/*
 * @(#)TimeZone.java	1.63 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

/*
 * (C) Copyright Taligent, Inc. 1996 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996 - All Rights Reserved
 *
 *   The original version of this source code and documentation is copyrighted
 * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
 * materials are provided under terms of a License Agreement between Taligent
 * and Sun. This technology is protected by multiple US and International
 * patents. This notice and attribution to Taligent may not be removed.
 *   Taligent is a registered trademark of Taligent, Inc.
 *
 */

package java.util;
import java.io.Serializable;
import java.lang.ref.SoftReference;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.text.SimpleDateFormat;
import sun.security.action.GetPropertyAction;
import sun.util.calendar.ZoneInfo;
import sun.util.calendar.ZoneInfoFile;

/**
 * <code>TimeZone</code> represents a time zone offset, and also figures out daylight
 * savings.
 *
 * <p>
 * Typically, you get a <code>TimeZone</code> using <code>getDefault</code>
 * which creates a <code>TimeZone</code> based on the time zone where the program
 * is running. For example, for a program running in Japan, <code>getDefault</code>
 * creates a <code>TimeZone</code> object based on Japanese Standard Time.
 *
 * <p>
 * You can also get a <code>TimeZone</code> using <code>getTimeZone</code>
 * along with a time zone ID. For instance, the time zone ID for the
 * U.S. Pacific Time zone is "America/Los_Angeles". So, you can get a
 * U.S. Pacific Time <code>TimeZone</code> object with:
 * <blockquote><pre>
 * TimeZone tz = TimeZone.getTimeZone("America/Los_Angeles");
 * </pre></blockquote>
 * You can use the <code>getAvailableIDs</code> method to iterate through
 * all the supported time zone IDs. You can then choose a
 * supported ID to get a <code>TimeZone</code>.
 * If the time zone you want is not represented by one of the
 * supported IDs, then a custom time zone ID can be specified to
 * produce a TimeZone. The syntax of a custom time zone ID is:
 *
 * <blockquote><pre>
 * <a name="CustomID"><i>CustomID:</i></a>
 *         <code>GMT</code> <i>Sign</i> <i>Hours</i> <code>:</code> <i>Minutes</i>
 *         <code>GMT</code> <i>Sign</i> <i>Hours</i> <i>Minutes</i>
 *         <code>GMT</code> <i>Sign</i> <i>Hours</i>
 * <i>Sign:</i> one of
 *         <code>+ -</code>
 * <i>Hours:</i>
 *         <i>Digit</i>
 *         <i>Digit</i> <i>Digit</i>
 * <i>Minutes:</i>
 *         <i>Digit</i> <i>Digit</i>
 * <i>Digit:</i> one of
 *         <code>0 1 2 3 4 5 6 7 8 9</code>
 * </pre></blockquote>
 *
 * <i>Hours</i> must be between 0 to 23 and <i>Minutes</i> must be
 * between 00 to 59.  For example, "GMT+10" and "GMT+0010" mean ten
 * hours and ten minutes ahead of GMT, respectively.
 * <p>
 * The format is locale independent and digits must be taken from the
 * Basic Latin block of the Unicode standard. No daylight saving time
 * transition schedule can be specified with a custom time zone ID. If
 * the specified string doesn't match the syntax, <code>"GMT"</code>
 * is used.
 * <p>
 * When creating a <code>TimeZone</code>, the specified custom time
 * zone ID is normalized in the following syntax:
 * <blockquote><pre>
 * <a name="NormalizedCustomID"><i>NormalizedCustomID:</i></a>
 *         <code>GMT</code> <i>Sign</i> <i>TwoDigitHours</i> <code>:</code> <i>Minutes</i>
 * <i>Sign:</i> one of
 *         <code>+ -</code>
 * <i>TwoDigitHours:</i>
 *         <i>Digit</i> <i>Digit</i>
 * <i>Minutes:</i>
 *         <i>Digit</i> <i>Digit</i>
 * <i>Digit:</i> one of
 *         <code>0 1 2 3 4 5 6 7 8 9</code>
 * </pre></blockquote>
 * For example, TimeZone.getTimeZone("GMT-8").getID() returns "GMT-08:00".
 *
 * <h4>Three-letter time zone IDs</h4>
 * 
 * For compatibility with JDK 1.1.x, some other three-letter time zone IDs
 * (such as "PST", "CTT", "AST") are also supported. However, <strong>their
 * use is deprecated</strong> because the same abbreviation is often used
 * for multiple time zones (for example, "CST" could be U.S. "Central Standard
 * Time" and "China Standard Time"), and the Java platform can then only
 * recognize one of them.
 *
 *
 * @see          Calendar
 * @see          GregorianCalendar
 * @see          SimpleTimeZone
 * @version      1.63 01/23/03
 * @author       Mark Davis, David Goldsmith, Chen-Lieh Huang, Alan Liu
 * @since        JDK1.1
 */
abstract public class TimeZone implements Serializable, Cloneable {
    /**
     * Sole constructor.  (For invocation by subclass constructors, typically
     * implicit.)
     */
    public TimeZone() {
    }

