/**
    *
    * Copyright 2003-2005 The Apache Software Foundation
    *
    *  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.apache.geronimo.javamail.store.nntp.newsrc;
  
  import java.io.IOException;
  import java.io.Writer;
  import java.util.ArrayList;
  import java.util.StringTokenizer;
  
  /**
   * Manage a list of ranges values from a newsrc file.
   */
  public class RangeList {
      boolean dirty = false;
  
      ArrayList ranges = new ArrayList();
  
      /**
       * Create a RangeList instance from a newsrc range line. Values are saved as
       * a comma separated set of range values. A range value is either a single
       * number or a hypenated pair of numbers.
       * 
       * @param line
       *            The newsrc range line.
       */
      public RangeList(String line) {
  
          // we might be creating an first time list, so nothing to parse.
          if (line != null) {
              // ranges are comma delimited tokens
              StringTokenizer tokenizer = new StringTokenizer(line, ",");
  
              while (tokenizer.hasMoreTokens()) {
                  String rangeString = (String) tokenizer.nextToken();
                  rangeString = rangeString.trim();
                  if (rangeString.length() != 0) {
                      Range range = Range.parse(rangeString);
                      if (range != null) {
                          insert(range);
                      }
                  }
              }
          }
          // make sure we start out in a clean state. Any changes from this point
          // will flip on the dirty flat.
          dirty = false;
      }
  
      /**
       * Insert a range item into our list. If possible, the inserted range will
       * be merged with existing ranges.
       * 
       * @param newRange
       *            The new range item.
       */
      public void insert(Range newRange) {
          // first find the insertion point
          for (int i = 0; i < ranges.size(); i++) {
              Range range = (Range) ranges.get(i);
              // does an existing range fully contain the new range, we don't need
              // to insert anything.
              if (range.contains(newRange)) {
                  return;
              }
  
              // does the current one abutt or overlap with the inserted range?
              if (range.abutts(newRange) || range.overlaps(newRange)) {
                  // rats, we have an overlap...and it is possible that we could
                  // overlap with
                  // the next range after this one too. Therefore, we merge these
                  // two ranges together,
                  // remove the place where we're at, and then recursively insert
                  // the larger range into
                  // the list.
                  dirty = true;
                  newRange.merge(range);
                  ranges.remove(i);
                  insert(newRange);
                  return;
              }
  
              // ok, we don't touch the current one at all. If it is completely
              // above
              // range we're adding, we can just poke this into the list here.
             if (newRange.lessThan(range)) {
                 dirty = true;
                 ranges.add(i, newRange);
                 return;
             }
         }
         dirty = true;
         // this is easy (and fairly common)...we just tack this on to the end.
         ranges.add(newRange);
     }
 
     /**
      * Test if a given article point falls within one of the contained Ranges.
      * 
      * @param article
      *            The test point.
      * 
      * @return true if this falls within one of our current mark Ranges, false
      *         otherwise.
      */
     public boolean isMarked(int article) {
         for (int i = 0; i < ranges.size(); i++) {
             Range range = (Range) ranges.get(i);
             if (range.contains(article)) {
                 return true;
             }
             // we've passed the point where a match is possible.
             if (range.greaterThan(article)) {
                 return false;
             }
         }
         return false;
     }
 
     /**
      * Mark a target article as having been seen.
      * 
      * @param article
      *            The target article number.
      */
     public void setMarked(int article) {
         // go through the insertion logic.
         insert(new Range(article, article));
     }
 
     /**
      * Clear the seen mark for a target article.
      * 
      * @param article
      *            The target article number.
      */
     public void setUnmarked(int article) {
         for (int i = 0; i < ranges.size(); i++) {
             Range range = (Range) ranges.get(i);
             // does this fall within an existing range? We don't need to do
             // anything here.
             if (range.contains(article)) {
                 // ok, we've found where to insert, now to figure out how to
                 // insert
                 // article is at the beginning of the range. We can just
                 // increment the lower
                 // bound, or if this is a single element range, we can remove it
                 // entirely.
                 if (range.getStart() == article) {
                     if (range.getEnd() == article) {
                         // piece of cake!
                         ranges.remove(i);
                     } else {
                         // still pretty easy.
                         range.setStart(article + 1);
                     }
                 } else if (range.getEnd() == article) {
                     // pretty easy also
                     range.setEnd(article - 1);
                 } else {
                     // split this into two ranges and insert the trailing piece
                     // after this.
                     Range section = range.split(article);
                     ranges.add(i + 1, section);
                 }
                 dirty = true;
                 return;
             }
             // did we find a point where any articles are greater?
             if (range.greaterThan(article)) {
                 // nothing to do
                 return;
             }
         }
         // didn't find it at all. That was easy!
     }
 
     /**
      * Save this List of Ranges out to a .newsrc file. This creates a
      * comma-separated list of range values from each of the Ranges.
      * 
      * @param out
      *            The target output stream.
      * 
      * @exception IOException
      */
     public void save(Writer out) throws IOException {
         // we have an empty list
         if (ranges.size() == 0) {
             return;
         }
 
         Range range = (Range) ranges.get(0);
         range.save(out);
 
         for (int i = 1; i < ranges.size(); i++) {
             out.write(",");
             range = (Range) ranges.get(i);
             range.save(out);
         }
     }
 
     /**
      * Return the state of the dirty flag.
      * 
      * @return True if the range list information has changed, false otherwise.
      */
     public boolean isDirty() {
         return dirty;
     }
 }