/*
    * Copyright 2012 the original author or authors.
    *
    * Licensed 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.openehealth.ipf.platform.camel.ihe.hl7v2.intercept.consumer;
  
  import org.apache.camel.Exchange;
  import org.apache.commons.lang3.Validate;
  import org.openehealth.ipf.platform.camel.core.util.Exchanges;
  import org.openehealth.ipf.platform.camel.ihe.core.InterceptorSupport;
  import org.openehealth.ipf.platform.camel.ihe.hl7v2.HL7v2Endpoint;
  
  /**
   * Consumer-side HL7v2 interceptor which echoes one segment from
   * the request message in the corresponding response message.
   * When multiple segments with the same name exist in the request
   * and/or response message, the first occurrence will be processed.
   *
   * @author Dmytro Rud
   */
  public class ConsumerSegmentEchoingInterceptor extends InterceptorSupport<HL7v2Endpoint> {
      private final String segmentName;
  
  
      /**
       * @param segmentName
       *      name of the segment to be echoed.
       */
      public ConsumerSegmentEchoingInterceptor(String segmentName) {
          this.segmentName = Validate.notEmpty(segmentName);
          addBefore(ConsumerMarshalInterceptor.class.getName());
      }
  
  
      @Override
      public void process(Exchange exchange) throws Exception {
          // determine segment boundaries in the request message
          String request = exchange.getIn().getBody(String.class);
          int[] requestQpdBoundaries = getQpdBoundaries(request);
  
          // run the route
          getWrappedProcessor().process(exchange);
  
          // replace the segment in the response message by the one from the request
          if (requestQpdBoundaries != null) {
              String response = Exchanges.resultMessage(exchange).getBody(String.class);
              int[] responseQpdBoundaries = getQpdBoundaries(response);
              if (responseQpdBoundaries != null) {
                  Exchanges.resultMessage(exchange).setBody(new StringBuilder()
                          .append(response, 0, responseQpdBoundaries[0])
                          .append(request, requestQpdBoundaries[0], requestQpdBoundaries[1])
                          .append(response, responseQpdBoundaries[1], response.length())
                          .toString());
              }
          }
      }
  
  
      private int[] getQpdBoundaries(String s) {
          int pos1 = s.indexOf("\r" + segmentName + s.charAt(3));
          int pos2 = (pos1 > 0) ? s.indexOf("\r", pos1 + 4) : -1;
          return (pos2 > 0) ? new int[] {pos1, pos2} : null;
      }
  }