/*
    * 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.
   */
  package org.apache.commons.pool2.impl;
  
  import java.io.PrintWriter;
  import java.time.Clock;
  import java.time.Duration;
  import java.time.Instant;
  import java.util.Deque;
  
  import org.apache.commons.pool2.PooledObject;
  import org.apache.commons.pool2.PooledObjectState;
  import org.apache.commons.pool2.TrackedUse;
  
  /**
   * This wrapper is used to track the additional information, such as state, for
   * the pooled objects.
   * <p>
   * This class is intended to be thread-safe.
   * </p>
   *
   * @param <T> the type of object in the pool
   * @since 2.0
   */
  public class DefaultPooledObject<T> implements PooledObject<T> {
  
      private final T object;
      private PooledObjectState state = PooledObjectState.IDLE; // @GuardedBy("this") to ensure transitions are valid
      private final Clock systemClock = Clock.systemUTC();
      private final Instant createInstant = now();
  
      private volatile Instant lastBorrowInstant = createInstant;
      private volatile Instant lastUseInstant = createInstant;
      private volatile Instant lastReturnInstant = createInstant;
      private volatile boolean logAbandoned;
      private volatile CallStack borrowedBy = NoOpCallStack.INSTANCE;
      private volatile CallStack usedBy = NoOpCallStack.INSTANCE;
      private volatile long borrowedCount;
  
      /**
       * Creates a new instance that wraps the provided object so that the pool can
       * track the state of the pooled object.
       *
       * @param object The object to wrap
       */
      public DefaultPooledObject(final T object) {
          this.object = object;
      }
  
      /**
       * Allocates the object.
       *
       * @return {@code true} if the original state was {@link PooledObjectState#IDLE IDLE}
       */
      @Override
      public synchronized boolean allocate() {
          if (state == PooledObjectState.IDLE) {
              state = PooledObjectState.ALLOCATED;
              lastBorrowInstant = now();
              lastUseInstant = lastBorrowInstant;
              borrowedCount++;
              if (logAbandoned) {
                  borrowedBy.fillInStackTrace();
              }
              return true;
          }
          if (state == PooledObjectState.EVICTION) {
              // TODO Allocate anyway and ignore eviction test
              state = PooledObjectState.EVICTION_RETURN_TO_HEAD;
          }
          // TODO if validating and testOnBorrow == true then pre-allocate for
          // performance
          return false;
      }
  
      @Override
      public int compareTo(final PooledObject<T> other) {
          final int compareTo = getLastReturnInstant().compareTo(other.getLastReturnInstant());
          if (compareTo == 0) {
              // Make sure the natural ordering is broadly consistent with equals
              // although this will break down if distinct objects have the same
              // identity hash code.
              // see java.lang.Comparable Javadocs
              return System.identityHashCode(this) - System.identityHashCode(other);
          }
         return compareTo;
     }
 
     /**
      * Deallocates the object and sets it {@link PooledObjectState#IDLE IDLE}
      * if it is currently {@link PooledObjectState#ALLOCATED ALLOCATED}
      * or {@link PooledObjectState#RETURNING RETURNING}.
      *
      * @return {@code true} if the state was {@link PooledObjectState#ALLOCATED ALLOCATED}
      *         or {@link PooledObjectState#RETURNING RETURNING}.
      */
     @Override
     public synchronized boolean deallocate() {
         if (state == PooledObjectState.ALLOCATED || state == PooledObjectState.RETURNING) {
             state = PooledObjectState.IDLE;
             lastReturnInstant = now();
             borrowedBy.clear();
             return true;
         }
 
         return false;
     }
 
     @Override
     public synchronized boolean endEvictionTest(
             final Deque<PooledObject<T>> idleQueue) {
         if (state == PooledObjectState.EVICTION) {
             state = PooledObjectState.IDLE;
             return true;
         }
         if (state == PooledObjectState.EVICTION_RETURN_TO_HEAD) {
             state = PooledObjectState.IDLE;
             idleQueue.offerFirst(this);
         }
 
         return false;
     }
 
     @Override
     public long getActiveTimeMillis() {
         return getActiveDuration().toMillis();
     }
 
     /**
      * Gets the number of times this object has been borrowed.
      * @return The number of times this object has been borrowed.
      * @since 2.1
      */
     @Override
     public long getBorrowedCount() {
         return borrowedCount;
     }
 
     @Override
     public Instant getCreateInstant() {
         return createInstant;
     }
 
     @Override
     public long getCreateTime() {
         return createInstant.toEpochMilli();
     }
 