    /**
     * A style specifier for <code>getDisplayName()</code> indicating
     * a short name, such as "PST."
     * @see #LONG
     * @since 1.2
     */
    public static final int SHORT = 0;

    /**
     * A style specifier for <code>getDisplayName()</code> indicating
     * a long name, such as "Pacific Standard Time."
     * @see #SHORT
     * @since 1.2
     */
    public static final int LONG  = 1;

    // Constants used internally; unit is milliseconds
    private static final int ONE_MINUTE = 60*1000;
    private static final int ONE_HOUR   = 60*ONE_MINUTE;
    private static final int ONE_DAY    = 24*ONE_HOUR;

    /**
     * Cache to hold the SimpleDateFormat objects for a Locale.
     */
    private static Hashtable cachedLocaleData = new Hashtable(3);

    // Proclaim serialization compatibility with JDK 1.1
    static final long serialVersionUID = 3581463369166924961L;

    /**
     * Gets the time zone offset, for current date, modified in case of
     * daylight savings. This is the offset to add to UTC to get local time.
     * <p>
     * This method returns a historically correct offset if an
     * underlying <code>TimeZone</code> implementation subclass
     * supports historical Daylight Saving Time schedule and GMT
     * offset changes.
     *
     * @param era the era of the given date.
     * @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 offset in milliseconds to add to GMT to get local time.
     *
     * @see Calendar#ZONE_OFFSET
     * @see Calendar#DST_OFFSET
     */
    public abstract int getOffset(int era, int year, int month, int day,
                                  int dayOfWeek, int milliseconds);

    /**
     * Returns the offset of this time zone from UTC at the specified
     * date. If Daylight Saving Time is in effect at the specified
     * date, the offset value is adjusted with the amount of daylight
     * saving.
     * <p>
     * This method returns a historically correct offset value if an
     * underlying TimeZone implementation subclass supports historical
     * Daylight Saving Time schedule and GMT offset changes.
     *
     * @param date the date represented in milliseconds since January 1, 1970 00:00:00 GMT
     * @return the amount of time in milliseconds to add to UTC to get local time.
     *
     * @see Calendar#ZONE_OFFSET
     * @see Calendar#DST_OFFSET
     * @since 1.4
     */
    public int getOffset(long date) {
	if (inDaylightTime(new Date(date))) {
	    return getRawOffset() + getDSTSavings();
	}
	return getRawOffset();
    }

