/*
 * Copyright (C) 2012 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.deskclock;

import android.animation.Animator;
import android.animation.AnimatorSet;
import android.animation.ObjectAnimator;
import android.animation.TimeInterpolator;
import android.annotation.TargetApi;
import android.app.AlarmManager;
import android.content.ContentResolver;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffColorFilter;
import android.graphics.Typeface;
import android.os.Build;
import android.os.Handler;
import android.os.Looper;
import android.preference.PreferenceManager;
import android.provider.Settings;
import android.support.v4.content.ContextCompat;
import android.support.v4.os.BuildCompat;
import android.text.Spannable;
import android.text.SpannableString;
import android.text.TextUtils;
import android.text.format.DateFormat;
import android.text.format.DateUtils;
import android.text.format.Time;
import android.text.style.RelativeSizeSpan;
import android.text.style.StyleSpan;
import android.text.style.TypefaceSpan;
import android.util.ArraySet;
import android.view.View;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.DecelerateInterpolator;
import android.widget.TextClock;
import android.widget.TextView;

import com.android.deskclock.data.DataModel;
import com.android.deskclock.provider.AlarmInstance;
import com.android.deskclock.provider.DaysOfWeek;
import com.android.deskclock.settings.SettingsActivity;

import java.io.File;
import java.text.DateFormatSymbols;
import java.text.NumberFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Collection;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Locale;
import java.util.TimeZone;

public class Utils {
    // Single-char version of day name, e.g.: 'S', 'M', 'T', 'W', 'T', 'F', 'S'
    private static String[] sShortWeekdays = null;
    private static final String DATE_FORMAT_SHORT = "ccccc";

    // Long-version of day name, e.g.: 'Sunday', 'Monday', 'Tuesday', etc
    private static String[] sLongWeekdays = null;
    private static final String DATE_FORMAT_LONG = "EEEE";

    public static final int DEFAULT_WEEK_START = Calendar.getInstance().getFirstDayOfWeek();

    private static Locale sLocaleUsedForWeekdays;

    /**
     * Temporary array used by {@link #obtainStyledColor(Context, int, int)}.
     */
    private static final int[] TEMP_ARRAY = new int[1];

    /**
     * The background colors of the app - it changes throughout out the day to mimic the sky.
     */
    private static final int[] BACKGROUND_SPECTRUM = {
            0xFF212121 /* 12 AM */,
            0xFF20222A /*  1 AM */,
            0xFF202233 /*  2 AM */,
            0xFF1F2242 /*  3 AM */,
            0xFF1E224F /*  4 AM */,
            0xFF1D225C /*  5 AM */,
            0xFF1B236B /*  6 AM */,
            0xFF1A237E /*  7 AM */,
            0xFF1D2783 /*  8 AM */,
            0xFF232E8B /*  9 AM */,
            0xFF283593 /* 10 AM */,
            0xFF2C3998 /* 11 AM */,
            0xFF303F9F /* 12 PM */,
            0xFF2C3998 /*  1 PM */,
            0xFF283593 /*  2 PM */,
            0xFF232E8B /*  3 PM */,
            0xFF1D2783 /*  4 PM */,
            0xFF1A237E /*  5 PM */,
            0xFF1B236B /*  6 PM */,
            0xFF1D225C /*  7 PM */,
            0xFF1E224F /*  8 PM */,
            0xFF1F2242 /*  9 PM */,
            0xFF202233 /* 10 PM */,
            0xFF20222A /* 11 PM */
    };

    public static void enforceMainLooper() {
        if (Looper.getMainLooper() != Looper.myLooper()) {
            throw new IllegalAccessError("May only call from main thread.");
        }
    }

    public static void enforceNotMainLooper() {
        if (Looper.getMainLooper() == Looper.myLooper()) {
            throw new IllegalAccessError("May not call from main thread.");
        }
    }

