package net.lax1dude.eaglercraft.sp;

public class EaglerUUID {

    private final long mostSigBits;
    private final long leastSigBits;

    private EaglerUUID(byte[] data) {
        long msb = 0;
        long lsb = 0;
        assert data.length == 16 : "data must be 16 bytes in length";
        for (int i = 0; i < 8; i++)
            msb = (msb << 8) | (data[i] & 0xff);
        for (int i = 8; i < 16; i++)
            lsb = (lsb << 8) | (data[i] & 0xff);
        this.mostSigBits = msb;
        this.leastSigBits = lsb;
    }

    public EaglerUUID(long mostSigBits, long leastSigBits) {
        this.mostSigBits = mostSigBits;
        this.leastSigBits = leastSigBits;
    }

    private static final EaglercraftRandom random = new EaglercraftRandom();

    public static EaglerUUID randomUUID() {
        byte[] randomBytes = new byte[16];
        random.nextBytes(randomBytes);
        randomBytes[6] &= 0x0f;  /* clear version        */
        randomBytes[6] |= 0x40;  /* set to version 4     */
        randomBytes[8] &= 0x3f;  /* clear variant        */
        randomBytes[8] |= 0x80;  /* set to IETF variant  */
        return new EaglerUUID(randomBytes);
    }

    private static final MD5Digest yee = new MD5Digest();

    public static EaglerUUID nameUUIDFromBytes(byte[] name) {
        yee.update(name, 0, name.length);
        byte[] md5Bytes = new byte[16];
        yee.doFinal(md5Bytes, 0);
        md5Bytes[6] &= 0x0f;  /* clear version        */
        md5Bytes[6] |= 0x30;  /* set to version 3     */
        md5Bytes[8] &= 0x3f;  /* clear variant        */
        md5Bytes[8] |= 0x80;  /* set to IETF variant  */
        return new EaglerUUID(md5Bytes);
    }

    public static EaglerUUID fromString(String name) {
        String[] components = name.split("-");
        if (components.length != 5)
            throw new IllegalArgumentException("Invalid UUID string: " + name);
        for (int i = 0; i < 5; i++)
            components[i] = "0x" + components[i];

        long mostSigBits = Long.decode(components[0]).longValue();
        mostSigBits <<= 16;
        mostSigBits |= Long.decode(components[1]).longValue();
        mostSigBits <<= 16;
        mostSigBits |= Long.decode(components[2]).longValue();

        long leastSigBits = Long.decode(components[3]).longValue();
        leastSigBits <<= 48;
        leastSigBits |= Long.decode(components[4]).longValue();

        return new EaglerUUID(mostSigBits, leastSigBits);
    }

    public long getLeastSignificantBits() {
        return leastSigBits;
    }

    public long getMostSignificantBits() {
        return mostSigBits;
    }

    /**
     * The version number associated with this {@code UUID}.  The version
     * number describes how this {@code UUID} was generated.
     * <p>
     * The version number has the following meaning:
     * <ul>
     * <li>1    Time-based UUID
     * <li>2    DCE security UUID
     * <li>3    Name-based UUID
     * <li>4    Randomly generated UUID
     * </ul>
     *
     * @return The version number of this {@code UUID}
     */
    public int version() {
        // Version is bits masked by 0x000000000000F000 in MS long
        return (int) ((mostSigBits >> 12) & 0x0f);
    }

    /**
     * The variant number associated with this {@code UUID}.  The variant
     * number describes the layout of the {@code UUID}.
     * <p>
     * The variant number has the following meaning:
     * <ul>
     * <li>0    Reserved for NCS backward compatibility
     * <li>2    <a href="http://www.ietf.org/rfc/rfc4122.txt">IETF&nbsp;RFC&nbsp;4122</a>
     * (Leach-Salz), used by this class
     * <li>6    Reserved, Microsoft Corporation backward compatibility
     * <li>7    Reserved for future definition
     * </ul>
     *
     * @return The variant number of this {@code UUID}
     */
    public int variant() {
        // This field is composed of a varying number of bits.
        // 0    -    -    Reserved for NCS backward compatibility
        // 1    0    -    The IETF aka Leach-Salz variant (used by this class)
        // 1    1    0    Reserved, Microsoft backward compatibility
        // 1    1    1    Reserved for future definition.
        return (int) ((leastSigBits >>> (64 - (leastSigBits >>> 62)))
                & (leastSigBits >> 63));
    }

    public long timestamp() {
        if (version() != 1) {
            throw new UnsupportedOperationException("Not a time-based UUID");
        }

        return (mostSigBits & 0x0FFFL) << 48
                | ((mostSigBits >> 16) & 0x0FFFFL) << 32
                | mostSigBits >>> 32;
    }

    /**
     * The clock sequence value associated with this UUID.
     *
     * <p> The 14 bit clock sequence value is constructed from the clock
     * sequence field of this UUID.  The clock sequence field is used to
     * guarantee temporal uniqueness in a time-based UUID.
     *
     * <p> The {@code clockSequence} value is only meaningful in a time-based
     * UUID, which has version type 1.  If this UUID is not a time-based UUID
     * then this method throws UnsupportedOperationException.
     *
     * @return The clock sequence of this {@code UUID}
     * @throws UnsupportedOperationException If this UUID is not a version 1 UUID
     */
    public int clockSequence() {
        if (version() != 1) {
            throw new UnsupportedOperationException("Not a time-based UUID");
        }

        return (int) ((leastSigBits & 0x3FFF000000000000L) >>> 48);
    }

    public String toString() {
        return (digits(mostSigBits >> 32, 8) + "-" +
                digits(mostSigBits >> 16, 4) + "-" +
                digits(mostSigBits, 4) + "-" +
                digits(leastSigBits >> 48, 4) + "-" +
                digits(leastSigBits, 12));
    }

    private static String digits(long val, int digits) {
        long hi = 1L << (digits * 4);
        return Long.toHexString(hi | (val & (hi - 1))).substring(1);
    }

    public int hashCode() {
        long hilo = mostSigBits ^ leastSigBits;
        return ((int) (hilo >> 32)) ^ (int) hilo;
    }

    public boolean equals(Object obj) {
        if ((null == obj) || !(obj instanceof EaglerUUID))
            return false;
        EaglerUUID id = (EaglerUUID) obj;
        return (mostSigBits == id.mostSigBits &&
                leastSigBits == id.leastSigBits);
    }

    public int compareTo(EaglerUUID val) {
        return (this.mostSigBits < val.mostSigBits ? -1 :
                (this.mostSigBits > val.mostSigBits ? 1 :
                        (this.leastSigBits < val.leastSigBits ? -1 :
                                (this.leastSigBits > val.leastSigBits ? 1 :
                                        0))));
    }
}