/*
 * Copyright (c) 2008-2014 MongoDB, 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.
 */

package org.bson.types;

import java.net.NetworkInterface;
import java.nio.ByteBuffer;
import java.util.Date;
import java.util.Enumeration;
import java.util.Random;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * <p>A globally unique identifier for objects.</p>
 *
 * <p>Consists of 12 bytes, divided as follows:</p> 
 * <table border="1">
 *     <caption>ObjectID layout</caption>
 *     <tr>
 *         <td>0</td><td>1</td><td>2</td><td>3</td><td>4</td><td>5</td><td>6</td><td>7</td><td>8</td><td>9</td><td>10</td><td>11</td> 
 *     </tr> 
 *     <tr>
 *         <td colspan="4">time</td><td colspan="3">machine</td> <td colspan="2">pid</td><td colspan="3">inc</td> 
 *     </tr> 
 * </table>
 *
 * <p>Instances of this class are immutable.</p>
 *
 * @mongodb.driver.manual core/object-id ObjectId
 */
public class ObjectId implements Comparable<ObjectId> , java.io.Serializable {

    private static final long serialVersionUID = -4415279469780082174L;

    static final Logger LOGGER = Logger.getLogger( "org.bson.ObjectId" );

    /**
     * Gets a new object id.
     *
     * @return the new id
     */
    public static ObjectId get(){
        return new ObjectId();
    }

    /**
     * <p>Creates an ObjectId using time, machine and inc values.  The Java driver used to create all ObjectIds this way, but it does not
     * match the <a href="http://docs.mongodb.org/manual/reference/object-id/">ObjectId specification</a>, which requires four values, not
     * three. This major release of the Java driver conforms to the specification, but still supports clients that are relying on the
     * behavior of the previous major release by providing this explicit factory method that takes three parameters instead of four.</p>
     *
     * <p>Ordinary users of the driver will not need this method.  It's only for those that have written there own BSON decoders.</p>
     *
     * <p>NOTE: This will not break any application that use ObjectIds.  The 12-byte representation will be round-trippable from old to new
     * driver releases.</p>
     *
     * @param time    time in seconds
     * @param machine machine ID
     * @param inc     incremental value
     * @return a new {@code ObjectId} created from the given values
     * @since 2.12.0
     */
    public static ObjectId createFromLegacyFormat(final int time, final int machine, final int inc) {
        return new ObjectId(time, machine, inc);
    }


    /**
     * Checks if a string could be an {@code ObjectId}.
     *
     * @param s a potential ObjectId as a String.
     * @return whether the string could be an object id
     * @throws IllegalArgumentException if hexString is null
     */
    public static boolean isValid( String s ){
        if ( s == null )
            return false;

        final int len = s.length();
        if ( len != 24 )
            return false;

        for ( int i=0; i<len; i++ ){
            char c = s.charAt( i );
            if ( c >= '0' && c <= '9' )
                continue;
            if ( c >= 'a' && c <= 'f' )
                continue;
            if ( c >= 'A' && c <= 'F' )
                continue;

            return false;
        }

        return true;
    }

    /**
     * Turn an object into an {@code ObjectId}, if possible. Strings will be converted into {@code ObjectId}s, if possible, and
     * {@code ObjectId}s will be cast and returned.  Passing in {@code null} returns {@code null}.
     *
     * @param o the object to convert
     * @return an {@code ObjectId} if it can be massaged, null otherwise
     * @deprecated This method is NOT a part of public API and will be dropped in 3.x versions.
     */
    @Deprecated
    public static ObjectId massageToObjectId( Object o ){
        if ( o == null )
            return null;

        if ( o instanceof ObjectId )
            return (ObjectId)o;

        if ( o instanceof String ){
            String s = o.toString();
            if ( isValid( s ) )
                return new ObjectId( s );
        }

        return null;
    }

    /**
     * Constructs a new instance using the given date.
     *
     * @param time the date
     */
    public ObjectId(Date time) {
        this(time, _genmachine, _nextInc.getAndIncrement());
    }

    /**
     * Constructs a new instances using the given date and counter.
     *
     * @param time the date
     * @param inc  the counter
     * @throws IllegalArgumentException if the high order byte of counter is not zero
     */
    public ObjectId(Date time, int inc) {
        this(time, _genmachine, inc);
    }

