/*

  * #%L

  * ObjectId.java - mongodb-async-driver - Allanbank Consulting, Inc.

  * %%

  * Copyright (C) 2011 - 2014 Allanbank Consulting, Inc.

  * %%

  * Licensed 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.

  * #L%

  */

 package com.allanbank.mongodb.bson.element;

 import java.io.Serializable;

 import java.lang.management.ManagementFactory;

 import java.lang.management.RuntimeMXBean;

 import java.net.InetAddress;

 import java.net.NetworkInterface;

 import java.security.MessageDigest;

 import java.security.SecureRandom;

 import java.util.Enumeration;

 import java.util.concurrent.TimeUnit;

 import java.util.concurrent.atomic.AtomicLong;

 import com.allanbank.mongodb.bson.io.EndianUtils;

 import com.allanbank.mongodb.util.IOUtils;

 /**

  * An Object Id.

  * 

  * @api.yes This class is part of the driver's API. Public and protected members

  *          will be deprecated for at least 1 non-bugfix release (version

  *          numbers are <major>.<minor>.<bugfix>) before being

  *          removed or modified.

  * @copyright 2011-2013, Allanbank Consulting, Inc., All Rights Reserved

  */

 public class ObjectId implements Serializable, Comparable<ObjectId> {

     /** The current process's machine id. */

     public static final long MACHINE_ID;

     /** The counter to add to the machine id. */

     private static final AtomicLong COUNTER;

     /** Serialization version for the class. */

     private static final long serialVersionUID = -3035334151717895487L;

     static {

         long value = 0;

         final SecureRandom rand = new SecureRandom();

         try {

             boolean foundIface = true;

             final MessageDigest md5 = MessageDigest.getInstance("MD5");

             try {

                 final Enumeration<NetworkInterface> ifaces = NetworkInterface

                         .getNetworkInterfaces();

                 while (ifaces.hasMoreElements()) {

                     try {

                         final NetworkInterface iface = ifaces.nextElement();

                         if (!iface.isLoopback()) {

                             md5.update(iface.getHardwareAddress());

                             foundIface = true;

                         }

                     }

                     catch (final Throwable tryAnotherIface) {

                         // Noting to do. Try the next one.

                         tryAnotherIface.hashCode(); // PMD - Shhhh.

                     }

                 }

             }

             catch (final Throwable tryTheHostName) {

                 // Nothing to do here. Fall through.

                 tryTheHostName.hashCode(); // PMD - Shhhh.

             }

             if (!foundIface) {

                 md5.update(InetAddress.getLocalHost().getHostName()

                         .getBytes("UTF8"));

             }

             final byte[] hash = md5.digest();

             value += (hash[0] & 0xFF);

             value <<= Byte.SIZE;

             value += (hash[1] & 0xFF);

             value <<= Byte.SIZE;

             value += (hash[2] & 0xFF);

             value <<= Byte.SIZE;

         }

         catch (final Throwable t) {

             // Degenerate to a random machine id.

             for (int i = 0; i < 3; ++i) {

                 value += rand.nextInt(256);

                 value <<= Byte.SIZE;

             }

         }

         // Try and find the process id from the runtime.

         int processId;

         try {

             final RuntimeMXBean runtime = ManagementFactory.getRuntimeMXBean();

             final String processName = runtime.getName();

             final int atLoc = processName.indexOf('@');

             if (atLoc >= 0) {

                 final String pidString = processName.substring(0, atLoc);

                 processId = Integer.parseInt(pidString);

             }

             else {

                 // Degenerate to a random process id.

                 processId = rand.nextInt();

             }

         }

         catch (final Throwable t) {

             // Degenerate to a random process id.

             processId = rand.nextInt();

         }

         value += ((processId >> Byte.SIZE) & 0xFF);

         value <<= Byte.SIZE;

         value += (processId & 0xFF);

         MACHINE_ID = (value << 24);

         COUNTER = new AtomicLong(rand.nextLong() & 0xFFFFFFL);

     }

     /**

      * Generates the current timestamp value. This is the number of

      * <b>seconds</b> since the Unix Epoch.

      * 

      * @return The unique object id value.

      */

     private static int now() {

         return (int) TimeUnit.MILLISECONDS

                 .toSeconds(System.currentTimeMillis());

     }

     /**

      * Generates the current timestamp value. This is the number of

      * <b>seconds</b> since the Unix Epoch.

      * 

      * @return The unique object id value.

      */

     private static long processId() {

         return MACHINE_ID + (COUNTER.incrementAndGet() & 0xFFFFFFL);

     }

     /** The BSON Object Id's machine identifier. */

     private final long myMachineId;

     /** The BSON ObjectId's timestamp. */

     private final int myTimestamp;

     /**

      * Constructs a new {@link ObjectId}.

