/*
 * Copyright 2016 Groupon, Inc
 * Copyright 2016 The Billing Project, LLC
 *
 * The Billing Project licenses this file to you 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.killbill.billing.callcontext;

import java.util.Date;

import org.joda.time.DateTime;
import org.joda.time.DateTimeZone;
import org.joda.time.LocalDate;
import org.joda.time.LocalTime;

// TODO Cache the accountTimeZone, reference time and clock in the context
public class TimeAwareContext {

    /// Generic functions
    /// TODO Move to ClockUtil

    // From JDK to Joda (see http://www.joda.org/joda-time/userguide.html#JDK_Interoperability)
    public DateTime toUTCDateTime(final Date date) {
        return toUTCDateTime(new DateTime(date));
    }

    // Create a DateTime object forcing the time zone to be UTC
    public DateTime toUTCDateTime(final DateTime dateTime) {
        return toDateTime(dateTime, DateTimeZone.UTC);
    }

    // Create a DateTime object using the specified timezone (usually, the one on the account)
    public DateTime toDateTime(final DateTime dateTime, final DateTimeZone accountTimeZone) {
        return dateTime.toDateTime(accountTimeZone);
    }

    /// DateTime <-> LocalDate transformations

    // Create a DateTime object using the specified reference time and timezone (usually, the one on the account)
    public DateTime toUTCDateTime(final LocalDate localDate, final DateTime referenceDateTime, final DateTimeZone accountTimeZone) {
        final DateTimeZone normalizedAccountTimezone = getNormalizedAccountTimezone(referenceDateTime, accountTimeZone);

        final LocalTime referenceLocalTime = toDateTime(referenceDateTime, normalizedAccountTimezone).toLocalTime();

        final DateTime targetDateTime = new DateTime(localDate.getYear(),
                                                     localDate.getMonthOfYear(),
                                                     localDate.getDayOfMonth(),
                                                     referenceLocalTime.getHourOfDay(),
                                                     referenceLocalTime.getMinuteOfHour(),
                                                     referenceLocalTime.getSecondOfMinute(),
                                                     normalizedAccountTimezone);

        return toUTCDateTime(targetDateTime);
    }

    // Create a LocalDate object using the specified timezone (usually, the one on the account), respecting the offset at the time of the referenceDateTime
    public LocalDate toLocalDate(final DateTime dateTime, final DateTime referenceDateTime, final DateTimeZone accountTimeZone) {
        final DateTimeZone normalizedAccountTimezone = getNormalizedAccountTimezone(referenceDateTime, accountTimeZone);
        return new LocalDate(dateTime, normalizedAccountTimezone);
    }

    private DateTimeZone getNormalizedAccountTimezone(final DateTime referenceDateTime, final DateTimeZone accountTimeZone) {
        // Check if DST was in effect at the reference date time
        final boolean shouldUseDST = !accountTimeZone.isStandardOffset(referenceDateTime.getMillis());
        if (shouldUseDST) {
            return DateTimeZone.forOffsetMillis(accountTimeZone.getOffset(referenceDateTime.getMillis()));
        } else {
            return DateTimeZone.forOffsetMillis(accountTimeZone.getStandardOffset(referenceDateTime.getMillis()));
        }
    }
}
