Reachability.swift

/*
Copyright (c) 2014, Ashley Mills
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/

import SystemConfiguration
import Foundation

enum ReachabilityError: Error {
    case FailedToCreateWithAddress(sockaddr_in)
    case FailedToCreateWithHostname(String)
    case UnableToSetCallback
    case UnableToSetDispatchQueue
    case UnableToGetInitialFlags
}

@available(*, unavailable, renamed: "Notification.Name.reachabilityChanged")
let ReachabilityChangedNotification = NSNotification.Name("ReachabilityChangedNotification")

extension Notification.Name {
    static let reachabilityChanged = Notification.Name("reachabilityChanged")
}

class Reachability {

    typealias NetworkReachable = (Reachability) -> ()
    typealias NetworkUnreachable = (Reachability) -> ()

    @available(*, unavailable, renamed: "Connection")
    enum NetworkStatus: CustomStringConvertible {
        case notReachable, reachableViaWiFi, reachableViaWWAN
        var description: String {
            switch self {
            case .reachableViaWWAN: return "Cellular"
            case .reachableViaWiFi: return "WiFi"
            case .notReachable: return "No Connection"
            }
        }
    }

    enum Connection: CustomStringConvertible {
        case none, wifi, cellular
        var description: String {
            switch self {
            case .cellular: return "Cellular"
            case .wifi: return "WiFi"
            case .none: return "No Connection"
            }
        }
    }

    var whenReachable: NetworkReachable?
    var whenUnreachable: NetworkUnreachable?

    /// Set to `false` to force Reachability.connection to .none when on cellular connection (default value `true`)
    var allowsCellularConnection: Bool

    // The notification center on which "reachability changed" events are being posted
    var notificationCenter: NotificationCenter = NotificationCenter.default

    @available(*, unavailable, renamed: "connection")
    var currentReachabilityStatus: Connection {
        return connection
    }

    var connection: Connection {
        if flags == nil {
            try? setReachabilityFlags()
        }
        
        switch flags?.connection {
        case .none?, nil: return .none
        case .cellular?: return allowsCellularConnection ? .cellular : .none
        case .wifi?: return .wifi
        }
    }

    fileprivate var isRunningOnDevice: Bool = {
        #if targetEnvironment(simulator)
            return false
        #else
            return true
        #endif
    }()

    fileprivate var notifierRunning = false
    fileprivate let reachabilityRef: SCNetworkReachability
    fileprivate let reachabilitySerialQueue: DispatchQueue
    fileprivate(set) var flags: SCNetworkReachabilityFlags? {
        didSet {
            guard flags != oldValue else { return }
            reachabilityChanged()
        }
    }

    required init(reachabilityRef: SCNetworkReachability, queueQoS: DispatchQoS = .default, targetQueue: DispatchQueue? = nil) {
        self.allowsCellularConnection = true
        self.reachabilityRef = reachabilityRef
        self.reachabilitySerialQueue = DispatchQueue(label: "uk.co.ashleymills.reachability", qos: queueQoS, target: targetQueue)
    }

    convenience init?(hostname: String, queueQoS: DispatchQoS = .default, targetQueue: DispatchQueue? = nil) {
        guard let ref = SCNetworkReachabilityCreateWithName(nil, hostname) else { return nil }
        self.init(reachabilityRef: ref, queueQoS: queueQoS, targetQueue: targetQueue)
    }

    convenience init?(queueQoS: DispatchQoS = .default, targetQueue: DispatchQueue? = nil) {
        var zeroAddress = sockaddr()
        zeroAddress.sa_len = UInt8(MemoryLayout<sockaddr>.size)
        zeroAddress.sa_family = sa_family_t(AF_INET)

        guard let ref = SCNetworkReachabilityCreateWithAddress(nil, &zeroAddress) else { return nil }

        self.init(reachabilityRef: ref, queueQoS: queueQoS, targetQueue: targetQueue)
    }

    deinit {
        stopNotifier()
    }
}

extension Reachability {

    // MARK: - *** Notifier methods ***
    func startNotifier() throws {
        guard !notifierRunning else { return }

        let callback: SCNetworkReachabilityCallBack = { (reachability, flags, info) in
            guard let info = info else { return }

            let reachability = Unmanaged<Reachability>.fromOpaque(info).takeUnretainedValue()
            reachability.flags = flags
        }

        var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil)
        context.info = UnsafeMutableRawPointer(Unmanaged<Reachability>.passUnretained(self).toOpaque())
        if !SCNetworkReachabilitySetCallback(reachabilityRef, callback, &context) {
            stopNotifier()
            throw ReachabilityError.UnableToSetCallback
        }

        if !SCNetworkReachabilitySetDispatchQueue(reachabilityRef, reachabilitySerialQueue) {
            stopNotifier()
            throw ReachabilityError.UnableToSetDispatchQueue
        }

