/*
 * Copyright (c) 2016, grossmann
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * * Neither the name of the jo-widgets.org nor the
 *   names of its contributors may be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL jo-widgets.org 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.jowidgets.util.collection;

import java.util.Iterator;
import java.util.NoSuchElementException;

import org.jowidgets.util.Assert;
import org.jowidgets.util.IFilter;

public final class FilteredIterator<VALUE_TYPE> implements Iterator<VALUE_TYPE> {

    private final Iterator<VALUE_TYPE> original;
    private final IFilter<VALUE_TYPE> filter;

    private VALUE_TYPE prefetched;

    public FilteredIterator(final Iterator<VALUE_TYPE> original, final IFilter<VALUE_TYPE> filter) {
        Assert.getParamNotNull(original, "original");
        Assert.getParamNotNull(filter, "filter");
        this.original = original;
        this.filter = filter;

        prefetch();
    }

    @Override
    public boolean hasNext() {
        return prefetched != null;
    }

    @Override
    public VALUE_TYPE next() {
        if (prefetched == null) {
            throw new NoSuchElementException();
        }
        final VALUE_TYPE result = prefetched;
        prefetched = null;
        prefetch();
        return result;
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("The filtered itertaor is readonly");
    }

    private void prefetch() {
        if (original.hasNext()) {
            prefetched = original.next();
            if (!filter.accept(prefetched)) {
                prefetched = null;
                prefetch();
            }
        }
        else {
            prefetched = null;
        }
    }

}