//  SKANSnippet.h

#import <Foundation/Foundation.h>

@interface SKANSnippet : NSObject

// Register for SKAdNetwork attribution.
// Call this method as soon as possible once app is launched
+ (void)registerAppForAdNetworkAttribution;

// Track retention and cohorts by calling after each session.
// Reports session details and updates conversion value if needed.
// Conversion value updates only if new value greater than previous.
// Optional callback runs once conversion value updated.
+ (void)updateConversionValueAsync:(void(^)(int, NSError*))handler;

// Track conversion events by calling after each event.
// Reports event details and updates conversion value if needed.
// Optional callback runs once conversion value updated.
+ (void)updateConversionValueAsync:(NSString*)eventName
               withCompletionHandler:(void(^)(int, NSError*))handler;

// Track revenue by calling before each revenue event.
// Updates total revenue for next conversion value calculation.
// Note:
// 1. Call before 'updateConversionValueAsync' to ensure revenue included
// 2. Avoid calling on event retries to prevent double-counting
+ (void)updateRevenue:(double)amount andCurrency:(NSString*)currency;

// Gets current conversion value (nil if none set)
+ (NSNumber *)getConversionValue;

@end

//  SKANSnippet.m

#import "SKANSnippet.h"
#import <StoreKit/SKAdNetwork.h>

#define SESSION_EVENT_NAME @"__SESSION__" 
#define SINGULAR_API_URL @"https://sdk-api-v1.singular.net/api/v1/conversion_value"

// Keys for UserDefaults storage
#define CONVERSION_VALUE_KEY @"skan_conversion_value"
#define FIRST_SKAN_CALL_TIMESTAMP @"skan_first_call_to_skadnetwork_timestamp"
#define LAST_SKAN_CALL_TIMESTAMP @"skan_last_call_to_skadnetwork_timestamp"
#define TOTAL_REVENUE_BY_CURRENCY_KEY @"skan_total_revenue_by_currency"
#define SECONDS_PER_DAY 86400

static NSLock *lockObject;

@implementation SKANSnippet

+ (void)registerAppForAdNetworkAttribution {
    if ([SKANSnippet getFirstSkanCallTimestamp] != 0) {
        return;
    }

    if (@available(iOS 11.3, *)) {
        [SKAdNetwork registerAppForAdNetworkAttribution];
        [SKANSnippet setFirstSkanCallTimestamp];
        [SKANSnippet setLastSkanCallTimestamp];
    }
}

+ (void)updateConversionValueAsync:(void(^)(int, NSError*))handler {
    [SKANSnippet updateConversionValueAsync:SESSION_EVENT_NAME withCompletionHandler:handler];
}

+ (void)updateConversionValueAsync:(NSString*)eventName withCompletionHandler:(void(^)(int, NSError*))handler {
    if (@available(iOS 14, *)) {
        if ([SKANSnippet isSkanUpdateWindowOver]) {
            return;
        }
        
        [SKANSnippet getConversionValueFromServer:eventName withCompletionHandler:handler];
    }
}

+ (void)updateRevenue:(double)amount andCurrency:(NSString*)currency {
    if (@available(iOS 14, *)) {
        
        // Update total revenues
        if (amount != 0 && currency) {
            NSMutableDictionary* revenues = [[SKANSnippet getTotalRevenue] mutableCopy];
            NSNumber* currentRevenue = @(0);
            
            if ([revenues objectForKey:currency]) {
                currentRevenue = [revenues objectForKey:currency];
            }
            
            currentRevenue = @([currentRevenue floatValue] + amount);
            [revenues setObject:currentRevenue forKey:currency];
            
            [SKANSnippet setTotalRevenue:revenues];
        }
    }
}

+ (NSNumber *)getConversionValue {
    NSUserDefaults* userDefaults = [NSUserDefaults standardUserDefaults];
    if (![userDefaults objectForKey:CONVERSION_VALUE_KEY]) {
        return nil;
    }
    return @([userDefaults integerForKey:CONVERSION_VALUE_KEY]);
}

+ (void)getConversionValueFromServer:(NSString*)eventName withCompletionHandler:(void(^)(int, NSError*))handler {
    if (!lockObject) {
        lockObject = [NSLock new];
    }
    
    // Making the lock async so it will not freeze the calling thread
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void) {
        
        [lockObject lock];
        
