/*
    * ====================================================================
    * 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.pool;
  
  import java.io.IOException;
  import java.util.Date;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.LinkedList;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.Future;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  import java.util.concurrent.locks.Lock;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.http.annotation.ThreadSafe;
  import org.apache.http.concurrent.FutureCallback;
  
  /**
   * Abstract synchronous (blocking) pool of connections.
   * <p/>
   * Please note that this class does not maintain its own pool of execution {@link Thread}s.
   * Therefore, one <b>must</b> call {@link Future#get()} or {@link Future#get(long, TimeUnit)}
   * method on the {@link Future} object returned by the
   * {@link #lease(Object, Object, FutureCallback)} method in order for the lease operation
   * to complete.
   *
   * @param <T> the route type that represents the opposite endpoint of a pooled
   *   connection.
   * @param <C> the connection type.
   * @param <E> the type of the pool entry containing a pooled connection.
   * @since 4.2
   */
  @ThreadSafe
  public abstract class AbstractConnPool<T, C, E extends PoolEntry<T, C>>
                                                 implements ConnPool<T, E>, ConnPoolControl<T> {
  
      private final Lock lock;
      private final ConnFactory<T, C> connFactory;
      private final Map<T, RouteSpecificPool<T, C, E>> routeToPool;
      private final Set<E> leased;
      private final LinkedList<E> available;
      private final LinkedList<PoolEntryFuture<E>> pending;
      private final Map<T, Integer> maxPerRoute;
  
      private volatile boolean isShutDown;
      private volatile int defaultMaxPerRoute;
      private volatile int maxTotal;
  
      public AbstractConnPool(
              final ConnFactory<T, C> connFactory,
              int defaultMaxPerRoute,
              int maxTotal) {
          super();
          if (connFactory == null) {
              throw new IllegalArgumentException("Connection factory may not null");
          }
          if (defaultMaxPerRoute <= 0) {
              throw new IllegalArgumentException("Max per route value may not be negative or zero");
          }
          if (maxTotal <= 0) {
              throw new IllegalArgumentException("Max total value may not be negative or zero");
          }
          this.lock = new ReentrantLock();
          this.connFactory = connFactory;
          this.routeToPool = new HashMap<T, RouteSpecificPool<T, C, E>>();
          this.leased = new HashSet<E>();
          this.available = new LinkedList<E>();
          this.pending = new LinkedList<PoolEntryFuture<E>>();
          this.maxPerRoute = new HashMap<T, Integer>();
          this.defaultMaxPerRoute = defaultMaxPerRoute;
          this.maxTotal = maxTotal;
     }
 
     /**
      * Creates a new entry for the given connection with the given route.
      */
     protected abstract E createEntry(T route, C conn);
 
     public boolean isShutdown() {
         return this.isShutDown;
     }
 
     /**
      * Shuts down the pool.
      */
     public void shutdown() throws IOException {
         if (this.isShutDown) {
             return ;
         }
         this.isShutDown = true;
         this.lock.lock();
         try {
             for (E entry: this.available) {
                 entry.close();
             }
             for (E entry: this.leased) {
                 entry.close();
             }
             for (RouteSpecificPool<T, C, E> pool: this.routeToPool.values()) {
                 pool.shutdown();
             }
             this.routeToPool.clear();
             this.leased.clear();
             this.available.clear();
         } finally {
             this.lock.unlock();
         }
     }
 
     private RouteSpecificPool<T, C, E> getPool(final T route) {
         RouteSpecificPool<T, C, E> pool = this.routeToPool.get(route);
         if (pool == null) {
             pool = new RouteSpecificPool<T, C, E>(route) {
 
                 @Override
                 protected E createEntry(C conn) {
                     return AbstractConnPool.this.createEntry(route, conn);
                 }
 
             };
             this.routeToPool.put(route, pool);
         }
         return pool;
     }
 
     /**
      * {@inheritDoc}
      * <p/>
      * Please note that this class does not maintain its own pool of execution
      * {@link Thread}s. Therefore, one <b>must</b> call {@link Future#get()}
      * or {@link Future#get(long, TimeUnit)} method on the {@link Future}
      * returned by this method in order for the lease operation to complete.
      */
     public Future<E> lease(final T route, final Object state, final FutureCallback<E> callback) {
         if (route == null) {
             throw new IllegalArgumentException("Route may not be null");
         }
         if (this.isShutDown) {
             throw new IllegalStateException("Connection pool shut down");
         }
         return new PoolEntryFuture<E>(this.lock, callback) {
 
