/*

 * Copyright (c) 2014, 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 jdk.internal.jrtfs;

import java.nio.file.DirectoryStream;

import java.nio.file.ClosedDirectoryStreamException;

import java.nio.file.DirectoryIteratorException;

import java.nio.file.NotDirectoryException;

import java.nio.file.Path;

import java.util.Iterator;

import java.util.NoSuchElementException;

import java.io.IOException;

final class JrtDirectoryStream implements DirectoryStream<Path> {

    private final JrtFileSystem jrtfs;

    private final byte[] path;

    // prefix to be used for children of this directory

    // so that child path are reported relatively (if needed)

    private final String childPrefix;

    private final DirectoryStream.Filter<? super Path> filter;

    private volatile boolean isClosed;

    private volatile Iterator<Path> itr;

    JrtDirectoryStream(JrtPath jrtPath,

                       DirectoryStream.Filter<? super java.nio.file.Path> filter)

        throws IOException

    {

        this.jrtfs = jrtPath.getFileSystem();

        this.path = jrtPath.getResolvedPath();

        // sanity check

        if (!jrtfs.isDirectory(path))

            throw new NotDirectoryException(jrtPath.toString());

        // absolute path and does not have funky chars in front like /./java.base

        if (jrtPath.isAbsolute() && (path.length == jrtPath.getPathLength())) {

            childPrefix = null;

        } else {

            // cases where directory content needs to modified with prefix

            // like ./java.base, /./java.base, java.base and so on.

            String dirName = jrtPath.toString();

            int idx = dirName.indexOf(JrtFileSystem.getString(path).substring(1));

            childPrefix = dirName.substring(0, idx);

        }

        this.filter = filter;

    }

    @Override

    public synchronized Iterator<Path> iterator() {

        if (isClosed)

            throw new ClosedDirectoryStreamException();

        if (itr != null)

            throw new IllegalStateException("Iterator has already been returned");

        try {

            itr = jrtfs.iteratorOf(path, childPrefix);

        } catch (IOException e) {

            throw new IllegalStateException(e);

        }

        return new Iterator<Path>() {

            /*

             * next Path value to return from this iterator.

             * null value means hasNext() not called yet

             * or last hasNext() returned false or resulted

             * in exception. If last hasNext() returned true,

             * then this field has non-null value.

             */

            private Path next;

            // get-and-clear and set-next by these methods

            private Path getAndClearNext() {

                assert next != null;

                Path result = this.next;

                this.next = null;

                return result;

            }

            private void setNext(Path path) {

                assert path != null;

                this.next = path;

            }

            // if hasNext() returns true, 'next' field has non-null Path

            @Override

            public synchronized boolean hasNext() {

                if (next != null) {

                    return true;

                }

                if (isClosed) {

                    return false;

                }

                if (filter == null) {

                    if (itr.hasNext()) {

                        setNext(itr.next());

                        return true;

                    } else {

                        return false;

                    }

                } else {

                    while (itr.hasNext()) {

                        Path tmpPath = itr.next();

                        try {

                            if (filter.accept(tmpPath)) {

                                setNext(tmpPath);

                                return true;

                            }

                        } catch (IOException ioe) {

                            throw new DirectoryIteratorException(ioe);

                        }

                    }

                    return false;

                }

            }

            @Override

            public synchronized Path next() {

                if (next != null) {

                    return getAndClearNext();

                }

                if (isClosed) {

                    throw new NoSuchElementException();

                }

                if (next == null && itr.hasNext()) {

                    // missing hasNext() between next() calls.

                    if (hasNext()) {

                        return getAndClearNext();

                    }

                }

                throw new NoSuchElementException();

            }

            @Override

            public void remove() {

                throw new UnsupportedOperationException();

            }

        };

    }

    @Override

    public synchronized void close() throws IOException {

        isClosed = true;

    }

}