/*
    * ====================================================================
    * 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.TimeUnit;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.http.annotation.Contract;
  import org.apache.http.annotation.ThreadingBehavior;
  import org.apache.http.conn.ClientConnectionManager;
  import org.apache.http.conn.ClientConnectionOperator;
  import org.apache.http.conn.ClientConnectionRequest;
  import org.apache.http.conn.ManagedClientConnection;
  import org.apache.http.conn.routing.HttpRoute;
  import org.apache.http.conn.routing.RouteTracker;
  import org.apache.http.conn.scheme.SchemeRegistry;
  import org.apache.http.params.HttpParams;
  import org.apache.http.util.Args;
  import org.apache.http.util.Asserts;
  
  /**
   * A connection manager for a single connection. This connection manager
   * maintains only one active connection at a time. Even though this class
   * is thread-safe it ought to be used by one execution thread only.
   * <p>
   * SingleClientConnManager 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.
   *
   * @since 4.0
   *
   * @deprecated (4.2)  use {@link BasicClientConnectionManager}
   */
  @Contract(threading = ThreadingBehavior.SAFE)
  @Deprecated
  public class SingleClientConnManager implements ClientConnectionManager {
  
      private final Log log = LogFactory.getLog(getClass());
  
      /** The message to be logged on multiple allocation. */
      public final static String MISUSE_MESSAGE =
      "Invalid use of SingleClientConnManager: connection still allocated.\n" +
      "Make sure to release the connection before allocating another one.";
  
      /** The schemes supported by this connection manager. */
      protected final SchemeRegistry schemeRegistry;
  
      /** The operator for opening and updating connections. */
      protected final ClientConnectionOperator connOperator;
  
      /** Whether the connection should be shut down  on release. */
      protected final boolean alwaysShutDown;
  
      /** The one and only entry in this pool. */
      protected volatile PoolEntry uniquePoolEntry;
  
      /** The currently issued managed connection, if any. */
      protected volatile ConnAdapter managedConn;
  
      /** The time of the last connection release, or -1. */
      protected volatile long lastReleaseTime;
  
      /** The time the last released connection expires and shouldn't be reused. */
      protected volatile long connectionExpiresTime;
  
      /** Indicates whether this connection manager is shut down. */
      protected volatile boolean isShutDown;
  
      /**
      * Creates a new simple connection manager.
      *
      * @param params    the parameters for this manager
      * @param schreg    the scheme registry
      *
      * @deprecated (4.1)  use {@link SingleClientConnManager#SingleClientConnManager(SchemeRegistry)}
      */
     @Deprecated
     public SingleClientConnManager(final HttpParams params,
                                    final SchemeRegistry schreg) {
         this(schreg);
     }
     /**
      * Creates a new simple connection manager.
      *
      * @param schreg    the scheme registry
      */
     public SingleClientConnManager(final SchemeRegistry schreg) {
         Args.notNull(schreg, "Scheme registry");
         this.schemeRegistry  = schreg;
         this.connOperator    = createConnectionOperator(schreg);
         this.uniquePoolEntry = new PoolEntry();
         this.managedConn     = null;
         this.lastReleaseTime = -1L;
         this.alwaysShutDown  = false; //@@@ from params? as argument?
         this.isShutDown      = false;
     }
 
     /**
      * @since 4.1
      */
     public SingleClientConnManager() {
         this(SchemeRegistryFactory.createDefault());
     }
 
     @Override
     protected void finalize() throws Throwable {
         try {
             shutdown();
         } finally { // Make sure we call overridden method even if shutdown barfs
             super.finalize();
         }
     }
 
     @Override
     public SchemeRegistry getSchemeRegistry() {
         return this.schemeRegistry;
     }
 
     /**
      * 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 to use, or {@code null}
      *
      * @return  the connection operator to use
      */
     protected ClientConnectionOperator
         createConnectionOperator(final SchemeRegistry schreg) {
         return new DefaultClientConnectionOperator(schreg);
     }
 
     /**
      * Asserts that this manager is not shut down.
      *
      * @throws IllegalStateException    if this manager is shut down
      */
     protected final void assertStillUp() throws IllegalStateException {
         Asserts.check(!this.isShutDown, "Manager is shut down");
     }
 
     @Override
     public final ClientConnectionRequest requestConnection(
             final HttpRoute route,
             final Object state) {
 
         return new ClientConnectionRequest() {
 
             @Override
             public void abortRequest() {
                 // Nothing to abort, since requests are immediate.
             }
 
             @Override
             public ManagedClientConnection getConnection(
                     final long timeout, final TimeUnit timeUnit) {
                 return SingleClientConnManager.this.getConnection(
                         route, state);
             }
 
         };
     }
 
     /**
      * Obtains a connection.
      *
      * @param route     where the connection should point to
      *
      * @return  a connection that can be used to communicate
      *          along the given route
      */
     public ManagedClientConnection getConnection(final HttpRoute route, final Object state) {
         Args.notNull(route, "Route");
         assertStillUp();
 
         if (log.isDebugEnabled()) {
             log.debug("Get connection for route " + route);
         }
 
         synchronized (this) {
 
             Asserts.check(managedConn == null, MISUSE_MESSAGE);
 
             // check re-usability of the connection
             boolean recreate = false;
             boolean shutdown = false;
 
