/*
    * 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.directory.api.ldap.model.cursor;
  
  
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.Set;
  
  import org.apache.directory.api.i18n.I18n;
  import org.apache.directory.api.ldap.model.constants.Loggers;
  import org.apache.directory.api.ldap.model.exception.LdapException;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * A simple implementation of a Cursor on a {@link Set}.  Optionally, the
   * Cursor may be limited to a specific range within the list.
   *
   * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
   * @param <E> The element on which this cursor will iterate
   */
  public class SetCursor<E> extends AbstractCursor<E>
  {
      /** A dedicated log for cursors */
      private static final Logger LOG_CURSOR = LoggerFactory.getLogger( Loggers.CURSOR_LOG.getName() );
  
      /** Speedup for logs */
      private static final boolean IS_DEBUG = LOG_CURSOR.isDebugEnabled();
  
      /** The inner Set */
      private final E[] set;
  
      /** The associated comparator */
      private final Comparator<E> comparator;
  
      /** The current position in the list */
      private int index = -1;
  
  
      /**
       * Creates a new SetCursor.
       *
       * As with all Cursors, this SetCursor requires a successful return from
       * advance operations (next() or previous()) to properly return values
       * using the get() operation.
       *
       * @param comparator an optional comparator to use for ordering
       * @param set the Set this StCursor operates on
       */
      @SuppressWarnings("unchecked")
      public SetCursor( Comparator<E> comparator, Set<E> set )
      {
          if ( set == null )
          {
              set = Collections.EMPTY_SET;
          }
  
          if ( IS_DEBUG )
          {
              LOG_CURSOR.debug( "Creating SetCursor {}", this );
          }
  
          this.comparator = comparator;
          this.set = ( E[] ) set.toArray();
      }
  
  
      /**
       * Creates a new SetCursor
       *
       * As with all Cursors, this SetCursor requires a successful return from
       * advance operations (next() or previous()) to properly return values
       * using the get() operation.
       *
       * @param set the Set this SetCursor operates on
       */
      public SetCursor( Set<E> set )
      {
          this( null, set );
      }
  
 
     /**
      * Creates a new SetCursor without any elements.
      */
     @SuppressWarnings("unchecked")
     public SetCursor()
     {
         this( null, Collections.EMPTY_SET );
     }
 
 
     /**
      * Creates a new SetCursor without any elements. We also provide 
      * a comparator.
      * 
      * @param comparator The comparator to use for the <E> elements
      */
     @SuppressWarnings("unchecked")
     public SetCursor( Comparator<E> comparator )
     {
         this( comparator, Collections.EMPTY_SET );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean available()
     {
         return ( index >= 0 ) && ( index < set.length );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void before( E element ) throws LdapException, CursorException
     {
         checkNotClosed( "before()" );
 
         if ( comparator == null )
         {
             throw new IllegalStateException();
         }
 
         // handle some special cases
         if ( set.length == 0 )
         {
             return;
         }
         else if ( set.length == 1 )
         {
             if ( comparator.compare( element, set[0] ) <= 0 )
             {
                 beforeFirst();
             }
             else
             {
                 afterLast();
             }
         }
 
         throw new UnsupportedOperationException( I18n.err( I18n.ERR_02008_LIST_MAY_BE_SORTED ) );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void after( E element ) throws LdapException, CursorException
     {
         checkNotClosed( "after()" );
 
         if ( comparator == null )
         {
             throw new IllegalStateException();
         }
 
         // handle some special cases
         if ( set.length == 0 )
         {
             return;
         }
         else if ( set.length == 1 )
         {
             if ( comparator.compare( element, set[0] ) >= 0 )
             {
                 afterLast();
             }
             else
             {
                 beforeFirst();
             }
         }
 
         throw new UnsupportedOperationException( I18n.err( I18n.ERR_02008_LIST_MAY_BE_SORTED ) );
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void beforeFirst() throws LdapException, CursorException
     {
         checkNotClosed( "beforeFirst()" );
         this.index = -1;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public void afterLast() throws LdapException, CursorException
     {
         checkNotClosed( "afterLast()" );
         this.index = set.length;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean first() throws LdapException, CursorException
     {
         checkNotClosed( "first()" );
 
         if ( set.length > 0 )
         {
             index = 0;
 
             return true;
         }
 
         return false;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean last() throws LdapException, CursorException
     {
         checkNotClosed( "last()" );
 
         if ( set.length > 0 )
         {
             index = set.length - 1;
 
             return true;
         }
 
         return false;
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean isFirst()
     {
         return ( set.length > 0 ) && ( index == 0 );
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean isLast()
     {
         return ( set.length > 0 ) && ( index == set.length - 1 );
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean isAfterLast()
     {
         return index == set.length;
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public boolean isBeforeFirst()
     {
         return index == -1;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean previous() throws LdapException, CursorException
     {
         checkNotClosed( "previous()" );
 
         // if parked at -1 we cannot go backwards
         if ( index == -1 )
         {
             return false;
         }
 
         // if the index moved back is still greater than or eq to start then OK
         if ( index - 1 >= 0 )
         {
             index--;
 
             return true;
         }
 
         // if the index currently less than or equal to start we need to park it at -1 and return false
         if ( index <= 0 )
         {
             index = -1;
 
             return false;
         }
 
         if ( set.length <= 0 )
         {
             index = -1;
         }
 
         return false;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public boolean next() throws LdapException, CursorException
     {
         checkNotClosed( "next()" );
 
         // if parked at -1 we advance to the start index and return true
         if ( ( set.length > 0 ) && ( index == -1 ) )
         {
             index = 0;
 
             return true;
         }
 
         // if the index plus one is less than the end then increment and return true
         if ( ( set.length > 0 ) && ( index + 1 < set.length ) )
         {
             index++;
 
             return true;
         }
 
         // if the index plus one is equal to the end then increment and return false
         if ( ( set.length > 0 ) && ( index + 1 == set.length ) )
         {
             index++;
 
             return false;
         }
 
         if ( set.length <= 0 )
         {
             index = set.length;
         }
 
         return false;
     }
 
 
     /**
      * {@inheritDoc}
      */
     public E get() throws CursorException
     {
         checkNotClosed( "get()" );
 
         if ( ( index < 0 ) || ( index >= set.length ) )
         {
             throw new CursorException( I18n.err( I18n.ERR_02009_CURSOR_NOT_POSITIONED ) );
         }
 
         return set[index];
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close()
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing ListCursor {}", this );
         }
 
         super.close();
     }
 
 
     /**
      * {@inheritDoc}
      */
     @Override
     public void close( Exception cause )
     {
         if ( IS_DEBUG )
         {
             LOG_CURSOR.debug( "Closing ListCursor {}", this );
         }
 
         super.close( cause );
     }
 
 
     /**
      * @see Object#toString()
      */
     public String toString( String tabs )
     {
         StringBuilder sb = new StringBuilder();
 
         sb.append( tabs ).append( "SetCursor :\n" );
         sb.append( tabs ).append( "    Index : " ).append( index ).append( "\n" );
 
         if ( ( set != null ) && ( set.length > 0 ) )
         {
             sb.append( tabs ).append( "    Size : " ).append( set.length ).append( "\n" );
 
             int counter = 0; // Don't print more than 100 elements...
 
             for ( E e : set )
             {
                 sb.append( tabs ).append( "    " ).append( e ).append( "\n" );
                 counter++;
 
                 if ( counter == 100 )
                 {
                     break;
                 }
             }
         }
 
         return sb.toString();
     }
 
 
     /**
      * @see Object#toString()
      */
     public String toString()
     {
         return toString( "" );
     }
 }