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	/*
	* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
	* 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
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	*/

	package sun.util.calendar;

	import java.util.TimeZone;
	import java.util.concurrent.ConcurrentHashMap;
	import java.util.concurrent.ConcurrentMap;

	/**
	* <code>CalendarSystem</code> is an abstract class that defines the
	* programming interface to deal with calendar date and time.
	*
	* <p><code>CalendarSystem</code> instances are singletons. For
	* example, there exists only one Gregorian calendar instance in the
	* Java runtime environment. A singleton instance can be obtained
	* calling one of the static factory methods.
	*
	* <h4>CalendarDate</h4>
	*
	* <p>For the methods in a <code>CalendarSystem</code> that manipulate
	* a <code>CalendarDate</code>, <code>CalendarDate</code>s that have
	* been created by the <code>CalendarSystem</code> must be
	* specified. Otherwise, the methods throw an exception. This is
	* because, for example, a Chinese calendar date can't be understood
	* by the Hebrew calendar system.
	*
	* <h4>Calendar names</h4>
	*
	* Each calendar system has a unique name to be identified. The Java
	* runtime in this release supports the following calendar systems.
	*
	* <pre>
	* Name Calendar System
	* ---------------------------------------
	* gregorian Gregorian Calendar
	* julian Julian Calendar
	* japanese Japanese Imperial Calendar
	* </pre>
	*
	* @see CalendarDate
	* @author Masayoshi Okutsu
	* @since 1.5
	*/

	public abstract class CalendarSystem {

	/////////////////////// Calendar Factory Methods /////////////////////////

	private static volatile boolean initialized;

	// Map of calendar names and calendar class names
	private static ConcurrentMap<String, String> names;

	// Map of calendar names and CalendarSystem instances
	private static ConcurrentMap<String,CalendarSystem> calendars;

	private static final String PACKAGE_NAME = "sun.util.calendar.";

	private static final String[] namePairs = {
	"gregorian", "Gregorian",
	"japanese", "LocalGregorianCalendar",
	"julian", "JulianCalendar",
	/*
	"hebrew", "HebrewCalendar",
	"iso8601", "ISOCalendar",
	"taiwanese", "LocalGregorianCalendar",
	"thaibuddhist", "LocalGregorianCalendar",
	*/
	};

	private static void initNames() {
	ConcurrentMap<String,String> nameMap = new ConcurrentHashMap<>();

	// Associate a calendar name with its class name and the
	// calendar class name with its date class name.
	StringBuilder clName = new StringBuilder();
	for (int i = 0; i < namePairs.length; i += 2) {
	clName.setLength(0);
	String cl = clName.append(PACKAGE_NAME).append(namePairs[i+1]).toString();
	nameMap.put(namePairs[i], cl);
	}
	synchronized (CalendarSystem.class) {
	if (!initialized) {
	names = nameMap;
	calendars = new ConcurrentHashMap<>();
	initialized = true;
	}
	}
	}

	private static final Gregorian GREGORIAN_INSTANCE = new Gregorian();

	/**
	* Returns the singleton instance of the <code>Gregorian</code>
	* calendar system.
	*
	* @return the <code>Gregorian</code> instance
	*/
	public static Gregorian getGregorianCalendar() {
	return GREGORIAN_INSTANCE;
	}

	/**
	* Returns a <code>CalendarSystem</code> specified by the calendar
	* name. The calendar name has to be one of the supported calendar
	* names.
	*
	* @param calendarName the calendar name
	* @return the <code>CalendarSystem</code> specified by
	* <code>calendarName</code>, or null if there is no
	* <code>CalendarSystem</code> associated with the given calendar name.
	*/
	public static CalendarSystem forName(String calendarName) {
	if ("gregorian".equals(calendarName)) {
	return GREGORIAN_INSTANCE;
	}

	if (!initialized) {
	initNames();
	}

	CalendarSystem cal = calendars.get(calendarName);
	if (cal != null) {
	return cal;
	}

	String className = names.get(calendarName);
	if (className == null) {
	return null; // Unknown calendar name
	}

	if (className.endsWith("LocalGregorianCalendar")) {
	// Create the specific kind of local Gregorian calendar system
	cal = LocalGregorianCalendar.getLocalGregorianCalendar(calendarName);
	} else {
	try {
	@SuppressWarnings("deprecation")
	Object tmp = Class.forName(className).newInstance();
	cal = (CalendarSystem) tmp;
	} catch (Exception e) {
	throw new InternalError(e);
	}
	}
	if (cal == null) {
	return null;
	}
	CalendarSystem cs = calendars.putIfAbsent(calendarName, cal);
	return (cs == null) ? cal : cs;
	}

	//////////////////////////////// Calendar API //////////////////////////////////

	/**
	* Returns the name of this calendar system.
	*/
	public abstract String getName();

	public abstract CalendarDate getCalendarDate();

	/**
	* Calculates calendar fields from the specified number of
	* milliseconds since the Epoch, January 1, 1970 00:00:00 UTC
	* (Gregorian). This method doesn't check overflow or underflow
	* when adjusting the millisecond value (representing UTC) with
	* the time zone offsets (i.e., the GMT offset and amount of
	* daylight saving).
	*
	* @param millis the offset value in milliseconds from January 1,
	* 1970 00:00:00 UTC (Gregorian).
	* @return a <code>CalendarDate</code> instance that contains the
	* calculated calendar field values.
	*/
	public abstract CalendarDate getCalendarDate(long millis);

	public abstract CalendarDate getCalendarDate(long millis, CalendarDate date);

	public abstract CalendarDate getCalendarDate(long millis, TimeZone zone);

