feat: session id support for payloads

PostHog.xcodeproj/project.pbxproj

@@ -90,6 +90,9 @@
 		EADEB8F31DECD335005322DA /* PostHogTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = EADEB8E71DECD335005322DA /* PostHogTests.swift */; };
 		EADEB8F41DECD335005322DA /* ContextTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = EADEB8E81DECD335005322DA /* ContextTest.swift */; };
 		EADEB8F51DECD335005322DA /* CryptoTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = EADEB8E91DECD335005322DA /* CryptoTest.swift */; };
+		F250ADE0288B401B0045FA7E /* PHGSession.m in Sources */ = {isa = PBXBuildFile; fileRef = F250ADDF288B401B0045FA7E /* PHGSession.m */; };
+		F250ADE2288ED2E20045FA7E /* SessionTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = F250ADE1288ED2E20045FA7E /* SessionTest.swift */; };
+		F250ADE3288ED4910045FA7E /* PHGSession.h in Headers */ = {isa = PBXBuildFile; fileRef = F250ADDE288B3ED80045FA7E /* PHGSession.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		F2A54FB028772F97006C53FF /* FeatureFlagTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = F2A54FAF28772F97006C53FF /* FeatureFlagTests.swift */; };
 		F2A54FB128772F97006C53FF /* FeatureFlagTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = F2A54FAF28772F97006C53FF /* FeatureFlagTests.swift */; };
 		F2A54FB32877582E006C53FF /* PHGGroupPayload.m in Sources */ = {isa = PBXBuildFile; fileRef = F2A54FB22877582E006C53FF /* PHGGroupPayload.m */; };
@@ -197,6 +200,9 @@
 		EADEB8FF1DED3711005322DA /* circle.yml */ = {isa = PBXFileReference; lastKnownFileType = text; path = circle.yml; sourceTree = "<group>"; };
 		EADEB9001DED3711005322DA /* PostHog.podspec */ = {isa = PBXFileReference; lastKnownFileType = text; path = PostHog.podspec; sourceTree = "<group>"; };
 		EADEB9011DED3711005322DA /* Podfile.lock */ = {isa = PBXFileReference; lastKnownFileType = text; path = Podfile.lock; sourceTree = "<group>"; };
+		F250ADDE288B3ED80045FA7E /* PHGSession.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = PHGSession.h; sourceTree = "<group>"; };
+		F250ADDF288B401B0045FA7E /* PHGSession.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = PHGSession.m; sourceTree = "<group>"; };
+		F250ADE1288ED2E20045FA7E /* SessionTest.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SessionTest.swift; sourceTree = "<group>"; };
 		F2A54FAF28772F97006C53FF /* FeatureFlagTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FeatureFlagTests.swift; sourceTree = "<group>"; };
 		F2A54FB22877582E006C53FF /* PHGGroupPayload.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = PHGGroupPayload.m; sourceTree = "<group>"; };
 		F2A54FB42877583C006C53FF /* PHGGroupPayload.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = PHGGroupPayload.h; sourceTree = "<group>"; };
@@ -341,6 +347,7 @@
 				6EEC1C702017EA370089C478 /* EndToEndTests.swift */,
 				A31958EE2385AC3A00A47EFA /* SerializationTests.m */,
 				F2A54FAF28772F97006C53FF /* FeatureFlagTests.swift */,
+				F250ADE1288ED2E20045FA7E /* SessionTest.swift */,
 			);
 			indentWidth = 2;
 			path = PostHogTests;
@@ -376,6 +383,8 @@
 				BF8C89BCDF12D1B64E9475F1 /* PHGCrypto.h */,
 				F2A54FB22877582E006C53FF /* PHGGroupPayload.m */,
 				F2A54FB42877583C006C53FF /* PHGGroupPayload.h */,
+				F250ADDE288B3ED80045FA7E /* PHGSession.h */,
+				F250ADDF288B401B0045FA7E /* PHGSession.m */,
 			);
 			path = Classes;
 			sourceTree = "<group>";
@@ -423,6 +432,7 @@
 				BF8C8AD1FBFBB6941DE29D3B /* PHGFileStorage.h in Headers */,
 				BF8C845A65AB5AD06E1EE26B /* PHGStorage.h in Headers */,
 				BF8C890FADEC88022E7A3588 /* NSData+PHGGZIP.h in Headers */,
+				F250ADE3288ED4910045FA7E /* PHGSession.h in Headers */,
 				BF8C8181F96E1C8CB86D783D /* PHGPostHogUtils.h in Headers */,
 				BF8C8FCEC80B47BF2236236E /* PHGUtils.h in Headers */,
 				BF8C8DCC18E3AA39CCB330BC /* PHGStoreKitCapturer.h in Headers */,
@@ -713,6 +723,7 @@
 				BF8C8A634BCECED539A18D57 /* PHGPostHogIntegration.m in Sources */,
 				BF8C8735F5CF80C193F5AEDF /* PHGAliasPayload.m in Sources */,
 				BF8C8374E0D8F97469715282 /* PHGPayload.m in Sources */,
+				F250ADE0288B401B0045FA7E /* PHGSession.m in Sources */,
 				BF8C86ED787477703D8BCD6C /* PHGScreenPayload.m in Sources */,
 				BF8C8334DB2564A7CFA7A87A /* PHGPayloadManager.m in Sources */,
 				BF8C87E4B70CA478721EB11D /* PHGCapturePayload.m in Sources */,
@@ -726,6 +737,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				F250ADE2288ED2E20045FA7E /* SessionTest.swift in Sources */,
 				EADEB8F51DECD335005322DA /* CryptoTest.swift in Sources */,
 				EADEB8F21DECD335005322DA /* UserDefaultsStorageTest.swift in Sources */,
 				EAA542771EB4035400945DA7 /* CapturingTests.swift in Sources */,