        NSURLComponents *components = [NSURLComponents componentsWithString:SINGULAR_API_URL];
        
        NSString* bundleIdentifier = [[NSBundle mainBundle] bundleIdentifier];
        
        components.queryItems = @[
            [NSURLQueryItem queryItemWithName:@"a" value:@"YOUR_SDK_KEY"],
            [NSURLQueryItem queryItemWithName:@"i" value:bundleIdentifier],
            [NSURLQueryItem queryItemWithName:@"app_v" value:@"YOUR_APP_VERSION"],
            [NSURLQueryItem queryItemWithName:@"n" value:eventName],
            [NSURLQueryItem queryItemWithName:@"p" value:@"iOS"],
            [NSURLQueryItem queryItemWithName:@"idfv" value:@"YOUR_IDFV"],
            [NSURLQueryItem queryItemWithName:@"idfa" value:@"YOUR_IDFA"],
            [NSURLQueryItem queryItemWithName:@"conversion_value"  value:[[SKANSnippet getConversionValue] stringValue]],
            [NSURLQueryItem queryItemWithName:@"total_revenue_by_currency"  value:[SKANSnippet dictionaryToJsonString:[SKANSnippet getTotalRevenue]]],
            [NSURLQueryItem queryItemWithName:@"first_call_to_skadnetwork_timestamp"  value:[NSString stringWithFormat:@"%ld", [SKANSnippet getFirstSkanCallTimestamp]]],
            [NSURLQueryItem queryItemWithName:@"last_call_to_skadnetwork_timestamp"  value:[NSString stringWithFormat:@"%ld", [SKANSnippet getLastSkanCallTimestamp]]],
        ];
        
        [[[NSURLSession sharedSession] dataTaskWithURL:components.URL
                                     completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
            if (error) {
                [lockObject unlock];
                if (handler) {
                    handler(-1, error);
                }
                return;
            }
            
            NSDictionary* parsedResponse = [SKANSnippet jsonDataToDictionary:data];
            
            if (!parsedResponse) {
                [lockObject unlock];
                if (handler) {
                    handler(-1, [NSError errorWithDomain:bundleIdentifier
                                                    code:0
                                                userInfo:@{NSLocalizedDescriptionKey:@"Failed parsing server response"}]);
                }
                return;
            }
            
            NSNumber *conversionValue = [parsedResponse objectForKey:@"conversion_value"];
            
            if (!conversionValue) {
                [lockObject unlock];
                NSString *status = [parsedResponse objectForKey:@"status"];
                
                if (!status || ![status isEqualToString:@"ok"]) {
                    if (handler) {
                    NSString *reason = [parsedResponse objectForKey:@"reason"];
                        if (!reason) {
                            reason = @"Got error from server";
                        }
                        
                        handler(-1, [NSError errorWithDomain:bundleIdentifier
                                                        code:0
                                                    userInfo:@{NSLocalizedDescriptionKey:reason}]);
                    }
                }
                return;
            }
            
            NSNumber* currentValue = [SKANSnippet getConversionValue];
            if ([conversionValue intValue] <= [currentValue intValue]) {
                [lockObject unlock];
                return;
            }
            
            [SKANSnippet setConversionValue:[conversionValue intValue]];
            [SKANSnippet setLastSkanCallTimestamp];
            
            if (![SKANSnippet getFirstSkanCallTimestamp]) {
                [SKANSnippet setFirstSkanCallTimestamp];
            }
            
            [lockObject unlock];
            
            if (handler) {
                handler([conversionValue intValue], error);
            }
        }] resume];
    });
}

+ (BOOL)isSkanUpdateWindowOver {        
    NSInteger timeDiff = [SKANSnippet getCurrentUnixTimestamp] - [SKANSnippet getLastSkanCallTimestamp];
    return SECONDS_PER_DAY <= timeDiff;
}

@end

+ (NSInteger)getFirstSkanCallTimestamp {
    NSUserDefaults* userDefaults = [NSUserDefaults standardUserDefaults];
    return [userDefaults integerForKey:FIRST_SKAN_CALL_TIMESTAMP];
}

+ (NSInteger)getLastSkanCallTimestamp {
    NSUserDefaults* userDefaults = [NSUserDefaults standardUserDefaults];
    return [userDefaults integerForKey:LAST_SKAN_CALL_TIMESTAMP];
}

