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/**
 * Copyright (c) 2013, impossibl.com
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *  * Neither the name of impossibl.com nor the names of its contributors may
 *    be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package com.impossibl.postgres.jdbc;

import java.lang.ref.PhantomReference;
import java.lang.ref.ReferenceQueue;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.logging.Level;
import java.util.logging.Logger;



/**
 * Housekeeper that spins up a daemon thread to execute clean ups.
 *
 * @author kdubb
 *
 */
public class ThreadedHousekeeper implements Housekeeper {

  private static final Logger logger = Logger.getLogger(ThreadedHousekeeper.class.getName());

  private static long instanceRefs = 0;
  private static ThreadedHousekeeper instance;

  public class Ref implements Housekeeper.Ref {

    private AtomicBoolean released = new AtomicBoolean(false);

    @Override
    public ThreadedHousekeeper get() {
      return ThreadedHousekeeper.this;
    }

    @Override
    public void release() {
      if (released.getAndSet(true)) return;
      ThreadedHousekeeper.release();
    }

    @Override
    public  Object add(T reference, CleanupRunnable cleanup) {
      return ThreadedHousekeeper.this.add(reference, cleanup);
    }

    @Override
    public void remove(Object cleanupKey) {
      ThreadedHousekeeper.this.remove(cleanupKey);
    }

  }

  public static synchronized Ref acquire() {

    if (instanceRefs == 0) {
      instance = new ThreadedHousekeeper();
    }
    ++instanceRefs;
    return instance.new Ref();
  }

  private static synchronized void release() {
    if (instanceRefs <= 0) {
      throw new IllegalStateException("Release when reference count 0");
    }

    --instanceRefs;
    if (instanceRefs == 0) {
      instance.close();
      instance = null;
    }
  }

  private class HousekeeperReference extends PhantomReference {

    int id;
    CleanupRunnable cleanup;

    HousekeeperReference(CleanupRunnable cleanup, T referent, ReferenceQueue q) {
      super(referent, q);

      if (cleanup == referent) {
        throw new IllegalArgumentException("target cannot be the referent");
      }

      this.id = System.identityHashCode(referent);
      this.cleanup = cleanup;
    }

    void cleanup() {

      if (logLeaks) {
        String allocationTrace = printStackTrace(getSimplifiedAllocationStackTrace());
        logger.log(
            Level.WARNING,
            "Cleaning up leaked " + cleanup.getKind() + "\n"
                + "Allocation occurred @\n" + allocationTrace);
      }

      cleanup.run();
    }

    StackTraceElement[] getSimplifiedAllocationStackTrace() {

      StackTraceElement[] allocationTrace = cleanup.getAllocationStackTrace();

      // Find the first non driver related class
      for (int c = 0; c < allocationTrace.length; ++c) {

        StackTraceElement e = allocationTrace[c];

        String className = e.getClassName();
        String pkgName = className.substring(0, className.lastIndexOf('.'));

        String rootPkgName = "com.impossibl.postgres";
        String sqlPkgName = "java.sql";

        if ((!pkgName.startsWith(rootPkgName) && !pkgName.startsWith(sqlPkgName)) ||
            (pkgName.startsWith(rootPkgName) && className.endsWith("Test"))) {
          return Arrays.copyOfRange(allocationTrace, c, allocationTrace.length);

        }

      }

      return new StackTraceElement[0];
    }

    String printStackTrace(StackTraceElement[] trace) {

      StringBuilder sb = new StringBuilder();

      for (StackTraceElement traceElement : trace) {

        sb.append("  at ").append(traceElement).append('\n');

      }

      return sb.toString();
    }

  }

  private boolean logLeaks = true;
  private ReferenceQueue