	/**
	* Constructs a <code>CalendarDate</code> that is specific to this
	* calendar system. All calendar fields have their initial
	* values. The {@link TimeZone#getDefault() default time zone} is
	* set to the instance.
	*
	* @return a <code>CalendarDate</code> instance that contains the initial
	* calendar field values.
	*/
	public abstract CalendarDate newCalendarDate();

	public abstract CalendarDate newCalendarDate(TimeZone zone);

	/**
	* Returns the number of milliseconds since the Epoch, January 1,
	* 1970 00:00:00 UTC (Gregorian), represented by the specified
	* <code>CalendarDate</code>.
	*
	* @param date the <code>CalendarDate</code> from which the time
	* value is calculated
	* @return the number of milliseconds since the Epoch.
	*/
	public abstract long getTime(CalendarDate date);

	/**
	* Returns the length in days of the specified year by
	* <code>date</code>. This method does not perform the
	* normalization with the specified <code>CalendarDate</code>. The
	* <code>CalendarDate</code> must be normalized to get a correct
	* value.
	*/
	public abstract int getYearLength(CalendarDate date);

	/**
	* Returns the number of months of the specified year. This method
	* does not perform the normalization with the specified
	* <code>CalendarDate</code>. The <code>CalendarDate</code> must
	* be normalized to get a correct value.
	*/
	public abstract int getYearLengthInMonths(CalendarDate date);

	/**
	* Returns the length in days of the month specified by the calendar
	* date. This method does not perform the normalization with the
	* specified calendar date. The <code>CalendarDate</code> must
	* be normalized to get a correct value.
	*
	* @param date the date from which the month value is obtained
	* @return the number of days in the month
	* @exception IllegalArgumentException if the specified calendar date
	* doesn't have a valid month value in this calendar system.
	*/
	public abstract int getMonthLength(CalendarDate date); // no setter

	/**
	* Returns the length in days of a week in this calendar
	* system. If this calendar system has multiple radix weeks, this
	* method returns only one of them.
	*/
	public abstract int getWeekLength();

	/**
	* Returns the <code>Era</code> designated by the era name that
	* has to be known to this calendar system. If no Era is
	* applicable to this calendar system, null is returned.
	*
	* @param eraName the name of the era
	* @return the <code>Era</code> designated by
	* <code>eraName</code>, or <code>null</code> if no Era is
	* applicable to this calendar system or the specified era name is
	* not known to this calendar system.
	*/
	public abstract Era getEra(String eraName);

	/**
	* Returns valid <code>Era</code>s of this calendar system. The
	* return value is sorted in the descendant order. (i.e., the first
	* element of the returned array is the oldest era.) If no era is
	* applicable to this calendar system, <code>null</code> is returned.
	*
	* @return an array of valid <code>Era</code>s, or
	* <code>null</code> if no era is applicable to this calendar
	* system.
	*/
	public abstract Era[] getEras();

	/**
	* @throws IllegalArgumentException if the specified era name is
	* unknown to this calendar system.
	* @see Era
	*/
	public abstract void setEra(CalendarDate date, String eraName);

	/**
	* Returns a <code>CalendarDate</code> of the n-th day of week
	* which is on, after or before the specified date. For example, the
	* first Sunday in April 2002 (Gregorian) can be obtained as
	* below:
	*
	* <pre><code>
	* Gregorian cal = CalendarSystem.getGregorianCalendar();
	* CalendarDate date = cal.newCalendarDate();
	* date.setDate(2004, cal.APRIL, 1);
	* CalendarDate firstSun = cal.getNthDayOfWeek(1, cal.SUNDAY, date);
	* // firstSun represents April 4, 2004.
	* </code></pre>
	*
	* This method returns a new <code>CalendarDate</code> instance
	* and doesn't modify the original date.
	*
	* @param nth specifies the n-th one. A positive number specifies
	* <em>on or after</em> the <code>date</code>. A non-positive number
	* specifies <em>on or before</em> the <code>date</code>.
	* @param dayOfWeek the day of week
	* @param date the date
	* @return the date of the nth <code>dayOfWeek</code> after
	* or before the specified <code>CalendarDate</code>
	*/
	public abstract CalendarDate getNthDayOfWeek(int nth, int dayOfWeek,
	CalendarDate date);

	public abstract CalendarDate setTimeOfDay(CalendarDate date, int timeOfDay);

	/**
	* Checks whether the calendar fields specified by <code>date</code>
	* represents a valid date and time in this calendar system. If the
	* given date is valid, <code>date</code> is marked as <em>normalized</em>.
	*
	* @param date the <code>CalendarDate</code> to be validated
	* @return <code>true</code> if all the calendar fields are consistent,
	* otherwise, <code>false</code> is returned.
	* @exception NullPointerException if the specified
	* <code>date</code> is <code>null</code>
	*/
	public abstract boolean validate(CalendarDate date);

	/**
	* Normalizes calendar fields in the specified
	* <code>date</code>. Also all {@link CalendarDate#FIELD_UNDEFINED
	* undefined} fields are set to correct values. The actual
	* normalization process is calendar system dependent.
	*
	* @param date the calendar date to be validated
	* @return <code>true</code> if all fields have been normalized;
	* <code>false</code> otherwise.
	* @exception NullPointerException if the specified
	* <code>date</code> is <code>null</code>
	*/
	public abstract boolean normalize(CalendarDate date);
	}

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