ListenSDPandCandidate.swift

func listenSdp(from person: String) {
    Firestore.firestore().collection(person).document("sdp")
      .addSnapshotListener { documentSnapshot, error in
        guard let document = documentSnapshot else {
          print("Error fetching sdp: \(error!)")
          return
        }
        guard let data = document.data() else {
          print("Firestore sdp data was empty.")
          return
        }
        print("Firestore sdp data: \(data)")
        do {
          let jsonData = try JSONSerialization.data(withJSONObject: data, options: .prettyPrinted)
          let sessionDescription = try self.decoder.decode(SessionDescription.self, from: jsonData)
          self.delegate?.signalClient(self, didReceiveRemoteSdp: sessionDescription.rtcSessionDescription)
        }
        catch {
          debugPrint("Warning: Could not decode sdp data: \(error)")
          return
        }
    }
  }
  
  func listenCandidate(from person: String) {
    Firestore.firestore()
      .collection(person)
      .document("candidate")
      .collection("candidates")
      .addSnapshotListener { (querySnapshot, err) in
        guard let documents = querySnapshot?.documents else {
          print("Error fetching documents: \(err!)")
          return
        }

        querySnapshot!.documentChanges.forEach { diff in
          if (diff.type == .added) {
            do {
              let jsonData = try JSONSerialization.data(withJSONObject: documents.first!.data(), options: .prettyPrinted)
              let iceCandidate = try self.decoder.decode(IceCandidate.self, from: jsonData)
              self.delegate?.signalClient(self, didReceiveCandidate: iceCandidate.rtcIceCandidate)
            }
            catch {
              debugPrint("Warning: Could not decode candidate data: \(error)")
              return
            }
          }
        }
    }
  }