/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 *

 *  (C) Copyright IBM Corp. 1999 All Rights Reserved.

 *  Copyright 1997 The Open Group Research Institute.  All rights reserved.

 */

package sun.security.krb5.internal;

import sun.security.krb5.Asn1Exception;

import sun.security.krb5.Config;

import sun.security.krb5.KrbException;

import sun.security.util.DerInputStream;

import sun.security.util.DerOutputStream;

import sun.security.util.DerValue;

import java.io.IOException;

import java.time.Instant;

import java.util.Calendar;

import java.util.Date;

import java.util.TimeZone;

/**

 * Implements the ASN.1 KerberosTime type. This is an immutable class.

 *

 * {@code KerberosTime ::= GeneralizedTime} -- with no fractional seconds

 *

 * The timestamps used in Kerberos are encoded as GeneralizedTimes. A

 * KerberosTime value shall not include any fractional portions of the

 * seconds.  As required by the DER, it further shall not include any

 * separators, and it shall specify the UTC time zone (Z).

 *

 * <p>

 * This definition reflects the Network Working Group RFC 4120

 * specification available at

 * <a href="http://www.ietf.org/rfc/rfc4120.txt">

 * http://www.ietf.org/rfc/rfc4120.txt</a>.

 *

 * The implementation also includes the microseconds info so that the

 * same class can be used as a precise timestamp in Authenticator etc.

 */

public class KerberosTime {

    private final long kerberosTime; // milliseconds since epoch, Date.getTime()

    private final int  microSeconds; // last 3 digits of the real microsecond

    // The time when this class is loaded. Used in setNow()

    private static long initMilli = System.currentTimeMillis();

    private static long initMicro = System.nanoTime() / 1000;

    private static boolean DEBUG = Krb5.DEBUG;

    // Do not make this public. It's a little confusing that micro

    // is only the last 3 digits of microsecond.

    private KerberosTime(long time, int micro) {

        kerberosTime = time;

        microSeconds = micro;

    }

    /**

     * Creates a KerberosTime object from milliseconds since epoch.

     */

    public KerberosTime(long time) {

        this(time, 0);

    }

    // This constructor is used in the native code

    // src/windows/native/sun/security/krb5/NativeCreds.c

    public KerberosTime(String time) throws Asn1Exception {

        this(toKerberosTime(time), 0);

    }

    private static long toKerberosTime(String time) throws Asn1Exception {

        // ASN.1 GeneralizedTime format:

        // "19700101000000Z"

        //  |   | | | | | |

        //  0   4 6 8 | | |

        //           10 | |

        //             12 |

        //               14

        if (time.length() != 15)

            throw new Asn1Exception(Krb5.ASN1_BAD_TIMEFORMAT);

        if (time.charAt(14) != 'Z')

            throw new Asn1Exception(Krb5.ASN1_BAD_TIMEFORMAT);

        int year = Integer.parseInt(time.substring(0, 4));

        Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));

        calendar.clear(); // so that millisecond is zero

        calendar.set(year,

                     Integer.parseInt(time.substring(4, 6)) - 1,

                     Integer.parseInt(time.substring(6, 8)),

                     Integer.parseInt(time.substring(8, 10)),

                     Integer.parseInt(time.substring(10, 12)),

                     Integer.parseInt(time.substring(12, 14)));

        return calendar.getTimeInMillis();

    }

    /**

     * Creates a KerberosTime object from a Date object.

     */

    public KerberosTime(Date time) {

        this(time.getTime(), 0);

    }

    /**

     * Creates a KerberosTime object from an Instant object

     */

    public KerberosTime(Instant instant) {

        this(instant.getEpochSecond()*1000 + instant.getNano()/1000000L,

                instant.getNano()/1000%1000);

    }

    /**

     * Creates a KerberosTime object for now. It uses System.nanoTime()

     * to get a more precise time than "new Date()".

     */

    public static KerberosTime now() {

        long newMilli = System.currentTimeMillis();

        long newMicro = System.nanoTime() / 1000;

        long microElapsed = newMicro - initMicro;

        long calcMilli = initMilli + microElapsed/1000;

        if (calcMilli - newMilli > 100 || newMilli - calcMilli > 100) {

            if (DEBUG) {

                System.out.println("System time adjusted");

            }

            initMilli = newMilli;

            initMicro = newMicro;

            return new KerberosTime(newMilli, 0);

        } else {

            return new KerberosTime(calcMilli, (int)(microElapsed % 1000));

        }

    }

    /**

     * Returns a string representation of KerberosTime object.

     * @return a string representation of this object.

