xref: /frameworks/opt/datetimepicker/src/com/android/datetimepicker/Utils.java

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * 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 com.android.datetimepicker;

import android.os.Build;
import android.text.format.Time;

import java.util.Calendar;

/**
 * Utility helper functions for time and date pickers.
 */
public class Utils {

    public static final int MONDAY_BEFORE_JULIAN_EPOCH = Time.EPOCH_JULIAN_DAY - 3;

    static final String SHARED_PREFS_NAME = "com.android.calendar_preferences";

    public static boolean isJellybeanOrLater() {
      return Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN;
    }

    public static int getDaysInMonth(int month, int year) {
        switch (month) {
            case Calendar.JANUARY:
            case Calendar.MARCH:
            case Calendar.MAY:
            case Calendar.JULY:
            case Calendar.AUGUST:
            case Calendar.OCTOBER:
            case Calendar.DECEMBER:
                return 31;
            case Calendar.APRIL:
            case Calendar.JUNE:
            case Calendar.SEPTEMBER:
            case Calendar.NOVEMBER:
                return 30;
            case Calendar.FEBRUARY:
                return (year % 4 == 0) ? 29 : 28;
            default:
                throw new IllegalArgumentException("Invalid Month");
        }
    }

    /**
     * Takes a number of weeks since the epoch and calculates the Julian day of
     * the Monday for that week.
     *
     * This assumes that the week containing the {@link Time#EPOCH_JULIAN_DAY}
     * is considered week 0. It returns the Julian day for the Monday
     * {@code week} weeks after the Monday of the week containing the epoch.
     *
     * @param week Number of weeks since the epoch
     * @return The julian day for the Monday of the given week since the epoch
     */
    public static int getJulianMondayFromWeeksSinceEpoch(int week) {
        return MONDAY_BEFORE_JULIAN_EPOCH + week * 7;
    }

    /**
     * Returns the week since {@link Time#EPOCH_JULIAN_DAY} (Jan 1, 1970)
     * adjusted for first day of week.
     *
     * This takes a julian day and the week start day and calculates which
     * week since {@link Time#EPOCH_JULIAN_DAY} that day occurs in, starting
     * at 0. *Do not* use this to compute the ISO week number for the year.
     *
     * @param julianDay The julian day to calculate the week number for
     * @param firstDayOfWeek Which week day is the first day of the week,
     *          see {@link Time#SUNDAY}
     * @return Weeks since the epoch
     */
    public static int getWeeksSinceEpochFromJulianDay(int julianDay, int firstDayOfWeek) {
        int diff = Time.THURSDAY - firstDayOfWeek;
        if (diff < 0) {
            diff += 7;
        }
        int refDay = Time.EPOCH_JULIAN_DAY - diff;
        return (julianDay - refDay) / 7;
    }
}