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/**
 * Copyright (C) 2011 Ovea 
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.ovea.system.tunnel;

import com.ovea.system.pipe.*;
import com.ovea.system.util.IoUtils;

import java.io.IOException;
import java.net.Socket;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicReference;

/**
 * @author Mathieu Carbou ([email protected])
 */
public final class Tunnel {

    private static enum State {OPENED, CLOSED, INTERRUPTED, BROKEN}

    private static final TunnelListener EMPTY = new TunnelListenerAdapter();

    private final AtomicReference state = new AtomicReference(null);
    private final CountDownLatch latch = new CountDownLatch(2);
    private final String name;
    private final TunnelListener listener;

    private PipeConnection up;
    private PipeConnection down;

    private BrokenTunnelException brokenTunnelException;

    private Tunnel(String name, Pipe up, Pipe down, TunnelListener listener) {
        this.name = name;
        this.listener = new OnceTunnelListener(listener);
        this.up = up.listenedBy(new Listener(down, listener)).connect();
        this.down = down.listenedBy(new Listener(up, listener)).connect();
    }

    public boolean isOpened() {
        return state.get() == State.OPENED;
    }

    public boolean isClosed() {
        return state.get() == State.CLOSED;
    }

    public boolean isBroken() {
        return state.get() == State.BROKEN;
    }

    public boolean isInterrupted() {
        return state.get() == State.INTERRUPTED;
    }

    public void interrupt() {
        if (state.compareAndSet(null, State.INTERRUPTED) || state.compareAndSet(State.OPENED, State.INTERRUPTED)) {
            up.interrupt();
            down.interrupt();
            up = down = null;
            listener.onInterrupt(Tunnel.this);
        }
    }

    @Override
    public String toString() {
        return name;
    }

    public void await(long time, TimeUnit unit) throws InterruptedException, BrokenTunnelException, TimeoutException {
        if (Thread.interrupted())
            throw new InterruptedException();
        try {
            if (latch.await(time, unit)) {
                if (isBroken()) {
                    throw brokenTunnelException;
                }
            } else {
                throw new TimeoutException();
            }
        } catch (InterruptedException e) {
            interrupt();
            throw e;
        }
    }

    public void await() throws InterruptedException, BrokenTunnelException {
        if (Thread.interrupted())
            throw new InterruptedException();
        try {
            latch.await();
            if (isBroken()) {
                throw brokenTunnelException;
            }
        } catch (InterruptedException e) {
            interrupt();
            throw e;
        }
    }

    private class Listener implements PipeListener {

        private Pipe other;
        private TunnelListener listener;

        private Listener(Pipe other, TunnelListener listener) {
            this.other = other;
            this.listener = listener;
        }

        @Override
        public void onConnect(Pipe pipe) {
            if (state.compareAndSet(null, State.OPENED)) {
                listener.onConnect(Tunnel.this);
            }
        }

        @Override
        public void onClose(Pipe pipe) {
            if (state.compareAndSet(null, State.CLOSED) || state.compareAndSet(State.OPENED, State.CLOSED)) {
                other.connect().interrupt();
                listener.onClose(Tunnel.this);
                other = null;
                listener = null;
            }
            latch.countDown();
        }

        @Override
        public void onBroken(Pipe pipe, BrokenPipeException e) {
            if (state.compareAndSet(null, State.BROKEN) || state.compareAndSet(State.OPENED, State.BROKEN)) {
                other.connect().interrupt();
                listener.onBroken(Tunnel.this, brokenTunnelException = new BrokenTunnelException(e));
                other = null;
                listener = null;
            }
            latch.countDown();
        }

        @Override
        public void onInterrupt(Pipe pipe) {
            if (state.compareAndSet(null, State.INTERRUPTED) || state.compareAndSet(State.OPENED, State.INTERRUPTED)) {
                other.connect().interrupt();
                listener.onInterrupt(Tunnel.this);
                other = null;
                listener = null;
            }
            latch.countDown();
        }
    }

    public static Tunnel connect(Socket left, Socket right) throws IOException {
        return connect(left, right, EMPTY);
    }

    public static Tunnel connect(final Socket left, final Socket right, TunnelListener listener) throws IOException {
        if (left == null) throw new IllegalArgumentException("Missing left socket");
        if (right == null) throw new IllegalArgumentException("Missing right socket");
        if (listener == null) throw new IllegalArgumentException("Missing tunnel listener");
        String l = left.getInetAddress().getHostAddress() + ":" + left.getPort();
        String r = right.getInetAddress().getHostAddress() + ":" + right.getPort();
        return new Tunnel(
                l + "<=>" + r,
                Pipes.create(l + "=>" + r, left.getInputStream(), right.getOutputStream()),
                Pipes.create(r + "=>" + l, right.getInputStream(), left.getOutputStream()),
                new TunnelListeners(new TunnelListenerAdapter() {
                    @Override
                    public void onClose(Tunnel tunnel) {
                        IoUtils.close(left, right);
                    }

                    @Override
                    public void onBroken(Tunnel tunnel, BrokenTunnelException e) {
                        onClose(tunnel);
                    }

                    @Override
                    public void onInterrupt(Tunnel tunnel) {
                        onClose(tunnel);
                    }
                }, listener));
    }
}