/*
 *  Copyright 2001-2014 Stephen Colebourne
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.joda.time.chrono;

import java.util.concurrent.ConcurrentHashMap;

import org.joda.time.Chronology;
import org.joda.time.DateTime;
import org.joda.time.DateTimeConstants;
import org.joda.time.DateTimeField;
import org.joda.time.DateTimeFieldType;
import org.joda.time.DateTimeZone;
import org.joda.time.DurationFieldType;
import org.joda.time.field.DelegatedDateTimeField;
import org.joda.time.field.DividedDateTimeField;
import org.joda.time.field.OffsetDateTimeField;
import org.joda.time.field.RemainderDateTimeField;
import org.joda.time.field.SkipUndoDateTimeField;
import org.joda.time.field.UnsupportedDurationField;

A chronology that matches the BuddhistCalendar class supplied by Sun.

The chronology is identical to the Gregorian/Julian, except that the
year is offset by +543 and the era is named 'BE' for Buddhist Era.

This class was intended by Sun to model the calendar used in Thailand.
However, the actual rules for Thailand are much more involved than
this class covers. (This class is accurate after 1941-01-01 ISO).

This chronology is being retained for those who want a same effect
replacement for the Sun class. It is hoped that community support will
enable a more accurate chronology for Thailand, to be developed.

BuddhistChronology is thread-safe and immutable.
Author:
Stephen Colebourne, Brian S O'Neill
Since:
1.0/**
 * A chronology that matches the BuddhistCalendar class supplied by Sun.
 * <p>
 * The chronology is identical to the Gregorian/Julian, except that the
 * year is offset by +543 and the era is named 'BE' for Buddhist Era.
 * <p>
 * This class was intended by Sun to model the calendar used in Thailand.
 * However, the actual rules for Thailand are much more involved than
 * this class covers. (This class is accurate after 1941-01-01 ISO).
 * <p>
 * This chronology is being retained for those who want a same effect
 * replacement for the Sun class. It is hoped that community support will
 * enable a more accurate chronology for Thailand, to be developed.
 * <p>
 * BuddhistChronology is thread-safe and immutable.
 *
 * @author Stephen Colebourne
 * @author Brian S O'Neill
 * @since 1.0
 */
public final class BuddhistChronology extends AssembledChronology {
    
    
Serialization lock /** Serialization lock */
    private static final long serialVersionUID = -3474595157769370126L;

    
Constant value for 'Buddhist Era', equivalent to the value returned
for AD/CE. Note that this differs from the constant in BuddhistCalendar.
/**
     * Constant value for 'Buddhist Era', equivalent to the value returned
     * for AD/CE. Note that this differs from the constant in BuddhistCalendar.
     */
    public static final int BE = DateTimeConstants.CE;

    
A singleton era field. /** A singleton era field. */
    private static final DateTimeField ERA_FIELD = new BasicSingleEraDateTimeField("BE");

    
Number of years difference in calendars. /** Number of years difference in calendars. */
    private static final int BUDDHIST_OFFSET = 543;

    
Cache of zone to chronology /** Cache of zone to chronology */
    private static final ConcurrentHashMap<DateTimeZone, BuddhistChronology> cCache = new ConcurrentHashMap<DateTimeZone, BuddhistChronology>();

    
UTC instance of the chronology /** UTC instance of the chronology */
    private static final BuddhistChronology INSTANCE_UTC = getInstance(DateTimeZone.UTC);

    
Standard instance of a Buddhist Chronology, that matches
Sun's BuddhistCalendar class. This means that it follows the
GregorianJulian calendar rules with a cutover date.

The time zone of the returned instance is UTC.
/**
     * Standard instance of a Buddhist Chronology, that matches
     * Sun's BuddhistCalendar class. This means that it follows the
     * GregorianJulian calendar rules with a cutover date.
     * <p>
     * The time zone of the returned instance is UTC.
     */
    public static BuddhistChronology getInstanceUTC() {
        return INSTANCE_UTC;
    }

    
Standard instance of a Buddhist Chronology, that matches
Sun's BuddhistCalendar class. This means that it follows the
GregorianJulian calendar rules with a cutover date.
/**
     * Standard instance of a Buddhist Chronology, that matches
     * Sun's BuddhistCalendar class. This means that it follows the
     * GregorianJulian calendar rules with a cutover date.
     */
    public static BuddhistChronology getInstance() {
        return getInstance(DateTimeZone.getDefault());
    }

