enum Events {
    enum User : String, Event {
        case didSelectBeatle
        case didSelectAlbum
        case didRateAlbum
    }

    enum App : String, Event {
        case started
        case didBecomeActive
        case didEnterBackground
        case terminated
    }

    enum AlbumListVC : String, Event {
        case didAppear
    }
}

enum Keys : String, Key {
    case beatleName
    case albumName
    case userLikesAlbum
    case previousVC

    enum App : String, Key {
        case uptime
        case reachabilityStatus
    }
}

// Example:

import UIKit
import Trackable

class AlbumDetailVC: UIViewController {

    var album : Album!

    @IBOutlet weak var yesButton: UIButton!
    @IBOutlet weak var noButton: UIButton!

    @IBAction func didPressButton(sender: UIButton) {
        let userLikesAlbum = (sender === yesButton)
        track(Events.User.didRateAlbum, trackedProperties: [Keys.userLikesAlbum ~>> userLikesAlbum])
    }
}

extension AlbumDetailVC : TrackableClass { }

// Example:
track(Events.User.didRateAlbum, trackedProperties: [Keys.userLikesAlbum ~>> userLikesAlbum])

// Example:
import UIKit
import Trackable

class AlbumListTVC: UITableViewController {
	… code …

    // MARK: - Navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        let destinationVC = segue.destinationViewController as! AlbumDetailVC
        destinationVC.setupTrackableChain([Keys.previousVC ~>> "Album list"]) // all events tracked on destinationVC will have previousVC property included automatically
    }
}

extension AlbumListTVC : TrackableClass { }

// Example:
class AlbumListTVC: UITableViewController {
    var albums : [Album]!

    override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
        track(Events.User.didSelectAlbum) // selectedAlbum property will be added automatically
    }

    var selectedAlbum : Album? {
        if let indexPath = tableView.indexPathForSelectedRow {
            return albums[indexPath.row]
        } else {
            return nil
        }
    }
}

extension AlbumListTVC : TrackableClass {
    var trackedProperties : Set<TrackedProperty> {
        return [Keys.albumName ~>> selectedAlbum?.name ?? "none"]
    }
}

// Example:
import UIKit
import Trackable

class AlbumListTVC: UITableViewController {

	… some code here …

    // MARK: - Navigation
    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
        let destinationVC = segue.destinationViewController as! AlbumDetailVC
        destinationVC.setupTrackableChain([Keys.previousVC ~>> "Album list"], parent: self)
    }

    var selectedAlbum : Album? {
        if let indexPath = tableView.indexPathForSelectedRow {
            return albums[indexPath.row]
        } else {
            return nil
        }
    }
}

extension AlbumListTVC : TrackableClass {
    var trackedProperties : Set<TrackedProperty> {
        return [Keys.albumName ~>> selectedAlbum?.name ?? "none"]
    }
}

// All events tracked later on destinationVC will automatically have previousVC and albumName properties,
// without destinationVC even knowing those values exist!

// Example:
import Foundation
import Mixpanel
import Trackable

let analytics = Analytics() // singleton (yay!)

class Analytics {
    let mixpanel = Mixpanel.sharedInstanceWithToken("<token>")

    init() {
        Trackable.trackEventToRemoteServiceClosure = trackEventToMixpanel
        setupTrackableChain() // allows self to be part of the trackable chain
    }

    func trackEventToMixpanel(eventName: String, trackedProperties: [String: AnyObject]) {        
        mixpanel.track(eventName, properties: trackedProperties)
    }
}

extension Analytics : TrackableClass { }

extension Analytics : TrackableClass {
    var trackedProperties : Set<TrackedProperty> {
        return [Keys.App.uptime ~>> NSDate().timeIntervalSinceDate(startTime)]
    }
}

// Example:
import UIKit
import Trackable

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    var window: UIWindow?

    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject : AnyObject]?) -> Bool {
        setupTrackableChain(parent: analytics)
        return true
    }

    func applicationDidBecomeActive(application: UIApplication) {
        track(Events.App.didBecomeActive)
    }

    func applicationDidEnterBackground(application: UIApplication) {
        track(Events.App.didEnterBackground)
    }

    func applicationWillTerminate(application: UIApplication) {
        track(Events.App.terminated)
    }

}

extension AppDelegate : TrackableClass { }