package de.thedevstack.conversationsplus.xmpp.time;

import java.util.Locale;
import java.util.TimeZone;

import de.thedevstack.conversationsplus.generator.AbstractGenerator;
import de.thedevstack.conversationsplus.xml.Element;
import de.thedevstack.conversationsplus.xmpp.stanzas.IqPacket;
import de.thedevstack.conversationsplus.xmpp.stanzas.IqPacketGenerator;

/**
 * Generates the IQ Packets for Entity Time
 * as defined in XEP-0202.
 * @see <a href="http://xmpp.org/extensions/xep-0202.html">http://xmpp.org/extensions/xep-0202.html</a>
 */
public final class TimePacketGenerator {

    /**
     * Generates the IqPacket to reply the entity time.
     * <pre>
     * <iq type='result'
     *     from='juliet@capulet.com/balcony'
     *     to='romeo@montague.net/orchard'
     *     id='time_1'>
     *   <time xmlns='urn:xmpp:time'>
     *      <tzo>-06:00</tzo>
     *      <utc>2006-12-19T17:58:35Z</utc>
     *   </time>
     * </iq>
     * </pre>
     * @param packet
     * @return
     */
    public static IqPacket generateResponse(IqPacket packet) {
        IqPacket responsePacket = IqPacketGenerator.generateIqResultResponse(packet);

        Element time = responsePacket.addChild(EntityTime.ELEMENT, EntityTime.NAMESPACE);
        final long now = System.currentTimeMillis();
        time.addChild("utc").setContent(AbstractGenerator.getTimestamp(now));
        TimeZone ourTimezone = TimeZone.getDefault();
        long offsetSeconds = ourTimezone.getOffset(now) / 1000;
        long offsetMinutes = Math.abs((offsetSeconds % 3600) / 60);
        long offsetHours = offsetSeconds / 3600;
        String hours;
        if (offsetHours < 0) {
            hours = String.format(Locale.US, "%03d", offsetHours);
        } else {
            hours = String.format(Locale.US, "%02d", offsetHours);
        }
        String minutes = String.format(Locale.US, "%02d", offsetMinutes);
        time.addChild("tzo").setContent(hours + ":" + minutes);

        return responsePacket;
    }

    private TimePacketGenerator() {}
}