/*
    * 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.dbcp2;
  
  import java.lang.ref.WeakReference;
  import java.sql.SQLException;
  import java.time.Instant;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.function.Consumer;
  
  import org.apache.commons.pool2.TrackedUse;
  
  /**
   * Tracks connection usage for recovering and reporting abandoned connections.
   * <p>
   * The JDBC Connection, Statement, and ResultSet classes extend this class.
   * </p>
   *
   * @since 2.0
   */
  public class AbandonedTrace implements TrackedUse, AutoCloseable {
  
      static void add(final AbandonedTrace receiver, final AbandonedTrace trace) {
          if (receiver != null) {
              receiver.addTrace(trace);
          }
      }
  
      /** A list of objects created by children of this object. */
      private final List<WeakReference<AbandonedTrace>> traceList = new ArrayList<>();
  
      /** Last time this connection was used. */
      private volatile Instant lastUsedInstant = Instant.EPOCH;
  
      /**
       * Creates a new AbandonedTrace without config and without doing abandoned tracing.
       */
      public AbandonedTrace() {
          init(null);
      }
  
      /**
       * Constructs a new AbandonedTrace with a parent object.
       *
       * @param parent
       *            AbandonedTrace parent object.
       */
      public AbandonedTrace(final AbandonedTrace parent) {
          init(parent);
      }
  
      /**
       * Adds an object to the list of objects being traced.
       *
       * @param trace
       *            AbandonedTrace object to add.
       */
      protected void addTrace(final AbandonedTrace trace) {
          synchronized (this.traceList) {
              this.traceList.add(new WeakReference<>(trace));
          }
          setLastUsed();
      }
  
      /**
       * Clears the list of objects being traced by this object.
       */
      protected void clearTrace() {
          synchronized (this.traceList) {
              this.traceList.clear();
          }
      }
  
      /**
       * Subclasses can implement this nop.
       *
       * @throws SQLException Ignored here, for subclasses.
       * @since 2.10.0
       */
      @Override
      public void close() throws SQLException {
          // nop
     }
 
     /**
      * Closes this resource and if an exception is caught, then calls {@code exceptionHandler}.
      *
      * @param exceptionHandler Consumes exception thrown closing this resource.
      * @since 2.10.0
      */
     protected void close(final Consumer<Exception> exceptionHandler) {
         Utils.close(this, exceptionHandler);
     }
 
     /**
      * Gets the last time this object was used in milliseconds.
      *
      * @return long time in milliseconds.
      */
     @Override
     @Deprecated
     public long getLastUsed() {
         return lastUsedInstant.toEpochMilli();
     }
 
     @Override
     public Instant getLastUsedInstant() {
         return lastUsedInstant;
     }
 
     /**
      * Gets a list of objects being traced by this object.
      *
      * @return List of objects.
      */
     protected List<AbandonedTrace> getTrace() {
         final int size = traceList.size();
         if (size == 0) {
             return Collections.emptyList();
         }
         final ArrayList<AbandonedTrace> result = new ArrayList<>(size);
         synchronized (this.traceList) {
             final Iterator<WeakReference<AbandonedTrace>> iter = traceList.iterator();
             while (iter.hasNext()) {
                 final AbandonedTrace trace = iter.next().get();
                 if (trace == null) {
                     // Clean-up since we are here anyway
                     iter.remove();
                 } else {
                     result.add(trace);
                 }
             }
         }
         return result;
     }
 
     /**
      * Initializes abandoned tracing for this object.
      *
      * @param parent
      *            AbandonedTrace parent object.
      */
     private void init(final AbandonedTrace parent) {
         AbandonedTrace.add(parent, this);
     }
 
     /**
      * Removes this object the source object is tracing.
      *
      * @param source The object tracing
      * @since 2.7.0
      */
     protected void removeThisTrace(final Object source) {
         if (source instanceof AbandonedTrace) {
             AbandonedTrace.class.cast(source).removeTrace(this);
         }
     }
 
     /**
      * Removes a child object this object is tracing.
      *
      * @param trace
      *            AbandonedTrace object to remove.
      */
     protected void removeTrace(final AbandonedTrace trace) {
         synchronized (this.traceList) {
             final Iterator<WeakReference<AbandonedTrace>> iter = traceList.iterator();
             while (iter.hasNext()) {
                 final AbandonedTrace traceInList = iter.next().get();
                 if (trace != null && trace.equals(traceInList)) {
                     iter.remove();
                     break;
                 }
                 if (traceInList == null) {
                     // Clean-up since we are here anyway
                     iter.remove();
                 }
             }
         }
     }
 
     /**
      * Sets the time this object was last used to the current time in milliseconds.
      */
     protected void setLastUsed() {
         lastUsedInstant = Instant.now();
     }
 
     /**
      * Sets the instant this object was last used.
      *
      * @param lastUsedInstant
      *            instant.
      * @since 2.10.0
      */
     protected void setLastUsed(final Instant lastUsedInstant) {
         this.lastUsedInstant = lastUsedInstant;
     }
 
     /**
      * Sets the time in milliseconds this object was last used.
      *
      * @param lastUsedMillis
      *            time in milliseconds.
      * @deprecated Use {@link #setLastUsed(Instant)}
      */
     @Deprecated
     protected void setLastUsed(final long lastUsedMillis) {
         this.lastUsedInstant = Instant.ofEpochMilli(lastUsedMillis);
     }
 }