/*

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

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Displays energy-related information retrieved from HealthKit.

*/

#import "AAPLEnergyViewController.h"

#import "HKHealthStore+AAPLExtensions.h"

@interface AAPLEnergyViewController()

@property (nonatomic, weak) IBOutlet UILabel *activeEnergyBurnedValueLabel;

@property (nonatomic, weak) IBOutlet UILabel *restingEnergyBurnedValueLabel;

@property (nonatomic, weak) IBOutlet UILabel *consumedEnergyValueLabel;

@property (nonatomic, weak) IBOutlet UILabel *netEnergyValueLabel;

@property (nonatomic) double activeEnergyBurned;

@property (nonatomic) double restingEnergyBurned;

@property (nonatomic) double energyConsumed;

@property (nonatomic) double netEnergy;

@end

@implementation AAPLEnergyViewController

#pragma mark - View Life Cycle

- (void)viewWillAppear:(BOOL)animated {

    [super viewWillAppear:animated];

    [self.refreshControl addTarget:self action:@selector(refreshStatistics) forControlEvents:UIControlEventValueChanged];

    [self refreshStatistics];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(refreshStatistics) name:UIApplicationDidBecomeActiveNotification object:nil];

}

- (void)dealloc {

    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidBecomeActiveNotification object:nil];

}

#pragma mark - Reading HealthKit Data

- (void)refreshStatistics {

    [self.refreshControl beginRefreshing];

    HKQuantityType *energyConsumedType = [HKObjectType quantityTypeForIdentifier:HKQuantityTypeIdentifierDietaryEnergyConsumed];

    HKQuantityType *activeEnergyBurnType = [HKObjectType quantityTypeForIdentifier:HKQuantityTypeIdentifierActiveEnergyBurned];

    // First, fetch the sum of energy consumed samples from HealthKit. Populate this by creating your

    // own food logging app or using the food journal view controller.

    [self fetchSumOfSamplesTodayForType:energyConsumedType unit:[HKUnit jouleUnit] completion:^(double totalJoulesConsumed, NSError *error) {

        // Next, fetch the sum of active energy burned from HealthKit. Populate this by creating your

        // own calorie tracking app or the Health app.

        [self fetchSumOfSamplesTodayForType:activeEnergyBurnType unit:[HKUnit jouleUnit] completion:^(double activeEnergyBurned, NSError *error) {

            // Last, calculate the user's basal energy burn so far today.

            [self fetchTotalBasalBurn:^(HKQuantity *basalEnergyBurn, NSError *error) {

                if (!basalEnergyBurn) {

                    NSLog(@"An error occurred trying to compute the basal energy burn. In your app, handle this gracefully. Error: %@", error);

                }

                // Update the UI with all of the fetched values.

                dispatch_async(dispatch_get_main_queue(), ^{

                    self.activeEnergyBurned = activeEnergyBurned;

                    self.restingEnergyBurned = [basalEnergyBurn doubleValueForUnit:[HKUnit jouleUnit]];

                    self.energyConsumed = totalJoulesConsumed;

                    self.netEnergy = self.energyConsumed - self.activeEnergyBurned - self.restingEnergyBurned;

                    [self.refreshControl endRefreshing];

                });

            }];

        }];

    }];

}

- (void)fetchSumOfSamplesTodayForType:(HKQuantityType *)quantityType unit:(HKUnit *)unit completion:(void (^)(double, NSError *))completionHandler {

    NSPredicate *predicate = [self predicateForSamplesToday];

    HKStatisticsQuery *query = [[HKStatisticsQuery alloc] initWithQuantityType:quantityType quantitySamplePredicate:predicate options:HKStatisticsOptionCumulativeSum completionHandler:^(HKStatisticsQuery *query, HKStatistics *result, NSError *error) {

        HKQuantity *sum = [result sumQuantity];

        if (completionHandler) {

            double value = [sum doubleValueForUnit:unit];

            completionHandler(value, error);

        }

    }];

    [self.healthStore executeQuery:query];

}

// Calculates the user's total basal (resting) energy burn based off of their height, weight, age,

// and biological sex. If there is not enough information, return an error.

- (void)fetchTotalBasalBurn:(void(^)(HKQuantity *basalEnergyBurn, NSError *error))completion {

    NSPredicate *todayPredicate = [self predicateForSamplesToday];

    HKQuantityType *weightType = [HKObjectType quantityTypeForIdentifier:HKQuantityTypeIdentifierBodyMass];

    HKQuantityType *heightType = [HKObjectType quantityTypeForIdentifier:HKQuantityTypeIdentifierHeight];

    [self.healthStore aapl_mostRecentQuantitySampleOfType:weightType predicate:nil completion:^(HKQuantity *weight, NSError *error) {

        if (!weight) {

            completion(nil, error);

            return;

        }

        [self.healthStore aapl_mostRecentQuantitySampleOfType:heightType predicate:todayPredicate completion:^(HKQuantity *height, NSError *error) {

            if (!height) {

                completion(nil, error);

                return;

            }

            NSDate *dateOfBirth = [self.healthStore dateOfBirthWithError:&error];

            if (!dateOfBirth) {

                completion(nil, error);

                return;

            }

            HKBiologicalSexObject *biologicalSexObject = [self.healthStore biologicalSexWithError:&error];

            if (!biologicalSexObject) {

                completion(nil, error);

                return;

            }

            // Once we have pulled all of the information without errors, calculate the user's total basal energy burn

