experiment default metrics pixels

.swiftpm/xcode/xcshareddata/xcschemes/BrowserServicesKit-Package.xcscheme

@@ -553,6 +553,20 @@
                ReferencedContainer = "container:">
             </BuildableReference>
          </BuildActionEntry>
+         <BuildActionEntry
+            buildForTesting = "YES"
+            buildForRunning = "YES"
+            buildForProfiling = "YES"
+            buildForArchiving = "YES"
+            buildForAnalyzing = "YES">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "PixelExperimentKit"
+               BuildableName = "PixelExperimentKit"
+               BlueprintName = "PixelExperimentKit"
+               ReferencedContainer = "container:">
+            </BuildableReference>
+         </BuildActionEntry>
       </BuildActionEntries>
    </BuildAction>
    <TestAction
@@ -842,6 +856,16 @@
                ReferencedContainer = "container:">
             </BuildableReference>
          </TestableReference>
+         <TestableReference
+            skipped = "NO">
+            <BuildableReference
+               BuildableIdentifier = "primary"
+               BlueprintIdentifier = "PixelExperimentKitTests"
+               BuildableName = "PixelExperimentKitTests"
+               BlueprintName = "PixelExperimentKitTests"
+               ReferencedContainer = "container:">
+            </BuildableReference>
+         </TestableReference>
       </Testables>
    </TestAction>
    <LaunchAction

Package.swift

@@ -44,6 +44,7 @@ let package = Package(
         .library(name: "DuckPlayer", targets: ["DuckPlayer"]),
         .library(name: "MaliciousSiteProtection", targets: ["MaliciousSiteProtection"]),
         .library(name: "Onboarding", targets: ["Onboarding"]),
+        .library(name: "PixelExperimentKit", targets: ["PixelExperimentKit"]),
         .library(name: "BrokenSitePrompt", targets: ["BrokenSitePrompt"]),
         .library(name: "PageRefreshMonitor", targets: ["PageRefreshMonitor"]),
         .library(name: "PrivacyStats", targets: ["PrivacyStats"]),
@@ -433,6 +434,19 @@ let package = Package(
                 .define("DEBUG", .when(configuration: .debug))
             ]
         ),
+        .target(
+            name: "PixelExperimentKit",
+            dependencies: [
+                "PixelKit",
+                "BrowserServicesKit"
+            ],
+            resources: [
+                .process("Resources")
+            ],
+            swiftSettings: [
+                .define("DEBUG", .when(configuration: .debug))
+            ]
+        ),
         .target(
             name: "BrokenSitePrompt",
             dependencies: [
@@ -683,6 +697,12 @@ let package = Package(
                 "Onboarding"
             ]
         ),
+        .testTarget(
+            name: "PixelExperimentKitTests",
+            dependencies: [
+                "PixelExperimentKit"
+            ]
+        ),
         .testTarget(
             name: "SpecialErrorPagesTests",
             dependencies: [

Sources/BrowserServicesKit/FeatureFlagger/ExperimentCohortsManager.swift

@@ -72,6 +72,7 @@ public class ExperimentCohortsManager: ExperimentCohortsManaging {
     private var store: ExperimentsDataStoring
     private let randomizer: (Range<Double>) -> Double
     private let queue = DispatchQueue(label: "com.ExperimentCohortsManager.queue")
+    private let fireCohortAssigned: (_ subfeatureID: SubfeatureID, _ experiment: ExperimentData) -> Void
 
     public var experiments: Experiments? {
         get {
@@ -81,9 +82,11 @@ public class ExperimentCohortsManager: ExperimentCohortsManaging {
         }
     }
 
-    public init(store: ExperimentsDataStoring = ExperimentsDataStore(), randomizer: @escaping (Range<Double>) -> Double = Double.random(in:)) {
+    public init(store: ExperimentsDataStoring = ExperimentsDataStore(), randomizer: @escaping (Range<Double>) -> Double = Double.random(in:),
+                fireCohortAssigned: @escaping (_ subfeatureID: SubfeatureID, _ experiment: ExperimentData) -> Void) {
         self.store = store
         self.randomizer = randomizer
+        self.fireCohortAssigned = fireCohortAssigned
     }
 
     public func resolveCohort(for experiment: ExperimentSubfeature, allowCohortReassignment: Bool) -> CohortID? {
@@ -113,6 +116,7 @@ extension ExperimentCohortsManager {
             cumulativeWeight += Double(cohort.weight)
             if randomValue < cumulativeWeight {
                 saveCohort(cohort.name, in: subfeature.subfeatureID, parentID: subfeature.parentID)
+                fireCohortAssigned(subfeature.subfeatureID, ExperimentData(parentID: subfeature.parentID, cohortID: cohort.name, enrollmentDate: Date()))
                 return cohort.name
             }
         }

Sources/PixelExperimentKit/ExperimentEventTracker.swift

@@ -0,0 +1,80 @@
+//
+//  ExperimentEventTracker.swift
+//
+//  Copyright © 2024 DuckDuckGo. All rights reserved.
+//
+//  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.
+//
+
+import Foundation
+
+public typealias ThresholdCheckResult = Bool
+public typealias ExprimentPixelNameAndParameters = String
+public typealias NumberOfActions = Int
+
+public protocol ExperimentActionPixelStore {
+     func removeObject(forKey defaultName: String)
+     func integer(forKey defaultName: String) -> Int
+     func set(_ value: Int, forKey defaultName: String)
+ }
+
+public protocol ExperimentEventTracking {
+    /// Increments the count for a given event key and checks if the threshold has been exceeded.
+    ///
+    /// This method performs the following actions:
+    /// 1. If the `isInWindow` parameter is `false`, it removes the stored count for the key and returns `false`.
+    /// 2. If `isInWindow` is `true`, it increments the count for the key.
+    /// 3. If the updated count meets or exceeds the specified `threshold`, the stored count is removed, and the method returns `true`.
+    /// 4. If the updated count does not meet the threshold, it updates the count and returns `false`.
+    ///
+    /// - Parameters:
+    ///   - key: The key used to store and retrieve the count.
+    ///   - threshold: The count threshold that triggers a return of `true`.
+    ///   - isInWindow: A flag indicating if the count should be considered (e.g., within a time window).
+    /// - Returns: `true` if the threshold is exceeded and the count is reset, otherwise `false`.
+    func incrementAndCheckThreshold(forKey key: ExprimentPixelNameAndParameters, threshold: NumberOfActions, isInWindow: Bool) -> ThresholdCheckResult
+}
+
+public struct ExperimentEventTracker: ExperimentEventTracking {
+    private let store: ExperimentActionPixelStore
+    private let syncQueue = DispatchQueue(label: "com.pixelkit.experimentActionSyncQueue")
+
+    public init(store: ExperimentActionPixelStore = UserDefaults.standard) {
+        self.store = store
+    }
+
+    public func incrementAndCheckThreshold(forKey key: ExprimentPixelNameAndParameters, threshold: NumberOfActions, isInWindow: Bool) -> ThresholdCheckResult {
+        syncQueue.sync {
+            // Remove the key if is not in window
+            guard isInWindow else {
+                store.removeObject(forKey: key)
+                return false
+            }
+
+            // Increment the current count
+            let currentCount = store.integer(forKey: key)
+            let newCount = currentCount + 1
+            store.set(newCount, forKey: key)
+
+            // Check if the threshold is exceeded
+            if newCount >= threshold {
+                store.removeObject(forKey: key)
+                return true
+            }
+            return false
+        }
+    }
+
+}
+
+extension UserDefaults: ExperimentActionPixelStore {}