WatchInfo.swift - Quickly get connected Apple Watch and installed Watch app state

WatchInfo.swift

//
//  WatchInfo.swift
//
//  Created by AppleBetas on 2016-12-10.
//  Copyright © 2016 AppleBetas. All rights reserved.
//

import Foundation
import WatchConnectivity

class WatchInfo: NSObject, WCSessionDelegate {
    private var session: WCSession?
    weak var delegate: WatchInfoDelegate?
    
    override init() {
        super.init()
        if WCSession.isSupported() {
            session = WCSession.default()
        }
        oldAppState = _appState
        session?.delegate = self
    }
    
    enum WatchAppState {
        case unsupported, noWatch, notInstalled, installed
        
        var description: String {
            switch self {
            case .unsupported:
                return "This device does not support pairing with Apple Watch."
            case .noWatch:
                return "No Apple Watch is paired with iPhone."
            case .notInstalled:
                return "This app is not installed on the paired Apple Watch."
            case .installed:
                return "This app is installed on the paired Apple Watch."
            }
        }
    }
    
    // What state is the watch app in
    var appState: WatchAppState {
        let appState = _appState
        oldAppState = appState
        return appState
    }
    
    private var _appState: WatchAppState {
        if let session = session {
            if session.isPaired {
                if session.isWatchAppInstalled {
                    return .installed
                }
                return .notInstalled
            }
            return .noWatch
        }
        return .unsupported
    }
    private var oldAppState: WatchAppState!
    
    var complicationEnabled: Bool {
        if appState == .installed {
            return session?.isComplicationEnabled ?? false
        }
        return false
    }
    
    // MARK - Watch Session Delegate
    
    func sessionWatchStateDidChange(_ session: WCSession) {
        let currentState = _appState
        if currentState != oldAppState {
            // New app state
            oldAppState = currentState
            delegate?.watchAppStateChanged(to: _appState)
        }
    }
    
    func session(_ session: WCSession, activationDidCompleteWith activationState: WCSessionActivationState, error: Error?) {}
    func sessionDidBecomeInactive(_ session: WCSession) {}
    func sessionDidDeactivate(_ session: WCSession) {}
}

protocol WatchInfoDelegate: class {
    func watchAppStateChanged(to watchAppState: WatchInfo.WatchAppState)
}