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package sun.util.calendar;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.util.Date;

import java.util.Map;

import java.util.SimpleTimeZone;

import java.util.TimeZone;

/**

 * <code>ZoneInfo</code> is an implementation subclass of {@link

 * java.util.TimeZone TimeZone} that represents GMT offsets and

 * daylight saving time transitions of a time zone.

 * <p>

 * The daylight saving time transitions are described in the {@link

 * #transitions transitions} table consisting of a chronological

 * sequence of transitions of GMT offset and/or daylight saving time

 * changes. Since all transitions are represented in UTC, in theory,

 * <code>ZoneInfo</code> can be used with any calendar systems except

 * for the {@link #getOffset(int,int,int,int,int,int) getOffset}

 * method that takes Gregorian calendar date fields.

 * <p>

 * This table covers transitions from 1900 until 2037 (as of version

 * 1.4), Before 1900, it assumes that there was no daylight saving

 * time and the <code>getOffset</code> methods always return the

 * {@link #getRawOffset} value. No Local Mean Time is supported. If a

 * specified date is beyond the transition table and this time zone is

 * supposed to observe daylight saving time in 2037, it delegates

 * operations to a {@link java.util.SimpleTimeZone SimpleTimeZone}

 * object created using the daylight saving time schedule as of 2037.

 * <p>

 * The date items, transitions, GMT offset(s), etc. are read from a database

 * file. See {@link ZoneInfoFile} for details.

 * @see java.util.SimpleTimeZone

 * @since 1.4

 */

public class ZoneInfo extends TimeZone {

    private static final int UTC_TIME = 0;

    private static final int STANDARD_TIME = 1;

    private static final int WALL_TIME = 2;

    private static final long OFFSET_MASK = 0x0fL;

    private static final long DST_MASK = 0xf0L;

    private static final int DST_NSHIFT = 4;

    // this bit field is reserved for abbreviation support

    private static final long ABBR_MASK = 0xf00L;

    private static final int TRANSITION_NSHIFT = 12;

    /**

     * The raw GMT offset in milliseconds between this zone and GMT.

     * Negative offsets are to the west of Greenwich.  To obtain local

     * <em>standard</em> time, add the offset to GMT time.

     * @serial

     */

    private int rawOffset;

    /**

     * Difference in milliseconds from the original GMT offset in case

     * the raw offset value has been modified by calling {@link

     * #setRawOffset}. The initial value is 0.

     * @serial

     */

    private int rawOffsetDiff = 0;

    /**

     * A CRC32 value of all pairs of transition time (in milliseconds

     * in <code>long</code>) in local time and its GMT offset (in

     * seconds in <code>int</code>) in the chronological order. Byte

     * values of each <code>long</code> and <code>int</code> are taken

     * in the big endian order (i.e., MSB to LSB).

     * @serial

     */

    private int checksum;

    /**

     * The amount of time in milliseconds saved during daylight saving

     * time. If <code>useDaylight</code> is false, this value is 0.

     * @serial

     */

    private int dstSavings;

    /**

     * This array describes transitions of GMT offsets of this time

     * zone, including both raw offset changes and daylight saving

     * time changes.

     * A long integer consists of four bit fields.

     * <ul>

     * <li>The most significant 52-bit field represents transition

     * time in milliseconds from Gregorian January 1 1970, 00:00:00

     * GMT.</li>

     * <li>The next 4-bit field is reserved and must be 0.</li>

     * <li>The next 4-bit field is an index value to {@link #offsets

     * offsets[]} for the amount of daylight saving at the

     * transition. If this value is zero, it means that no daylight

     * saving, not the index value zero.</li>

     * <li>The least significant 4-bit field is an index value to

     * {@link #offsets offsets[]} for <em>total</em> GMT offset at the

     * transition.</li>

     * </ul>

     * If this time zone doesn't observe daylight saving time and has

     * never changed any GMT offsets in the past, this value is null.

