/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.common.content.util;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.StringTokenizer;
  
  class Range {
  
      public long start;
  
      public long end;
  
      public long length;
  
      public static final String RANGE_UNIT = "bytes";
  
      public boolean validate() {
          if (end >= length) {
              //set 'end' to content size
              end = length - 1;
          }
          return start >= 0 && end >= 0 && start <= end && length > 0;
      }
  
      public static List<Range> parseRanges(final String rangeHeader, long fileLength) throws IllegalArgumentException {
          if (rangeHeader == null) {
              return null;
          }
  
          // We operate on byte level only
          if (!rangeHeader.startsWith(RANGE_UNIT)) {
              throw new IllegalArgumentException();
          }
  
          String rangeValue = rangeHeader.substring(RANGE_UNIT.length() + 1);
  
          final ArrayList<Range> result = new ArrayList<>();
          final StringTokenizer commaTokenizer = new StringTokenizer(rangeValue, ",");
  
          // Parsing the range list
          long lastByte = 0;
          while (commaTokenizer.hasMoreTokens()) {
              final String rangeDefinition = commaTokenizer.nextToken().trim();
  
              final Range currentRange = new Range();
              currentRange.length = fileLength;
  
              final int dashPos = rangeDefinition.indexOf('-');
  
              if (dashPos == -1) {
                  throw new IllegalArgumentException();
              }
  
              if (dashPos == 0) {
  
                  try {
                      //offset is negative
                      final long offset = Long.parseLong(rangeDefinition);
                      currentRange.start = fileLength + offset;
                      currentRange.end = fileLength - 1;
                  } catch (final NumberFormatException e) {
                      throw new IllegalArgumentException(e);
                  }
  
              } else {
  
                  try {
                      currentRange.start = Long.parseLong(rangeDefinition.substring(0, dashPos));
                      if (dashPos < rangeDefinition.length() - 1) {
                          currentRange.end = Long.parseLong(rangeDefinition.substring(dashPos + 1));
                      } else {
                          currentRange.end = fileLength - 1;
                      }
                  } catch (final NumberFormatException e) {
                      throw new IllegalArgumentException(e);
                  }
  
              }
  
              if (!currentRange.validate() || lastByte > currentRange.start) {
                  throw new IllegalArgumentException();
             }
             lastByte = currentRange.end;
             result.add(currentRange);
         }
         return result;
     }
 }