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/*
 * -----------------------------------------------------------------------
 * Copyright © 2013-2016 Meno Hochschild, 
 * -----------------------------------------------------------------------
 * This file (SingleOffsetTimezone.java) is part of project Time4J.
 *
 * Time4J is free software: You can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * Time4J 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Time4J. If not, see .
 * -----------------------------------------------------------------------
 */

package net.time4j.tz;

import net.time4j.base.GregorianDate;
import net.time4j.base.UnixTime;
import net.time4j.base.WallTime;

import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.Optional;


/**
 * Stellt eine Zeitzone ohne Übergänge und mit fester Verschiebung
 * dar. 
 *
 * @author      Meno Hochschild
 * @serial      include
 * @doctags.concurrency {immutable}
 */
final class SingleOffsetTimezone
    extends Timezone
    implements TransitionHistory {

    //~ Statische Felder/Initialisierungen --------------------------------

    private static final SingleOffsetTimezone UTC =
        new SingleOffsetTimezone(ZonalOffset.UTC);
    private static final long serialVersionUID = 7807230388259573234L;

    //~ Instanzvariablen --------------------------------------------------

    /**
     * @serial  fixed zone shift in full seconds
     */
    private final ZonalOffset offset;

    //~ Konstruktoren -----------------------------------------------------

    private SingleOffsetTimezone(ZonalOffset offset) {
        super();

        if (offset.getFractionalAmount() == 0) {
            this.offset = offset;
        } else {
            int total = offset.getIntegralAmount();
            if (offset.getFractionalAmount() < 0) {
                total--; // corresponding to floor-divide-algorithm
            }
            this.offset = ZonalOffset.ofTotalSeconds(total);
        }

    }

    //~ Methoden ----------------------------------------------------------

    @Override
    public TZID getID() {

        return this.offset;

    }

    @Override
    public ZonalOffset getOffset(UnixTime ut) {

        return this.offset;

    }

    @Override
    public ZonalOffset getStandardOffset(UnixTime ut) {

        return this.offset;

    }

    @Override
    public ZonalOffset getDaylightSavingOffset(UnixTime ut){

        return ZonalOffset.UTC;

    }

    @Override
    public ZonalOffset getOffset(
        GregorianDate localDate,
        WallTime localTime
    ) {

        return this.offset;

    }

    @Override
    public boolean isInvalid(
        GregorianDate localDate,
        WallTime localTime
    ) {

        return false;

    }

    @Override
    public boolean isDaylightSaving(UnixTime ut) {

        return false;

    }

    @Override
    public boolean isFixed() {

        return true;

    }

    @Override
    public boolean isEmpty() {

        return true;

    }

    @Override
    public TransitionHistory getHistory() {

        return this;

    }

    @Override
    public List getStdTransitions() {

        return Collections.emptyList();

    }

    @Override
    public List getTransitions(
        UnixTime startInclusive,
        UnixTime endExclusive
    ) {

        return Collections.emptyList();

    }

    @Override
    public List getValidOffsets(
        GregorianDate localDate,
        WallTime localTime
    ) {

        return Collections.singletonList(this.offset);

    }

    // optional
    @Override
    public ZonalTransition getStartTransition(UnixTime time) {

        return null;

    }

    // optional
    @Override
    public ZonalTransition getConflictTransition(
        GregorianDate localDate,
        WallTime localTime
    ) {

        return null;

    }

    // optional
    @Override
    public ZonalTransition getNextTransition(UnixTime ut) {

        return null;

    }

    @Override
    public Optional findStartTransition(UnixTime ut) {

        return Optional.empty();

    }

    @Override
    public Optional findConflictTransition(
        GregorianDate localDate,
        WallTime localTime
    ) {

        return Optional.empty();

    }

    @Override
    public Optional findNextTransition(UnixTime ut) {

        return Optional.empty();

    }

    @Override
    public Optional findPreviousTransition(UnixTime ut) {

        return Optional.empty();

    }

    @Override
    public ZonalOffset getInitialOffset() {

        return this.offset;

    }

    @Override
    public boolean equals(Object obj) {

        if (this == obj) {
            return true;
        } else if (obj instanceof SingleOffsetTimezone) {
            SingleOffsetTimezone that = (SingleOffsetTimezone) obj;
            return this.offset.equals(that.offset);
        } else {
            return false;
        }

    }

    @Override
    public int hashCode() {

        return this.offset.hashCode();

    }

    @Override
    public String toString() {

        StringBuilder sb = new StringBuilder(32);
        sb.append('[');
        sb.append(this.getClass().getName());
        sb.append(':');
        sb.append(this.offset);
        sb.append(']');
        return sb.toString();

    }

    @Override
    public String getDisplayName(
        NameStyle style,
        Locale locale
    ) {

        return (
            style.isAbbreviation()
            ? this.offset.toString()
            : this.offset.canonical()
        );

    }

    @Override
    public TransitionStrategy getStrategy() {

        return DEFAULT_CONFLICT_STRATEGY;

    }

    @Override
    public Timezone with(TransitionStrategy strategy) {

        return this;

    }

    /**
     * Fabrikmethode. 
     *
     * @param   offset  fixed shift of local time relative to UTC in seconds
     */
    static SingleOffsetTimezone of(ZonalOffset offset) {

        if (
            (offset.getIntegralAmount() == 0)
            && (offset.getFractionalAmount() == 0)
        ) {
            return UTC;
        } else {
            return new SingleOffsetTimezone(offset);
        }

    }

    /**
     * @serialData  Checks the consistency.
     * @param       in      object input stream
     * @throws      InvalidObjectException in case of inconsistencies
     * @throws      ClassNotFoundException if class-loading fails
     */
    private void readObject(ObjectInputStream in)
        throws IOException, ClassNotFoundException {

        in.defaultReadObject();

        if (this.offset.getFractionalAmount() != 0) {
            throw new InvalidObjectException("Fractional offset is invalid.");
        }

    }

}