    
Standard instance of a Buddhist Chronology, that matches
Sun's BuddhistCalendar class. This means that it follows the
GregorianJulian calendar rules with a cutover date.
Params:
zone –  the time zone to use, null is default/**
     * Standard instance of a Buddhist Chronology, that matches
     * Sun's BuddhistCalendar class. This means that it follows the
     * GregorianJulian calendar rules with a cutover date.
     *
     * @param zone  the time zone to use, null is default
     */
    public static BuddhistChronology getInstance(DateTimeZone zone) {
        if (zone == null) {
            zone = DateTimeZone.getDefault();
        }
        BuddhistChronology chrono = cCache.get(zone);
        if (chrono == null) {
            // First create without a lower limit.
            chrono = new BuddhistChronology(GJChronology.getInstance(zone, null), null);
            // Impose lower limit and make another BuddhistChronology.
            DateTime lowerLimit = new DateTime(1, 1, 1, 0, 0, 0, 0, chrono);
            chrono = new BuddhistChronology(LimitChronology.getInstance(chrono, lowerLimit, null), "");
            BuddhistChronology oldChrono = cCache.putIfAbsent(zone, chrono);
            if (oldChrono != null) {
                chrono = oldChrono;
            }
        }
        return chrono;
    }

    // Constructors and instance variables
    //-----------------------------------------------------------------------
    
    
Restricted constructor.
Params:
param – if non-null, then don't change the field set/**
     * Restricted constructor.
     *
     * @param param if non-null, then don't change the field set
     */
    private BuddhistChronology(Chronology base, Object param) {
        super(base, param);
    }

    
Serialization singleton
/**
     * Serialization singleton
     */
    private Object readResolve() {
        Chronology base = getBase();
        return base == null ? getInstanceUTC() : getInstance(base.getZone());
    }

    // Conversion
    //-----------------------------------------------------------------------
    
Gets the Chronology in the UTC time zone.
Returns:
the chronology in UTC/**
     * Gets the Chronology in the UTC time zone.
     * 
     * @return the chronology in UTC
     */
    public Chronology withUTC() {
        return INSTANCE_UTC;
    }

    
Gets the Chronology in a specific time zone.
Params:
zone –  the zone to get the chronology in, null is default
Returns:
the chronology/**
     * Gets the Chronology in a specific time zone.
     * 
     * @param zone  the zone to get the chronology in, null is default
     * @return the chronology
     */
    public Chronology withZone(DateTimeZone zone) {
        if (zone == null) {
            zone = DateTimeZone.getDefault();
        }
        if (zone == getZone()) {
            return this;
        }
        return getInstance(zone);
    }

    //-----------------------------------------------------------------------
    
Checks if this chronology instance equals another.
Params:
obj –  the object to compare to
Returns:
true if equal
Since:
1.6/**
     * Checks if this chronology instance equals another.
     * 
     * @param obj  the object to compare to
     * @return true if equal
     * @since 1.6
     */
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj instanceof BuddhistChronology) {
            BuddhistChronology chrono = (BuddhistChronology) obj;
            return getZone().equals(chrono.getZone());
        }
        return false;
    }

    
A suitable hash code for the chronology.
Returns:
the hash code
Since:
1.6/**
     * A suitable hash code for the chronology.
     * 
     * @return the hash code
     * @since 1.6
     */
    public int hashCode() {
        return "Buddhist".hashCode() * 11 + getZone().hashCode();
    }

    // Output
    //-----------------------------------------------------------------------
    
Gets a debugging toString.
Returns:
a debugging string/**
     * Gets a debugging toString.
     * 
     * @return a debugging string
     */
    public String toString() {
        String str = "BuddhistChronology";
        DateTimeZone zone = getZone();
        if (zone != null) {
            str = str + '[' + zone.getID() + ']';
        }
        return str;
    }

    protected void assemble(Fields fields) {
        if (getParam() == null) {
            // force init as used below
            fields.eras = UnsupportedDurationField.getInstance(DurationFieldType.eras());
            
            // julian chrono removed zero, but we need to put it back
            DateTimeField field = fields.year;
            fields.year = new OffsetDateTimeField(
                    new SkipUndoDateTimeField(this, field), BUDDHIST_OFFSET);
            
            // one era, so yearOfEra is the same
            field = fields.yearOfEra;
            fields.yearOfEra = new DelegatedDateTimeField(
                fields.year, fields.eras, DateTimeFieldType.yearOfEra());
            
            // julian chrono removed zero, but we need to put it back
            field = fields.weekyear;
            fields.weekyear = new OffsetDateTimeField(
                    new SkipUndoDateTimeField(this, field), BUDDHIST_OFFSET);
            
            field = new OffsetDateTimeField(fields.yearOfEra, 99);
            fields.centuryOfEra = new DividedDateTimeField(
                field, fields.eras, DateTimeFieldType.centuryOfEra(), 100);
            fields.centuries = fields.centuryOfEra.getDurationField();
            
            field = new RemainderDateTimeField(
                (DividedDateTimeField) fields.centuryOfEra);
            fields.yearOfCentury = new OffsetDateTimeField(
                field, DateTimeFieldType.yearOfCentury(), 1);
            
            field = new RemainderDateTimeField(
                fields.weekyear, fields.centuries, DateTimeFieldType.weekyearOfCentury(), 100);
            fields.weekyearOfCentury = new OffsetDateTimeField(
                field, DateTimeFieldType.weekyearOfCentury(), 1);
            
            fields.era = ERA_FIELD;
        }
    }
   
}