    /**
     * Constructs an ObjectId using  time, machine and inc values.  The Java driver has done it this way for a long time, but it does not
     * match the <a href="http://docs.mongodb.org/manual/reference/object-id/">ObjectId specification</a>, which requires four values, not
     * three.  The next major release of the Java driver will conform to this specification, but will still need to support clients that are
     * relying on the current behavior.  To that end, this constructor is now deprecated in favor of the more explicit factory method
     * ObjectId#createFromLegacyFormat(int, int, int)}, and in the next major release this constructor will be removed.
     *
     * @param time    the date
     * @param machine the machine identifier
     * @param inc     the counter
     * @see ObjectId#createFromLegacyFormat(int, int, int)
     * @deprecated {@code ObjectId}'s constructed this way do not conform to the 
     * <a href="http://docs.mongodb.org/manual/reference/object-id/">ObjectId specification</a>. Please 
     * use {@link org.bson.types.ObjectId#ObjectId(byte[])} or {@link ObjectId#createFromLegacyFormat(int, int, int)} instead.
     */
    @Deprecated
    public ObjectId( Date time , int machine , int inc ){
        _time = (int)(time.getTime() / 1000);
        _machine = machine;
        _inc = inc;
        _new = false;
    }

    /** Creates a new instance from a string.
     * @param s the string to convert
     * @throws IllegalArgumentException if the string is not a valid id
     */
    public ObjectId( String s ){
        this( s , false );
    }

    /**
     * Constructs a new instance of {@code ObjectId} from a string.
     * @param s the string representation of ObjectId. Can contains only [0-9]|[a-f]|[A-F] characters.
     * @param babble if {@code true} - convert to 'babble' objectId format
     *
     * @deprecated 'babble' format is deprecated. Please use {@link #ObjectId(String)} instead.
     */
    @Deprecated
    public ObjectId( String s , boolean babble ){

        if ( ! isValid( s ) )
            throw new IllegalArgumentException( "invalid ObjectId [" + s + "]" );

        if ( babble )
            s = babbleToMongod( s );

        byte b[] = new byte[12];
        for ( int i=0; i<b.length; i++ ){
            b[i] = (byte)Integer.parseInt( s.substring( i*2 , i*2 + 2) , 16 );
        }
        ByteBuffer bb = ByteBuffer.wrap( b );
        _time = bb.getInt();
        _machine = bb.getInt();
        _inc = bb.getInt();
        _new = false;
    }

    /**
     * Constructs an ObjectId given its 12-byte binary representation.
     * @param b a byte array of length 12
     */
    public ObjectId( byte[] b ){
        if ( b.length != 12 )
            throw new IllegalArgumentException( "need 12 bytes" );
        ByteBuffer bb = ByteBuffer.wrap( b );
        _time = bb.getInt();
        _machine = bb.getInt();
        _inc = bb.getInt();
        _new = false;
    }

    /**
     * Constructs an ObjectId using  time, machine and inc values.  The Java driver has done it this way for a long time, but it
     * does not match the <a href="http://docs.mongodb.org/manual/reference/object-id/">ObjectId specification</a>,
     * which requires four values, not three.  The next major release of the Java driver will conform to this specification,
     * but we will still need to support clients that are relying on the current behavior.  To that end,
     * this constructor is now deprecated in favor of the more explicit factory method ObjectId#createFromLegacyFormat(int, int, int)},
     * and in the next major release this constructor will be removed.
     *
     * @param time time in seconds
     * @param machine machine ID
     * @param inc incremental value
     * @see ObjectId#createFromLegacyFormat(int, int, int)
     * @deprecated {@code ObjectId}'s constructed this way do not conform to
     *             the <a href="http://docs.mongodb.org/manual/reference/object-id/">ObjectId specification</a>.
     *             Please use {@link org.bson.types.ObjectId#ObjectId(byte[])} or
     *             {@link ObjectId#createFromLegacyFormat(int, int, int)} instead.
     */
    @Deprecated
    public ObjectId(int time, int machine, int inc) {
        _time = time;
        _machine = machine;
        _inc = inc;
        _new = false;
    }

    /**
     * Create a new object id.
     */
    public ObjectId(){
        _time = (int) (System.currentTimeMillis() / 1000);
        _machine = _genmachine;
        _inc = _nextInc.getAndIncrement();
        _new = true;
    }

    @Override
    public int hashCode(){
        int x = _time;
        x += ( _machine * 111 );
        x += ( _inc * 17 );
        return x;
    }

    @Override
    public boolean equals( Object o ){
        if ( this == o )
            return true;