    /**
     * @return {@code true} if the device is prior to {@link Build.VERSION_CODES#LOLLIPOP}
     */
    public static boolean isPreL() {
        return Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP;
    }

    /**
     * @return {@code true} if the device is {@link Build.VERSION_CODES#LOLLIPOP} or
     *      {@link Build.VERSION_CODES#LOLLIPOP_MR1}
     */
    public static boolean isLOrLMR1() {
        final int sdkInt = Build.VERSION.SDK_INT;
        return sdkInt == Build.VERSION_CODES.LOLLIPOP || sdkInt == Build.VERSION_CODES.LOLLIPOP_MR1;
    }

    /**
     * @return {@code true} if the device is {@link Build.VERSION_CODES#LOLLIPOP} or later
     */
    public static boolean isLOrLater() {
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP;
    }

    /**
     * @return {@code true} if the device is {@link Build.VERSION_CODES#LOLLIPOP_MR1} or later
     */
    public static boolean isLMR1OrLater() {
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP_MR1;
    }

    /**
     * @return {@code true} if the device is {@link Build.VERSION_CODES#M} or later
     */
    public static boolean isMOrLater() {
        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.M;
    }

    /**
     * @return {@code true} if the device is {@link Build.VERSION_CODES#N} or later
     */
    public static boolean isNOrLater() {
        return BuildCompat.isAtLeastN();
    }

    /**
     * Calculate the amount by which the radius of a CircleTimerView should be offset by any
     * of the extra painted objects.
     */
    public static float calculateRadiusOffset(
            float strokeSize, float dotStrokeSize, float markerStrokeSize) {
        return Math.max(strokeSize, Math.max(dotStrokeSize, markerStrokeSize));
    }

    /**
     * Uses {@link Utils#calculateRadiusOffset(float, float, float)} after fetching the values
     * from the resources.
     */
    public static float calculateRadiusOffset(Resources resources) {
        if (resources != null) {
            float strokeSize = resources.getDimension(R.dimen.circletimer_circle_size);
            float dotStrokeSize = resources.getDimension(R.dimen.circletimer_dot_size);
            float markerStrokeSize = resources.getDimension(R.dimen.circletimer_marker_size);
            return calculateRadiusOffset(strokeSize, dotStrokeSize, markerStrokeSize);
        } else {
            return 0f;
        }
    }

    /** Runnable for use with screensaver and dream, to move the clock every minute.
     *  registerViews() must be called prior to posting.
     */
    public static class ScreensaverMoveSaverRunnable implements Runnable {
        static final long MOVE_DELAY = 60000; // DeskClock.SCREEN_SAVER_MOVE_DELAY;
        static final long SLIDE_TIME = 10000;
        static final long FADE_TIME = 3000;

        static final boolean SLIDE = false;

        private View mContentView, mSaverView;
        private final Handler mHandler;

        private static TimeInterpolator mSlowStartWithBrakes;


        public ScreensaverMoveSaverRunnable(Handler handler) {
            mHandler = handler;
            mSlowStartWithBrakes = new TimeInterpolator() {
                @Override
                public float getInterpolation(float x) {
                    return (float)(Math.cos((Math.pow(x,3) + 1) * Math.PI) / 2.0f) + 0.5f;
                }
            };
        }

        public void registerViews(View contentView, View saverView) {
            mContentView = contentView;
            mSaverView = saverView;
        }

