/*

 * Copyright (c) 2012, 2018, 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.jfr.internal;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.nio.ByteBuffer;

import java.nio.channels.FileChannel;

import java.nio.channels.ReadableByteChannel;

import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;

final class ChunksChannel implements ReadableByteChannel {

    private final Iterator<RepositoryChunk> chunks;

    private RepositoryChunk                 current;

    private ReadableByteChannel             channel;

    public ChunksChannel(List<RepositoryChunk> chunks) throws IOException {

        if (chunks.isEmpty()) {

            throw new FileNotFoundException("No chunks");

        }

        List<RepositoryChunk> l = new ArrayList<>(chunks.size());

        for (RepositoryChunk c : chunks) {

            c.use(); // keep alive while we're reading.

            l.add(c);

        }

        this.chunks = l.iterator();

        nextChannel();

    }

    private boolean nextChunk() {

        if (!chunks.hasNext()) {

            return false;

        }

        current = chunks.next();

        return true;

    }

    private boolean nextChannel() throws IOException {

        if (!nextChunk()) {

            return false;

        }

        channel = current.newChannel();

        return true;

    }

    @Override

    public int read(ByteBuffer dst) throws IOException {

        for (;;) {

            if (channel != null) {

                assert current != null;

                int r = channel.read(dst);

                if (r != -1) {

                    return r;

                }

                channel.close();

                current.release();

                channel = null;

                current = null;

            }

            if (!nextChannel()) {

                return -1;

            }

        }

    }

    public long transferTo(FileChannel out) throws IOException {

        long pos = 0;

        for (;;) {

            if (channel != null) {

                assert current != null;

                long rem = current.getSize();

                while (rem > 0) {

                    long n = Math.min(rem, 1024 * 1024);

                    long w = out.transferFrom(channel, pos, n);

                    pos += w;

                    rem -= w;

                }

                channel.close();

                current.release();

                channel = null;

                current = null;

            }

            if (!nextChannel()) {

                return pos;

            }

        }

    }

    @Override

    public void close() throws IOException {

        if (channel != null) {

            channel.close();

            channel = null;

        }

        while (current != null) {

            current.release();

            current = null;

            if (!nextChunk()) {

                return;

            }

        }

    }

    @Override

    public boolean isOpen() {

        return channel != null;

    }

    @Override

    @SuppressWarnings("deprecation")

    protected void finalize() throws Throwable {

        super.finalize();

        close();

    }

}