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The UnboundID LDAP SDK for Java is a fast, comprehensive, and easy-to-use Java API for communicating with LDAP directory servers and performing related tasks like reading and writing LDIF, encoding and decoding data using base64 and ASN.1 BER, and performing secure communication. This package contains the Commercial Edition of the LDAP SDK, which includes all of the general-purpose functionality contained in the Standard Edition, plus additional functionality specific to UnboundID server products.

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/*
 * Copyright 2011-2017 UnboundID Corp.
 * All Rights Reserved.
 */
/*
 * Copyright (C) 2011-2017 UnboundID Corp.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License (GPLv2 only)
 * or the terms of the GNU Lesser General Public License (LGPLv2.1 only)
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see .
 */
package com.unboundid.ldap.sdk;



import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Random;

import com.unboundid.util.NotMutable;
import com.unboundid.util.ThreadLocalRandom;
import com.unboundid.util.ThreadSafety;
import com.unboundid.util.ThreadSafetyLevel;



/**
 * This class provides a data structure for holding information about a set of
 * DNS SRV records with the same priority.  Records are organized into those
 * with nonzero weights and those with zero weights.
 */
@NotMutable()
@ThreadSafety(level=ThreadSafetyLevel.COMPLETELY_THREADSAFE)
final class SRVRecordPrioritySet
      implements Serializable
{
  /**
   * The serial version UID for this serializable class.
   */
  private static final long serialVersionUID = -7722028520625558942L;



  // The priority for all records in this set.
  private final long priority;

  // The total weight for all servers in this set.
  private final long totalWeight;

  // The set of all records in this set.
  private final List allRecords;

  // The set of records with nonzero weights.
  private final List nonzeroWeightRecords;

  // The set of records with zero weights.
  private final List zeroWeightRecords;



  /**
   * Creates a new SRV record priority set with the provided records.
   *
   * @param  priority  The priority for all records in this set.
   * @param  records   The set of records with the same priority.  It must not
   *                   be {@code null} or empty.
   */
  SRVRecordPrioritySet(final long priority, final List records)
  {
    this.priority = priority;

    long w = 0L;

    final ArrayList nRecords =
         new ArrayList(records.size());
    final ArrayList zRecords =
         new ArrayList(records.size());

    for (final SRVRecord r : records)
    {
      if (r.getWeight() == 0L)
      {
        zRecords.add(r);
      }
      else
      {
        nRecords.add(r);
        w += r.getWeight();
      }
    }

    totalWeight = w;

    allRecords           = Collections.unmodifiableList(records);
    nonzeroWeightRecords = Collections.unmodifiableList(nRecords);
    zeroWeightRecords    = Collections.unmodifiableList(zRecords);
  }



  /**
   * Retrieves the priority for all records in this set.
   *
   * @return  The priority for all records in this set.
   */
  long getPriority()
  {
    return priority;
  }



  /**
   * Retrieves a list of SRV records in the order that they should be accessed.
   *
   * @return  A list of SRV records in the order that they should be accessed.
   */
  List getOrderedRecords()
  {
    final ArrayList records =
         new ArrayList(allRecords.size());

    if (! nonzeroWeightRecords.isEmpty())
    {
      if (nonzeroWeightRecords.size() == 1)
      {
        records.addAll(nonzeroWeightRecords);
      }
      else
      {
        final Random r = ThreadLocalRandom.get();
        long tw = totalWeight;
        final ArrayList rl =
             new ArrayList(nonzeroWeightRecords);
        while (! rl.isEmpty())
        {
          long w = ((r.nextLong() & 0x7FFFFFFFFFFFFFFFL) % tw);
          final Iterator iterator = rl.iterator();
          while (iterator.hasNext())
          {
            final SRVRecord record = iterator.next();
            if ((w < record.getWeight()) || (! iterator.hasNext()))
            {
              iterator.remove();
              records.add(record);
              tw -= record.getWeight();
              break;
            }
            else
            {
              w -= record.getWeight();
            }
          }
        }
      }
    }

    records.addAll(zeroWeightRecords);
    return records;
  }



  /**
   * Retrieves a string representation of this priority server set.
   *
   * @return  A string representation of this priority server set.
   */
  @Override()
  public String toString()
  {
    final StringBuilder buffer = new StringBuilder();
    toString(buffer);
    return buffer.toString();
  }



  /**
   * Appends a string representation of this priority buffer set to the provided
   * buffer.
   *
   * @param  buffer  The buffer to which the information should be appended.
   */
  void toString(final StringBuilder buffer)
  {
    buffer.append("SRVRecordPrioritySet(records={");

    final Iterator iterator = allRecords.iterator();
    while (iterator.hasNext())
    {
      buffer.append(iterator.next().toString());
      if (iterator.hasNext())
      {
        buffer.append(", ");
      }
    }

    buffer.append("})");
  }
}