/*
 * (c) Copyright 2010-2011 by Volker Bergmann. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, is permitted under the terms of the
 * GNU General Public License (GPL).
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * WITHOUT A WARRANTY OF ANY KIND. ALL EXPRESS OR IMPLIED CONDITIONS,
 * REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE
 * HEREBY EXCLUDED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

package org.databene.benerator.wrapper;

import java.util.Random;

import org.databene.benerator.Generator;

/**
 * {@link GeneratorProxy} implementation which injects a given quota of null values in the 
 * original generator's results.<br/><br/>
 * Created: 26.01.2010 10:32:58
 * @since 0.6.0
 * @author Volker Bergmann
 */
public class NullInjectingGeneratorProxy<E> extends GeneratorProxy<E> {
	
	private float nullQuota;
	
	private Random random;
	boolean closed;

    public NullInjectingGeneratorProxy(Generator<E> source, double nullQuota) {
    	super(source);
    	if (nullQuota < 0 || nullQuota > 1)
    		throw new IllegalArgumentException("Illegal null quota: " + nullQuota);
	    this.nullQuota = (float) nullQuota;
		random = new Random();
		closed = false;
    }

    /**
     * First checks if a null value should be returned, if so it returns a wrapper that wraps a null value, 
     * otherwise a wrapper that wraps a value generated by the underlying source generator. If that generator
     * is not available any more, <code>null</code> is returned. 
     */
    @Override
	public ProductWrapper<E> generate(ProductWrapper<E> wrapper) {
    	if (closed)
    		return null;
    	if (shouldNullify())
    		return wrapper.wrap(null);
    	else
    		return super.generate(wrapper);
    }

	protected boolean shouldNullify() {
		return random.nextFloat() < nullQuota;
	}

	@Override
	public String toString() {
	    return getClass().getSimpleName() + "[" + nullQuota + ", " + getSource() + "]";
	}
    
}