        @Override
        public void run() {
            long delay = MOVE_DELAY;
            if (mContentView == null || mSaverView == null) {
                mHandler.removeCallbacks(this);
                mHandler.postDelayed(this, delay);
                return;
            }

            final float xrange = mContentView.getWidth() - mSaverView.getWidth();
            final float yrange = mContentView.getHeight() - mSaverView.getHeight();

            if (xrange == 0 && yrange == 0) {
                delay = 500; // back in a split second
            } else {
                final int nextx = (int) (Math.random() * xrange);
                final int nexty = (int) (Math.random() * yrange);

                if (mSaverView.getAlpha() == 0f) {
                    // jump right there
                    mSaverView.setX(nextx);
                    mSaverView.setY(nexty);
                    ObjectAnimator.ofFloat(mSaverView, "alpha", 0f, 1f)
                        .setDuration(FADE_TIME)
                        .start();
                } else {
                    AnimatorSet s = new AnimatorSet();
                    Animator xMove   = ObjectAnimator.ofFloat(mSaverView,
                                         "x", mSaverView.getX(), nextx);
                    Animator yMove   = ObjectAnimator.ofFloat(mSaverView,
                                         "y", mSaverView.getY(), nexty);

                    Animator xShrink = ObjectAnimator.ofFloat(mSaverView, "scaleX", 1f, 0.85f);
                    Animator xGrow   = ObjectAnimator.ofFloat(mSaverView, "scaleX", 0.85f, 1f);

                    Animator yShrink = ObjectAnimator.ofFloat(mSaverView, "scaleY", 1f, 0.85f);
                    Animator yGrow   = ObjectAnimator.ofFloat(mSaverView, "scaleY", 0.85f, 1f);
                    AnimatorSet shrink = new AnimatorSet(); shrink.play(xShrink).with(yShrink);
                    AnimatorSet grow = new AnimatorSet(); grow.play(xGrow).with(yGrow);

                    Animator fadeout = ObjectAnimator.ofFloat(mSaverView, "alpha", 1f, 0f);
                    Animator fadein = ObjectAnimator.ofFloat(mSaverView, "alpha", 0f, 1f);


                    if (SLIDE) {
                        s.play(xMove).with(yMove);
                        s.setDuration(SLIDE_TIME);

                        s.play(shrink.setDuration(SLIDE_TIME/2));
                        s.play(grow.setDuration(SLIDE_TIME/2)).after(shrink);
                        s.setInterpolator(mSlowStartWithBrakes);
                    } else {
                        AccelerateInterpolator accel = new AccelerateInterpolator();
                        DecelerateInterpolator decel = new DecelerateInterpolator();

                        shrink.setDuration(FADE_TIME).setInterpolator(accel);
                        fadeout.setDuration(FADE_TIME).setInterpolator(accel);
                        grow.setDuration(FADE_TIME).setInterpolator(decel);
                        fadein.setDuration(FADE_TIME).setInterpolator(decel);
                        s.play(shrink);
                        s.play(fadeout);
                        s.play(xMove.setDuration(0)).after(FADE_TIME);
                        s.play(yMove.setDuration(0)).after(FADE_TIME);
                        s.play(fadein).after(FADE_TIME);
                        s.play(grow).after(FADE_TIME);
                    }
                    s.start();
                }

                long now = System.currentTimeMillis();
                long adjust = (now % 60000);
                delay = delay
                        + (MOVE_DELAY - adjust) // minute aligned
                        - (SLIDE ? 0 : FADE_TIME) // start moving before the fade
                        ;
            }

            mHandler.removeCallbacks(this);
            mHandler.postDelayed(this, delay);
        }
    }

    /** Setup to find out when the quarter-hour changes (e.g. Kathmandu is GMT+5:45) **/
    public static long getAlarmOnQuarterHour() {
        final Calendar calendarInstance = Calendar.getInstance();
        final long now = System.currentTimeMillis();
        return getAlarmOnQuarterHour(calendarInstance, now);
    }

    static long getAlarmOnQuarterHour(Calendar calendar, long now) {
        //  Set 1 second to ensure quarter-hour threshold passed.
        calendar.set(Calendar.SECOND, 1);
        calendar.set(Calendar.MILLISECOND, 0);
        int minute = calendar.get(Calendar.MINUTE);
        calendar.add(Calendar.MINUTE, 15 - (minute % 15));
        long alarmOnQuarterHour = calendar.getTimeInMillis();