     * @serial

     */

    private long[] transitions;

    /**

     * This array holds all unique offset values in

     * milliseconds. Index values to this array are stored in the

     * transitions array elements.

     * @serial

     */

    private int[] offsets;

    /**

     * SimpleTimeZone parameter values. It has to have either 8 for

     * {@link java.util.SimpleTimeZone#SimpleTimeZone(int, String,

     * int, int , int , int , int , int , int , int , int) the

     * 11-argument SimpleTimeZone constructor} or 10 for {@link

     * java.util.SimpleTimeZone#SimpleTimeZone(int, String, int, int,

     * int , int , int , int , int , int , int, int, int) the

     * 13-argument SimpleTimeZone constructor} parameters.

     * @serial

     */

    private int[] simpleTimeZoneParams;

    /**

     * True if the raw GMT offset value would change after the time

     * zone data has been generated; false, otherwise. The default

     * value is false.

     * @serial

     */

    private boolean willGMTOffsetChange = false;

    /**

     * True if the object has been modified after its instantiation.

     */

    private transient boolean dirty = false;

    @java.io.Serial

    private static final long serialVersionUID = 2653134537216586139L;

    /**

     * A constructor.

     */

    public ZoneInfo() {

    }

    /**

     * A Constructor for CustomID.

     */

    public ZoneInfo(String ID, int rawOffset) {

        this(ID, rawOffset, 0, 0, null, null, null, false);

    }

    /**

     * Constructs a ZoneInfo instance.

     *

     * @param ID time zone name

     * @param rawOffset GMT offset in milliseconds

     * @param dstSavings daylight saving value in milliseconds or 0

     * (zero) if this time zone doesn't observe Daylight Saving Time.

     * @param checksum CRC32 value with all transitions table entry

     * values

     * @param transitions transition table

     * @param offsets offset value table

     * @param simpleTimeZoneParams parameter values for constructing

     * SimpleTimeZone

     * @param willGMTOffsetChange the value of willGMTOffsetChange

     */

    ZoneInfo(String ID,

             int rawOffset,

             int dstSavings,

             int checksum,

             long[] transitions,

             int[] offsets,

             int[] simpleTimeZoneParams,

             boolean willGMTOffsetChange) {

        setID(ID);

        this.rawOffset = rawOffset;

        this.dstSavings = dstSavings;

        this.checksum = checksum;

        this.transitions = transitions;

        this.offsets = offsets;

        this.simpleTimeZoneParams = simpleTimeZoneParams;

        this.willGMTOffsetChange = willGMTOffsetChange;

    }

    /**

     * Returns the difference in milliseconds between local time and UTC

     * of given time, taking into account both the raw offset and the

     * effect of daylight savings.

     *

     * @param date the milliseconds in UTC

     * @return the milliseconds to add to UTC to get local wall time

     */

    public int getOffset(long date) {

        return getOffsets(date, null, UTC_TIME);

    }

    public int getOffsets(long utc, int[] offsets) {

        return getOffsets(utc, offsets, UTC_TIME);

    }

    public int getOffsetsByStandard(long standard, int[] offsets) {

        return getOffsets(standard, offsets, STANDARD_TIME);

    }

    public int getOffsetsByWall(long wall, int[] offsets) {

        return getOffsets(wall, offsets, WALL_TIME);

    }

    private int getOffsets(long date, int[] offsets, int type) {

        // if dst is never observed, there is no transition.

        if (transitions == null) {

            int offset = getLastRawOffset();

            if (offsets != null) {

                offsets[0] = offset;

                offsets[1] = 0;

            }

            return offset;

        }

        date -= rawOffsetDiff;

        int index = getTransitionIndex(date, type);

        // prior to the transition table, returns the raw offset.