PostHog/Classes/PHGSession.h

@@ -0,0 +1,16 @@
+#import <Foundation/Foundation.h>
+#import "PHGStorage.h"
+
+@class PHGSession;
+
+
+@interface PHGSession : NSObject
+
+- (instancetype _Nonnull)initWithStorage:(id<PHGStorage> _Nonnull)fileStorage userDefaultsStorage:(id<PHGStorage> _Nonnull)userDefaultsStorage;
+- (NSString *_Nullable)getId;
+
+- (void)checkAndSetSessionId:(NSTimeInterval)timestamp;
+- (void)checkAndSetSessionId;
+- (void)resetSession;
+
+@end

PostHog/Classes/PHGSession.m

@@ -0,0 +1,111 @@
+//
+//  PHGSession.m
+//  PostHog
+//
+//  Created by Eric Duong on 7/22/22.
+//  Copyright © 2022 PostHog. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+#import "PHGSession.h"
+#import "PHGPostHogUtils.h"
+#import "PHGStorage.h"
+
+static int const SESSION_CHANGE_THRESHOLD = 1800;
+
+static NSString *const PHGSessionId = @"PHGSessionId";
+static NSString *const kPHGSessionId = @"posthog.sessionId";
+
+static NSString *const PHGSessionLastTimestamp = @"PHGSessionLastTimestamp";
+static NSString *const kPHGSessionLastTimestamp = @"posthog.sessionlastTimestamp";
+
+@interface PHGSession ()
+
+@property (nonatomic, strong) id<PHGStorage> fileStorage;
+@property (nonatomic, strong) id<PHGStorage> userDefaultsStorage;
+
+@end
+
+@implementation PHGSession
+
+- (instancetype _Nonnull)initWithStorage:(id<PHGStorage>)fileStorage userDefaultsStorage:(id<PHGStorage>)userDefaultsStorage;
+{
+    if (self = [super init]) {
+        self.fileStorage = fileStorage;
+        self.userDefaultsStorage = userDefaultsStorage;
+
+    }
+    return self;
+}
+
+- (void)checkAndSetSessionId
+{
+    NSTimeInterval now = [[NSDate date] timeIntervalSince1970];
+    [self checkAndSetSessionId:now];
+}
+
+- (void)checkAndSetSessionId:(NSTimeInterval)timestamp
+{
+    NSString *sessionId = [self getSessionId];
+    NSTimeInterval sessionLastTimestamp = [self getSessionLastTimestamp];
+    if (sessionId == nil || sessionLastTimestamp == 0 || fabs(timestamp - sessionLastTimestamp) > SESSION_CHANGE_THRESHOLD) {
+        NSString *newSessionId = createUUIDString();
+        [self saveSessionId:newSessionId sessionLastTimestamp:timestamp];
+    }
+}
+
+- (void)saveSessionId:(NSString *)sessionId sessionLastTimestamp:(NSTimeInterval)sessionLastTimestamp
+{
+
+#if TARGET_OS_TV
+    [self.userDefaultsStorage setString:sessionId forKey:PHGSessionId];
+#else
+    [self.fileStorage setString:sessionId forKey:kPHGSessionId];
+#endif
+
+    NSNumber* nsSessionLastTimestamp = [NSNumber numberWithDouble:sessionLastTimestamp];
+#if TARGET_OS_TV
+    [self.userDefaultsStorage setString:distinctId forKey:PHGSessionLastTimestamp];
+#else
+    [self.fileStorage setNumber:nsSessionLastTimestamp forKey:kPHGSessionLastTimestamp];
+#endif
+}
+
+- (NSString *)getSessionId
+{
+#if TARGET_OS_TV
+    return [[NSUserDefaults standardUserDefaults] valueForKey:PHGSessionId];
+#else
