/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

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 */

package com.sun.xml.internal.xsom.util;

import java.util.ArrayList;

import java.util.Collection;

import java.util.Iterator;

import java.util.List;

import java.util.NoSuchElementException;

/**

 * {@link Collection} that returns the view of objects which are actually fetched

 * lazily from an {@link Iterator}.

 *

 * @author Kohsuke Kawaguchi

 */

public class DeferedCollection<T> implements Collection<T> {

    /**

     * The iterator that lazily evaluates SCD query.

     */

    private final Iterator<T> result;

    /**

     * Stores values that are already fetched from {@link #result}.

     */

    private final List<T> archive = new ArrayList<T>();

    public DeferedCollection(Iterator<T> result) {

        this.result = result;

    }

    public boolean isEmpty() {

        if(archive.isEmpty())

            fetch();

        return archive.isEmpty();

    }

    public int size() {

        fetchAll();

        return archive.size();

    }

    public boolean contains(Object o) {

        if(archive.contains(o))

            return true;

        while(result.hasNext()) {

            T value = result.next();

            archive.add(value);

            if(value.equals(o))

                return true;

        }

        return false;

    }

    public boolean containsAll(Collection<?> c) {

        for (Object o : c) {

            if(!contains(o))

                return false;

        }

        return true;

    }

    public Iterator<T> iterator() {

        return new Iterator<T>() {

            int idx=0;

            public boolean hasNext() {

                if(idx<archive.size())

                    return true;

                return result.hasNext();

            }

            public T next() {

                if(idx==archive.size())

                    fetch();

                if(idx==archive.size())

                    throw new NoSuchElementException();

                return archive.get(idx++);

            }

            public void remove() {

                // TODO

            }

        };

    }

    public Object[] toArray() {

        fetchAll();

        return archive.toArray();

    }

    public <T>T[] toArray(T[] a) {

        fetchAll();

        return archive.toArray(a);

    }

    private void fetchAll() {

        while(result.hasNext())

            archive.add(result.next());

    }

    /**

     * Fetches another item from {@link

     */

    private void fetch() {

        if(result.hasNext())

            archive.add(result.next());

    }

// mutation methods are unsupported

    public boolean add(T o) {

        throw new UnsupportedOperationException();

    }

    public boolean remove(Object o) {

        throw new UnsupportedOperationException();

    }

    public boolean addAll(Collection<? extends T> c) {

        throw new UnsupportedOperationException();

    }

    public boolean removeAll(Collection<?> c) {

        throw new UnsupportedOperationException();

    }

    public boolean retainAll(Collection<?> c) {

        throw new UnsupportedOperationException();

    }

    public void clear() {

        throw new UnsupportedOperationException();

    }

}