        // FIXME: should support LMT.

        if (index < 0) {

            int offset = getLastRawOffset();

            if (offsets != null) {

                offsets[0] = offset;

                offsets[1] = 0;

            }

            return offset;

        }

        if (index < transitions.length) {

            long val = transitions[index];

            int offset = this.offsets[(int)(val & OFFSET_MASK)] + rawOffsetDiff;

            if (offsets != null) {

                int dst = (int)((val >>> DST_NSHIFT) & 0xfL);

                int save = (dst == 0) ? 0 : this.offsets[dst];

                offsets[0] = offset - save;

                offsets[1] = save;

            }

            return offset;

        }

        // beyond the transitions, delegate to SimpleTimeZone if there

        // is a rule; otherwise, return the offset of the last transition.

        SimpleTimeZone tz = getLastRule();

        if (tz != null) {

            int rawoffset = tz.getRawOffset();

            long msec = date;

            if (type != UTC_TIME) {

                msec -= rawOffset;

            }

            int dstoffset = tz.getOffset(msec) - rawOffset;

            // Check if it's in a standard-to-daylight transition.

            if (dstoffset > 0 && tz.getOffset(msec - dstoffset) == rawoffset) {

                dstoffset = 0;

            }

            if (offsets != null) {

                offsets[0] = rawoffset;

                offsets[1] = dstoffset;

            }

            return rawoffset + dstoffset;

        } else {

            // use the last transition

            long val = transitions[transitions.length - 1];

            int offset = this.offsets[(int)(val & OFFSET_MASK)] + rawOffsetDiff;

            if (offsets != null) {

                int dst = (int)((val >>> DST_NSHIFT) & 0xfL);

                int save = (dst == 0) ? 0 : this.offsets[dst];

                offsets[0] = offset - save;

                offsets[1] = save;

            }

            return offset;

        }

    }

    private int getTransitionIndex(long date, int type) {

        int low = 0;

        int high = transitions.length - 1;

        while (low <= high) {

            int mid = (low + high) / 2;

            long val = transitions[mid];

            long midVal = val >> TRANSITION_NSHIFT; // sign extended

            if (type != UTC_TIME) {

                midVal += offsets[(int)(val & OFFSET_MASK)]; // wall time

            }

            if (type == STANDARD_TIME) {

                int dstIndex = (int)((val >>> DST_NSHIFT) & 0xfL);

                if (dstIndex != 0) {

                    midVal -= offsets[dstIndex]; // make it standard time

                }

            }

            if (midVal < date) {

                low = mid + 1;

            } else if (midVal > date) {

                high = mid - 1;

            } else {

                return mid;

            }

        }

        // if beyond the transitions, returns that index.

        if (low >= transitions.length) {

            return low;

        }

        return low - 1;

    }

   /**

     * Returns the difference in milliseconds between local time and

     * UTC, taking into account both the raw offset and the effect of

     * daylight savings, for the specified date and time.  This method

     * assumes that the start and end month are distinct.  This method

     * assumes a Gregorian calendar for calculations.

     * <p>

     * <em>Note: In general, clients should use

     * {@link Calendar#ZONE_OFFSET Calendar.get(ZONE_OFFSET)} +

     * {@link Calendar#DST_OFFSET Calendar.get(DST_OFFSET)}

     * instead of calling this method.</em>

     *

     * @param era       The era of the given date. The value must be either

     *                  GregorianCalendar.AD or GregorianCalendar.BC.

     * @param year      The year in the given date.

     * @param month     The month in the given date. Month is 0-based. e.g.,

     *                  0 for January.

     * @param day       The day-in-month of the given date.

     * @param dayOfWeek The day-of-week of the given date.

     * @param milliseconds The milliseconds in day in <em>standard</em> local time.

     * @return The milliseconds to add to UTC to get local time.