        // Verify that alarmOnQuarterHour is within the next 15 minutes
        long delta = alarmOnQuarterHour - now;
        if (0 >= delta || delta > 901000) {
            // Something went wrong in the calculation, schedule something that is
            // about 15 minutes. Next time , it will align with the 15 minutes border.
            alarmOnQuarterHour = now + 901000;
        }
        return alarmOnQuarterHour;
    }

    // Setup a thread that starts at midnight plus one second. The extra second is added to ensure
    // the date has changed.
    public static void setMidnightUpdater(Handler handler, Runnable runnable) {
        String timezone = TimeZone.getDefault().getID();
        if (handler == null || runnable == null || timezone == null) {
            return;
        }
        long now = System.currentTimeMillis();
        Time time = new Time(timezone);
        time.set(now);
        long runInMillis = ((24 - time.hour) * 3600 - time.minute * 60 - time.second + 1) * 1000;
        handler.removeCallbacks(runnable);
        handler.postDelayed(runnable, runInMillis);
    }

    // Stop the midnight update thread
    public static void cancelMidnightUpdater(Handler handler, Runnable runnable) {
        if (handler == null || runnable == null) {
            return;
        }
        handler.removeCallbacks(runnable);
    }

    // Setup a thread that starts at the quarter-hour plus one second. The extra second is added to
    // ensure dates have changed.
    public static void setQuarterHourUpdater(Handler handler, Runnable runnable) {
        String timezone = TimeZone.getDefault().getID();
        if (handler == null || runnable == null || timezone == null) {
            return;
        }
        long runInMillis = getAlarmOnQuarterHour() - System.currentTimeMillis();
        // Ensure the delay is at least one second.
        if (runInMillis < 1000) {
            runInMillis = 1000;
        }
        handler.removeCallbacks(runnable);
        handler.postDelayed(runnable, runInMillis);
    }

    // Stop the quarter-hour update thread
    public static void cancelQuarterHourUpdater(Handler handler, Runnable runnable) {
        if (handler == null || runnable == null) {
            return;
        }
        handler.removeCallbacks(runnable);
    }

    /**
     * For screensavers to set whether the digital or analog clock should be displayed.
     * Returns the view to be displayed.
     */
    public static View setClockStyle(View digitalClock, View analogClock) {
        final DataModel.ClockStyle clockStyle = DataModel.getDataModel().getClockStyle();
        switch (clockStyle) {
            case ANALOG:
                digitalClock.setVisibility(View.GONE);
                analogClock.setVisibility(View.VISIBLE);
                return analogClock;
            case DIGITAL:
                digitalClock.setVisibility(View.VISIBLE);
                analogClock.setVisibility(View.GONE);
                return digitalClock;
        }

        throw new IllegalStateException("unexpected clock style: " + clockStyle);
    }

    /**
     * For screensavers to set whether the digital or analog clock should be displayed.
     * Returns the view to be displayed.
     */
    public static View setScreensaverClockStyle(View digitalClock, View analogClock) {
        final DataModel.ClockStyle clockStyle = DataModel.getDataModel().getScreensaverClockStyle();
        switch (clockStyle) {
            case ANALOG:
                digitalClock.setVisibility(View.GONE);
                analogClock.setVisibility(View.VISIBLE);
                return analogClock;
            case DIGITAL:
                digitalClock.setVisibility(View.VISIBLE);
                analogClock.setVisibility(View.GONE);
                return digitalClock;
        }

        throw new IllegalStateException("unexpected clock style: " + clockStyle);
    }

    /**
     * For screensavers to dim the lights if necessary.
     */
    public static void dimClockView(boolean dim, View clockView) {
        Paint paint = new Paint();
        paint.setColor(Color.WHITE);
        paint.setColorFilter(new PorterDuffColorFilter(
                        (dim ? 0x40FFFFFF : 0xC0FFFFFF),
                PorterDuff.Mode.MULTIPLY));
        clockView.setLayerType(View.LAYER_TYPE_HARDWARE, paint);
    }

