/**
 * A FingerprintAuth handles communication with a specific fingerprint api,
 * MarshmallowDelegate and SpassDelegate,
 * also by  FingerprintAuthManager that is exposed to client.
 */

interface FingerprintAuth {

    companion object {
        /**
         * Factory method:
         * first tries to take MarshmallowDelegate
         * if failed - device doesn't support Android's Fingerprint Authentication Api
         * than takes SpassDelegate.
         * if failed - device doesn't have fingerprint scanning sensor,
         * than StubDelegate is return
         */
        fun getDelegate(context: Context) =
                           take { MarshmallowDelegate(context) }
                        ?: take { SpassDelegate(context) }
                        ?: take { StubDelegate() }

        private fun <T> take (create: () -> T): T? {
            return try {
                create.invoke()
            } catch (ignored: Exception) {
                null
            }
        }
    }

    /**
     * Checks if device has fingerprint scanning sensor
     */
    fun isSupportedByPlatform(): Boolean

    /**
     * Checks if the feature is usable: enabled and enrolled
     */
    fun isUsable(): Boolean

    /**
     * Start a fingerprint authentication request
     * if both isSupportedByPlatform() and isUsable() return true
     * it should be possible to call this method
     *
     * @param callback A listener that will be notified of the authentication result.
     */
    fun startFingerprintScan(callback: AuthCallback)

    /**
     * Stop a fingerprint authentication request
     */
    fun stopFingerprintScan()


    interface AuthCallback {
        /**
         * Fingerprint successfully validated callback
         */
        fun onAuthenticationSucceeded()
       /**
         * Unrecoverable error callback
         * @param error unified error that is exposed to user
         * @param type  retry auth on {@link Type.RECOVERABLE}
         *              restart auth on {@link Type.UNRECOVERABLE}
         */
       fun onAuthenticationError (error: AuthError, type: Type)
        /**
         * Fingerprint auth failed callback
         */
        fun onAuthenticationFailed()
    }

}