    /**
     * Gets the raw GMT offset and the amount of daylight saving of this
     * time zone at the given time.
     * @param date the milliseconds (since January 1, 1970,
     * 00:00:00.000 GMT) at which the time zone offset and daylight
     * saving amount are found
     * @param offset an array of int where the raw GMT offset
     * (offset[0]) and daylight saving amount (offset[1]) are stored,
     * or null if those values are not needed. The method assumes that
     * the length of the given array is two or larger.
     * @return the total amount of the raw GMT offset and daylight
     * saving at the specified date.
     *
     * @see Calendar#ZONE_OFFSET
     * @see Calendar#DST_OFFSET
     */
    int getOffsets(long date, int[] offsets) {
	int rawoffset = getRawOffset();
	int dstoffset = 0;
	if (inDaylightTime(new Date(date))) {
	    dstoffset = getDSTSavings();
	}
	if (offsets != null) {
	    offsets[0] = rawoffset;
	    offsets[1] = dstoffset;
	}
	return rawoffset + dstoffset;
    }

    /**
     * Sets the base time zone offset to GMT.
     * This is the offset to add to UTC to get local time.
     * <p>
     * If an underlying <code>TimeZone</code> implementation subclass
     * supports historical GMT offset changes, the specified GMT
     * offset is set as the latest GMT offset and the difference from
     * the known latest GMT offset value is used to adjust all
     * historical GMT offset values.
     *
     * @param offsetMillis the given base time zone offset to GMT.
     */
    abstract public void setRawOffset(int offsetMillis);

    /**
     * Returns the amount of time in milliseconds to add to UTC to get
     * standard time in this time zone. Because this value is not
     * affected by daylight saving time, it is called <I>raw
     * offset</I>.
     * <p>
     * If an underlying <code>TimeZone</code> implementation subclass
     * supports historical GMT offset changes, the method returns the
     * raw offset value of the current date. In Honolulu, for example,
     * its raw offset changed from GMT-10:30 to GMT-10:00 in 1947, and
     * this method always returns -36000000 milliseconds (i.e., -10
     * hours).
     *
     * @return the amount of raw offset time in milliseconds to add to UTC.
     * @see Calendar#ZONE_OFFSET
     */
    public abstract int getRawOffset();

    /**
     * Gets the ID of this time zone.
     * @return the ID of this time zone.
     */
    public String getID()
    {
        return ID;
    }

    /**
     * Sets the time zone ID. This does not change any other data in
     * the time zone object.
     * @param ID the new time zone ID.
     */
    public void setID(String ID)
    {
        if (ID == null) {
            throw new NullPointerException();
        }
        this.ID = ID;
    }

    /**
     * Returns a name of this time zone suitable for presentation to the user
     * in the default locale.
     * This method returns the long name, not including daylight savings.
     * If the display name is not available for the locale,
     * then this method returns a string in the 
     * <a href="#NormalizedCustomID">normalized custom ID format</a>.
     * @return the human-readable name of this time zone in the default locale.
     * @since 1.2
     */
    public final String getDisplayName() {
        return getDisplayName(false, LONG, Locale.getDefault());
    }

    /**
     * Returns a name of this time zone suitable for presentation to the user
     * in the specified locale.
     * This method returns the long name, not including daylight savings.
     * If the display name is not available for the locale,
     * then this method returns a string in the 
     * <a href="#NormalizedCustomID">normalized custom ID format</a>.
     * @param locale the locale in which to supply the display name.
     * @return the human-readable name of this time zone in the given locale
     * or in the default locale if the given locale is not recognized.
     * @since 1.2
     */
    public final String getDisplayName(Locale locale) {
        return getDisplayName(false, LONG, locale);
    }

    /**
     * Returns a name of this time zone suitable for presentation to the user
     * in the default locale.
     * If the display name is not available for the locale, then this
     * method returns a string in the 
     * <a href="#NormalizedCustomID">normalized custom ID format</a>.
     * @param daylight if true, return the daylight savings name.
     * @param style either <code>LONG</code> or <code>SHORT</code>
     * @return the human-readable name of this time zone in the default locale.
     * @since 1.2
     */
    public final String getDisplayName(boolean daylight, int style) {
        return getDisplayName(daylight, style, Locale.getDefault());
    }