             // Kill the connection if it expired.
             closeExpiredConnections();
 
             if (uniquePoolEntry.connection.isOpen()) {
                 final RouteTracker tracker = uniquePoolEntry.tracker;
                 shutdown = (tracker == null || // can happen if method is aborted
                             !tracker.toRoute().equals(route));
             } else {
                 // If the connection is not open, create a new PoolEntry,
                 // as the connection may have been marked not reusable,
                 // due to aborts -- and the PoolEntry should not be reused
                 // either.  There's no harm in recreating an entry if
                 // the connection is closed.
                 recreate = true;
             }
 
             if (shutdown) {
                 recreate = true;
                 try {
                     uniquePoolEntry.shutdown();
                 } catch (final IOException iox) {
                     log.debug("Problem shutting down connection.", iox);
                 }
             }
 
             if (recreate) {
                 uniquePoolEntry = new PoolEntry();
             }
 
             managedConn = new ConnAdapter(uniquePoolEntry, route);
 
             return managedConn;
         }
     }
 
     @Override
     public void releaseConnection(
             final ManagedClientConnection conn,
             final long validDuration, final TimeUnit timeUnit) {
         Args.check(conn instanceof ConnAdapter, "Connection class mismatch, " +
             "connection not obtained from this manager");
         assertStillUp();
 
         if (log.isDebugEnabled()) {
             log.debug("Releasing connection " + conn);
         }
 
         final ConnAdapter sca = (ConnAdapter) conn;
         synchronized (sca) {
             if (sca.poolEntry == null)
              {
                 return; // already released
             }
             final ClientConnectionManager manager = sca.getManager();
             Asserts.check(manager == this, "Connection not obtained from this manager");
             try {
                 // make sure that the response has been read completely
                 if (sca.isOpen() && (this.alwaysShutDown ||
                                      !sca.isMarkedReusable())
                     ) {
                     if (log.isDebugEnabled()) {
                         log.debug
                             ("Released connection open but not reusable.");
                     }
 
                     // make sure this connection will not be re-used
                     // we might have gotten here because of a shutdown trigger
                     // shutdown of the adapter also clears the tracked route
                     sca.shutdown();
                 }
             } catch (final IOException iox) {
                 if (log.isDebugEnabled()) {
                     log.debug("Exception shutting down released connection.",
                               iox);
                 }
             } finally {
                 sca.detach();
                 synchronized (this) {
                     managedConn = null;
                     lastReleaseTime = System.currentTimeMillis();
                     if(validDuration > 0) {
                         connectionExpiresTime = timeUnit.toMillis(validDuration) + lastReleaseTime;
                     } else {
                         connectionExpiresTime = Long.MAX_VALUE;
                     }
                 }
             }
         }
     }
 
     @Override
     public void closeExpiredConnections() {
         final long time = connectionExpiresTime;
         if (System.currentTimeMillis() >= time) {
             closeIdleConnections(0, TimeUnit.MILLISECONDS);
         }
     }
 
     @Override
     public void closeIdleConnections(final long idletime, final TimeUnit timeUnit) {
         assertStillUp();
 
         // idletime can be 0 or negative, no problem there
         Args.notNull(timeUnit, "Time unit");
 
         synchronized (this) {
             if ((managedConn == null) && uniquePoolEntry.connection.isOpen()) {
                 final long cutoff =
                     System.currentTimeMillis() - timeUnit.toMillis(idletime);
                 if (lastReleaseTime <= cutoff) {
                     try {
                         uniquePoolEntry.close();
                     } catch (final IOException iox) {
                         // ignore
                         log.debug("Problem closing idle connection.", iox);
                     }
                 }
             }
         }
     }
 
     @Override
     public void shutdown() {
         this.isShutDown = true;
         synchronized (this) {
             try {
                 if (uniquePoolEntry != null) {
                     uniquePoolEntry.shutdown();
                 }
             } catch (final IOException iox) {
                 // ignore
                 log.debug("Problem while shutting down manager.", iox);
             } finally {
                 uniquePoolEntry = null;
                 managedConn = null;
             }
         }
     }
 
     protected void revokeConnection() {
         final ConnAdapter conn = managedConn;
         if (conn == null) {
             return;
         }
         conn.detach();
 
         synchronized (this) {
             try {
                 uniquePoolEntry.shutdown();
             } catch (final IOException iox) {
                 // ignore
                 log.debug("Problem while shutting down connection.", iox);
             }
         }
     }
 
     /**
      * The pool entry for this connection manager.
      */
     protected class PoolEntry extends AbstractPoolEntry {
 
         /**
          * Creates a new pool entry.
          *
          */
         protected PoolEntry() {
             super(SingleClientConnManager.this.connOperator, null);
         }
 
         /**
          * Closes the connection in this pool entry.
          */
         protected void close() throws IOException {
             shutdownEntry();
             if (connection.isOpen()) {
                 connection.close();
             }
         }
 
         /**
          * Shuts down the connection in this pool entry.
          */
         protected void shutdown() throws IOException {
             shutdownEntry();
             if (connection.isOpen()) {
                 connection.shutdown();
             }
         }
 
     }
 
     /**
      * The connection adapter used by this manager.
      */
     protected class ConnAdapter extends AbstractPooledConnAdapter {
 
         /**
          * Creates a new connection adapter.
          *
          * @param entry   the pool entry for the connection being wrapped
          * @param route   the planned route for this connection
          */
         protected ConnAdapter(final PoolEntry entry, final HttpRoute route) {
             super(SingleClientConnManager.this, entry);
             markReusable();
             entry.route = route;
         }
 
     }
 
 }