     */

    public int getOffset(int era, int year, int month, int day,

                         int dayOfWeek, int milliseconds) {

        if (milliseconds < 0 || milliseconds >= AbstractCalendar.DAY_IN_MILLIS) {

            throw new IllegalArgumentException();

        }

        if (era == java.util.GregorianCalendar.BC) { // BC

            year = 1 - year;

        } else if (era != java.util.GregorianCalendar.AD) {

            throw new IllegalArgumentException();

        }

        Gregorian gcal = CalendarSystem.getGregorianCalendar();

        CalendarDate date = gcal.newCalendarDate(null);

        date.setDate(year, month + 1, day);

        if (gcal.validate(date) == false) {

            throw new IllegalArgumentException();

        }

        // bug-for-bug compatible argument checking

        if (dayOfWeek < java.util.GregorianCalendar.SUNDAY

            || dayOfWeek > java.util.GregorianCalendar.SATURDAY) {

            throw new IllegalArgumentException();

        }

        if (transitions == null) {

            return getLastRawOffset();

        }

        long dateInMillis = gcal.getTime(date) + milliseconds;

        dateInMillis -= (long) rawOffset; // make it UTC

        return getOffsets(dateInMillis, null, UTC_TIME);

    }

    /**

     * Sets the base time zone offset from GMT. This operation

     * modifies all the transitions of this ZoneInfo object, including

     * historical ones, if applicable.

     *

     * @param offsetMillis the base time zone offset to GMT.

     * @see getRawOffset

     */

    public synchronized void setRawOffset(int offsetMillis) {

        if (offsetMillis == rawOffset + rawOffsetDiff) {

            return;

        }

        rawOffsetDiff = offsetMillis - rawOffset;

        if (lastRule != null) {

            lastRule.setRawOffset(offsetMillis);

        }

        dirty = true;

    }

    /**

     * Returns the GMT offset of the current date. This GMT offset

     * value is not modified during Daylight Saving Time.

     *

     * @return the GMT offset value in milliseconds to add to UTC time

     * to get local standard time

     */

    public int getRawOffset() {

        if (!willGMTOffsetChange) {

            return rawOffset + rawOffsetDiff;

        }

        int[] offsets = new int[2];

        getOffsets(System.currentTimeMillis(), offsets, UTC_TIME);

        return offsets[0];

    }

    public boolean isDirty() {

        return dirty;

    }

    private int getLastRawOffset() {

        return rawOffset + rawOffsetDiff;

    }

    /**

     * Queries if this time zone uses Daylight Saving Time in the last known rule.

     */

    public boolean useDaylightTime() {

        return (simpleTimeZoneParams != null);

    }

    @Override

    public boolean observesDaylightTime() {

        if (simpleTimeZoneParams != null) {

            return true;

        }

        if (transitions == null) {

            return false;

        }

        // Look up the transition table to see if it's in DST right

        // now or if there's any standard-to-daylight transition at

        // any future.

        long utc = System.currentTimeMillis() - rawOffsetDiff;

        int index = getTransitionIndex(utc, UTC_TIME);

        // before transitions in the transition table

        if (index < 0) {

            return false;

        }

        // the time is in the table range.

        for (int i = index; i < transitions.length; i++) {

            if ((transitions[i] & DST_MASK) != 0) {

                return true;

            }

        }

        // No further DST is observed.

        return false;

    }

    /**

     * Queries if the specified date is in Daylight Saving Time.

     */

    public boolean inDaylightTime(Date date) {

        if (date == null) {

            throw new NullPointerException();

        }

        if (transitions == null) {

            return false;

        }

        long utc = date.getTime() - rawOffsetDiff;

        int index = getTransitionIndex(utc, UTC_TIME);

        // before transitions in the transition table

        if (index < 0) {

            return false;

        }

        // the time is in the table range.

        if (index < transitions.length) {

            return (transitions[index] & DST_MASK) != 0;

        }

        // beyond the transition table

        SimpleTimeZone tz = getLastRule();

        if (tz != null) {

            return tz.inDaylightTime(date);

        } else {

            // use the last transition

            return (transitions[transitions.length - 1] & DST_MASK) != 0;

        }

    }

    /**

     * Returns the amount of time in milliseconds that the clock is advanced

     * during daylight saving time is in effect in its last daylight saving time rule.

     *

     * @return the number of milliseconds the time is advanced with respect to

     * standard time when daylight saving time is in effect.