    /**
     * Returns a name of this time zone suitable for presentation to the user
     * in the specified locale.
     * If the display name is not available for the locale,
     * then this method returns a string in the 
     * <a href="#NormalizedCustomID">normalized custom ID format</a>.
     * @param daylight if true, return the daylight savings name.
     * @param style either <code>LONG</code> or <code>SHORT</code>
     * @param locale the locale in which to supply the display name.
     * @return the human-readable name of this time zone in the given locale
     * or in the default locale if the given locale is not recognized.
     * @exception IllegalArgumentException style is invalid.
     * @since 1.2
     */
    public String getDisplayName(boolean daylight, int style, Locale locale) {
        /* NOTES:
         * (1) We use SimpleDateFormat for simplicity; we could do this
         * more efficiently but it would duplicate the SimpleDateFormat code
         * here, which is undesirable.
         * (2) Attempts to move the code from SimpleDateFormat to here also run
         * around because this requires SimpleDateFormat to keep a Locale
         * object around, which it currently doesn't; to synthesize such a
         * locale upon resurrection; and to somehow handle the special case of
         * construction from a DateFormatSymbols object.
         */
        if (style != SHORT && style != LONG) {
            throw new IllegalArgumentException("Illegal style: " + style);
        }
        // We keep a cache, indexed by locale.  The cache contains a
        // SimpleDateFormat object, which we create on demand.
        SoftReference data = (SoftReference)cachedLocaleData.get(locale);
        SimpleDateFormat format;
        if (data == null ||
            (format = (SimpleDateFormat)data.get()) == null) {
            format = new SimpleDateFormat("", locale);
            cachedLocaleData.put(locale, new SoftReference(format));
        }
        // Create a new SimpleTimeZone as a stand-in for this zone; the stand-in
        // will have no DST, or DST during January, but the same ID and offset,
        // and hence the same display name.  We don't cache these because
        // they're small and cheap to create.
        SimpleTimeZone tz;
        if (daylight && useDaylightTime()) {
            int savings = getDSTSavings();
            tz = new SimpleTimeZone(getRawOffset(), getID(),
                                    Calendar.JANUARY, 1, 0, 0,
                                    Calendar.FEBRUARY, 1, 0, 0,
                                    savings);
        } else {
            tz = new SimpleTimeZone(getRawOffset(), getID());
        }
        format.applyPattern(style == LONG ? "zzzz" : "z");      
        format.setTimeZone(tz);
        // Format a date in January.  We use the value 10*ONE_DAY == Jan 11 1970
        // 0:00 GMT.
        return format.format(new Date(864000000L));
    }

    /**
     * Returns the amount of time to be added to local standard time
     * to get local wall clock time.
     * <p>
     * The default implementation always returns 3600000 milliseconds
     * (i.e., one hour) if this time zone observes Daylight Saving
     * Time. Otherwise, 0 (zero) is returned.
     * <p>
     * If an underlying TimeZone implementation subclass supports
     * historical Daylight Saving Time changes, this method returns
     * the known latest daylight saving value.
     *
     * @return the amount of saving time in milliseconds
     * @since 1.4
     */
    public int getDSTSavings() {
	if (useDaylightTime()) {
	    return 3600000;
	}
	return 0;
    }

    /**
     * Queries if this time zone uses daylight savings time.
     * <p>
     * If an underlying <code>TimeZone</code> implementation subclass
     * supports historical Daylight Saving Time schedule changes, the
     * method refers to the latest Daylight Saving Time schedule
     * information.
     *
     * @return true if this time zone uses daylight savings time,
     * false, otherwise.
     */
    public abstract boolean useDaylightTime();

    /**
     * Queries if the given date is in daylight savings time in
     * this time zone.
     * @param date the given Date.
     * @return true if the given date is in daylight savings time,
     * false, otherwise.
     */
    abstract public boolean inDaylightTime(Date date);

