/*
 * Copyright (c) 2013 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.protocol.framework;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelOption;
import io.netty.util.concurrent.DefaultPromise;
import io.netty.util.concurrent.EventExecutor;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.FutureListener;
import io.netty.util.concurrent.Promise;

import java.net.InetSocketAddress;

import javax.annotation.concurrent.GuardedBy;
import javax.annotation.concurrent.ThreadSafe;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Preconditions;

@ThreadSafe
final class ProtocolSessionPromise<S extends ProtocolSession<?>> extends DefaultPromise<S> {
    private static final Logger LOG = LoggerFactory.getLogger(ProtocolSessionPromise.class);
    private final ReconnectStrategy strategy;
    private final InetSocketAddress address;
    private final Bootstrap b;

    @GuardedBy("this")
    private Future<?> pending;

    ProtocolSessionPromise(final EventExecutor executor, final InetSocketAddress address, final ReconnectStrategy strategy,
            final Bootstrap b) {
        super(executor);
        this.strategy = Preconditions.checkNotNull(strategy);
        this.address = Preconditions.checkNotNull(address);
        this.b = Preconditions.checkNotNull(b);
    }

    synchronized void connect() {
        final Object lock = this;

        try {
            final int timeout = this.strategy.getConnectTimeout();

            LOG.debug("Promise {} attempting connect for {}ms", lock, timeout);

            this.b.option(ChannelOption.CONNECT_TIMEOUT_MILLIS, timeout);
            this.pending = this.b.connect(this.address).addListener(new ChannelFutureListener() {
                @Override
                public void operationComplete(final ChannelFuture cf) throws Exception {
                    synchronized (lock) {

                        LOG.debug("Promise {} connection resolved", lock);

                        // Triggered when a connection attempt is resolved.
                        Preconditions.checkState(ProtocolSessionPromise.this.pending.equals(cf));

                        /*
                         * The promise we gave out could have been cancelled,
                         * which cascades to the connect getting cancelled,
                         * but there is a slight race window, where the connect
                         * is already resolved, but the listener has not yet
                         * been notified -- cancellation at that point won't
                         * stop the notification arriving, so we have to close
                         * the race here.
                         */
                        if (isCancelled()) {
                            if (cf.isSuccess()) {
                                LOG.debug("Closing channel for cancelled promise {}", lock);
                                cf.channel().close();
                            }
                            return;
                        }

                        if (!cf.isSuccess()) {
                            LOG.warn("Attempt to connect to connect to {} failed", ProtocolSessionPromise.this.address, cf.cause());
                            final Future<Void> rf = ProtocolSessionPromise.this.strategy.scheduleReconnect(cf.cause());
                            rf.addListener(new FutureListener<Void>() {
                                @Override
                                public void operationComplete(final Future<Void> sf) {
                                    synchronized (lock) {
                                        // Triggered when a connection attempt is to be made.
                                        Preconditions.checkState(ProtocolSessionPromise.this.pending.equals(sf));

                                        /*
                                         * The promise we gave out could have been cancelled,
                                         * which cascades to the reconnect attempt getting
                                         * cancelled, but there is a slight race window, where
                                         * the reconnect attempt is already enqueued, but the
                                         * listener has not yet been notified -- if cancellation
                                         * happens at that point, we need to catch it here.
                                         */
                                        if (!isCancelled()) {
                                            if (sf.isSuccess()) {
                                                connect();
                                            } else {
                                                setFailure(sf.cause());
                                            }
                                        }
                                    }
                                }
                            });

                            ProtocolSessionPromise.this.pending = rf;
                        } else {
                            LOG.debug("Promise {} connection successful", lock);
                        }
                    }
                }
            });
        } catch (final Exception e) {
            LOG.info("Failed to connect to {}", e);
            setFailure(e);
        }
    }

    @Override
    public synchronized boolean cancel(final boolean mayInterruptIfRunning) {
        if (super.cancel(mayInterruptIfRunning)) {
            this.pending.cancel(mayInterruptIfRunning);
            return true;
        }

        return false;
    }

    @Override
    public synchronized Promise<S> setSuccess(final S result) {
        LOG.debug("Promise {} completed", this);
        this.strategy.reconnectSuccessful();
        return super.setSuccess(result);
    }
}