        // Perform an initial check
        try setReachabilityFlags()

        notifierRunning = true
    }

    func stopNotifier() {
        defer { notifierRunning = false }

        SCNetworkReachabilitySetCallback(reachabilityRef, nil, nil)
        SCNetworkReachabilitySetDispatchQueue(reachabilityRef, nil)
    }

    var description: String {
        guard let flags = flags else { return "unavailable flags" }
        let W = isRunningOnDevice ? (flags.isOnWWANFlagSet ? "W" : "-") : "X"
        let R = flags.isReachableFlagSet ? "R" : "-"
        let c = flags.isConnectionRequiredFlagSet ? "c" : "-"
        let t = flags.isTransientConnectionFlagSet ? "t" : "-"
        let i = flags.isInterventionRequiredFlagSet ? "i" : "-"
        let C = flags.isConnectionOnTrafficFlagSet ? "C" : "-"
        let D = flags.isConnectionOnDemandFlagSet ? "D" : "-"
        let l = flags.isLocalAddressFlagSet ? "l" : "-"
        let d = flags.isDirectFlagSet ? "d" : "-"

        return "\(W)\(R) \(c)\(t)\(i)\(C)\(D)\(l)\(d)"
    }
}

fileprivate extension Reachability {

    func setReachabilityFlags() throws {
        try reachabilitySerialQueue.sync { [unowned self] in
            var flags = SCNetworkReachabilityFlags()
            if !SCNetworkReachabilityGetFlags(self.reachabilityRef, &flags) {
                self.stopNotifier()
                throw ReachabilityError.UnableToGetInitialFlags
            }
            
            self.flags = flags
        }
    }
    
    func reachabilityChanged() {
        let block = connection != .none ? whenReachable : whenUnreachable

        DispatchQueue.main.async { [weak self] in
            guard let strongSelf = self else { return }
            block?(strongSelf)
            strongSelf.notificationCenter.post(name: .reachabilityChanged, object: strongSelf)
        }
    }
}

extension SCNetworkReachabilityFlags {

    typealias Connection = Reachability.Connection

    var connection: Connection {
        guard isReachableFlagSet else { return .none }

        // If we're reachable, but not on an iOS device (i.e. simulator), we must be on WiFi
        #if targetEnvironment(simulator)
        return .wifi
        #else
        var connection = Connection.none

        if !isConnectionRequiredFlagSet {
            connection = .wifi
        }

        if isConnectionOnTrafficOrDemandFlagSet {
            if !isInterventionRequiredFlagSet {
                connection = .wifi
            }
        }

        if isOnWWANFlagSet {
            connection = .cellular
        }

        return connection
        #endif
    }

    var isOnWWANFlagSet: Bool {
        #if os(iOS)
        return contains(.isWWAN)
        #else
        return false
        #endif
    }
    var isReachableFlagSet: Bool {
        return contains(.reachable)
    }
    var isConnectionRequiredFlagSet: Bool {
        return contains(.connectionRequired)
    }
    var isInterventionRequiredFlagSet: Bool {
        return contains(.interventionRequired)
    }
    var isConnectionOnTrafficFlagSet: Bool {
        return contains(.connectionOnTraffic)
    }
    var isConnectionOnDemandFlagSet: Bool {
        return contains(.connectionOnDemand)
    }
    var isConnectionOnTrafficOrDemandFlagSet: Bool {
        return !intersection([.connectionOnTraffic, .connectionOnDemand]).isEmpty
    }
    var isTransientConnectionFlagSet: Bool {
        return contains(.transientConnection)
    }
    var isLocalAddressFlagSet: Bool {
        return contains(.isLocalAddress)
    }
    var isDirectFlagSet: Bool {
        return contains(.isDirect)
    }
    var isConnectionRequiredAndTransientFlagSet: Bool {
        return intersection([.connectionRequired, .transientConnection]) == [.connectionRequired, .transientConnection]
    }
}