/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.neo4j.adversaries.fs;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileLock;
import org.neo4j.adversaries.Adversary;
import org.neo4j.io.fs.StoreChannel;
import org.neo4j.io.fs.StoreFileChannel;

@SuppressWarnings("unchecked")
public class AdversarialFileChannel extends StoreFileChannel {
    private final StoreChannel delegate;
    private final Adversary adversary;

    public static StoreFileChannel wrap(StoreFileChannel channel, Adversary adversary) {
        return new AdversarialFileChannel(channel, adversary);
    }

    private AdversarialFileChannel(StoreFileChannel channel, Adversary adversary) {
        super(channel);
        this.delegate = channel;
        this.adversary = adversary;
    }

    @Override
    public long write(ByteBuffer[] srcs) throws IOException {
        if (adversary.injectFailureOrMischief(IOException.class)) {
            ByteBuffer mischievousBuffer = srcs[srcs.length - 1];
            int oldLimit = mischiefLimit(mischievousBuffer);
            long written = delegate.write(srcs);
            mischievousBuffer.limit(oldLimit);
            return written;
        }
        return delegate.write(srcs);
    }

    @Override
    public void writeAll(ByteBuffer src, long position) throws IOException {
        adversary.injectFailure(IOException.class);
        delegate.writeAll(src, position);
    }

    @Override
    public void writeAll(ByteBuffer src) throws IOException {
        adversary.injectFailure(IOException.class);
        delegate.writeAll(src);
    }

    @Override
    public long write(ByteBuffer[] srcs, int offset, int length) throws IOException {
        if (adversary.injectFailureOrMischief(IOException.class)) {
            length = length == 1 ? 1 : length / 2;
            ByteBuffer mischievousBuffer = srcs[offset + length - 1];
            int oldLimit = mischiefLimit(mischievousBuffer);
            long written = delegate.write(srcs, offset, length);
            mischievousBuffer.limit(oldLimit);
            return written;
        }
        return delegate.write(srcs, offset, length);
    }

    @Override
    public StoreFileChannel truncate(long size) throws IOException {
        adversary.injectFailure(IOException.class);
        return (StoreFileChannel) delegate.truncate(size);
    }

    @Override
    public StoreFileChannel position(long newPosition) throws IOException {
        adversary.injectFailure(IOException.class);
        return (StoreFileChannel) delegate.position(newPosition);
    }

    @Override
    public int read(ByteBuffer dst, long position) throws IOException {
        if (adversary.injectFailureOrMischief(IOException.class)) {
            int oldLimit = mischiefLimit(dst);
            int read = delegate.read(dst, position);
            dst.limit(oldLimit);
            return read;
        }
        return delegate.read(dst, position);
    }

    private static int mischiefLimit(ByteBuffer buf) {
        int oldLimit = buf.limit();
        int newLimit = oldLimit - buf.remaining() / 2;
        buf.limit(newLimit);
        return oldLimit;
    }

    @Override
    public void force(boolean metaData) throws IOException {
        adversary.injectFailure(IOException.class);
        delegate.force(metaData);
    }

    @Override
    public int read(ByteBuffer dst) throws IOException {
        if (adversary.injectFailureOrMischief(IOException.class)) {
            int oldLimit = mischiefLimit(dst);
            int read = delegate.read(dst);
            dst.limit(oldLimit);
            return read;
        }
        return delegate.read(dst);
    }

    @Override
    public long read(ByteBuffer[] dsts, int offset, int length) throws IOException {
        if (adversary.injectFailureOrMischief(IOException.class)) {
            ByteBuffer lastBuf = dsts[dsts.length - 1];
            int oldLimit = mischiefLimit(lastBuf);
            long read = delegate.read(dsts, offset, length);
            lastBuf.limit(oldLimit);
            return read;
        }
        return delegate.read(dsts, offset, length);
    }

    @Override
    public long position() throws IOException {
        adversary.injectFailure(IOException.class);
        return delegate.position();
    }

    @Override
    public FileLock tryLock() throws IOException {
        adversary.injectFailure(IOException.class);
        return delegate.tryLock();
    }

    @Override
    public boolean isOpen() {
        adversary.injectFailure();
        return delegate.isOpen();
    }

    @Override
    public long read(ByteBuffer[] dsts) throws IOException {
        if (adversary.injectFailureOrMischief(IOException.class)) {
            ByteBuffer lastBuf = dsts[dsts.length - 1];
            int oldLimit = mischiefLimit(lastBuf);
            long read = delegate.read(dsts);
            lastBuf.limit(oldLimit);
            return read;
        }
        return delegate.read(dsts);
    }

    @Override
    public int write(ByteBuffer src) throws IOException {
        if (adversary.injectFailureOrMischief(IOException.class)) {
            int oldLimit = mischiefLimit(src);
            int written = delegate.write(src);
            src.limit(oldLimit);
            return written;
        }
        return delegate.write(src);
    }

    @Override
    public void close() throws IOException {
        adversary.injectFailure(IOException.class);
        delegate.close();
    }

    @Override
    public long size() throws IOException {
        adversary.injectFailure(IOException.class);
        return delegate.size();
    }

    @Override
    public void flush() throws IOException {
        force(false);
    }
}
