/*

 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.

 * 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

 * questions.

 */

package java.nio.file;

import java.io.Closeable;

import java.io.IOException;

import java.io.UncheckedIOException;

import java.util.Arrays;

import java.util.Iterator;

import java.util.NoSuchElementException;

import java.util.Objects;

import java.nio.file.FileTreeWalker.Event;

/**

 * An {@code Iterator to iterate over the nodes of a file tree.

 *

 * <pre>{@code

 *     try (FileTreeIterator iterator = new FileTreeIterator(start, maxDepth, options)) {

 *         while (iterator.hasNext()) {

 *             Event ev = iterator.next();

 *             Path path = ev.file();

 *             BasicFileAttributes attrs = ev.attributes();

 *         }

 *     }

 * }</pre>

 */

class FileTreeIterator implements Iterator<Event>, Closeable {

    private final FileTreeWalker walker;

    private Event next;

    /**

     * Creates a new iterator to walk the file tree starting at the given file.

     *

     * @throws  IllegalArgumentException

     *          if {@code maxDepth} is negative

     * @throws  IOException

     *          if an I/O errors occurs opening the starting file

     * @throws  SecurityException

     *          if the security manager denies access to the starting file

     * @throws  NullPointerException

     *          if {@code start} or {@code options} is {@ocde null} or

     *          the options array contains a {@code null} element

     */

    FileTreeIterator(Path start, int maxDepth, FileVisitOption... options)

        throws IOException

    {

        this.walker = new FileTreeWalker(Arrays.asList(options), maxDepth);

        this.next = walker.walk(start);

        assert next.type() == FileTreeWalker.EventType.ENTRY ||

               next.type() == FileTreeWalker.EventType.START_DIRECTORY;

        // IOException if there a problem accessing the starting file

        IOException ioe = next.ioeException();

        if (ioe != null)

            throw ioe;

    }

    private void fetchNextIfNeeded() {

        if (next == null) {

            FileTreeWalker.Event ev = walker.next();

            while (ev != null) {

                IOException ioe = ev.ioeException();

                if (ioe != null)

                    throw new UncheckedIOException(ioe);

                // END_DIRECTORY events are ignored

                if (ev.type() != FileTreeWalker.EventType.END_DIRECTORY) {

                    next = ev;

                    return;

                }

                ev = walker.next();

            }

        }

    }

    @Override

    public boolean hasNext() {

        if (!walker.isOpen())

            throw new IllegalStateException();

        fetchNextIfNeeded();

        return next != null;

    }

    @Override

    public Event next() {

        if (!walker.isOpen())

            throw new IllegalStateException();

        fetchNextIfNeeded();

        if (next == null)

            throw new NoSuchElementException();

        Event result = next;

        next = null;

        return result;

    }

    @Override

    public void close() {

        walker.close();

    }

}