FOOM logger

OOM.swift

private final class AppInfo {
    private struct Keys {
        static let lastKnownAppVersion = "app_data.last_known_app_version"
        static let appWasInBackground = "app_data.app_was_in_background"
        static let appWasTerminated = "app_data.app_was_terminated"
    }

    struct State {
        let appVersionIsChanged: Bool
        let appWasInBackground: Bool
        let appWasTerminated: Bool

        func wasFOOM(wasCrash: Bool) -> Bool {
            return !wasCrash && !appVersionIsChanged && !appWasInBackground && !appWasTerminated
        }
    }

    let savedState: State

    init() {
        let currentAppVersion = Bundle.main.appShortVersion

        savedState = State(
            appVersionIsChanged: currentAppVersion != AppInfo.lastKnownAppVersion,
            appWasInBackground: AppInfo.appWasInBackground,
            appWasTerminated: AppInfo.appWasTerminated
        )

        AppInfo.lastKnownAppVersion = currentAppVersion
        AppInfo.appWasInBackground = false
        AppInfo.appWasTerminated = false

        NotificationCenter.default.addObserver(
            self,
            selector: #selector(applicationWillTerminate),
            name: UIApplication.willTerminateNotification,
            object: nil
        )

        NotificationCenter.default.addObserver(
            self,
            selector: #selector(applicationDidEnterBackground),
            name: UIApplication.didEnterBackgroundNotification,
            object: nil
        )

        NotificationCenter.default.addObserver(
            self,
            selector: #selector(applicationWillEnterForeground),
            name: UIApplication.willEnterForegroundNotification,
            object: nil
        )
    }

    deinit {
        NotificationCenter.default.removeObserver(self)
    }

    // MARK: -

    @objc
    private func applicationWillTerminate() {
        AppInfo.appWasTerminated = true
    }

    @objc
    private func applicationDidEnterBackground() {
        AppInfo.appWasInBackground = true
    }

    @objc
    private func applicationWillEnterForeground() {
        AppInfo.appWasInBackground = false
    }

    // MARK: -

    private static var lastKnownAppVersion: String {
        get { return UserDefaults.standard.string(forKey: Keys.lastKnownAppVersion) ?? "" }
        set { UserDefaults.standard.set(newValue, forKey: Keys.lastKnownAppVersion) }
    }

    private static var appWasInBackground: Bool {
        get { return UserDefaults.standard.bool(forKey: Keys.appWasInBackground) }
        set { UserDefaults.standard.set(newValue, forKey: Keys.appWasInBackground) }
    }

    private static var appWasTerminated: Bool {
        get { return UserDefaults.standard.bool(forKey: Keys.appWasTerminated) }
        set { UserDefaults.standard.set(newValue, forKey: Keys.appWasTerminated) }
    }
}