/*

  * #%L

  * ShardedConnection.java - mongodb-async-driver - Allanbank Consulting, Inc.

  * %%

  * Copyright (C) 2011 - 2014 Allanbank Consulting, Inc.

  * %%

  * 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.

  * #L%

  */

 package com.allanbank.mongodb.client.connection.sharded;

 import java.io.IOException;

 import java.util.Collections;

 import java.util.List;

 import com.allanbank.mongodb.MongoClientConfiguration;

 import com.allanbank.mongodb.MongoDbException;

 import com.allanbank.mongodb.ReadPreference;

 import com.allanbank.mongodb.client.Message;

 import com.allanbank.mongodb.client.connection.Connection;

 import com.allanbank.mongodb.client.connection.proxy.AbstractProxyMultipleConnection;

 import com.allanbank.mongodb.client.connection.proxy.ConnectionInfo;

 import com.allanbank.mongodb.client.connection.proxy.ProxiedConnectionFactory;

 import com.allanbank.mongodb.client.state.Cluster;

 import com.allanbank.mongodb.client.state.Server;

 import com.allanbank.mongodb.client.state.ServerSelector;

 import com.allanbank.mongodb.util.log.Log;

 import com.allanbank.mongodb.util.log.LogFactory;

 /**

  * Provides a {@link Connection} implementation for connecting to a sharded

  * environment via mongos servers.

  * 

  * @api.no This class is <b>NOT</b> part of the drivers API. This class may be

  *         mutated in incompatible ways between any two releases of the driver.

  * @copyright 2011-2013, Allanbank Consulting, Inc., All Rights Reserved

  */

 public class ShardedConnection extends AbstractProxyMultipleConnection<Server> {

     /** The logger for the {@link ShardedConnection}. */

     private static final Log LOG = LogFactory.getLog(ShardedConnection.class);

     /** The selector for the server when we need to reconnect. */

     private final ServerSelector mySelector;

     /**

      * Creates a new {@link ShardedConnection}.

      * 

      * @param proxiedConnection

      *            The connection being proxied.

      * @param server

      *            The primary server this connection is connected to.

      * @param cluster

      *            The state of the cluster for finding secondary connections.

      * @param selector

      *            The selector for servers when we need to reconnect.

      * @param factory

      *            The connection factory for opening secondary connections.

      * @param config

      *            The MongoDB client configuration.

      */

     public ShardedConnection(final Connection proxiedConnection,

             final Server server, final Cluster cluster,

             final ServerSelector selector,

             final ProxiedConnectionFactory factory,

             final MongoClientConfiguration config) {

         super(proxiedConnection, server, cluster, factory, config);

         mySelector = selector;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to return the canonical name of the primary.

      * </p>

      */

     @Override

     public String getServerName() {

         if (myMainKey != null) {

             return myMainKey.getCanonicalName();

         }

         return "UNKNOWN";

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to create a connection to the server.

      * </p>

      */

     @Override

     protected Connection connect(final Server server) {

         Connection conn = null;

         try {

             conn = myFactory.connect(server, myConfig);

             conn = cacheConnection(server, conn);

         }

         catch (final IOException e) {

             LOG.info(e, "Could not connect to the server '{}': {}",

                     server.getCanonicalName(), e.getMessage());

         }

         return conn;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden for testing access.

      * </p>

      */

     @Override

     protected Connection connection(final Server server) {

         LOG.debug("Lookup connection for server: {}", server.getCanonicalName());

         return super.connection(server);

     }

     /**

      * Locates the set of servers that can be used to send the specified

      * messages. This method will attempt to connect to the primary server if

      * there is not a current connection to the primary.

      * 

      * @param message1

      *            The first message to send.

      * @param message2

      *            The second message to send. May be <code>null</code>.

      * @return The servers that can be used.

      * @throws MongoDbException

      *             On a failure to locate a server that all messages can be sent

      *             to.

      */

     @Override

     protected List<Server> findPotentialKeys(final Message message1,

             final Message message2) throws MongoDbException {

         List<Server> servers = resolveServerReadPreference(message1, message2);

         if (servers.isEmpty()) {

             // If we get here and a reconnect is in progress then

             // block for the reconnect. Once the reconnect is complete, try

             // again.

             if (myMainKey == null) {

                 // Wait for a reconnect.

                 final ConnectionInfo<Server> newConnInfo = reconnectMain();

                 if (newConnInfo != null) {

                     updateMain(newConnInfo);

                     servers = resolveServerReadPreference(message1, message2);

                 }

             }

             if (servers.isEmpty()) {

                 throw createReconnectFailure(message1, message2);

             }

         }

         return servers;

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to return the string {@code Sharded}.

      * </p>

      */

     @Override

     protected String getConnectionType() {

         return "Sharded";

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden creates a connection back to the primary server.

      * </p>

      */

     @Override

     protected ConnectionInfo<Server> reconnectMain() {

         for (final Server server : mySelector.pickServers()) {

             try {

                 final Connection conn = myFactory.connect(server, myConfig);

                 return new ConnectionInfo<Server>(conn, server);

             }

             catch (final IOException ioe) {

                 // Ignored. Will return null.

                 LOG.debug(ioe, "Could not connect to '{}': {}",

                         server.getCanonicalName(), ioe.getMessage());

             }

         }

         return null;

     }

     /**

      * Locates the set of servers that can be used to send the specified

      * messages.

      * 

      * @param message1

      *            The first message to send.

      * @param message2

      *            The second message to send. May be <code>null</code>.

      * @return The servers that can be used.

      */

     private List<Server> resolveServerReadPreference(final Message message1,

             final Message message2) {

         List<Server> servers = Collections.emptyList();

         final Server main = myMainKey;

         if (main != null) {

             servers = Collections.singletonList(main);

         }

         if (message1 != null) {

             ReadPreference pref = message1.getReadPreference();

             if (pref.getServer() != null) {

                 servers = Collections.singletonList(myCluster.get(pref

                         .getServer()));

             }

             else if (message2 != null) {

                 pref = message2.getReadPreference();

                 if (pref.getServer() != null) {

                     servers = Collections.singletonList(myCluster.get(pref

                             .getServer()));

                 }

             }

         }

         return servers;

     }

 }