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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.openejb.client;

import org.apache.openejb.client.event.BootstrappingConnection;
import org.apache.openejb.client.event.FailoverSelection;

import java.io.IOException;
import java.net.URI;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.locks.ReentrantLock;

/**
 * @version $Rev$ $Date$
 */
public abstract class AbstractConnectionStrategy implements ConnectionStrategy {

    private final ReentrantLock lock = new ReentrantLock(true);

    @Override
    public Connection connect(final ClusterMetaData cluster, final ServerMetaData server) throws IOException {

        final ReentrantLock l = lock;
        l.lock();

        try {
            final Set failed = Client.getFailed();
            final Set remaining = new HashSet();

            boolean failover = false;

            final Iterable iterable = getIterable(cluster);
            for (final URI uri : iterable) {
                if (failed.contains(uri)) {
                    continue;
                }

                if (failover) {
                    Client.fireEvent(createFailureEvent(remaining, failed, uri));
                }

                try {
                    return connect(cluster, uri);
                } catch (final IOException e) {

                    if (!failover) {
                        Collections.addAll(remaining, cluster.getLocations());
                        remaining.removeAll(failed);
                    }

                    failed.add(uri);
                    remaining.remove(uri);
                    failover = true;
                }
            }

            final URI uri = server.getLocation();

            if (uri == null) {
                throw new RemoteFailoverException("Attempted to connect to " + failed.size() + " servers.");
            }

            Client.fireEvent(new BootstrappingConnection(uri));

            return connect(cluster, uri);
        } finally {
            l.unlock();
        }
    }

    private Iterable getIterable(final ClusterMetaData cluster) {
        final Context context = cluster.getContext();
        final StrategyData data = context.getComponent(StrategyData.class);

        if (data != null) {
            return data.getIterable();
        }

        context.setComponent(StrategyData.class, new StrategyData(createIterable(cluster)));

        return getIterable(cluster);
    }

    protected abstract FailoverSelection createFailureEvent(Set remaining, Set failed, URI uri);

    protected abstract Iterable createIterable(ClusterMetaData cluster);

    protected Connection connect(final ClusterMetaData cluster, final URI uri) throws IOException {
        final Connection connection = ConnectionManager.getConnection(uri);

        // Grabbing the URI from the associated connection allows the ConnectionFactory to
        // employ discovery to find and connect to a server.  We then attempt to connect
        // to the discovered server rather than repeat the discovery process again.
        cluster.setLastLocation(connection.getURI());
        return connection;
    }

    private static class StrategyData {

        private final Iterable iterable;

        private StrategyData(final Iterable iterable) {
            this.iterable = iterable;
        }

        public Iterable getIterable() {
            return iterable;
        }
    }
}