Reachability.swift

import Foundation
import SystemConfiguration

class Reachability {
    var hostname: String?
    var isRunning = false
    var isReachableOnWWAN: Bool
    var reachability: SCNetworkReachability?
    var reachabilityFlags = SCNetworkReachabilityFlags()
    let reachabilitySerialQueue = DispatchQueue(label: "ReachabilityQueue")
    init(hostname: String) throws {
        guard let reachability = SCNetworkReachabilityCreateWithName(nil, hostname) else {
            throw Network.Error.failedToCreateWith(hostname)
        }
        self.reachability = reachability
        self.hostname = hostname
        isReachableOnWWAN = true
        try start()
    }
    
    init() throws {
        var zeroAddress = sockaddr_in()
        zeroAddress.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
        zeroAddress.sin_family = sa_family_t(AF_INET)
        guard let reachability = withUnsafePointer(to: &zeroAddress, {
            $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
                SCNetworkReachabilityCreateWithAddress(nil, $0)
            }
        }) else {
            throw Network.Error.failedToInitializeWith(zeroAddress)
        }
        self.reachability = reachability
        isReachableOnWWAN = true
        try start()
    }
    func callout(reachability: SCNetworkReachability, flags: SCNetworkReachabilityFlags, info: UnsafeMutableRawPointer?) {
        guard let info = info else { return }
        DispatchQueue.main.async {
            Unmanaged<Reachability>
                .fromOpaque(info)
                .takeUnretainedValue()
                .flagsChanged()
        }
    }
    var status: Network.Status {
        return  !isConnectedToNetwork ? .unreachable :
            isReachableViaWiFi    ? .wifi :
            isRunningOnDevice     ? .wwan : .unreachable
    }
    var isRunningOnDevice: Bool = {
        #if targetEnvironment(simulator)
        return false
        #else
        return true
        #endif
    }()
    deinit { stop() }
    
    
    struct Network {
        static var reachability: Reachability!
        enum Status: String {
            case unreachable, wifi, wwan
        }
        enum Error: Swift.Error {
            case failedToSetCallout
            case failedToSetDispatchQueue
            case failedToCreateWith(String)
            case failedToInitializeWith(sockaddr_in)
        }
    }
}