import UIKit
import Alamofire

enum ReachabilityManagerError: Error {
    case notReachable
}

struct ReachabilityManager {

    /// singleton
    static let `default` : ReachabilityManager = {
        let manager = ReachabilityManager()
        // configuration
        return manager
    }()

    /// Alamofire (NetworkReachabilityManager)
    let networkManager = NetworkReachabilityManager()!

    /// key to send notification by changing the status of the network
    let listenerNetworkStatusChanged = NSNotification.Name(rawValue:"NSNotificationKeyListenerNetworkStatusChanged")

//MARK:-
//MARK: check network

    /// check internet connection
    ///
    /// - returns: network status
    func checkInternetConnection() -> Bool {
        switch networkManager.networkReachabilityStatus {
        case NetworkReachabilityManager.NetworkReachabilityStatus.notReachable, NetworkReachabilityManager.NetworkReachabilityStatus.unknown:
            return false
        default:
            return true
        }
    }

    /// check internet connection (throws)
    ///
    /// - throws: in the absence of network
    func checkConnection() throws {
        switch networkManager.networkReachabilityStatus {
        case NetworkReachabilityManager.NetworkReachabilityStatus.notReachable,
             NetworkReachabilityManager.NetworkReachabilityStatus.unknown:
            throw ReachabilityManagerError.notReachable
        default: return
        }
    }

//MARK:-
//MARK: listening

    /// start
    ///
    func startNetworkListening() {
        networkManager.listener = { status in

            /// - unknown:      It is unknown whether the network is reachable.
            /// - notReachable: The network is not reachable.
            /// - reachable:    The network is reachable.

            NotificationCenter.default.post(name: self.listenerNetworkStatusChanged,
                                            object: nil,
                                            userInfo: ["NetworkStatus": status])
        }

        networkManager.startListening()
    }

    /// stop
    ///
    func stopNetworkListening() {
        networkManager.stopListening()
    }

}