package org.richardsson.woloc.time;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

public class TimeUtil {
    private TimeUtil() {}

    public static GregorianCalendar startOfDay(GregorianCalendar reference) {
        final int year = reference.get(Calendar.YEAR);
        final int month = reference.get(Calendar.MONTH);
        final int day = reference.get(Calendar.DAY_OF_MONTH);

        return createCalendar(year, month, day);
    }

    public static GregorianCalendar endOfDay(GregorianCalendar reference) {
        final GregorianCalendar calendar = startOfDay(reference);
        calendar.add(Calendar.DAY_OF_YEAR, 1);

        return calendar;
    }

    public static GregorianCalendar startOfWeek(GregorianCalendar reference) {
        final GregorianCalendar calendarWithMondayAsFirstDayOfWeek = startOfDay(reference);

        int daysToShiftToMonday = calculateDaysToShiftToMonday(calendarWithMondayAsFirstDayOfWeek);
        calendarWithMondayAsFirstDayOfWeek.add(Calendar.DAY_OF_YEAR, daysToShiftToMonday);

        return calendarWithMondayAsFirstDayOfWeek;
    }

    public static GregorianCalendar endOfWeek(GregorianCalendar reference) {
        final GregorianCalendar calendar = startOfWeek(reference);

        calendar.add(Calendar.DAY_OF_YEAR, 7);

        return calendar;
    }

    public static GregorianCalendar startOfMonth(GregorianCalendar reference) {
        final int year = reference.get(Calendar.YEAR);
        final int month = reference.get(Calendar.MONTH);

        return createCalendar(year, month, 1);
    }

    public static GregorianCalendar endOfMonth(GregorianCalendar reference) {
        final GregorianCalendar calendar = startOfMonth(reference);
        calendar.add(Calendar.MONTH, 1);

        return calendar;
    }

    public static int daysInMonth(long reference) {
        final GregorianCalendar timeInMonthAsCalendar = createCalendar(reference);
        return timeInMonthAsCalendar.getActualMaximum(Calendar.DAY_OF_MONTH);
    }

    public static GregorianCalendar createCalendar(long time) {
        final GregorianCalendar calendar = createCalendar();
        calendar.setTime(new Date(time));

        return calendar;
    }

    public static GregorianCalendar createCalendar(int year, int month, int day) {
        final GregorianCalendar calendar = createCalendar();
        calendar.set(year, month, day);

        return calendar;
    }

    private static GregorianCalendar createCalendar() {
        final GregorianCalendar calendar = new GregorianCalendar();
        calendar.clear();
        calendar.setFirstDayOfWeek(Calendar.MONDAY);
        return calendar;
    }

    private static int calculateDaysToShiftToMonday(GregorianCalendar reference) {
        final int dayOfWeek = reference.get(Calendar.DAY_OF_WEEK);

        int daysToShiftToMonday = Calendar.MONDAY - dayOfWeek;
        if (dayOfWeek < reference.getFirstDayOfWeek()) {
            daysToShiftToMonday = daysToShiftToMonday - 7;
        }

        return daysToShiftToMonday;
    }
}