/*
    * ====================================================================
    *
    *  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.IOException;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.Future;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.http.annotation.ThreadSafe;
  import org.apache.http.conn.routing.HttpRoute;
  import org.apache.http.conn.scheme.SchemeRegistry;
  import org.apache.http.conn.ClientConnectionManager;
  import org.apache.http.conn.ClientConnectionOperator;
  import org.apache.http.conn.ClientConnectionRequest;
  import org.apache.http.conn.ConnectionPoolTimeoutException;
  import org.apache.http.conn.ManagedClientConnection;
  import org.apache.http.conn.OperatedClientConnection;
  import org.apache.http.pool.ConnPoolControl;
  import org.apache.http.pool.PoolStats;
  import org.apache.http.impl.conn.DefaultClientConnectionOperator;
  import org.apache.http.impl.conn.SchemeRegistryFactory;
  import org.apache.http.conn.DnsResolver;
  
  /**
   * Manages a pool of {@link OperatedClientConnection client connections} and
   * is able to service connection requests from multiple execution threads.
   * Connections are pooled on a per route basis. A request for a route which
   * already the manager has persistent connections for available in the pool
   * will be services by leasing a connection from the pool rather than
   * creating a brand new connection.
   * <p>
   * PoolingConnectionManager maintains a maximum limit of connection on
   * a per route basis and in total. Per default this implementation will
   * create no more than than 2 concurrent connections per given route
   * and no more 20 connections in total. For many real-world applications
   * these limits may prove too constraining, especially if they use HTTP
   * as a transport protocol for their services. Connection limits, however,
   * can be adjusted using HTTP parameters.
   *
   * @since 4.2
   */
  @ThreadSafe
  public class PoolingClientConnectionManager implements ClientConnectionManager, ConnPoolControl<HttpRoute> {
  
      private final Log log = LogFactory.getLog(getClass());
  
      private final SchemeRegistry schemeRegistry;
  
      private final HttpConnPool pool;
  
      private final ClientConnectionOperator operator;
  
      /** the custom-configured DNS lookup mechanism. */
      private final DnsResolver dnsResolver;
  
      public PoolingClientConnectionManager(final SchemeRegistry schreg) {
          this(schreg, -1, TimeUnit.MILLISECONDS);
      }
  
      public PoolingClientConnectionManager(final SchemeRegistry schreg,final DnsResolver dnsResolver) {
          this(schreg, -1, TimeUnit.MILLISECONDS,dnsResolver);
      }
  
      public PoolingClientConnectionManager() {
          this(SchemeRegistryFactory.createDefault());
      }
  
      public PoolingClientConnectionManager(
              final SchemeRegistry schemeRegistry,
              final long timeToLive, final TimeUnit tunit) {
          this(schemeRegistry, timeToLive, tunit, new SystemDefaultDnsResolver());
     }
 
     public PoolingClientConnectionManager(final SchemeRegistry schemeRegistry,
                 final long timeToLive, final TimeUnit tunit,
                 final DnsResolver dnsResolver) {
         super();
         if (schemeRegistry == null) {
             throw new IllegalArgumentException("Scheme registry may not be null");
         }
         if (dnsResolver == null) {
             throw new IllegalArgumentException("DNS resolver may not be null");
         }
         this.schemeRegistry = schemeRegistry;
         this.dnsResolver  = dnsResolver;
         this.operator = createConnectionOperator(schemeRegistry);
         this.pool = new HttpConnPool(this.log, this.operator, 2, 20, timeToLive, tunit);
     }
 
     @Override
     protected void finalize() throws Throwable {
         try {
             shutdown();
         } finally {
             super.finalize();
         }
     }
 
     /**
      * Hook for creating the connection operator.
      * It is called by the constructor.
      * Derived classes can override this method to change the
      * instantiation of the operator.
      * The default implementation here instantiates
      * {@link DefaultClientConnectionOperator DefaultClientConnectionOperator}.
      *
      * @param schreg    the scheme registry.
      *
      * @return  the connection operator to use
      */
     protected ClientConnectionOperator createConnectionOperator(SchemeRegistry schreg) {
             return new DefaultClientConnectionOperator(schreg, this.dnsResolver);
     }
 
     public SchemeRegistry getSchemeRegistry() {
         return this.schemeRegistry;
     }
 
     private String format(final HttpRoute route, final Object state) {
         StringBuilder buf = new StringBuilder();
         buf.append("[route: ").append(route).append("]");
         if (state != null) {
             buf.append("[state: ").append(state).append("]");
         }
         return buf.toString();
     }
 
     private String formatStats(final HttpRoute route) {
         StringBuilder buf = new StringBuilder();
         PoolStats totals = this.pool.getTotalStats();
         PoolStats stats = this.pool.getStats(route);
         buf.append("[total kept alive: ").append(totals.getAvailable()).append("; ");
         buf.append("route allocated: ").append(stats.getLeased() + stats.getAvailable());
         buf.append(" of ").append(stats.getMax()).append("; ");
         buf.append("total allocated: ").append(totals.getLeased() + totals.getAvailable());
         buf.append(" of ").append(totals.getMax()).append("]");
         return buf.toString();
     }
 
     private String format(final HttpPoolEntry entry) {
         StringBuilder buf = new StringBuilder();
         buf.append("[id: ").append(entry.getId()).append("]");
         buf.append("[route: ").append(entry.getRoute()).append("]");
         Object state = entry.getState();
         if (state != null) {
             buf.append("[state: ").append(state).append("]");
         }
         return buf.toString();
     }
 