+ (NSDictionary*)getTotalRevenue {
    NSUserDefaults* userDefaults = [NSUserDefaults standardUserDefaults];
    if (![userDefaults objectForKey:TOTAL_REVENUE_BY_CURRENCY_KEY]) {
        return [NSDictionary new];
    }
    return [userDefaults objectForKey:TOTAL_REVENUE_BY_CURRENCY_KEY];
}

+ (NSInteger)getCurrentUnixTimestamp {
    return [[NSDate date]timeIntervalSince1970];
}

+ (void)setConversionValue:(int)value {
    if (@available(iOS 14.0, *)) {
        if (value <= [[SKANSnippet getConversionValue] intValue]) {
            return;
        }
        
        [SKAdNetwork updateConversionValue:value];
        
        NSUserDefaults* userDefaults = [NSUserDefaults standardUserDefaults];
        [userDefaults setInteger:value forKey:CONVERSION_VALUE_KEY];
        [userDefaults synchronize];
    }
}

+ (void)setFirstSkanCallTimestamp {
    NSUserDefaults* userDefaults = [NSUserDefaults standardUserDefaults];
    [userDefaults setInteger:[SKANSnippet getCurrentUnixTimestamp] 
      forKey:FIRST_SKAN_CALL_TIMESTAMP];
    [userDefaults synchronize];
}

+ (void)setLastSkanCallTimestamp {
    NSUserDefaults* userDefaults = [NSUserDefaults standardUserDefaults];
    [userDefaults setInteger:[SKANSnippet getCurrentUnixTimestamp] 
      forKey:LAST_SKAN_CALL_TIMESTAMP];
    [userDefaults synchronize];
}

+ (void)setTotalRevenue:(NSDictionary *)values {
    NSUserDefaults* userDefaults = [NSUserDefaults standardUserDefaults];
    [userDefaults setObject:values forKey:TOTAL_REVENUE_BY_CURRENCY_KEY];
    [userDefaults synchronize];
}

+ (NSString*)dictionaryToJSONString:(NSDictionary*)dictionary {
    if (!dictionary || [dictionary count] == 0){
        return @"{}";
    }
    
    NSError *error;
    NSData *JSONData = [NSJSONSerialization dataWithJSONObject:dictionary
      options:0
      error:&error];
    if (error || !JSONData) {
        return @"{}";
    }
    
    return [[NSString alloc] initWithData:JSONData 
      encoding:NSUTF8StringEncoding];
}

+ (NSDictionary*)JSONDataToDictionary:(NSData*)JSONData {
    if (!JSONData) {
        return nil;
    }

    NSError * error;
    NSDictionary * parsedData = [NSJSONSerialization 
      JSONObjectWithData:JSONData
      options:kNilOptions error:&error];
      
    if (error || !parsedData) {
       return nil;
    }
    return parsedData;
}

@end

NSDictionary *skanMetadata = @{
    @"skan_conversion_value": 
        [[SKANSnippet getConversionValue] stringValue],
    @"skan_first_call_timestamp": 
        [NSString stringWithFormat:@"%ld", [SKANSnippet getFirstSkanCallTimestamp]],
    @"skan_last_call_timestamp": 
        [NSString stringWithFormat:@"%ld", [SKANSnippet getLastSkanCallTimestamp]]
};

// Forward skanMetadata to your server for S2S API enrichment

// On app launch (in applicationDidFinishLaunching)
[SKANSnippet registerAppForAdNetworkAttribution];

// After each session handled
[SKANSnippet updateConversionValueAsync:^(int value, NSError *error) {
    if (error) {
        NSLog(@"Conversion value update failed: %@", error);
    } else {
        NSLog(@"Conversion value updated to: %d", value);
    }
}];

// After handling non-revenue events
[SKANSnippet updateConversionValueAsync:@"event_name" 
                   withCompletionHandler:^(int value, NSError *error) {
    if (error) {
        NSLog(@"Event conversion value update failed: %@", error);
    } else {
        NSLog(@"Event conversion value updated to: %d", value);
    }
}];

// After handling revenue events
[SKANSnippet updateRevenue:15.53 andCurrency:@"USD"];
[SKANSnippet updateConversionValueAsync:@"revenue_event_name" 
                   withCompletionHandler:^(int value, NSError *error) {
    if (error) {
        NSLog(@"Revenue conversion value update failed: %@", error);
    } else {
        NSLog(@"Revenue conversion value updated to: %d", value);
    }
}];