    /**
     * @return The next alarm from {@link AlarmManager}
     */
    public static String getNextAlarm(Context context) {
        return isPreL() ? getNextAlarmPreL(context) : getNextAlarmLOrLater(context);
    }

    @TargetApi(Build.VERSION_CODES.KITKAT)
    private static String getNextAlarmPreL(Context context) {
        final ContentResolver cr = context.getContentResolver();
        return Settings.System.getString(cr, Settings.System.NEXT_ALARM_FORMATTED);
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private static String getNextAlarmLOrLater(Context context) {
        final AlarmManager am = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
        final AlarmManager.AlarmClockInfo info = am.getNextAlarmClock();
        if (info != null) {
            final long triggerTime = info.getTriggerTime();
            final Calendar alarmTime = Calendar.getInstance();
            alarmTime.setTimeInMillis(triggerTime);
            return AlarmUtils.getFormattedTime(context, alarmTime);
        }

        return null;
    }

    public static boolean isAlarmWithin24Hours(AlarmInstance alarmInstance) {
        final Calendar nextAlarmTime = alarmInstance.getAlarmTime();
        final long nextAlarmTimeMillis = nextAlarmTime.getTimeInMillis();
        return nextAlarmTimeMillis - System.currentTimeMillis() <= DateUtils.DAY_IN_MILLIS;
    }

    /** Clock views can call this to refresh their alarm to the next upcoming value. */
    public static void refreshAlarm(Context context, View clock) {
        final TextView nextAlarmView = (TextView) clock.findViewById(R.id.nextAlarm);
        if (nextAlarmView == null) {
            return;
        }

        final String alarm = getNextAlarm(context);
        if (!TextUtils.isEmpty(alarm)) {
            final String description = context.getString(R.string.next_alarm_description, alarm);
            nextAlarmView.setText(alarm);
            nextAlarmView.setContentDescription(description);
            nextAlarmView.setVisibility(View.VISIBLE);
        } else {
            nextAlarmView.setVisibility(View.GONE);
        }
    }

    /** Clock views can call this to refresh their date. **/
    public static void updateDate(String dateSkeleton, String descriptionSkeleton, View clock) {
        final TextView dateDisplay = (TextView) clock.findViewById(R.id.date);
        if (dateDisplay == null) {
            return;
        }

        final Locale l = Locale.getDefault();
        final String datePattern = DateFormat.getBestDateTimePattern(l, dateSkeleton);
        final String descriptionPattern = DateFormat.getBestDateTimePattern(l, descriptionSkeleton);

        final Date now = new Date();
        dateDisplay.setText(new SimpleDateFormat(datePattern, l).format(now));
        dateDisplay.setVisibility(View.VISIBLE);
        dateDisplay.setContentDescription(new SimpleDateFormat(descriptionPattern, l).format(now));
    }

    /***
     * Formats the time in the TextClock according to the Locale with a special
     * formatting treatment for the am/pm label.
     * @param context - Context used to get user's locale and time preferences
     * @param clock - TextClock to format
     */
    public static void setTimeFormat(Context context, TextClock clock) {
        if (clock != null) {
            // Get the best format for 12 hours mode according to the locale
            clock.setFormat12Hour(get12ModeFormat(context, true /* showAmPm */));
            // Get the best format for 24 hours mode according to the locale
            clock.setFormat24Hour(get24ModeFormat());
        }
    }

    /**
     * Returns {@code true} if the am / pm strings for the current locale are long and a reduced
     * text size should be used for displaying the digital clock.
     */
    public static boolean isAmPmStringLong() {
        final String[] amPmStrings = new DateFormatSymbols().getAmPmStrings();
        for (String amPmString : amPmStrings) {
            // Dots are small, so don't count them.
            final int amPmStringLength = amPmString.replace(".", "").length();
            if (amPmStringLength > 3) {
                return true;
            }
        }
        return false;
    }

