mixpanel-swift/Sources/SessionMetadata.swift

//
//  Metadata.swift
//  Mixpanel
//
//  Created by Yarden Eitan on 10/24/17.
//  Copyright © 2017 Mixpanel. All rights reserved.
//

import Foundation

class SessionMetadata {
  var eventsCounter: UInt64 = 0
  var peopleCounter: UInt64 = 0
  var sessionID: String = String.randomId()
  var sessionStartEpoch: UInt64 = 0
  var trackingQueue: DispatchQueue

  init(trackingQueue: DispatchQueue) {
    self.trackingQueue = trackingQueue
  }

  func applicationWillEnterForeground() {
    trackingQueue.async { [weak self] in
      guard let self = self else { return }

      self.eventsCounter = 0
      self.peopleCounter = 0
      self.sessionID = String.randomId()
      self.sessionStartEpoch = UInt64(Date().timeIntervalSince1970)
    }
  }

  func toDict(isEvent: Bool = true) -> InternalProperties {
    let dict: [String: Any] = [
      "$mp_metadata": [
        "$mp_event_id": String.randomId(),
        "$mp_session_id": sessionID,
        "$mp_session_seq_id": (isEvent ? eventsCounter : peopleCounter),
        "$mp_session_start_sec": sessionStartEpoch,
      ] as [String: Any]
    ]
    isEvent ? (eventsCounter += 1) : (peopleCounter += 1)
    return dict
  }
}

extension String {
  fileprivate static func randomId() -> String {
    return String(format: "%08x%08x", arc4random(), arc4random())
  }
}