WiFiScanUseCase.kt

class WiFiScanUseCase(private val context: Context) {
    
  private val wifiManager =
        context.applicationContext.getSystemService(Context.WIFI_SERVICE) as WifiManager

    private val wifiSSID = "My Network"

    operator fun invoke(): Completable {
        return startScanning()
    }

    private fun startScanning(): Completable {
        return Completable.create { emitter ->
            val intentFilter = IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION)
            val receiver = object : BroadcastReceiver() {
                override fun onReceive(ctx: Context?, intent: Intent?) {
                    val resultList = wifiManager.scanResults.toList()
                    val cmrList = resultList.filter { it.SSID == wifiSSID }
                    Timber.v("Filtered list: ${cmrList.map { it.SSID }}")
                    when {
                        cmrList.size == 1 -> emitter.onComplete()
                        cmrList.isEmpty() -> emitter.tryOnError(IllegalArgumentException("Can not find a device."))
                        else -> emitter.tryOnError(IllegalArgumentException("More than one items found."))
                    }
                }
            }

            Timber.v("Scanning for wifi networks...")
            context.registerReceiver(receiver, intentFilter)
            emitter.setCancellable {
                Timber.v("Unregistering scanning for wifi networks...")
                context.unregisterReceiver(receiver)
            }
            if (!wifiManager.startScan()) {
                Timber.w("error startScan")
                emitter.onError(IllegalArgumentException("Failed to start scan"))
            }
        }
    }
}