+    return [self.fileStorage stringForKey:kPHGSessionId];
+#endif
+}
+
+- (NSTimeInterval)getSessionLastTimestamp
+{
+    NSNumber *timestamp;
+#if TARGET_OS_TV
+    timestamp = [[NSUserDefaults standardUserDefaults] numberForKey:PHGSessionLastTimestamp];
+#else
+    timestamp = [self.fileStorage numberForKey:kPHGSessionLastTimestamp];
+#endif
+    return [timestamp doubleValue];
+}
+
+- (NSString *)getId
+{
+    [self checkAndSetSessionId];
+    return [self getSessionId];
+}
+
+- (void)resetSession
+{
+#if TARGET_OS_TV
+        [self.userDefaultsStorage removeKey:PHGSessionId];
+        [self.userDefaultsStorage removeKey:PHGSessionLastTimestamp];
+#else
+        [self.fileStorage removeKey:kPHGSessionId];
+        [self.fileStorage removeKey:kPHGSessionLastTimestamp];
+#endif
+}
+
+@end

PostHog/Internal/PHGFileStorage.m

@@ -114,6 +114,21 @@ - (void)setString:(nullable NSString *)string forKey:(NSString *)key
     [self setJSON:string forKey:key];
 }
 
+- (nullable NSNumber *)numberForKey:(NSString *)key
+{
+    NSDictionary *data = [self jsonForKey:key];
+    if (data) {
+        return data[key];
+    }
+    return nil;
+}
+
+
+- (void)setNumber:(nullable NSNumber *)number forKey:(NSString *)key
+{
+    [self setJSON:number forKey:key];
+}
+
 + (NSURL *)applicationSupportDirectoryURL
 {
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES);

PostHog/Internal/PHGPostHogIntegration.m

@@ -13,6 +13,7 @@
 #import "PHGScreenPayload.h"
 #import "PHGAliasPayload.h"
 #import "PHGGroupPayload.h"
+#import "PHGSession.h"
 
 #if TARGET_OS_IOS
 #import <CoreTelephony/CTCarrier.h>
@@ -54,6 +55,7 @@ @interface PHGPostHogIntegration ()
 @property (nonatomic, strong) NSURLSessionUploadTask *batchRequest;
 @property (nonatomic, assign) UIBackgroundTaskIdentifier flushTaskID;
 @property (nonatomic, strong) PHGReachability *reachability;
+@property (nonatomic, strong) PHGSession *sessionManager;
 @property (nonatomic, strong) NSTimer *flushTimer;
 @property (nonatomic, strong) dispatch_queue_t serialQueue;
 @property (nonatomic, strong) dispatch_queue_t backgroundTaskQueue;
@@ -79,6 +81,7 @@ - (id)initWithPostHog:(PHGPostHog *)posthog httpClient:(PHGHTTPClient *)httpClie
         self.fileStorage = fileStorage;
         self.userDefaultsStorage = userDefaultsStorage;
         self.distinctId = [self getDistinctId];
+        self.sessionManager = [[PHGSession alloc] initWithStorage:fileStorage userDefaultsStorage:userDefaultsStorage];
         self.reachability = [PHGReachability reachabilityWithHostname:@"google.com"];
         [self.reachability startNotifier];
         self.cachedStaticContext = [self staticContext];
@@ -226,6 +229,7 @@ - (NSDictionary *)liveContext
 
     context[@"$groups"] = [self getGroups];
     context[@"$active_feature_flags"] = [self getFeatureFlags];
+    context[@"$session_id"] = [self.sessionManager getId];
 