    /**
     * @param context - context used to get time format string resource
     * @param showAmPm - include the am/pm string if true
     * @return format string for 12 hours mode time
     */
    public static CharSequence get12ModeFormat(Context context, boolean showAmPm) {
        String pattern = DateFormat.getBestDateTimePattern(Locale.getDefault(), "hma");
        if (!showAmPm) {
            pattern = pattern.replaceAll("a", "").trim();
        }

        // Replace spaces with "Hair Space"
        pattern = pattern.replaceAll(" ", "\u200A");
        // Build a spannable so that the am/pm will be formatted
        int amPmPos = pattern.indexOf('a');
        if (amPmPos == -1) {
            return pattern;
        }

        final Resources resources = context.getResources();
        final float amPmProportion = resources.getFraction(R.fraction.ampm_font_size_scale, 1, 1);
        final Spannable sp = new SpannableString(pattern);
        sp.setSpan(new RelativeSizeSpan(amPmProportion), amPmPos, amPmPos + 1,
                Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        sp.setSpan(new StyleSpan(Typeface.NORMAL), amPmPos, amPmPos + 1,
                Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        sp.setSpan(new TypefaceSpan("sans-serif"), amPmPos, amPmPos + 1,
                Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

        // Make the font smaller for locales with long am/pm strings.
        if (Utils.isAmPmStringLong()) {
            final float proportion = resources.getFraction(
                    R.fraction.reduced_clock_font_size_scale, 1, 1);
            sp.setSpan(new RelativeSizeSpan(proportion), 0, pattern.length(),
                    Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
        return sp;
    }

    public static CharSequence get24ModeFormat() {
        return DateFormat.getBestDateTimePattern(Locale.getDefault(), "Hm");
    }

    /**
     * Returns string denoting the timezone hour offset (e.g. GMT -8:00)
     * @param useShortForm Whether to return a short form of the header that rounds to the
     *                     nearest hour and excludes the "GMT" prefix
     */
    public static String getGMTHourOffset(TimeZone timezone, boolean useShortForm) {
        final int gmtOffset = timezone.getRawOffset();
        final long hour = gmtOffset / DateUtils.HOUR_IN_MILLIS;
        final long min = (Math.abs(gmtOffset) % DateUtils.HOUR_IN_MILLIS) /
                DateUtils.MINUTE_IN_MILLIS;

        if (useShortForm) {
            return String.format("%+d", hour);
        } else {
            return String.format("GMT %+d:%02d", hour, min);
        }
    }

    /**
     * Convenience method for retrieving a themed color value.
     *
     * @param context  the {@link Context} to resolve the theme attribute against
     * @param attr     the attribute corresponding to the color to resolve
     * @param defValue the default color value to use if the attribute cannot be resolved
     * @return the color value of the resolve attribute
     */
    public static int obtainStyledColor(Context context, int attr, int defValue) {
        TEMP_ARRAY[0] = attr;
        final TypedArray a = context.obtainStyledAttributes(TEMP_ARRAY);
        try {
            return a.getColor(0, defValue);
        } finally {
            a.recycle();
        }
    }

    /**
     * Returns the background color to use based on the current time.
     */
    public static int getCurrentHourColor() {
        return BACKGROUND_SPECTRUM[Calendar.getInstance().get(Calendar.HOUR_OF_DAY)];
    }

    /**
     * @param firstDay is the result from getZeroIndexedFirstDayOfWeek
     * @return Single-char version of day name, e.g.: 'S', 'M', 'T', 'W', 'T', 'F', 'S'
     */
    public static String getShortWeekday(int position, int firstDay) {
        generateShortAndLongWeekdaysIfNeeded();
        return sShortWeekdays[(position + firstDay) % DaysOfWeek.DAYS_IN_A_WEEK];
    }

