/*
    * 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.commons.fileupload.util;
  
  import java.io.Serializable;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  
  import org.apache.commons.fileupload.FileItemHeaders;
  
  /**
   * Default implementation of the {@link FileItemHeaders} interface.
   *
   * @since 1.2.1
   *
   * @version $Id: FileItemHeadersImpl.java 1458379 2013-03-19 16:16:47Z britter $
   */
  public class FileItemHeadersImpl implements FileItemHeaders, Serializable {
  
      /**
       * Serial version UID, being used, if serialized.
       */
      private static final long serialVersionUID = -4455695752627032559L;
  
      /**
       * Map of <code>String</code> keys to a <code>List</code> of
       * <code>String</code> instances.
       */
      private final Map<String, List<String>> headerNameToValueListMap = new LinkedHashMap<String, List<String>>();
  
      /**
       * {@inheritDoc}
       */
      public String getHeader(String name) {
          String nameLower = name.toLowerCase(Locale.ENGLISH);
          List<String> headerValueList = headerNameToValueListMap.get(nameLower);
          if (null == headerValueList) {
              return null;
          }
          return headerValueList.get(0);
      }
  
      /**
       * {@inheritDoc}
       */
      public Iterator<String> getHeaderNames() {
          return headerNameToValueListMap.keySet().iterator();
      }
  
      /**
       * {@inheritDoc}
       */
      public Iterator<String> getHeaders(String name) {
          String nameLower = name.toLowerCase(Locale.ENGLISH);
          List<String> headerValueList = headerNameToValueListMap.get(nameLower);
          if (null == headerValueList) {
              headerValueList = Collections.emptyList();
          }
          return headerValueList.iterator();
      }
  
      /**
       * Method to add header values to this instance.
       *
       * @param name name of this header
       * @param value value of this header
       */
      public synchronized void addHeader(String name, String value) {
          String nameLower = name.toLowerCase(Locale.ENGLISH);
          List<String> headerValueList = headerNameToValueListMap.get(nameLower);
          if (null == headerValueList) {
              headerValueList = new ArrayList<String>();
              headerNameToValueListMap.put(nameLower, headerValueList);
          }
          headerValueList.add(value);
      }
  
  }