/*

 * 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 sun.nio.fs;

import java.nio.file.*;

import java.util.Iterator;

import java.util.NoSuchElementException;

import java.util.concurrent.locks.*;

import java.io.IOException;

import static sun.nio.fs.UnixNativeDispatcher.*;

/**

 * Unix implementation of java.nio.file.DirectoryStream

 */

class UnixDirectoryStream

    implements DirectoryStream<Path>

{

    // path to directory when originally opened

    private final UnixPath dir;

    // directory pointer (returned by opendir)

    private final long dp;

    // filter (may be null)

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

    // used to coorindate closing of directory stream

    private final ReentrantReadWriteLock streamLock =

        new ReentrantReadWriteLock(true);

    // indicates if directory stream is open (synchronize on closeLock)

    private volatile boolean isClosed;

    // directory iterator

    private Iterator<Path> iterator;

    /**

     * Initializes a new instance

     */

    UnixDirectoryStream(UnixPath dir, long dp, DirectoryStream.Filter<? super Path> filter) {

        this.dir = dir;

        this.dp = dp;

        this.filter = filter;

    }

    protected final UnixPath directory() {

        return dir;

    }

    protected final Lock readLock() {

        return streamLock.readLock();

    }

    protected final Lock writeLock() {

        return streamLock.writeLock();

    }

    protected final boolean isOpen() {

        return !isClosed;

    }

    protected final boolean closeImpl() throws IOException {

        if (!isClosed) {

            isClosed = true;

            try {

                closedir(dp);

            } catch (UnixException x) {

                throw new IOException(x.errorString());

            }

            return true;

        } else {

            return false;

        }

    }

    @Override

    public void close()

        throws IOException

    {

        writeLock().lock();

        try {

            closeImpl();

        } finally {

            writeLock().unlock();

        }

    }

    protected final Iterator<Path> iterator(DirectoryStream<Path> ds) {

        if (isClosed) {

            throw new IllegalStateException("Directory stream is closed");

        }

        synchronized (this) {

            if (iterator != null)

                throw new IllegalStateException("Iterator already obtained");

            iterator = new UnixDirectoryIterator(ds);

            return iterator;

        }

    }

    @Override

    public Iterator<Path> iterator() {

        return iterator(this);

    }

    /**

     * Iterator implementation

     */

    private class UnixDirectoryIterator implements Iterator<Path> {

        private final DirectoryStream<Path> stream;

        // true when at EOF

        private boolean atEof;

        // next entry to return

        private Path nextEntry;

        UnixDirectoryIterator(DirectoryStream<Path> stream) {

            atEof = false;

            this.stream = stream;

        }

        // Return true if file name is "." or ".."

        private boolean isSelfOrParent(byte[] nameAsBytes) {

            if (nameAsBytes[0] == '.') {

                if ((nameAsBytes.length == 1) ||

                    (nameAsBytes.length == 2 && nameAsBytes[1] == '.')) {

                    return true;

                }

            }

            return false;

        }

        // Returns next entry (or null)

        private Path readNextEntry() {

            assert Thread.holdsLock(this);

            for (;;) {

                byte[] nameAsBytes = null;

                // prevent close while reading

                readLock().lock();

                try {

                    if (isOpen()) {

                        nameAsBytes = readdir(dp);

                    }

                } catch (UnixException x) {

                    IOException ioe = x.asIOException(dir);

                    throw new DirectoryIteratorException(ioe);

                } finally {

                    readLock().unlock();

                }

                // EOF

                if (nameAsBytes == null) {

                    atEof = true;

                    return null;

                }

                // ignore "." and ".."

                if (!isSelfOrParent(nameAsBytes)) {

                    Path entry = dir.resolve(nameAsBytes);

                    // return entry if no filter or filter accepts it

                    try {

                        if (filter == null || filter.accept(entry))

                            return entry;

                    } catch (IOException ioe) {

                        throw new DirectoryIteratorException(ioe);

                    }

                }

            }

        }

        @Override

        public synchronized boolean hasNext() {

            if (nextEntry == null && !atEof)

                nextEntry = readNextEntry();

            return nextEntry != null;

        }

        @Override

        public synchronized Path next() {

            Path result;

            if (nextEntry == null && !atEof) {

                result = readNextEntry();

            } else {

                result = nextEntry;

                nextEntry = null;

            }

            if (result == null)

                throw new NoSuchElementException();

            return result;

        }

        @Override

        public void remove() {

            throw new UnsupportedOperationException();

        }

    }

}