/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.http.impl.conn;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.net.InetSocketAddress;
  import java.util.Date;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.http.HttpClientConnection;
  import org.apache.http.HttpHost;
  import org.apache.http.annotation.GuardedBy;
  import org.apache.http.annotation.ThreadSafe;
  import org.apache.http.config.ConnectionConfig;
  import org.apache.http.config.Lookup;
  import org.apache.http.config.Registry;
  import org.apache.http.config.RegistryBuilder;
  import org.apache.http.config.SocketConfig;
  import org.apache.http.conn.ConnectionRequest;
  import org.apache.http.conn.DnsResolver;
  import org.apache.http.conn.HttpClientConnectionManager;
  import org.apache.http.conn.HttpConnectionFactory;
  import org.apache.http.conn.SchemePortResolver;
  import org.apache.http.conn.ManagedHttpClientConnection;
  import org.apache.http.conn.routing.HttpRoute;
  import org.apache.http.conn.socket.ConnectionSocketFactory;
  import org.apache.http.conn.socket.PlainSocketFactory;
  import org.apache.http.conn.ssl.SSLSocketFactory;
  import org.apache.http.protocol.HttpContext;
  import org.apache.http.util.Args;
  import org.apache.http.util.Asserts;
  import org.apache.http.util.LangUtils;
  
  /**
   * A connection manager for a single connection. This connection manager maintains only one active
   * connection. Even though this class is fully thread-safe it ought to be used by one execution
   * thread only, as only one thread a time can lease the connection at a time.
   * <p/>
   * This connection manager will make an effort to reuse the connection for subsequent requests
   * with the same {@link HttpRoute route}. It will, however, close the existing connection and
   * open it for the given route, if the route of the persistent connection does not match that
   * of the connection request. If the connection has been already been allocated
   * {@link IllegalStateException} is thrown.
   * <p/>
   * This connection manager implementation should be used inside an EJB container instead of
   * {@link PoolingHttpClientConnectionManager}.
   *
   * @since 4.3
   */
  @ThreadSafe
  public class BasicHttpClientConnectionManager implements HttpClientConnectionManager, Closeable {
  
      private final Log log = LogFactory.getLog(getClass());
  
      private final HttpClientConnectionOperator connectionOperator;
      private final HttpConnectionFactory<ManagedHttpClientConnection> connFactory;
  
      @GuardedBy("this")
      private ManagedHttpClientConnection conn;
  
      @GuardedBy("this")
      private HttpRoute route;
  
      @GuardedBy("this")
      private Object state;
  
      @GuardedBy("this")
      private long updated;
  
      @GuardedBy("this")
      private long expiry;
 
     @GuardedBy("this")
     private boolean leased;
 
     @GuardedBy("this")
     private SocketConfig socketConfig;
 
     @GuardedBy("this")
     private ConnectionConfig connConfig;
 
     @GuardedBy("this")
     private volatile boolean shutdown;
 
     private static Registry<ConnectionSocketFactory> getDefaultRegistry() {
         return RegistryBuilder.<ConnectionSocketFactory>create()
                 .register("https", PlainSocketFactory.getSocketFactory())
                 .register("https", SSLSocketFactory.getSocketFactory())
                 .build();
     }
 
     public BasicHttpClientConnectionManager(
             final Lookup<ConnectionSocketFactory> socketFactoryRegistry,
             final HttpConnectionFactory<ManagedHttpClientConnection> connFactory,
             final SchemePortResolver schemePortResolver,
             final DnsResolver dnsResolver) {
         super();
         this.connectionOperator = new HttpClientConnectionOperator(
                 socketFactoryRegistry, schemePortResolver, dnsResolver);
         this.connFactory = connFactory != null ? connFactory : ManagedHttpClientConnectionFactory.INSTANCE;
         this.expiry = Long.MAX_VALUE;
         this.socketConfig = SocketConfig.DEFAULT;
         this.connConfig = ConnectionConfig.DEFAULT;
     }
 
     public BasicHttpClientConnectionManager(
             final Lookup<ConnectionSocketFactory> socketFactoryRegistry,
             final HttpConnectionFactory<ManagedHttpClientConnection> connFactory) {
         this(socketFactoryRegistry, connFactory, null, null);
     }
 
     public BasicHttpClientConnectionManager(
             final Lookup<ConnectionSocketFactory> socketFactoryRegistry) {
         this(socketFactoryRegistry, null, null, null);
     }
 
     public BasicHttpClientConnectionManager() {
         this(getDefaultRegistry(), null, null, null);
     }
 
     @Override
     protected void finalize() throws Throwable {
         try {
             shutdown();
         } finally { // Make sure we call overridden method even if shutdown barfs
             super.finalize();
         }
     }
 
     public void close() {
         shutdown();
     }
 
     HttpRoute getRoute() {
         return route;
     }
 
     Object getState() {
         return state;
     }
 
     public synchronized SocketConfig getSocketConfig() {
         return socketConfig;
     }
 
     public synchronized void setSocketConfig(final SocketConfig socketConfig) {
         this.socketConfig = socketConfig != null ? socketConfig : SocketConfig.DEFAULT;
     }
 
     public synchronized ConnectionConfig getConnectionConfig() {
         return connConfig;
     }
 
     public synchronized void setConnectionConfig(final ConnectionConfig connConfig) {
         this.connConfig = connConfig != null ? connConfig : ConnectionConfig.DEFAULT;
     }
 
     public final ConnectionRequest requestConnection(
             final HttpRoute route,
             final Object state) {
         Args.notNull(route, "Route");
         return new ConnectionRequest() {
 
             public boolean cancel() {
                 // Nothing to abort, since requests are immediate.
                 return false;
             }
 
             public HttpClientConnection get(final long timeout, final TimeUnit tunit) {
                 return BasicHttpClientConnectionManager.this.getConnection(
                         route, state);
             }
 
