//
//  Reachability.swift
//
//  Created by Amr Salman on 4/4/17.
//
//
import Foundation
import SystemConfiguration
import UIKit
import SystemConfiguration.CaptiveNetwork

public let ReachabilityStatusChangedNotification = "ReachabilityStatusChangedNotification"

public enum ReachabilityType: CustomStringConvertible {
  case WWAN
  case WiFi

  public var description: String {
    switch self {
    case .WWAN: return "WWAN"
    case .WiFi: return "WiFi"
    }
  }
}

public enum ReachabilityStatus: CustomStringConvertible  {
  case Offline
  case Online(ReachabilityType)
  case Unknown

  public var description: String {
    switch self {
    case .Offline: return "Offline"
    case .Online(let type): return "Online (\(type))"
    case .Unknown: return "Unknown"
    }
  }
}

public class Reachability {

  public init() { }

  public func connectionStatus() -> ReachabilityStatus {
    var zeroAddress = sockaddr_in()
    zeroAddress.sin_len = UInt8(MemoryLayout.size(ofValue: zeroAddress))
    zeroAddress.sin_family = sa_family_t(AF_INET)

    guard let defaultRouteReachability = (withUnsafePointer(to: &zeroAddress) {
      $0.withMemoryRebound(to: sockaddr.self, capacity: 1) { zeroSockAddress in
        SCNetworkReachabilityCreateWithAddress(nil, zeroSockAddress)
      }
    }) else {
      return .Unknown
    }

    var flags : SCNetworkReachabilityFlags = []
    if !SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) {
      return .Unknown
    }

    return ReachabilityStatus(reachabilityFlags: flags)
  }

  public func monitorReachabilityChanges() {
    let host = "google.com"
    var context = SCNetworkReachabilityContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil)
    let reachability = SCNetworkReachabilityCreateWithName(nil, host)!

    SCNetworkReachabilitySetCallback(reachability, { (_, flags, _) in
      let status = ReachabilityStatus(reachabilityFlags: flags)

      NotificationCenter.default.post(name: NSNotification.Name(rawValue: ReachabilityStatusChangedNotification), object: nil, userInfo: ["Status": status.description])}, &context)

    SCNetworkReachabilityScheduleWithRunLoop(reachability, CFRunLoopGetMain(), CFRunLoopMode.commonModes.rawValue)
  }
}

extension ReachabilityStatus {

  public init(reachabilityFlags flags: SCNetworkReachabilityFlags) {
    let connectionRequired = flags.contains(.connectionRequired)
    let isReachable = flags.contains(.reachable)
    let isWWAN = flags.contains(.isWWAN)

    if !connectionRequired && isReachable {
      if isWWAN {
        self = .Online(.WWAN)
      } else {
        self = .Online(.WiFi)
      }
    } else {
      self =  .Offline
    }
  }
}