    /**
     * @param firstDay is the result from getZeroIndexedFirstDayOfWeek
     * @return Long-version of day name, e.g.: 'Sunday', 'Monday', 'Tuesday', etc
     */
    public static String getLongWeekday(int position, int firstDay) {
        generateShortAndLongWeekdaysIfNeeded();
        return sLongWeekdays[(position + firstDay) % DaysOfWeek.DAYS_IN_A_WEEK];
    }

    // Return the first day of the week value corresponding to Calendar.<WEEKDAY> value, which is
    // 1-indexed starting with Sunday.
    public static int getFirstDayOfWeek(Context context) {
        return Integer.parseInt(getDefaultSharedPreferences(context)
                .getString(SettingsActivity.KEY_WEEK_START, String.valueOf(DEFAULT_WEEK_START)));
    }

    // Return the first day of the week value corresponding to a week with Sunday at 0 index.
    public static int getZeroIndexedFirstDayOfWeek(Context context) {
        return getFirstDayOfWeek(context) - 1;
    }

    private static boolean localeHasChanged() {
        return sLocaleUsedForWeekdays != Locale.getDefault();
    }

    /**
     * Generate arrays of short and long weekdays, starting from Sunday
     */
    private static void generateShortAndLongWeekdaysIfNeeded() {
        if (sShortWeekdays != null && sLongWeekdays != null && !localeHasChanged()) {
            // nothing to do
            return;
        }
        if (sShortWeekdays == null) {
            sShortWeekdays = new String[DaysOfWeek.DAYS_IN_A_WEEK];
        }
        if (sLongWeekdays == null) {
            sLongWeekdays = new String[DaysOfWeek.DAYS_IN_A_WEEK];
        }

        final SimpleDateFormat shortFormat = new SimpleDateFormat(DATE_FORMAT_SHORT);
        final SimpleDateFormat longFormat = new SimpleDateFormat(DATE_FORMAT_LONG);

        // Create a date (2014/07/20) that is a Sunday
        final long aSunday = new GregorianCalendar(2014, Calendar.JULY, 20).getTimeInMillis();

        for (int i = 0; i < DaysOfWeek.DAYS_IN_A_WEEK; i++) {
            final long dayMillis = aSunday + i * DateUtils.DAY_IN_MILLIS;
            sShortWeekdays[i] = shortFormat.format(new Date(dayMillis));
            sLongWeekdays[i] = longFormat.format(new Date(dayMillis));
        }

        // Track the Locale used to generate these weekdays
        sLocaleUsedForWeekdays = Locale.getDefault();
    }

    /**
     * @param id Resource id of the plural
     * @param quantity integer value
     * @return string with properly localized numbers
     */
    public static String getNumberFormattedQuantityString(Context context, int id, int quantity) {
        final String localizedQuantity = NumberFormat.getInstance().format(quantity);
        return context.getResources().getQuantityString(id, quantity, localizedQuantity);
    }

    public static <E> ArraySet<E> newArraySet(Collection<E> collection) {
        final ArraySet<E> arraySet = new ArraySet<>(collection.size());
        arraySet.addAll(collection);
        return arraySet;
    }

    /**
     * Return the default shared preferences.
     */
    public static SharedPreferences getDefaultSharedPreferences(Context context) {
        final Context storageContext;
        if (isNOrLater()) {
            // All N devices have split storage areas, but we may need to
            // migrate existing preferences into the new device protected
            // storage area, which is where our data lives from now on.
            final Context deviceContext = context.createDeviceProtectedStorageContext();
            if (!deviceContext.moveSharedPreferencesFrom(context,
                    PreferenceManager.getDefaultSharedPreferencesName(context))) {
                LogUtils.wtf("Failed to migrate shared preferences");
            }
            storageContext = deviceContext;
        } else {
            storageContext = context;
        }

        return PreferenceManager.getDefaultSharedPreferences(storageContext);
    }
}