taler-ios

TagEmulation.swift (7515B)

---

 //
 //  TagEmulation.swift
 //  HCEtest
 //
 //  Created by Marc Stibane on 2024-09-01.
 //
 
 import CoreNFC
 import os.log
 
 @available(iOS 17.7, *)
 @MainActor
 class TagEmulation: ObservableObject {
     public static let shared = TagEmulation()
     @Published var canUseHCE: Bool = false
 
     nonisolated let logger = Logger(subsystem: "net.taler.gnu", category: "TagEmulation")
     private var cardSession: CardSession? = nil
     private var presentmentIntent: NFCPresentmentIntentAssertion? = nil
 
     init() {
         if NFCReaderSession.readingAvailable {
             if CardSession.isSupported {
                 Task {
                     if await CardSession.isEligible {
                         logger.info("CardSession is eligible")
                         canUseHCE = true
                     } else { logger.error("❗️CardSession is not eligible"); canUseHCE = false }
                 }
             } else { logger.error("❗️CardSession is not supported"); canUseHCE = false }
         } else { logger.error("❗️NFCReaderSession is not available"); canUseHCE = false }
     }
 
     func emulateTag(_ emulatedData: String) {
         Task() {
             let result = await startEmulation(emulatedData)
             if result {
                 logger.info("Emulation was successful")
             } else {
                 logger.warning("❗️Emulation was not successful")
             }
         }
     }
 
     private func startEmulation(_ emulatedData: String) async -> Bool {
         // Hold a presentment intent assertion reference to prevent the
         // default contactless app from launching. In a real app, monitor
         // presentmentIntent.isValid to ensure the assertion remains active.
         var result = false
 
         guard emulatedData.count < 8192 else { return false }
         do {
             if presentmentIntent == nil {
                 presentmentIntent = try await NFCPresentmentIntentAssertion.acquire()
                 /// The presentment intent assertion expires if any of the following occur:
                 /// • The presentment intent assertion object deinitializes.
                 /// • Your app goes into the background.
                 /// • 15 seconds elapse.
                 /// After the presentment intent assertion expires, you must wait through a 15-second cool-down period before you can acquire a new instance.
                 logger.info("NFCPresentmentIntentAssertion acquired")
             } else {
                 logger.info("NFCPresentmentIntentAssertion exists")
             }
             if cardSession == nil {
                 cardSession = try await CardSession()
                 logger.info("CardSession launched")
             } else {
                 logger.info("❗️Yikes! CardSession exists")
             }
             if let cardSession {
                 logger.info("cardSession.startEmulation (without waiting for reader)")
                 try await cardSession.startEmulation()
 
                 logger.info("starting eventStream")
                 try await eventStream(cardSession, data: emulatedData)
                 logger.info("eventStream finished")
 
                 try? await Task.sleep(nanoseconds: 1_000_000_000 * 3)
 
                 logger.info("cardSession.invalidate")
                 await cardSession.invalidate()
                 result = true
             }
             cardSession = nil
         } catch let error {
             // Handle failure to acquire NFC presentment intent assertion or card session.
             logger.error("❗️NFCPresentmentIntentAssertion not possible: \(error.localizedDescription)")
             DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
                 self.presentmentIntent = nil /// Release presentment intent assertion.
             }
             return false
         }
         return result
     }
 
     func killEmulation() {
         Task() {
             if let session = cardSession {
                 await session.invalidate()
                 cardSession = nil
             }
             logger.info("NFCPresentmentIntentAssertion released")
             DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
                 if self.cardSession == nil {        // don't release if there is a new session
                     self.presentmentIntent = nil    // release presentment intent assertion
                 }
             }
         }
     }
 
     private func eventStream(_ mySession: CardSession, data emulatedData: String) async throws {
         let apdu = try APDU(emulatedData)
         // Iterate over events as the card session produces them.
         for try await event in mySession.eventStream {
 //            if presentmentIntent?.isValid ?? false {
                 switch event {
                     case .sessionStarted:
 #if DEBUG
                         let message = "sessionStarted"
                         mySession.alertMessage = message
                         logger.info("\(message)")
 #endif
                         break
 
                     case .readerDetected:
                         /// Start card emulation on first detection of an external reader.
                         logger.info("readerDetected")
 //                        logger.info("cardSession.startEmulation")
 //                        try await mySession.startEmulation()
 
                     case .readerDeselected:
                         /// Stop emulation on first notification of RF link loss.
                         logger.info("❗️readerDeselected. cardSession.stopEmulation")
                         await mySession.stopEmulation(status: .success)
                         return
 
                     case .received(let cardAPDU):
                         do {
                             /// Call handler to process received input and produce a response.
                             let responseAPDU = apdu.processAPDU(cardAPDU.payload)
 
                             logger.info("sending back data: \(responseAPDU.hexEncodedString())")
                             try await cardAPDU.respond(response: responseAPDU)
                         } catch {
                             /// Handle the error from respond(response:). If the error is
                             /// CardSession.Error.transmissionError, then retry by calling
                             /// CardSession.APDU.respond(response:) again.
                             logger.error("❗️Error while responding: \(error)")
                         }
 
                     case .sessionInvalidated(reason: _):
 #if DEBUG
                         mySession.alertMessage = "Ending communication with card reader."
                         logger.info("❗️cardSession invalidation")
 #endif
                         /// Handle the reason for session invalidation.
                         await mySession.stopEmulation(status: .failure)
                         return
 
                     default:
 #if DEBUG
                         let message = "Unknown event from card reader."
                         mySession.alertMessage = message
                         logger.info("❗️\(message)")
 #endif
                         break
                 }
 //            } else {
 //                logger.error("❗️presentmentIntent is not valid")
 //                await mySession.stopEmulation(status: .failure)
 //                presentmentIntent = nil /// Release presentment intent assertion.
 //                                        // TODO: stop eventStream?
 //            }
         } // cardSession.eventStream
     }
 }