             @Override
             public E getPoolEntry(
                     long timeout,
                     TimeUnit tunit)
                         throws InterruptedException, TimeoutException, IOException {
                 return getPoolEntryBlocking(route, state, timeout, tunit, this);
             }
 
         };
     }
 
     /**
      * Attempts to lease a connection for the given route and with the given
      * state from the pool.
      * <p/>
      * Please note that this class does not maintain its own pool of execution
      * {@link Thread}s. Therefore, one <b>must</b> call {@link Future#get()}
      * or {@link Future#get(long, TimeUnit)} method on the {@link Future}
      * returned by this method in order for the lease operation to complete.
      *
      * @param route route of the connection.
      * @param state arbitrary object that represents a particular state
      *  (usually a security principal or a unique token identifying
      *  the user whose credentials have been used while establishing the connection).
      *  May be <code>null</code>.
      * @return future for a leased pool entry.
      */
     public Future<E> lease(final T route, final Object state) {
         return lease(route, state, null);
     }
 
     private E getPoolEntryBlocking(
             final T route, final Object state,
             final long timeout, final TimeUnit tunit,
             final PoolEntryFuture<E> future)
                 throws IOException, InterruptedException, TimeoutException {
 
         Date deadline = null;
         if (timeout > 0) {
             deadline = new Date
                 (System.currentTimeMillis() + tunit.toMillis(timeout));
         }
 
         this.lock.lock();
         try {
             RouteSpecificPool<T, C, E> pool = getPool(route);
             E entry = null;
             while (entry == null) {
                 if (this.isShutDown) {
                     throw new IllegalStateException("Connection pool shut down");
                 }
                 for (;;) {
                     entry = pool.getFree(state);
                     if (entry == null) {
                         break;
                     }
                     if (entry.isClosed() || entry.isExpired(System.currentTimeMillis())) {
                         entry.close();
                         this.available.remove(entry);
                         pool.free(entry, false);
                     } else {
                         break;
                     }
                 }
                 if (entry != null) {
                     this.available.remove(entry);
                     this.leased.add(entry);
                     return entry;
                 }
 
                 // New connection is needed
                 int maxPerRoute = getMax(route);
                 // Shrink the pool prior to allocating a new connection
                 int excess = Math.max(0, pool.getAllocatedCount() + 1 - maxPerRoute);
                 if (excess > 0) {
                     for (int i = 0; i < excess; i++) {
                         E lastUsed = pool.getLastUsed();
                         if (lastUsed == null) {
                             break;
                         }
                         lastUsed.close();
                         this.available.remove(lastUsed);
                         pool.remove(lastUsed);
                     }
                 }
 
                 if (pool.getAllocatedCount() < maxPerRoute) {
                     int totalUsed = this.leased.size();
                     int freeCapacity = Math.max(this.maxTotal - totalUsed, 0);
                     if (freeCapacity > 0) {
                         int totalAvailable = this.available.size();
                         if (totalAvailable > freeCapacity - 1) {
                             if (!this.available.isEmpty()) {
                                 E lastUsed = this.available.removeLast();
                                 lastUsed.close();
                                 RouteSpecificPool<T, C, E> otherpool = getPool(lastUsed.getRoute());
                                 otherpool.remove(lastUsed);
                             }
                         }
                         C conn = this.connFactory.create(route);
                         entry = pool.add(conn);
                         this.leased.add(entry);
                         return entry;
                     }
                 }
 
                 boolean success = false;
                 try {
                     pool.queue(future);
                     this.pending.add(future);
                     success = future.await(deadline);
                 } finally {
                     // In case of 'success', we were woken up by the
                     // connection pool and should now have a connection
                     // waiting for us, or else we're shutting down.
                     // Just continue in the loop, both cases are checked.
                     pool.unqueue(future);
                     this.pending.remove(future);
                 }
                 // check for spurious wakeup vs. timeout
                 if (!success && (deadline != null) &&
                     (deadline.getTime() <= System.currentTimeMillis())) {
                     break;
                 }
             }
             throw new TimeoutException("Timeout waiting for connection");
         } finally {
             this.lock.unlock();
         }
     }
 
     private void notifyPending(final RouteSpecificPool<T, C, E> pool) {
         PoolEntryFuture<E> future = pool.nextPending();
         if (future != null) {
             this.pending.remove(future);
         } else {
             future = this.pending.poll();
         }
         if (future != null) {
             future.wakeup();
         }
     }
 
     public void release(E entry, boolean reusable) {
         this.lock.lock();
         try {
             if (this.leased.remove(entry)) {
                 RouteSpecificPool<T, C, E> pool = getPool(entry.getRoute());
                 pool.free(entry, reusable);
                 if (reusable && !this.isShutDown) {
                     this.available.addFirst(entry);
                 } else {
                     entry.close();
                 }
                 notifyPending(pool);
             }
         } finally {
             this.lock.unlock();
         }
     }
 