     @Override
     public Duration getIdleDuration() {
         // elapsed may be negative if:
         // - another thread updates lastReturnInstant during the calculation window
         // - System.currentTimeMillis() is not monotonic (e.g. system time is set back)
         final Duration elapsed = Duration.between(lastReturnInstant, now());
         return elapsed.isNegative() ? Duration.ZERO : elapsed;
     }
 
     @Override
     public Duration getIdleTime() {
         return getIdleDuration();
     }
 
     @Override
     public long getIdleTimeMillis() {
         return getIdleDuration().toMillis();
     }
 
     @Override
     public Instant getLastBorrowInstant() {
         return lastBorrowInstant;
     }
 
     @Override
     public long getLastBorrowTime() {
         return lastBorrowInstant.toEpochMilli();
     }
 
     @Override
     public Instant getLastReturnInstant() {
         return lastReturnInstant;
     }
 
     @Override
     public long getLastReturnTime() {
         return lastReturnInstant.toEpochMilli();
     }
 
     /**
      * Gets an estimate of the last time this object was used.  If the class
      * of the pooled object implements {@link TrackedUse}, what is returned is
      * the maximum of {@link TrackedUse#getLastUsedInstant()} and
      * {@link #getLastBorrowTime()}; otherwise this method gives the same
      * value as {@link #getLastBorrowTime()}.
      *
      * @return the last Instant this object was used.
      */
     @Override
     public Instant getLastUsedInstant() {
         if (object instanceof TrackedUse) {
             return PoolImplUtils.max(((TrackedUse) object).getLastUsedInstant(), lastUseInstant);
         }
         return lastUseInstant;
     }
 
     /**
      * Gets an estimate of the last time this object was used.  If the class
      * of the pooled object implements {@link TrackedUse}, what is returned is
      * the maximum of {@link TrackedUse#getLastUsedInstant()} and
      * {@link #getLastBorrowTime()}; otherwise this method gives the same
      * value as {@link #getLastBorrowTime()}.
      *
      * @return the last time this object was used
      */
     @Override
     public long getLastUsedTime() {
         return getLastUsedInstant().toEpochMilli();
     }
 
     @Override
     public T getObject() {
         return object;
     }
 
     /**
      * Gets the state of this object.
      * @return state
      */
     @Override
     public synchronized PooledObjectState getState() {
         return state;
     }
 
     /**
      * Sets the state to {@link PooledObjectState#INVALID INVALID}.
      */
     @Override
     public synchronized void invalidate() {
         state = PooledObjectState.INVALID;
     }
 
     /**
      * Marks the pooled object as {@link PooledObjectState#ABANDONED ABANDONED}.
      */
     @Override
     public synchronized void markAbandoned() {
         state = PooledObjectState.ABANDONED;
     }
 
     /**
      * Marks the pooled object as {@link PooledObjectState#RETURNING RETURNING}.
      */
     @Override
     public synchronized void markReturning() {
         state = PooledObjectState.RETURNING;
     }
 
     /**
      * Gets the current instant of the clock.
      *
      * @return the current instant of the clock.
      */
     private Instant now() {
         return systemClock.instant();
     }
 
     @Override
     public void printStackTrace(final PrintWriter writer) {
         boolean written = borrowedBy.printStackTrace(writer);
         written |= usedBy.printStackTrace(writer);
         if (written) {
             writer.flush();
         }
     }
 
     @Override
     public void setLogAbandoned(final boolean logAbandoned) {
         this.logAbandoned = logAbandoned;
     }
 
     /**
      * Configures the stack trace generation strategy based on whether or not fully
      * detailed stack traces are required. When set to false, abandoned logs may
      * only include caller class information rather than method names, line numbers,
      * and other normal metadata available in a full stack trace.
      *
      * @param requireFullStackTrace the new configuration setting for abandoned object
      *                              logging
      * @since 2.5
      */
     @Override
     public void setRequireFullStackTrace(final boolean requireFullStackTrace) {
         borrowedBy = CallStackUtils.newCallStack("'Pooled object created' " +
             "yyyy-MM-dd HH:mm:ss Z 'by the following code has not been returned to the pool:'",
             true, requireFullStackTrace);
         usedBy = CallStackUtils.newCallStack("The last code to use this object was:",
             false, requireFullStackTrace);
     }
 
     @Override
     public synchronized boolean startEvictionTest() {
         if (state == PooledObjectState.IDLE) {
             state = PooledObjectState.EVICTION;
             return true;
         }
         return false;
     }
 
     @Override
     public String toString() {
         final StringBuilder result = new StringBuilder();
         result.append("Object: ");
         result.append(object.toString());
         result.append(", State: ");
         synchronized (this) {
             result.append(state.toString());
         }
         return result.toString();
         // TODO add other attributes
     }
 
     @Override
     public void use() {
         lastUseInstant = now();
         usedBy.fillInStackTrace();
     }
 
 }