/*!
 * This program is free software; you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
 * Foundation.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
 * or from the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * This program 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 Lesser General Public License for more details.
 *
 * Copyright (c) 2002-2013 Pentaho Corporation..  All rights reserved.
 */

package org.pentaho.reporting.engine.classic.core.util;

import java.util.ArrayList;

public class RingBuffer<T> {
  private ArrayList<T> values;
  private int index;
  private int count;
  private int size;

  public RingBuffer( final int size ) {
    if ( size < 1 ) {
      throw new IllegalArgumentException();
    }
    this.size = size;
    this.values = new ArrayList<T>( size );
    for ( int i = 0; i < size; i += 1 ) {
      values.add( null );
    }
  }

  public void add( final T value ) {
    values.set( index, value );
    index += 1;
    count += 1;
    if ( index == size ) {
      index = 0;
    }
  }

  public void replaceLastAdded( final T value ) {
    if ( count == 0 ) {
      add( value );
      return;
    }

    count -= 1;
    if ( index == 0 ) {
      index = size - 1;
    } else {
      index -= 1;
    }
    add( value );
  }

  public T getFirstValue() {
    if ( count < size ) {
      return values.get( 0 );
    }
    return values.get( index );
  }

  public T getLastValue() {
    final int lastIndex;
    if ( index == 0 ) {
      lastIndex = size - 1;
    } else {
      lastIndex = index - 1;
    }
    return values.get( lastIndex );
  }

  public int size() {
    return size;
  }

  public T get( final int index ) {
    return values.get( index );
  }

  public void set( final int index, final T value ) {
    values.set( index, value );
  }

  public void resize( final int newSize ) {
    if ( newSize <= 0 ) {
      throw new IllegalStateException();
    }

    if ( newSize > values.size() ) {
      values.clear();
      for ( int i = 0; i < newSize; i += 1 ) {
        values.add( null );
      }
    }

    size = newSize;
  }
}