    /**
     * Gets the <code>TimeZone</code> for the given ID.
     *
     * @param ID the ID for a <code>TimeZone</code>, either an abbreviation
     * such as "PST", a full name such as "America/Los_Angeles", or a custom
     * ID such as "GMT-8:00". Note that the support of abbreviations is
     * for JDK 1.1.x compatibility only and full names should be used.
     *
     * @return the specified <code>TimeZone</code>, or the GMT zone if the given ID
     * cannot be understood.
     */
    public static synchronized TimeZone getTimeZone(String ID) {
	return getTimeZone(ID, true);
    }

    private static TimeZone getTimeZone(String ID, boolean fallback) {
	TimeZone tz = ZoneInfo.getTimeZone(ID);
	if (tz == null) {
	    tz = parseCustomTimeZone(ID);
	    if (tz == null && fallback) {
		tz = new ZoneInfo(GMT_ID, 0);
	    }
	}
	return tz;
    }

    /**
     * Gets the available IDs according to the given time zone offset.
     * @param rawOffset the given time zone GMT offset.
     * @return an array of IDs, where the time zone for that ID has
     * the specified GMT offset. For example, "America/Phoenix" and "America/Denver"
     * both have GMT-07:00, but differ in daylight savings behavior.
     */
    public static synchronized String[] getAvailableIDs(int rawOffset) {
	return ZoneInfo.getAvailableIDs(rawOffset);
    }

    /**
     * Gets all the available IDs supported.
     * @return an array of IDs.
     */
    public static synchronized String[] getAvailableIDs() {
	return ZoneInfo.getAvailableIDs();
    }
    
    /**
     * Gets the platform defined TimeZone ID.
     **/
    private static native String getSystemTimeZoneID(String javaHome, 
						     String country);

    /**
     * Gets the custom time zone ID based on the GMT offset of the
     * platform. (e.g., "GMT+08:00")
     */
    private static native String getSystemGMTOffsetID();

    /**
     * Gets the default <code>TimeZone</code> for this host.
     * The source of the default <code>TimeZone</code> 
     * may vary with implementation.
     * @return a default <code>TimeZone</code>.
     * @see #setDefault
     */
    public static synchronized TimeZone getDefault() {
      out:
        if (defaultZone == null) {
            // get the time zone ID from the system properties
	    String zoneID = (String) AccessController.doPrivileged(
		new GetPropertyAction("user.timezone"));

	    // if the time zone ID is not set (yet), perform the
	    // platform to Java time zone ID mapping.
	    if (zoneID == null || zoneID.equals("")) { 
		String country = (String) AccessController.doPrivileged(
		    new GetPropertyAction("user.country"));
		String javaHome = (String) AccessController.doPrivileged(
		    new GetPropertyAction("java.home"));
		try {
		    zoneID = getSystemTimeZoneID(javaHome, country);
		    if (zoneID == null) {
			zoneID = GMT_ID;
		    }
		}
		catch (NullPointerException e) {
		    zoneID = GMT_ID;
		}

		// Get the time zone for zoneID. But not fall back to
		// "GMT" here.
		defaultZone = getTimeZone(zoneID, false);

		if (defaultZone == null) {
		    // If the given zone ID is unknown in Java, try to
		    // get the GMT-offset-based time zone ID,
		    // a.k.a. custom time zone ID (e.g., "GMT-08:00").
		    String gmtOffsetID = getSystemGMTOffsetID();
		    if (gmtOffsetID != null) {
			zoneID = gmtOffsetID;
		    }
		}

		final String id = zoneID;
		AccessController.doPrivileged(new PrivilegedAction() {
		    public Object run() {
			System.setProperty("user.timezone", id);
			return null;
		    }
		});

		if (defaultZone != null) {
		    break out;
		}
	    }
            defaultZone = getTimeZone(zoneID, true);
        }
        return (TimeZone) defaultZone.clone();
    }

    /**
     * Sets the <code>TimeZone</code> that is
     * returned by the <code>getDefault</code> method.  If <code>zone</code>
     * is null, reset the default to the value it had originally when the
     * VM first started.
     * @param zone the new default time zone
     * @see #getDefault
     */
    public static synchronized void setDefault(TimeZone zone)
    {
        defaultZone = zone;
    }