      */

     public ObjectId() {

         this(now(), processId());

     }

     /**

      * Constructs a new {@link ObjectId}.

      * 

      * @param timestamp

      *            The BSON Object Id timestamp.

      * @param machineId

      *            The BSON Object Id machine id.

      */

     public ObjectId(final int timestamp, final long machineId) {

         myTimestamp = timestamp;

         myMachineId = machineId;

     }

     /**

      * Constructs a new {@link ObjectId}.

      * 

      * @param hexBytes

      *            The hex encoded byte value.

      * @throws IllegalArgumentException

      *             If the hex encoded string is not 24 characters.

      */

     public ObjectId(final String hexBytes) throws IllegalArgumentException {

         if (hexBytes.length() != 24) {

             throw new IllegalArgumentException(

                     "Invalid ObjectId value.  Must be a 24 character hex string.");

         }

         final byte[] bytes = IOUtils.hexToBytes(hexBytes);

         int timestamp = 0;

         for (int i = 0; i < 4; ++i) {

             int value = (bytes[i] & 0xFF);

             value <<= (Byte.SIZE * i);

             timestamp += value;

         }

         long machineId = 0;

         for (int i = 4; i < 12; ++i) {

             long value = (bytes[i] & 0xFF);

             value <<= (Byte.SIZE * (i - 4));

             machineId += value;

         }

         myTimestamp = EndianUtils.swap(timestamp);

         myMachineId = EndianUtils.swap(machineId);

     }

     /**

      * {@inheritDoc}

      * <p>

      * Overridden to compare the object ids based on the tuple (timestamp,

      * machineId).

      * </p>

      */

     @Override

     public int compareTo(final ObjectId other) {

         int result = myTimestamp - other.myTimestamp;

         if (result == 0) {

             result = (myMachineId < other.myMachineId) ? -1

                     : ((myMachineId == other.myMachineId) ? 0 : 1);

         }

         return result;

     }

     /**

      * Determines if the passed object is of this same type as this object and

      * if so that its fields are equal.

      * 

      * @param object

      *            The object to compare to.

      * 

      * @see java.lang.Object#equals(java.lang.Object)

      */

     @Override

     public boolean equals(final Object object) {

         boolean result = false;

         if (this == object) {

             result = true;

         }

         else if ((object != null) && (getClass() == object.getClass())) {

             final ObjectId other = (ObjectId) object;

             result = (myMachineId == other.myMachineId)

                     && (myTimestamp == other.myTimestamp);

         }

         return result;

     }

     /**

      * The low 3 byte value of the machine id.

      * 

      * @return The low 3 byte value of the machine id.

      */

     public int getCounterField() {

         return (int) (myMachineId & 0xFFFFFFL);

     }

     /**

      * The lower 8 bytes of the object id. This is the machine identifier field

      * and counter.

      * 

      * @return The lower 8 bytes of the object id.

      */

     public long getMachineId() {

         return myMachineId;

     }

     /**

      * The upper 3 bytes in the machine id.

      * 

      * @return The upper 3 bytes of the machine id.

      */

     public int getMachineIdentifier() {

         return (int) ((myMachineId >> 40) & 0xFFFFFFL);

     }

     /**

      * Middle 2 byte process id field from the machine id.

      * 

      * @return The middle 2 byte process id field from the machine id.

      */

     public int getPidField() {

         return (int) ((myMachineId >> 24) & 0xFFFFL);

     }

     /**

      * The upper 4 bytes of the object id. This is the <b>seconds</b> since the

      * UNIX Epoch.

      * 

      * @return The upper 4 bytes of the object id.

      */

     public int getTimestamp() {

         return myTimestamp;

     }

     /**

      * Computes a reasonable hash code.

      * 

      * @return The hash code value.

      */

     @Override

     public int hashCode() {

         int result = 0;

         result += (int) ((myMachineId >> 32) & 0xFFFFFFFF);

         result += (int) (myMachineId & 0xFFFFFFFF);

         result += myTimestamp;

         return result;

     }

     /**

      * Returns the HEX string form of the ObjectId.

      * 

      * @return The HEX string form of the ObjectId.

      */

     public String toHexString() {

         final StringBuilder builder = new StringBuilder();

         String hex = Integer.toHexString(myTimestamp);

         builder.append("00000000".substring(hex.length()));

         builder.append(hex);

         hex = Long.toHexString(myMachineId);

         builder.append("0000000000000000".substring(hex.length()));

         builder.append(hex);

         return builder.toString();

     }

     /**

      * String form of the object.

      * 

      * @return A human readable form of the object.

      * 

      * @see Object#toString()

      */

     @Override

     public String toString() {

         final StringBuilder builder = new StringBuilder();

         builder.append("ObjectId(");

         builder.append(toHexString());

         builder.append(")");

         return builder.toString();

     }

 }