     private int getMax(final T route) {
         Integer v = this.maxPerRoute.get(route);
         if (v != null) {
             return v.intValue();
         } else {
             return this.defaultMaxPerRoute;
         }
     }
 
     public void setMaxTotal(int max) {
         if (max <= 0) {
             throw new IllegalArgumentException("Max value may not be negative or zero");
         }
         this.lock.lock();
         try {
             this.maxTotal = max;
         } finally {
             this.lock.unlock();
         }
     }
 
     public int getMaxTotal() {
         this.lock.lock();
         try {
             return this.maxTotal;
         } finally {
             this.lock.unlock();
         }
     }
 
     public void setDefaultMaxPerRoute(int max) {
         if (max <= 0) {
             throw new IllegalArgumentException("Max value may not be negative or zero");
         }
         this.lock.lock();
         try {
             this.defaultMaxPerRoute = max;
         } finally {
             this.lock.unlock();
         }
     }
 
     public int getDefaultMaxPerRoute() {
         this.lock.lock();
         try {
             return this.defaultMaxPerRoute;
         } finally {
             this.lock.unlock();
         }
     }
 
     public void setMaxPerRoute(final T route, int max) {
         if (route == null) {
             throw new IllegalArgumentException("Route may not be null");
         }
         if (max <= 0) {
             throw new IllegalArgumentException("Max value may not be negative or zero");
         }
         this.lock.lock();
         try {
             this.maxPerRoute.put(route, max);
         } finally {
             this.lock.unlock();
         }
     }
 
     public int getMaxPerRoute(T route) {
         if (route == null) {
             throw new IllegalArgumentException("Route may not be null");
         }
         this.lock.lock();
         try {
             return getMax(route);
         } finally {
             this.lock.unlock();
         }
     }
 
     public PoolStats getTotalStats() {
         this.lock.lock();
         try {
             return new PoolStats(
                     this.leased.size(),
                     this.pending.size(),
                     this.available.size(),
                     this.maxTotal);
         } finally {
             this.lock.unlock();
         }
     }
 
     public PoolStats getStats(final T route) {
         if (route == null) {
             throw new IllegalArgumentException("Route may not be null");
         }
         this.lock.lock();
         try {
             RouteSpecificPool<T, C, E> pool = getPool(route);
             return new PoolStats(
                     pool.getLeasedCount(),
                     pool.getPendingCount(),
                     pool.getAvailableCount(),
                     getMax(route));
         } finally {
             this.lock.unlock();
         }
     }
 
     /**
      * Closes connections that have been idle longer than the given period
      * of time and evicts them from the pool.
      *
      * @param idletime maximum idle time.
      * @param tunit time unit.
      */
     public void closeIdle(long idletime, final TimeUnit tunit) {
         if (tunit == null) {
             throw new IllegalArgumentException("Time unit must not be null.");
         }
         long time = tunit.toMillis(idletime);
         if (time < 0) {
             time = 0;
         }
         long deadline = System.currentTimeMillis() - time;
         this.lock.lock();
         try {
             Iterator<E> it = this.available.iterator();
             while (it.hasNext()) {
                 E entry = it.next();
                 if (entry.getUpdated() <= deadline) {
                     entry.close();
                     RouteSpecificPool<T, C, E> pool = getPool(entry.getRoute());
                     pool.remove(entry);
                     it.remove();
                     notifyPending(pool);
                 }
             }
         } finally {
             this.lock.unlock();
         }
     }
 
     /**
      * Closes expired connections and evicts them from the pool.
      */
     public void closeExpired() {
         long now = System.currentTimeMillis();
         this.lock.lock();
         try {
             Iterator<E> it = this.available.iterator();
             while (it.hasNext()) {
                 E entry = it.next();
                 if (entry.isExpired(now)) {
                     entry.close();
                     RouteSpecificPool<T, C, E> pool = getPool(entry.getRoute());
                     pool.remove(entry);
                     it.remove();
                     notifyPending(pool);
                 }
             }
         } finally {
             this.lock.unlock();
         }
     }
 
     @Override
     public String toString() {
         StringBuilder buffer = new StringBuilder();
         buffer.append("[leased: ");
         buffer.append(this.leased);
         buffer.append("][available: ");
         buffer.append(this.available);
         buffer.append("][pending: ");
         buffer.append(this.pending);
         buffer.append("]");
         return buffer.toString();
     }
 
 }