        ObjectId other = massageToObjectId( o );
        if ( other == null )
            return false;

        return
            _time == other._time &&
            _machine == other._machine &&
            _inc == other._inc;
    }

    /**
     * @deprecated 'babble' format is deprecated and will be removed in 3.0. Please use {@link #toHexString()} instead.
     */
    @SuppressWarnings("JavaDoc")
    @Deprecated
    public String toStringBabble(){
        return babbleToMongod( toStringMongod() );
    }

    /**
     * Converts this instance into a 24-byte hexadecimal string representation.
     *
     * @return a string representation of the ObjectId in hexadecimal format
     */
    public String toHexString() {
        final StringBuilder buf = new StringBuilder(24);

        for (final byte b : toByteArray()) {
            buf.append(String.format("%02x", b & 0xff));
        }

        return buf.toString();
    }

    /**
     * @return a string representation of the ObjectId in hexadecimal format
     * @see ObjectId#toHexString()
     * @deprecated use {@link #toHexString()}
     */
    @Deprecated
    public String toStringMongod(){
        byte b[] = toByteArray();

        StringBuilder buf = new StringBuilder(24);

        for ( int i=0; i<b.length; i++ ){
            int x = b[i] & 0xFF;
            String s = Integer.toHexString( x );
            if ( s.length() == 1 )
                buf.append( "0" );
            buf.append( s );
        }

        return buf.toString();
    }

    /**
     * Convert to a byte array.  Note that the numbers are stored in big-endian order.
     *
     * @return the byte array
     */
    public byte[] toByteArray(){
        byte b[] = new byte[12];
        ByteBuffer bb = ByteBuffer.wrap( b );
        // by default BB is big endian like we need
        bb.putInt( _time );
        bb.putInt( _machine );
        bb.putInt( _inc );
        return b;
    }

    static String _pos( String s , int p ){
        return s.substring( p * 2 , ( p * 2 ) + 2 );
    }

    /**
     * @deprecated This method is NOT a part of public API and will be dropped in 3.x versions.
     */
    @Deprecated
    public static String babbleToMongod( String b ){
        if ( ! isValid( b ) )
            throw new IllegalArgumentException( "invalid object id: " + b );

        StringBuilder buf = new StringBuilder( 24 );
        for ( int i=7; i>=0; i-- )
            buf.append( _pos( b , i ) );
        for ( int i=11; i>=8; i-- )
            buf.append( _pos( b , i ) );

        return buf.toString();
    }

    public String toString(){
        return toStringMongod();
    }

    int _compareUnsigned( int i , int j ){
        long li = 0xFFFFFFFFL;
        li = i & li;
        long lj = 0xFFFFFFFFL;
        lj = j & lj;
        long diff = li - lj;
        if (diff < Integer.MIN_VALUE)
            return Integer.MIN_VALUE;
        if (diff > Integer.MAX_VALUE)
            return Integer.MAX_VALUE;
        return (int) diff;
    }

    public int compareTo( ObjectId id ){
        if ( id == null )
            return -1;

        int x = _compareUnsigned( _time , id._time );
        if ( x != 0 )
            return x;

        x = _compareUnsigned( _machine , id._machine );
        if ( x != 0 )
            return x;

        return _compareUnsigned( _inc , id._inc );
    }

    /**
     * Gets the timestamp (number of seconds since the Unix epoch).
     *
     * @return the timestamp
     */
    public int getTimestamp() {
        return _time;
    }

    /**
     * Gets the timestamp as a {@code Date} instance.
     *
     * @return the Date
     */
    public Date getDate() {
        return new Date(_time * 1000L);
    }

    /**
     * Gets the time of this instance, in milliseconds.
     *
     * @deprecated Use #getDate instead
     * @return the time component of this ID in milliseconds
     */
    @Deprecated
    public long getTime(){
        return _time * 1000L;
    }

    /**
     * Gets the time of this ID, in seconds.
     *
     * @deprecated Use #getTimestamp instead
     * @return the time component of this ID in seconds
     */
    @Deprecated
    public int getTimeSecond() {
        return _time;
    }

    /**
     * Gets the counter.
     *
     * @return the counter
     * @deprecated Please use the {@link #toByteArray()} instead.
     */
    @Deprecated
    public int getInc() {
        return _inc;
    }

    /**
     * Gets the timestamp.
     *
     * @return the timestamp
     * @deprecated Please use {@link #getTimestamp()} ()} instead.
     */
    @Deprecated
    public int _time(){
        return _time;
    }

