Transfer Target

data class MyTransferData(
    val id: String,
    val token: String
)

class MySampleTarget {

    val target: WPTTarget
    
    val config = WPTConfig(
        ParcelUuid.fromString("21f8190c-e4bc-11ed-b5ea-0242ac120001"), 
        WPTCoder.aes(
            "MyApplicationDemoSalt!".toByteArray(), // static data
            "7x9ZEvEVf4IqlBxuYmzKhw==".decodeBase64()!!.toByteArray() // 16 bytes encoded in Base64
        )
    )

    constructor(appContext: Context) {
        this.target = WPTTarget(appContext, config)
        this.target.start { result ->
            result.onSuccess {
                try {
                    // target start success, start QR scanning
                    // following is an example of how to process the scanned QR code
                    val scannedQRCode = "base64encodedStringRetrievedByQRScanner"
                    val plain = qrContent.decodeBase64()!!
                    val decoded = target.decode(plain.toByteArray())
                    val decodedString = String(decoded)
                    val result = Gson().fromJson(decodedString, MyTransferData::class.java)
                } catch (e: Exception) {
                    // process exception
                }
            }.onFailure { error ->
                if (error is WPTTargetError) {
                    // process WPTTargetError
                }
            }
        }
    }
} 

class WPTTarget {

    /**
     * Creates a new target.
     *  
     * @param context The application context.   
     * @param config The configuration of the target.
     */
    constructor(context: Context, config: WPTConfig)

    /**
     * Starts the broadcasting.
     *
     * @param completion The completion callback. When an error occurs, it is the type of [WPTTargetError]
     */
    fun start(completion: (Result<Unit>) -> Unit)
    
    /**
     * Stops the broadcasting.
     *
     * @param completion The completion callback. When an error occurs, it is the type of [WPTTargetError].
     */
    fun stop(completion: (Result<Unit>) -> Unit)
    
    /** Returns true if the target is broadcasting. */
    fun isRunning(): Bool
    
    /**
     * Decodes the data scanned via QR scanner
     *
     * @param data Data scanned via QR scanner.
     * @return Decoded data.
     */
    @Throws fun decode(data: ByteArray): ByteArray
}

class WPTTargetError: Throwable {

    /** The reason of the error. */
    val reason: Reason
    /** The permission that is missing in case of the [Reason.BLUETOOTH_PERMISSION_NOT_GRANTED]. */
    val permission: String?

    enum class Reason {
        /** Already started or stopped */
        WRONG_STATE,
        /** Bluetooth permission not granted. Use WPTPermissions to ask for permissions. */
        BLUETOOTH_PERMISSION_NOT_GRANTED,
        /** Bluetooth is turned off. */
        BLUETOOTH_NOT_ENABLED,
        /** Bluetooth is not supported by this device. */
        BLUETOOTH_MISSING,
        /** Data for the Bluetooth are too large (this is a library/platform error). */
        DATA_TOO_LARGE,
        /** Bluetooth is not supported by this device. */
        FEATURE_UNSUPPORTED,
        /** Internal Bluetooth error */
        INTERNAL_ERROR,
        /** Too many advertisers are advertising */
        TOO_MANY_ADVERTISERS,
        /** Unknown error */
        UNKNOWN