AmplitudeUserPropertiesUpdater.swift

import Amplitude_iOS
import Foundation
import ReactiveSwift
import UIKit

public final class AmplitudeUserPropertiesUpdater {
    private enum Constants {
        static let keyPrefix = "remoteSettings"

        static let applicationStateKey = "applicationState"
    }

    private let amplitude: Amplitude
    private let notificationCenter: NotificationCenter
    private let remoteSettings: RemoteConfig

    private let disposable = SerialDisposable()

    public static let shared = AmplitudeUserPropertiesUpdater()

    private init(
        amplitude: Amplitude = .instance(),
        notificationCenter: NotificationCenter = .default,
        remoteSettings: RemoteConfig = .shared
    ) {
        self.amplitude = amplitude
        self.notificationCenter = notificationCenter
        self.remoteSettings = remoteSettings
    }

    public func start() {
        disposable.inner = SignalProducer
            .merge(
                notificationsForApplicationState(),
                notificationsForRemoteSettings()
            )
            .startWithValues { [weak self] in self?.update() }
    }

    private func notificationsForApplicationState() -> SignalProducer<Void, Never> {
        SignalProducer
            .merge(
                notificationCenter.reactive.notifications(
                    forName: UIApplication.didEnterBackgroundNotification
                ),
                notificationCenter.reactive.notifications(
                    forName: UIApplication.willEnterForegroundNotification
                ),
                notificationCenter.reactive.notifications(
                    forName: UIApplication.didBecomeActiveNotification
                ),
                notificationCenter.reactive.notifications(
                    forName: UIApplication.willResignActiveNotification
                )
            )
            .map { _ in }
    }

    private func notificationsForRemoteSettings() -> SignalProducer<Void, Never> {
        remoteSettings
            .observer()
            .skipError()
            .map { _ in }
            .producer
    }

    private func update() {
        amplitude.clearUserProperties()

        var newUserProperties: [String: String] = [:]

        if let allKeyValues = remoteSettings.allKeyValues {
            let keysWithValues = allKeyValues
                .map { ("\(Constants.keyPrefix):\($0.key)", $0.value) }

            newUserProperties.merge(
                keysWithValues,
                uniquingKeysWith: { _, new in new }
            )
        }

        let app = UIApplication.shared
        newUserProperties[Constants.applicationStateKey] =
            app.applicationState.description

        amplitude.setUserProperties(newUserProperties)
    }
}

final class AmplitudeAppDelegate: NSObject {
    private let updater: AmplitudeUserPropertiesUpdater = .shared
}

// MARK: - UIApplicationDelegate

extension AmplitudeAppDelegate: UIApplicationDelegate {
    func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        updater.start()

        return true
    }
}