/*

 Copyright (C) 2016 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 Object to represent a time zone, caching various derived properties that are expensive to compute.

 */

#import "APLTimeZoneWrapper.h"

static NSString *today;

static NSString *tomorrow;

static NSString *yesterday;

static UIImage *q1Image;

static UIImage *q2Image;

static UIImage *q3Image;

static UIImage *q4Image;

@interface APLTimeZoneWrapper ()

@property (readwrite, nonatomic) NSString *extendedDetailText;

@property (readwrite, nonatomic) NSString *whichDay;

@property (readwrite, nonatomic) NSString *abbreviation;

@property (readwrite, nonatomic) NSString *gmtOffset;

@property (readwrite, nonatomic) UIImage *image;

@end

@implementation APLTimeZoneWrapper

+ (void)initialize {

    // Unlikely to have any subclasses, but check class nevertheless

    if (self == [APLTimeZoneWrapper class]) {

        today = NSLocalizedString(@"Today", "Today");

        tomorrow = NSLocalizedString(@"Tomorrow", "Tomorrow");

        yesterday = NSLocalizedString(@"Yesterday", "Yesterday");

        q1Image = [UIImage imageNamed:@"12AM-6AM.png"];

        q2Image = [UIImage imageNamed:@"6AM-12PM.png"];

        q3Image = [UIImage imageNamed:@"12PM-6PM.png"];

        q4Image = [UIImage imageNamed:@"6PM-12AM.png"];

    }

}

- (instancetype)init {

    NSAssert(NO, @"Invalid use of init; use initWithTimeZone:nameComponents: to create APLTimeZoneWrapper");

    return [self init];

}

- (instancetype)initWithTimeZone:(NSTimeZone *)aTimeZone nameComponents:(NSArray *)nameComponents {

    self = [super init];

    if (self) {

        _timeZone = aTimeZone;

        NSString *name = nil;

        if (nameComponents.count == 2) {

            name = nameComponents[1];

        }

        else if (nameComponents.count == 3) {

            name = [NSString stringWithFormat:@"%@ (%@)", nameComponents[2], nameComponents[1]];

        }

        _timeZoneLocaleName = [name stringByReplacingOccurrencesOfString:@"_" withString:@" "];

    }

    return self;

}

/*

 By default, we don't actually calculate whichDay, abreviation, gmtOffset or image.

 They're expensive to compute, and consume memory.  Calculate them on demand, then cache them.

 */

- (NSString *)whichDay {

    // Return "today", "tomorrow", or "yesterday" as appropriate for the time zone

    if (_whichDay == nil) {

        NSDateComponents *dateComponents;

        NSInteger myDay, tzDay;

        NSCalendar *calendar = self.calendar;

        NSDate *date = self.date;

        // Set the calendar's time zone to the default time zone.

        calendar.timeZone = [NSTimeZone defaultTimeZone];

        dateComponents = [calendar components:NSCalendarUnitWeekday fromDate:date];

        myDay = dateComponents.weekday;

        calendar.timeZone = self.timeZone;

        dateComponents = [calendar components:NSCalendarUnitWeekday fromDate:date];

        tzDay = dateComponents.weekday;

        NSRange dayRange = [calendar maximumRangeOfUnit:NSCalendarUnitWeekday];

        NSInteger maxDay = NSMaxRange(dayRange) - 1;

        if (myDay == tzDay) {

            _whichDay = today;

        } else {

            if ((tzDay - myDay) > 0) {

                _whichDay = tomorrow;

            } else {

                _whichDay = yesterday;

            }

            // Special cases for days at the end of the week

            if ((myDay == maxDay) && (tzDay == 1)) {

                self.whichDay = tomorrow;               

            }

            if ((myDay == 1) && (tzDay == maxDay)) {

                _whichDay = yesterday;

            }

        }

    }

    return _whichDay;

}

- (NSString *)abbreviation {

    // Return the abbreviation for the time zone

    if (_abbreviation == nil) {

        _abbreviation = [self.timeZone abbreviationForDate:self.date];

    }

    return _abbreviation;

}

- (NSString *)gmtOffset {

    // Return the offset from GMT for the time zone

    if (_gmtOffset == nil) {

        _gmtOffset = [self.timeZone localizedName:NSTimeZoneNameStyleShortStandard locale:[NSLocale currentLocale]];

    }

    return _gmtOffset;

}

- (NSString *)extendedDetailText {

    //  Return a string of concatendated property values for resizable detail text label

    if( _extendedDetailText == nil ) {

        //  Description

        NSString *detailText = [self.timeZone.description stringByReplacingOccurrencesOfString:@"_" withString:@" "];

        //  Daylight Savings

        if( !self.timeZone.daylightSavingTime ) {

            detailText = [detailText stringByAppendingString:@" (Not Daylight Savings)"];

        }

        //  Which Day

        detailText = [detailText stringByAppendingString:self.whichDay];

        _extendedDetailText = detailText;

    }

    return _extendedDetailText;

}

- (UIImage *)image {

    // Return an image that illustrates the quarter of the current day in the time zone

    if (_image == nil) {

        NSCalendar *calendar = self.calendar;

        NSDate *date = self.date;

        calendar.timeZone = self.timeZone;

        NSDateComponents *dateComponents = [calendar components:NSCalendarUnitHour fromDate:date];

        NSInteger hour = dateComponents.hour;

        if (hour > 17) {

            _image = q4Image;

        } else {

            if (hour > 11) {

                _image = q3Image;

            } else {

                if (hour > 5) {

                    _image = q2Image;

                } else {

                    _image = q1Image;

                }

            }

        }

    }

    return _image;

}

- (void)setDate:(NSDate *)newDate {

    /*

     Recalculating all the details is expensive.

     Only change the date if it is not actually equal to the current date.

     If the date is different, "fault" the receiver: nill out all the cached values -- if accessed, they will be recaulculated.

     */

    if ([newDate isEqualToDate:_date]) {

        return;

    }

    _date = newDate;

    self.abbreviation = nil;

    self.gmtOffset = nil;

    self.image = nil;

}

@end