package com.baeldung.datetime;

import java.text.SimpleDateFormat;
import java.time.Instant;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;

import org.joda.time.DateTime;
import org.joda.time.DateTimeZone;
import org.junit.Assert;
import org.junit.Test;

public class UseTimeZoneUnitTest {

    /* https://en.wikipedia.org/wiki/List_of_tz_database_time_zones */

    String timeZone = "Asia/Singapore";

    private static final String PATTERN = "E yyyy-MM-dd HH:mm:ss a";

    @Test
    public void givenDateWithoutTimeZone_WhenSetTimeZoneUsingJava7_ThenTimeZoneIsSetSuccessfully() {
        Date nowUtc = new Date();
        TimeZone asiaSingapore = TimeZone.getTimeZone(timeZone);

        Calendar nowAsiaSingapore = Calendar.getInstance(asiaSingapore);
        nowAsiaSingapore.setTime(nowUtc);

        SimpleDateFormat simpleDateFormat = new SimpleDateFormat(PATTERN);
        simpleDateFormat.setTimeZone(TimeZone.getTimeZone(timeZone));

        System.out.println(String.format("Java7: Time now in '%s' is '%s'", nowAsiaSingapore.getTimeZone()
            .getID(), simpleDateFormat.format(nowAsiaSingapore.getTime())));
        
        Assert.assertEquals(nowUtc.toInstant().getEpochSecond(), nowAsiaSingapore.toInstant().getEpochSecond());
        Assert.assertEquals(asiaSingapore, nowAsiaSingapore.getTimeZone());

    }

    @Test
    public void givenDateWithoutTimeZone_WhenSetTimeZoneUsingJava8_ThenTimeZoneIsSetSuccessfully() {
        Instant nowUtc = Instant.now();
        ZoneId asiaSingapore = ZoneId.of(timeZone);

        ZonedDateTime nowAsiaSingapore = ZonedDateTime.ofInstant(nowUtc, asiaSingapore);

        System.out.println(String.format("Java8: Time now in '%s' is '%s'", nowAsiaSingapore.getZone(), 
            nowAsiaSingapore.format(DateTimeFormatter.ofPattern(PATTERN))));

        Assert.assertEquals(nowUtc.getEpochSecond(), nowAsiaSingapore.toEpochSecond());
        Assert.assertEquals(asiaSingapore, nowAsiaSingapore.getZone());
    }

    @Test
    public void givenDateWithoutTimeZone_WhenSetTimeZoneUsingJodaTime_ThenTimeZoneIsSetSuccessfully() {
        org.joda.time.Instant nowUtc = org.joda.time.Instant.now();
        DateTimeZone asiaSingapore = DateTimeZone.forID(timeZone);

        DateTime nowAsiaSingapore = nowUtc.toDateTime(asiaSingapore);

        System.out.println(String.format("Joda-time: Time now in '%s' is '%s'", nowAsiaSingapore.getZone(), 
            nowAsiaSingapore.toString(PATTERN)));
        
        Assert.assertEquals(nowUtc.toInstant().getMillis(), nowAsiaSingapore.toInstant().getMillis());
        Assert.assertEquals(asiaSingapore, nowAsiaSingapore.getZone());
    }

}