REST Template configuration when calling a REST service.
   *
   */
  public class RequestContextHeaderInterceptor implements ClientHttpRequestInterceptor {
  
      private RequestContextMappings mappings = null;
  
      public RequestContextHeaderInterceptor(RequestContextMappings mappings) {
          this.mappings = mappings;
      }
  
      @Override
      public ClientHttpResponse intercept(HttpRequest httpRequest, byte[] body,
                                          ClientHttpRequestExecution clientHttpRequestExecution) throws IOException {
          Map<String, String> map = ThreadContext.getImmutableContext();
          HttpHeaders headers = httpRequest.getHeaders();
          for (Map.Entry<String, String> entry : map.entrySet()) {
              RequestContextMapping mapping = mappings.getMapping(entry.getKey());
              if (mapping != null && !mapping.isLocal()) {
                  String key = mappings.getHeaderPrefix() + mapping.getFieldName();
                  if (!headers.containsKey(key)) {
                      headers.add(key, entry.getValue());
                  }
              }
          }
          return clientHttpRequestExecution.execute(httpRequest, body);
      }
  }