     */

    public String toGeneralizedTimeString() {

        Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));

        calendar.clear();

        calendar.setTimeInMillis(kerberosTime);

        return String.format("%04d%02d%02d%02d%02d%02dZ",

                calendar.get(Calendar.YEAR),

                calendar.get(Calendar.MONTH) + 1,

                calendar.get(Calendar.DAY_OF_MONTH),

                calendar.get(Calendar.HOUR_OF_DAY),

                calendar.get(Calendar.MINUTE),

                calendar.get(Calendar.SECOND));

    }

    /**

     * Encodes this object to a byte array.

     * @return a byte array of encoded data.

     * @exception Asn1Exception if an error occurs while decoding an ASN1 encoded data.

     * @exception IOException if an I/O error occurs while reading encoded data.

     */

    public byte[] asn1Encode() throws Asn1Exception, IOException {

        DerOutputStream out = new DerOutputStream();

        out.putGeneralizedTime(this.toDate());

        return out.toByteArray();

    }

    public long getTime() {

        return kerberosTime;

    }

    public Date toDate() {

        return new Date(kerberosTime);

    }

    public int getMicroSeconds() {

        int temp_int = (int) ((kerberosTime % 1000L) * 1000L);

        return temp_int + microSeconds;

    }

    /**

     * Returns a new KerberosTime object with the original seconds

     * and the given microseconds.

     */

    public KerberosTime withMicroSeconds(int usec) {

        return new KerberosTime(

                kerberosTime - kerberosTime%1000L + usec/1000L,

                usec%1000);

    }

    private boolean inClockSkew(int clockSkew) {

        return java.lang.Math.abs(kerberosTime - System.currentTimeMillis())

                <= clockSkew * 1000L;

    }

    public boolean inClockSkew() {

        return inClockSkew(getDefaultSkew());

    }

    public boolean greaterThanWRTClockSkew(KerberosTime time, int clockSkew) {

        if ((kerberosTime - time.kerberosTime) > clockSkew * 1000L)

            return true;

        return false;

    }

    public boolean greaterThanWRTClockSkew(KerberosTime time) {

        return greaterThanWRTClockSkew(time, getDefaultSkew());

    }

    public boolean greaterThan(KerberosTime time) {

        return kerberosTime > time.kerberosTime ||

            kerberosTime == time.kerberosTime &&

                    microSeconds > time.microSeconds;

    }

    public boolean equals(Object obj) {

        if (this == obj) {

            return true;

        }

        if (!(obj instanceof KerberosTime)) {

            return false;

        }

        return kerberosTime == ((KerberosTime)obj).kerberosTime &&

                microSeconds == ((KerberosTime)obj).microSeconds;

    }

    public int hashCode() {

        int result = 37 * 17 + (int)(kerberosTime ^ (kerberosTime >>> 32));

        return result * 17 + microSeconds;

    }

    public boolean isZero() {

        return kerberosTime == 0 && microSeconds == 0;

    }

    public int getSeconds() {

        return (int) (kerberosTime / 1000L);

    }

    /**

     * Parse (unmarshal) a kerberostime from a DER input stream.  This form

     * parsing might be used when expanding a value which is part of

     * a constructed sequence and uses explicitly tagged type.

     *

     * @exception Asn1Exception on error.

     * @param data the Der input stream value, which contains

     *             one or more marshaled value.

     * @param explicitTag tag number.

     * @param optional indicates if this data field is optional

     * @return an instance of KerberosTime.

     *

     */

    public static KerberosTime parse(

            DerInputStream data, byte explicitTag, boolean optional)

            throws Asn1Exception, IOException {

        if ((optional) && (((byte)data.peekByte() & (byte)0x1F)!= explicitTag))

            return null;

        DerValue der = data.getDerValue();

        if (explicitTag != (der.getTag() & (byte)0x1F))  {

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        }

        else {

            DerValue subDer = der.getData().getDerValue();

            Date temp = subDer.getGeneralizedTime();

            return new KerberosTime(temp.getTime(), 0);

        }

    }

    public static int getDefaultSkew() {

        int tdiff = Krb5.DEFAULT_ALLOWABLE_CLOCKSKEW;

        try {

            if ((tdiff = Config.getInstance().getIntValue(

                    "libdefaults", "clockskew"))

                        == Integer.MIN_VALUE) {   //value is not defined

                tdiff = Krb5.DEFAULT_ALLOWABLE_CLOCKSKEW;

            }

        } catch (KrbException e) {

            if (DEBUG) {

                System.out.println("Exception in getting clockskew from " +

                                   "Configuration " +

                                   "using default value " +

                                   e.getMessage());

            }

        }

        return tdiff;

    }

    public String toString() {

        return toGeneralizedTimeString();

    }

}