     public ClientConnectionRequest requestConnection(
             final HttpRoute route,
             final Object state) {
         if (route == null) {
             throw new IllegalArgumentException("HTTP route may not be null");
         }
         if (this.log.isDebugEnabled()) {
             this.log.debug("Connection request: " + format(route, state) + formatStats(route));
         }
         final Future<HttpPoolEntry> future = this.pool.lease(route, state);
 
         return new ClientConnectionRequest() {
 
             public void abortRequest() {
                 future.cancel(true);
             }
 
             public ManagedClientConnection getConnection(
                     final long timeout,
                     final TimeUnit tunit) throws InterruptedException, ConnectionPoolTimeoutException {
                 return leaseConnection(future, timeout, tunit);
             }
 
         };
 
     }
 
     ManagedClientConnection leaseConnection(
             final Future<HttpPoolEntry> future,
             final long timeout,
             final TimeUnit tunit) throws InterruptedException, ConnectionPoolTimeoutException {
         HttpPoolEntry entry;
         try {
             entry = future.get(timeout, tunit);
             if (entry == null || future.isCancelled()) {
                 throw new InterruptedException();
             }
             if (entry.getConnection() == null) {
                 throw new IllegalStateException("Pool entry with no connection");
             }
             if (this.log.isDebugEnabled()) {
                 this.log.debug("Connection leased: " + format(entry) + formatStats(entry.getRoute()));
             }
             return new ManagedClientConnectionImpl(this, this.operator, entry);
         } catch (ExecutionException ex) {
             Throwable cause = ex.getCause();
             if (cause == null) {
                 cause = ex;
             }
             this.log.error("Unexpected exception leasing connection from pool", cause);
             // Should never happen
             throw new InterruptedException();
         } catch (TimeoutException ex) {
             throw new ConnectionPoolTimeoutException("Timeout waiting for connection from pool");
         }
     }
 
     public void releaseConnection(
             final ManagedClientConnection conn, final long keepalive, final TimeUnit tunit) {
 
         if (!(conn instanceof ManagedClientConnectionImpl)) {
             throw new IllegalArgumentException
                 ("Connection class mismatch, " +
                  "connection not obtained from this manager.");
         }
         ManagedClientConnectionImpl managedConn = (ManagedClientConnectionImpl) conn;
         if (managedConn.getManager() != this) {
             throw new IllegalStateException("Connection not obtained from this manager.");
         }
 
         synchronized (managedConn) {
             HttpPoolEntry entry = managedConn.detach();
             if (entry == null) {
                 return;
             }
             try {
                 if (managedConn.isOpen() && !managedConn.isMarkedReusable()) {
                     try {
                         managedConn.shutdown();
                     } catch (IOException iox) {
                         if (this.log.isDebugEnabled()) {
                             this.log.debug("I/O exception shutting down released connection", iox);
                         }
                     }
                 }
                 // Only reusable connections can be kept alive
                 if (managedConn.isMarkedReusable()) {
                     entry.updateExpiry(keepalive, tunit != null ? tunit : TimeUnit.MILLISECONDS);
                     if (this.log.isDebugEnabled()) {
                         String s;
                         if (keepalive > 0) {
                             s = "for " + keepalive + " " + tunit;
                         } else {
                             s = "indefinitely";
                         }
                         this.log.debug("Connection " + format(entry) + " can be kept alive " + s);
                     }
                 }
             } finally {
                 this.pool.release(entry, managedConn.isMarkedReusable());
             }
             if (this.log.isDebugEnabled()) {
                 this.log.debug("Connection released: " + format(entry) + formatStats(entry.getRoute()));
             }
         }
     }
 
     public void shutdown() {
         this.log.debug("Connection manager is shutting down");
         try {
             this.pool.shutdown();
         } catch (IOException ex) {
             this.log.debug("I/O exception shutting down connection manager", ex);
         }
         this.log.debug("Connection manager shut down");
     }
 
     public void closeIdleConnections(long idleTimeout, TimeUnit tunit) {
         if (this.log.isDebugEnabled()) {
             this.log.debug("Closing connections idle longer than " + idleTimeout + " " + tunit);
         }
         this.pool.closeIdle(idleTimeout, tunit);
     }
 
     public void closeExpiredConnections() {
         this.log.debug("Closing expired connections");
         this.pool.closeExpired();
     }
 
     public int getMaxTotal() {
         return this.pool.getMaxTotal();
     }
 
     public void setMaxTotal(int max) {
         this.pool.setMaxTotal(max);
     }
 
     public int getDefaultMaxPerRoute() {
         return this.pool.getDefaultMaxPerRoute();
     }
 
     public void setDefaultMaxPerRoute(int max) {
         this.pool.setDefaultMaxPerRoute(max);
     }
 
     public int getMaxPerRoute(final HttpRoute route) {
         return this.pool.getMaxPerRoute(route);
     }
 
     public void setMaxPerRoute(final HttpRoute route, int max) {
         this.pool.setMaxPerRoute(route, max);
     }
 
     public PoolStats getTotalStats() {
         return this.pool.getTotalStats();
     }
 
     public PoolStats getStats(final HttpRoute route) {
         return this.pool.getStats(route);
     }
 
 }