            HKQuantity *basalEnergyBurn = [self calculateBasalBurnTodayFromWeight:weight height:height dateOfBirth:dateOfBirth biologicalSex:biologicalSexObject];

            completion(basalEnergyBurn, nil);

        }];

    }];

}

- (HKQuantity *)calculateBasalBurnTodayFromWeight:(HKQuantity *)weight height:(HKQuantity *)height dateOfBirth:(NSDate *)dateOfBirth biologicalSex:(HKBiologicalSexObject *)biologicalSex {

    // Only calculate Basal Metabolic Rate (BMR) if we have enough information about the user

    if (!weight || !height || !dateOfBirth || !biologicalSex) {

        return nil;

    }

    // Note the difference between calling +unitFromString: vs creating a unit from a string with

    // a given prefix. Both of these are equally valid, however one may be more convenient for a given

    // use case.

    double heightInCentimeters = [height doubleValueForUnit:[HKUnit unitFromString:@"cm"]];

    double weightInKilograms = [weight doubleValueForUnit:[HKUnit gramUnitWithMetricPrefix:HKMetricPrefixKilo]];

    NSDate *now = [NSDate date];

    NSDateComponents *ageComponents = [[NSCalendar currentCalendar] components:NSCalendarUnitYear fromDate:dateOfBirth toDate:now options:NSCalendarWrapComponents];

    NSUInteger ageInYears = ageComponents.year;

    // BMR is calculated in kilocalories per day.

    double BMR = [self calculateBMRFromWeight:weightInKilograms height:heightInCentimeters age:ageInYears biologicalSex:[biologicalSex biologicalSex]];

    // Figure out how much of today has completed so we know how many kilocalories the user has burned.

    NSDate *startOfToday = [[NSCalendar currentCalendar] startOfDayForDate:now];

    NSDate *endOfToday = [[NSCalendar currentCalendar] dateByAddingUnit:NSCalendarUnitDay value:1 toDate:startOfToday options:0];

    NSTimeInterval secondsInDay = [endOfToday timeIntervalSinceDate:startOfToday];

    double percentOfDayComplete = [now timeIntervalSinceDate:startOfToday] / secondsInDay;

    double kilocaloriesBurned = BMR * percentOfDayComplete;

    return [HKQuantity quantityWithUnit:[HKUnit kilocalorieUnit] doubleValue:kilocaloriesBurned];

}

#pragma mark - Convenience

- (NSPredicate *)predicateForSamplesToday {

    NSCalendar *calendar = [NSCalendar currentCalendar];

    NSDate *now = [NSDate date];

    NSDate *startDate = [calendar startOfDayForDate:now];

    NSDate *endDate = [calendar dateByAddingUnit:NSCalendarUnitDay value:1 toDate:startDate options:0];

    return [HKQuery predicateForSamplesWithStartDate:startDate endDate:endDate options:HKQueryOptionStrictStartDate];

}

/// Returns BMR value in kilocalories per day. Note that there are different ways of calculating the

/// BMR. In this example we chose an arbitrary function to calculate BMR based on weight, height, age,

/// and biological sex.

- (double)calculateBMRFromWeight:(double)weightInKilograms height:(double)heightInCentimeters age:(NSUInteger)ageInYears biologicalSex:(HKBiologicalSex)biologicalSex {

    double BMR;

    // The BMR equation is different between males and females.

    if (biologicalSex == HKBiologicalSexMale) {

        BMR = 66.0 + (13.8 * weightInKilograms) + (5 * heightInCentimeters) - (6.8 * ageInYears);

    }

    else {

        BMR = 655 + (9.6 * weightInKilograms) + (1.8 * heightInCentimeters) - (4.7 * ageInYears);

    }

    return BMR;

}

#pragma mark - NSEnergyFormatter

- (NSEnergyFormatter *)energyFormatter {

    static NSEnergyFormatter *energyFormatter;

    static dispatch_once_t onceToken;

    dispatch_once(&onceToken, ^{

        energyFormatter = [[NSEnergyFormatter alloc] init];

        energyFormatter.unitStyle = NSFormattingUnitStyleLong;

        energyFormatter.forFoodEnergyUse = YES;

        energyFormatter.numberFormatter.maximumFractionDigits = 2;

    });

    return energyFormatter;

}

#pragma mark - Setter Overrides

- (void)setActiveEnergyBurned:(double)activeEnergyBurned {

    _activeEnergyBurned = activeEnergyBurned;

    NSEnergyFormatter *energyFormatter = [self energyFormatter];

    self.activeEnergyBurnedValueLabel.text = [energyFormatter stringFromJoules:activeEnergyBurned];

}

- (void)setEnergyConsumed:(double)energyConsumed {

    _energyConsumed = energyConsumed;

    NSEnergyFormatter *energyFormatter = [self energyFormatter];

    self.consumedEnergyValueLabel.text = [energyFormatter stringFromJoules:energyConsumed];

}

- (void)setRestingEnergyBurned:(double)restingEnergyBurned {

    _restingEnergyBurned = restingEnergyBurned;

    NSEnergyFormatter *energyFormatter = [self energyFormatter];

    self.restingEnergyBurnedValueLabel.text = [energyFormatter stringFromJoules:restingEnergyBurned];

}

- (void)setNetEnergy:(double)netEnergy {

    _netEnergy = netEnergy;

    NSEnergyFormatter *energyFormatter = [self energyFormatter];

    self.netEnergyValueLabel.text = [energyFormatter stringFromJoules:netEnergy];

}

@end