[Config] Port 'ConfigExperiment' to Swift

FirebaseRemoteConfig/SwiftNew/ConfigExperiment.swift

@@ -0,0 +1,192 @@
+// Copyright 2024 Google LLC
+//
+// 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 FirebaseABTesting
+import Foundation
+
+/// Handles experiment information update and persistence.
+/*@objc(RCNConfigExperiment)*/ open class ConfigExperiment: NSObject {
+  private static let experimentMetadataKeyLastStartTime = "last_experiment_start_time"
+  private static let serviceOrigin = "frc"
+
+  private var experimentPayloads: [Data]
+  private var experimentMetadata: [String: Any]?
+  private var activeExperimentPayloads: [Data]
+  private let dbManager: ConfigDBManager?
+  private let experimentController: ExperimentController
+  private let experimentStartTimeDateFormatter: DateFormatter
+
+  /// Designated initializer;
+  public init(DBManager: ConfigDBManager?,
+              experimentController controller: ExperimentController?) {
+    experimentPayloads = []
+    experimentMetadata = [:]
+    activeExperimentPayloads = []
+    experimentStartTimeDateFormatter = {
+      let dateFormatter = DateFormatter()
+      dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
+      dateFormatter.timeZone = TimeZone(secondsFromGMT: 0)
+      // Locale needs to be hardcoded. See
+      // https://developer.apple.com/library/ios/#qa/qa1480/_index.html for more details.
+      dateFormatter.locale = Locale(identifier: "en_US_POSIX")
+      // TODO(ncooke3): Trace back and see why timeZone is set twice.
+      dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
+      return dateFormatter
+    }()
+    dbManager = DBManager
+    experimentController = controller!
+    super.init()
+    loadExperimentFromTable()
+  }
+
+  private func loadExperimentFromTable() {
+    guard let dbManager else { return }
+
+    let completionHandler: (Bool, [String: Sendable]?) -> Void = { [weak self] _, result in
+      guard let self else { return }
+
+      if result?[ConfigConstants.experimentTableKeyPayload] != nil {
+        self.experimentPayloads.removeAll()
+        if let experiments = result?[ConfigConstants.experimentTableKeyPayload] as? [Data] {
+          for experiment in experiments {
+            do {
+              try JSONSerialization.jsonObject(with: experiment)
+              self.experimentPayloads.append(experiment)
+            } catch {
+              RCLog.warning("I-RCN000031", "Experiment payload could not be parsed as JSON.")
+            }
+          }
+        }
+      }
+
+      if result?[ConfigConstants.experimentTableKeyMetadata] != nil {
+        self
+          .experimentMetadata =
+          result?[ConfigConstants.experimentTableKeyMetadata] as? [String: Any]
+      }
+
+      if result?[ConfigConstants.experimentTableKeyActivePayload] != nil {
+        self.activeExperimentPayloads.removeAll()
+        if let experiments = result?[ConfigConstants.experimentTableKeyActivePayload] as? [Data] {
+          for experiment in experiments {
+            do {
+              try JSONSerialization.jsonObject(with: experiment)
+              self.activeExperimentPayloads.append(experiment)
+            } catch {
+              RCLog.warning(
+                "I-RCN000031",
+                "Activated experiment payload could not be parsed as JSON."
+              )
+            }
+          }
+        }
+      }
+    }
+
+    dbManager.loadExperiment(completionHandler: completionHandler)
+  }
+
+  /// Update/Persist experiment information from config fetch response.
+  open func updateExperiments(withResponse response: [[String: Any]]?) {
+    // Cache fetched experiment payloads.
+    experimentPayloads.removeAll()
+    dbManager?.deleteExperimentTable(forKey: ConfigConstants.experimentTableKeyPayload)
+
+    if let response {
+      for experiment in response {
+        do {
+          let jsonData = try JSONSerialization.data(withJSONObject: experiment)
+          experimentPayloads.append(jsonData)
+          dbManager?
+            .insertExperimentTable(
+              withKey: ConfigConstants.experimentTableKeyPayload,
+              value: jsonData
+            )
+        } catch {
+          RCLog.error("I-RCN000030", "Invalid experiment payload to be serialized.")
+        }
+      }
+    }
+  }
+
+  /// Update experiments to Firebase Analytics when `activateWithCompletion:` happens.
+  open func updateExperiments(handler: (((any Error)?) -> Void)? = nil) {
+    let lifecycleEvent = LifecycleEvents()
+
+    // Get the last experiment start time prior to the latest payload.
+    let lastStartTime = experimentMetadata?[Self.experimentMetadataKeyLastStartTime] as? Double
+
+    // Update the last experiment start time with the latest payload.
+    updateExperimentStartTime()
+    experimentController
+      .updateExperiments(
+        withServiceOrigin: Self.serviceOrigin,
+        events: lifecycleEvent,
+        policy: .discardOldest,
+        lastStartTime: lastStartTime,
+        payloads: experimentPayloads,
+        completionHandler: handler
+      )
+
+    // Update activated experiments payload and metadata in DB.
+    updateActiveExperimentsInDB()
+  }
+
+  private func updateExperimentStartTime() {
+    let existingLastStartTime =
+      experimentMetadata?[Self.experimentMetadataKeyLastStartTime] as? Double
+
+    let latestStartTime = latestStartTime(existingLastStartTime: existingLastStartTime ?? 0)
+
+    experimentMetadata?[Self.experimentMetadataKeyLastStartTime] = latestStartTime
+
+    guard let experimentMetadata, JSONSerialization.isValidJSONObject(experimentMetadata) else {
+      RCLog.error("I-RCN000028", "Invalid fetched experiment metadata to be serialized.")
+      return
+    }
+
+    if let serializedExperimentMetadata = try? JSONSerialization.data(
+      withJSONObject: experimentMetadata,
+      options: .prettyPrinted
+    ) {
+      dbManager?
+        .insertExperimentTable(
+          withKey: ConfigConstants.experimentTableKeyMetadata,
+          value: serializedExperimentMetadata
+        )
+    }
+  }
+
+  private func updateActiveExperimentsInDB() {
+    // Put current fetched experiment payloads into activated experiment DB.
+    activeExperimentPayloads.removeAll()
+    dbManager?.deleteExperimentTable(forKey: ConfigConstants.experimentTableKeyActivePayload)
+    for data in experimentPayloads {
+      activeExperimentPayloads.append(data)
+      dbManager?
+        .insertExperimentTable(
+          withKey: ConfigConstants.experimentTableKeyActivePayload,
+          value: data
+        )
+    }
+  }
+
+  private func latestStartTime(existingLastStartTime: Double) -> TimeInterval {
+    experimentController
+      .latestExperimentStartTimestampBetweenTimestamp(
+        existingLastStartTime,
+        andPayloads: experimentPayloads
+      )
+  }
+}