package org.apache.maven.doxia.index;
   
   /*
    * 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.
   */
  
  import java.util.List;
  import java.util.ArrayList;
  import java.util.Collections;
  
  import org.codehaus.plexus.util.StringUtils;
  
  /**
   * <p>IndexEntry class.</p>
   *
   * @author <a href="mailto:trygvis@inamo.no">Trygve Laugst&oslash;l</a>
   * @version $Id$
   */
  public class IndexEntry
  {
      /**
       * The parent entry.
       */
      private final IndexEntry parent;
  
      /**
       * The id of the entry.
       */
      private String id;
  
      /**
       * The entry title.
       */
      private String title;
  
      /**
       * The child entries.
       */
      private List<IndexEntry> childEntries = new ArrayList<>();
  
      /**
       * System-dependent EOL.
       */
      private static final String EOL = System.getProperty( "line.separator" );
  
      /**
       * Constructor.
       *
       * @param newId The id. May be null.
       */
      public IndexEntry( String newId )
      {
          this( null, newId );
      }
  
      /**
       * Constructor.
       *
       * @param newParent The parent. May be null.
       * @param newId     The id. May be null.
       */
      public IndexEntry( IndexEntry newParent, String newId )
      {
          this.parent = newParent;
          this.id = newId;
  
          if ( parent != null )
          {
              parent.childEntries.add( this );
          }
      }
  
      /**
       * Returns the parent entry.
       *
       * @return the parent entry.
       */
      public IndexEntry getParent()
      {
          return parent;
      }
  
      /**
       * Returns the id.
      *
      * @return the id.
      */
     public String getId()
     {
         return id;
     }
 
     /**
      * Set the id.
      *
      * @param id the id
      * @since 1.1.2
      */
     protected void setId( String id )
     {
         this.id = id;
     }
 
     /**
      * Returns the title.
      *
      * @return the title.
      */
     public String getTitle()
     {
         return title;
     }
 
     /**
      * Sets the title.
      *
      * @param newTitle the title.
      */
     public void setTitle( String newTitle )
     {
         this.title = newTitle;
     }
 
     /**
      * Returns an unmodifiableList of the child entries.
      *
      * @return child entries.
      */
     public List<IndexEntry> getChildEntries()
     {
         return Collections.unmodifiableList( childEntries );
     }
 
     /**
      * Sets the child entries or creates a new ArrayList if entries == null.
      *
      * @param entries the entries.
      */
     public void setChildEntries( List<IndexEntry> entries )
     {
         if ( entries == null )
         {
             childEntries = new ArrayList<>();
         }
 
         this.childEntries = entries;
     }
 
     // -----------------------------------------------------------------------
     // Utils
     // -----------------------------------------------------------------------
 
     /**
      * Returns the next entry.
      *
      * @return the next entry, or null if there is none.
      */
     public IndexEntry getNextEntry()
     {
         if ( parent == null )
         {
             return null;
         }
 
         List<IndexEntry> entries = parent.getChildEntries();
 
         int index = entries.indexOf( this );
 
         if ( index + 1 >= entries.size() )
         {
             return null;
         }
 
         return entries.get( index + 1 );
     }
 
     /**
      * Returns the previous entry.
      *
      * @return the previous entry, or null if there is none.
      */
     public IndexEntry getPrevEntry()
     {
         if ( parent == null )
         {
             return null;
         }
 
         List<IndexEntry> entries = parent.getChildEntries();
 
         int index = entries.indexOf( this );
 
         if ( index == 0 )
         {
             return null;
         }
 
         return entries.get( index - 1 );
     }
 
     /**
      * Returns the first entry.
      *
      * @return the first entry, or null if there is none.
      */
     public IndexEntry getFirstEntry()
     {
         List<IndexEntry> entries = getChildEntries();
 
         if ( entries.size() == 0 )
         {
             return null;
         }
 
         return entries.get( 0 );
     }
 
     /**
      * Returns the last entry.
      *
      * @return the last entry, or null if there is none.
      */
     public IndexEntry getLastEntry()
     {
         List<IndexEntry> entries = getChildEntries();
 
         if ( entries.size() == 0 )
         {
             return null;
         }
 
         return entries.get( entries.size() - 1 );
     }
 
     /**
      * Returns the root entry.
      *
      * @return the root entry, or null if there is none.
      */
     public IndexEntry getRootEntry()
     {
         List<IndexEntry> entries = getChildEntries();
 
         if ( entries.size() == 0 )
         {
             return null;
         }
         else if ( entries.size() > 1 )
         {
             throw new RuntimeException( "This index has more than one root entry" );
         }
         else
         {
             return entries.get( 0 );
         }
     }
 
     // -----------------------------------------------------------------------
     // Object Overrides
     // -----------------------------------------------------------------------
 
     /**
      * Returns a string representation of the object.
      */
     public String toString()
     {
         return toString( 0 );
     }
 
     /**
      * Returns a string representation of all objects to the given depth.
      *
      * @param depth The depth to descent to.
      * @return A string.
      */
     public String toString( int depth )
     {
         StringBuilder message = new StringBuilder();
 
         message.append( "Id: " ).append( id );
 
         if ( StringUtils.isNotEmpty( title ) )
         {
             message.append( ", title: " ).append( title );
         }
 
         message.append( EOL );
 
         StringBuilder indent = new StringBuilder();
 
         for ( int i = 0; i < depth; i++ )
         {
             indent.append( " " );
         }
 
         for ( IndexEntry entry : getChildEntries() )
         {
             message.append( indent ).append( entry.toString( depth + 1 ) );
         }
 
         return message.toString();
     }
 }