         };
     }
 
     private void closeConnection() {
         if (this.conn != null) {
             this.log.debug("Closing connection");
             try {
                 this.conn.close();
             } catch (final IOException iox) {
                 if (this.log.isDebugEnabled()) {
                     this.log.debug("I/O exception closing connection", iox);
                 }
             }
             this.conn = null;
         }
     }
 
     private void shutdownConnection() {
         if (this.conn != null) {
             this.log.debug("Shutting down connection");
             try {
                 this.conn.shutdown();
             } catch (final IOException iox) {
                 if (this.log.isDebugEnabled()) {
                     this.log.debug("I/O exception shutting down connection", iox);
                 }
             }
             this.conn = null;
         }
     }
 
     private void checkExpiry() {
         if (this.conn != null && System.currentTimeMillis() >= this.expiry) {
             if (this.log.isDebugEnabled()) {
                 this.log.debug("Connection expired @ " + new Date(this.expiry));
             }
             closeConnection();
         }
     }
 
     synchronized HttpClientConnection getConnection(final HttpRoute route, final Object state) {
         Asserts.check(!this.shutdown, "Connection manager has been shut down");
         if (this.log.isDebugEnabled()) {
             this.log.debug("Get connection for route " + route);
         }
         Asserts.check(!this.leased, "Connection is still allocated");
         if (!LangUtils.equals(this.route, route) || !LangUtils.equals(this.state, state)) {
             closeConnection();
         }
         this.route = route;
         this.state = state;
         checkExpiry();
         if (this.conn == null) {
             this.conn = this.connFactory.create(this.connConfig);
         }
         this.leased = true;
         return this.conn;
     }
 
     public synchronized void releaseConnection(
             final HttpClientConnection conn,
             final Object state,
             final long keepalive, final TimeUnit tunit) {
         Args.notNull(conn, "Connection");
         Asserts.check(conn == this.conn, "Connection not obtained from this manager");
         if (this.log.isDebugEnabled()) {
             this.log.debug("Releasing connection " + conn);
         }
         if (this.shutdown) {
             shutdownConnection();
             return;
         }
         try {
             this.updated = System.currentTimeMillis();
             if (!this.conn.isOpen()) {
                 this.conn = null;
                 this.route = null;
                 this.conn = null;
                 this.expiry = Long.MAX_VALUE;
             } else {
                 this.state = state;
                 if (this.log.isDebugEnabled()) {
                     String s;
                     if (keepalive > 0) {
                         s = "for " + keepalive + " " + tunit;
                     } else {
                         s = "indefinitely";
                     }
                     this.log.debug("Connection can be kept alive " + s);
                 }
                 if (keepalive > 0) {
                     this.expiry = this.updated + tunit.toMillis(keepalive);
                 } else {
                     this.expiry = Long.MAX_VALUE;
                 }
             }
         } finally {
             this.leased = false;
         }
     }
 
     public void connect(
             final HttpClientConnection conn,
             final HttpRoute route,
             final int connectTimeout,
             final HttpContext context) throws IOException {
         Args.notNull(conn, "Connection");
         Args.notNull(route, "HTTP route");
         Asserts.check(conn == this.conn, "Connection not obtained from this manager");
         HttpHost host;
         if (route.getProxyHost() != null) {
             host = route.getProxyHost();
         } else {
             host = route.getTargetHost();
         }
         final InetSocketAddress localAddress = route.getLocalSocketAddress();
         this.connectionOperator.connect(this.conn, host, localAddress,
                 connectTimeout, this.socketConfig, context);
     }
 
     public void upgrade(
             final HttpClientConnection conn,
             final HttpRoute route,
             final HttpContext context) throws IOException {
         Args.notNull(conn, "Connection");
         Args.notNull(route, "HTTP route");
         Asserts.check(conn == this.conn, "Connection not obtained from this manager");
         this.connectionOperator.upgrade(this.conn, route.getTargetHost(), context);
     }
 
     public void routeComplete(
             final HttpClientConnection conn,
             final HttpRoute route,
             final HttpContext context) throws IOException {
     }
 
     public synchronized void closeExpiredConnections() {
         if (this.shutdown) {
             return;
         }
         if (!this.leased) {
             checkExpiry();
         }
     }
 
     public synchronized void closeIdleConnections(final long idletime, final TimeUnit tunit) {
         Args.notNull(tunit, "Time unit");
         if (this.shutdown) {
             return;
         }
         if (!this.leased) {
             long time = tunit.toMillis(idletime);
             if (time < 0) {
                 time = 0;
             }
             final long deadline = System.currentTimeMillis() - time;
             if (this.updated <= deadline) {
                 closeConnection();
             }
         }
     }
 
     public synchronized void shutdown() {
         if (this.shutdown) {
             return;
         }
         this.shutdown = true;
         shutdownConnection();
     }
 
 }