retryWhenSample3.kt

internal typealias RETRY_PREDICATE = (Throwable) -> Boolean

internal const val MAX_RETRIES = 3L
internal const val DEFAULT_INTERVAL = 1L

internal val TIMEOUT: RETRY_PREDICATE = { it is SocketTimeoutException }
internal val NETWORK: RETRY_PREDICATE = { it is IOException }
internal val SERVICE_UNAVAILABLE: RETRY_PREDICATE = { it is HttpException && it.code() == 503 }

internal fun <T> applyRetryPolicy(
    vararg predicates: RETRY_PREDICATE, 
    maxRetries: Long = MAX_RETRIES, 
    interval: Long = DEFAULT_INTERVAL, 
    unit: TimeUnit = TimeUnit.SECONDS,
    resumeNext: (Throwable) -> SingleSource<T>
) = SingleTransformer<T, T> { single ->
    single.retryWhen { attempts ->
        Flowables.zip(
            attempts.map { error -> if (predicates.count { it(error) } > 0) error else throw error },
            Flowable.interval(interval, unit)
        ).map { (error, retryCount) -> if (retryCount >= maxRetries) throw error }
    }.onErrorResumeNext(resumeNext)
}