    /**
     * Gets the machine identifier.
     *
     * @return the machine identifier
     * @see #createFromLegacyFormat(int, int, int)
     * @deprecated Please use {@code #toByteArray()} instead.
     */
    @Deprecated
    public int getMachine() {
        return _machine;
    }

    /**
     * Gets the machine identifier.
     *
     * @return the machine identifier
     * @see #createFromLegacyFormat(int, int, int)
     * @deprecated Please use {@link #toByteArray()} instead.
     */
    @Deprecated
    public int _machine(){
        return _machine;
    }

    /**
     * Gets the counter.
     *
     * @return the counter
     * @see #createFromLegacyFormat(int, int, int)
     * @deprecated Please use {@link #toByteArray()} instead.
     */
    @Deprecated
    public int _inc(){
        return _inc;
    }

    /**
     * @deprecated 'new' flag breaks the immutability of the {@code ObjectId} class
     *             and will be dropped in 3.x versions of the driver
     */
    @Deprecated
    public boolean isNew() {
        return _new;
    }

    /**
     * @deprecated 'new' flag breaks the immutability of the {@code ObjectId} class
     *             and will be dropped in 3.x versions of the driver
     */
    @Deprecated
    public void notNew(){
        _new = false;
    }

    /**
     * Gets the machine identifier.
     *
     * @return the machine identifier
     * @see #createFromLegacyFormat(int, int, int)
     * @deprecated
     */
    @Deprecated
    public static int getGenMachineId() {
        return _genmachine;
    }

    /**
     * Gets the current value of the auto-incrementing counter.
     *
     * @return the current counter value.
     */
    public static int getCurrentCounter() {
        return _nextInc.get();
    }

    /**
     * Gets the current value of the auto-incrementing counter.
     *
     * @deprecated Please use {@link #getCurrentCounter()} instead.
     */
    @Deprecated
    public static int getCurrentInc() {
        return _nextInc.get();
    }

    final int _time;
    final int _machine;
    final int _inc;

    boolean _new;

    /**
     * @deprecated This method is NOT a part of public API and will be dropped in 3.x versions.
     */
    @Deprecated
    public static int _flip( int x ){
        int z = 0;
        z |= ( ( x << 24 ) & 0xFF000000 );
        z |= ( ( x << 8 )  & 0x00FF0000 );
        z |= ( ( x >> 8 )  & 0x0000FF00 );
        z |= ( ( x >> 24 ) & 0x000000FF );
        return z;
    }

    private static AtomicInteger _nextInc = new AtomicInteger( (new java.util.Random()).nextInt() );

    private static final int _genmachine;
    static {

        try {
            // build a 2-byte machine piece based on NICs info
            int machinePiece;
            {
                try {
                    StringBuilder sb = new StringBuilder();
                    Enumeration<NetworkInterface> e = NetworkInterface.getNetworkInterfaces();
                    while ( e.hasMoreElements() ){
                        NetworkInterface ni = e.nextElement();
                        sb.append( ni.toString() );
                    }
                    machinePiece = sb.toString().hashCode() << 16;
                } catch (Throwable e) {
                    // exception sometimes happens with IBM JVM, use random
                    LOGGER.log(Level.WARNING, e.getMessage(), e);
                    machinePiece = (new Random().nextInt()) << 16;
                }
                LOGGER.fine( "machine piece post: " + Integer.toHexString( machinePiece ) );
            }

            // add a 2 byte process piece. It must represent not only the JVM but the class loader.
            // Since static var belong to class loader there could be collisions otherwise
            final int processPiece;
            {
                int processId = new java.util.Random().nextInt();
                try {
                    processId = java.lang.management.ManagementFactory.getRuntimeMXBean().getName().hashCode();
                }
                catch ( Throwable t ){
                }

                ClassLoader loader = ObjectId.class.getClassLoader();
                int loaderId = loader != null ? System.identityHashCode(loader) : 0;

                StringBuilder sb = new StringBuilder();
                sb.append(Integer.toHexString(processId));
                sb.append(Integer.toHexString(loaderId));
                processPiece = sb.toString().hashCode() & 0xFFFF;
                LOGGER.fine( "process piece: " + Integer.toHexString( processPiece ) );
            }

            _genmachine = machinePiece | processPiece;
            LOGGER.fine( "machine : " + Integer.toHexString( _genmachine ) );
        }
        catch ( Exception e ){
            throw new RuntimeException( e );
        }

    }
}