     NSDictionary *flagsAndValues = [self getFeatureFlagsAndValues];
 
@@ -506,6 +510,7 @@ - (void)reset
 #else
         [self.fileStorage removeKey:kPHGDistinctIdFilename];
 #endif
+        [self.sessionManager resetSession];
         self.distinctId = nil;
     }];
 }

PostHog/Internal/PHGStorage.h

@@ -20,6 +20,9 @@
 - (void)setString:(NSString *_Nullable)string forKey:(NSString *_Nonnull)key;
 - (NSString *_Nullable)stringForKey:(NSString *_Nonnull)key;
 
-// Number and Booleans are intentionally omitted at the moment because they are not needed
+- (void)setNumber:(NSNumber *_Nullable)number forKey:(NSString *_Nonnull)key;
+- (nullable NSNumber *)numberForKey:(NSString *_Nonnull)key;
+
+// Booleans are intentionally omitted at the moment because they are not needed
 
 @end

PostHog/Internal/PHGUserDefaultsStorage.m

@@ -130,6 +130,27 @@ - (void)setString:(NSString *)string forKey:(NSString *)key
     [self setPlist:string forKey:key];
 }
 
+- (NSNumber *)numberForKey:(NSString *)key
+{
+    if (!self.crypto) {
+        key = [self namespacedKey:key];
+
+        double value = [self.defaults doubleForKey:key];
+        return [NSNumber numberWithDouble:value];
+    }
+    return [self plistForKey:key];
+}
+
+- (void)setNumber:(NSNumber *)number forKey:(NSString *)key
+{
+    if (!self.crypto) {
+        key = [self namespacedKey:key];
+        [self setObject:number forKey:key];
+        return;
+    }
+    [self setPlist:number forKey:key];
+}
+
 #pragma mark - Helpers
 
 - (id _Nullable)plistForKey:(NSString *)key

PostHog/PostHog.h

@@ -10,3 +10,4 @@ FOUNDATION_EXPORT const unsigned char PostHogVersionString[];
 #import "PHGPostHogIntegration.h"
 #import "PHGContext.h"
 #import "PHGMiddleware.h"
+#import "PHGSession.h"

PostHogTests/SessionTest.swift

@@ -0,0 +1,45 @@
+import Quick
+import Nimble
+import PostHog
+
+class SessionTest: QuickSpec {
+  override func spec() {
+
+    var sessionHandler: PHGSession!
+    var storage : PHGFileStorage!
+    var userDefaultsStorage : PHGUserDefaultsStorage!
+
+    beforeEach {
+      let url = PHGFileStorage.applicationSupportDirectoryURL()
+      expect(url).toNot(beNil())
+      expect(url?.pathComponents[url!.pathComponents.count - 2]) == "Application Support"
+      expect(url?.lastPathComponent) == Bundle.main.bundleIdentifier
+      storage = PHGFileStorage(folder: url!, crypto: nil)
+      userDefaultsStorage = PHGUserDefaultsStorage(defaults: UserDefaults.standard, namespacePrefix: nil, crypto: nil)
+      sessionHandler = PHGSession(storage: storage, userDefaultsStorage: userDefaultsStorage)
+    }
+
+    it("Generates a session id") {
+      let sessionId = sessionHandler.getId()
+      expect(sessionId).toNot(beNil())
+
+      let anotherSessionId = sessionHandler.getId()
+      expect(anotherSessionId).to(equal(sessionId))
+
+    }
+
+    it("Generates a new session id after refresh") {
+      let sessionId = sessionHandler.getId()
+      expect(sessionId).toNot(beNil())
+
+      let timeInterval = Date().addingTimeInterval(TimeInterval(40.0 * 60.0)).timeIntervalSince1970
+      sessionHandler.checkAndSetSessionId(timeInterval)
+
+      let anotherSessionId = sessionHandler.getId()
+      expect(anotherSessionId).toNot(equal(sessionId))
+
+    }
+
+  }
+
+}