package com.fasterxml.jackson.databind.ser.std;

import java.io.IOException;
import java.util.UUID;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.*;
import com.fasterxml.jackson.databind.util.TokenBuffer;

Specialized JsonSerializer to output UUIDs. Beyond optimized access and writing of textual representation (which is the default handling in most cases), it will alternatively allow serialization using raw binary output (as 16-byte block) if underlying data format has efficient means to access that. /**
 * Specialized {@link JsonSerializer} to output {@link java.util.UUID}s.
 * Beyond optimized access and writing of textual representation (which
 * is the default handling in most cases), it will alternatively
 * allow serialization using raw binary output (as 16-byte block)
 * if underlying data format has efficient means to access that.
 */
@SuppressWarnings("serial")
public class UUIDSerializer
    extends StdScalarSerializer<UUID>
{
    final static char[] HEX_CHARS = "0123456789abcdef".toCharArray();

    public UUIDSerializer() { super(UUID.class); }

    @Override
    public boolean isEmpty(SerializerProvider prov, UUID value)
    {
        // Null UUID is empty, so...
        if (value.getLeastSignificantBits() == 0L
                && value.getMostSignificantBits() == 0L) {
            return true;
        }
        return false;
    }

    @Override
    public void serialize(UUID value, JsonGenerator gen, SerializerProvider provider)
        throws IOException
    {
        // First: perhaps we could serialize it as raw binary data?
        if (gen.canWriteBinaryNatively()) {
            /* 07-Dec-2013, tatu: One nasty case; that of TokenBuffer. While it can
             *   technically retain binary data, we do not want to do use binary
             *   with it, as that results in UUIDs getting converted to Base64 for
             *   most conversions.
             */
            if (!(gen instanceof TokenBuffer)) {
                gen.writeBinary(_asBytes(value));
                return;
            }
        }
        
        // UUID.toString() works ok functionally, but we can make it go much faster
        // (by 4x with micro-benchmark)

        final char[] ch = new char[36];
        final long msb = value.getMostSignificantBits();
        _appendInt((int) (msb >> 32), ch, 0);
        ch[8] = '-';
        int i = (int) msb;
        _appendShort(i >>> 16, ch, 9);
        ch[13] = '-';
        _appendShort(i, ch, 14);
        ch[18] = '-';

        final long lsb = value.getLeastSignificantBits();
        _appendShort((int) (lsb >>> 48), ch, 19);
        ch[23] = '-';
        _appendShort((int) (lsb >>> 32), ch, 24);
        _appendInt((int) lsb, ch, 28);

        gen.writeString(ch, 0, 36);
    }

    private static void _appendInt(int bits, char[] ch, int offset)
    {
        _appendShort(bits >> 16, ch, offset);
        _appendShort(bits, ch, offset+4);
    }
    
    private static void _appendShort(int bits, char[] ch, int offset)
    {
        ch[offset] = HEX_CHARS[(bits >> 12) & 0xF];
        ch[++offset] = HEX_CHARS[(bits >> 8) & 0xF];
        ch[++offset] = HEX_CHARS[(bits >> 4) & 0xF];
        ch[++offset] = HEX_CHARS[bits  & 0xF];

    }

    private final static byte[] _asBytes(UUID uuid)
    {
        byte[] buffer = new byte[16];
        long hi = uuid.getMostSignificantBits();
        long lo = uuid.getLeastSignificantBits();
        _appendInt((int) (hi >> 32), buffer, 0);
        _appendInt((int) hi, buffer, 4);
        _appendInt((int) (lo >> 32), buffer, 8);
        _appendInt((int) lo, buffer, 12);
        return buffer;
    }

    private final static void _appendInt(int value, byte[] buffer, int offset)
    {
        buffer[offset] = (byte) (value >> 24);
        buffer[++offset] = (byte) (value >> 16);
        buffer[++offset] = (byte) (value >> 8);
        buffer[++offset] = (byte) value;
    }
}