    /**
     * Returns true if this zone has the same rule and offset as another zone.
     * That is, if this zone differs only in ID, if at all.  Returns false
     * if the other zone is null.
     * @param other the <code>TimeZone</code> object to be compared with
     * @return true if the other zone is not null and is the same as this one,
     * with the possible exception of the ID
     * @since 1.2
     */
    public boolean hasSameRules(TimeZone other) {
        return other != null && getRawOffset() == other.getRawOffset() &&
            useDaylightTime() == other.useDaylightTime();
    }

    /**
     * Creates a copy of this <code>TimeZone</code>.
     *
     * @return a clone of this <code>TimeZone</code>
     */
    public Object clone()
    {
        try {
            TimeZone other = (TimeZone) super.clone();
            other.ID = ID;
            return other;
        } catch (CloneNotSupportedException e) {
            throw new InternalError();
        }
    }

    // =======================privates===============================

    /**
     * The string identifier of this <code>TimeZone</code>.  This is a
     * programmatic identifier used internally to look up <code>TimeZone</code>
     * objects from the system table and also to map them to their localized
     * display names.  <code>ID</code> values are unique in the system
     * table but may not be for dynamically created zones.
     * @serial
     */
    private String           ID;
    private static TimeZone  defaultZone = null;

    static final String         GMT_ID        = "GMT";
    private static final int    GMT_ID_LENGTH = 3;

    /**
     * Parses a custom time zone identifier and returns a corresponding zone.
     * This method doesn't support the RFC 822 time zone format. (e.g., +hhmm)
     *
     * @param id a string of the <a href="#CustomID">custom ID form</a>.
     * @return a newly created TimeZone with the given offset and
     * no daylight saving time, or null if the id cannot be parsed.
     */
    private static final TimeZone parseCustomTimeZone(String id) {
	int length;

	// Error if the length of id isn't long enough or id doesn't
	// start with "GMT".
	if ((length = id.length()) < (GMT_ID_LENGTH + 2) ||
	    id.indexOf(GMT_ID) != 0) {
	    return null;
	}

	ZoneInfo zi;

	// First, we try to find it in the cache with the given
	// id. Even the id is not normalized, the returned ZoneInfo
	// should have its normalized id.
	zi = ZoneInfoFile.getZoneInfo(id);
	if (zi != null) {
	    return zi;
	}

	int index = GMT_ID_LENGTH;
	boolean negative = false;
	char c = id.charAt(index++);
	if (c == '-') {
	    negative = true;
	} else if (c != '+') {
	    return null;
	}

	int hours = 0;
	int num = 0;
	int countDelim = 0;
	int len = 0;
	while (index < length) {
	    c = id.charAt(index++);
	    if (c == ':') {
		if (countDelim > 0) {
		    return null;
		}
		if (len > 2) {
		    return null;
		}
		hours = num;
		countDelim++;
		num = 0;
		len = 0;
		continue;
	    }
	    if (c < '0' || c > '9') {
		return null;
	    }
	    num = num * 10 + (c - '0');
	    len++;
	}
	if (index != length) {
	    return null;
	}
	if (countDelim == 0) {
	    if (len <= 2) {
		hours = num;
		num = 0;
	    } else {
		hours = num / 100;
		num %= 100;
	    }
	} else {
	    if (len != 2) {
		return null;
	    }
	}
	if (hours > 23 || num > 59) {
	    return null;
	}
	int gmtOffset =  hours * 60 + num;

	if (gmtOffset == 0) {
	    zi = ZoneInfoFile.getZoneInfo(GMT_ID);
	    if (negative) {
		zi.setID("GMT-00:00");
	    } else {
		zi.setID("GMT+00:00");
	    }
	} else {
	    zi = ZoneInfoFile.getCustomTimeZone(id, negative ? -gmtOffset : gmtOffset);
	}
	return zi;
    }
}