vitusortner

import kotlin.contracts.ExperimentalContracts
import kotlin.contracts.InvocationKind
import kotlin.contracts.contract

@ExperimentalContracts
inline fun guard(predicate: Boolean, block: () -> Nothing) {
    contract {
        returns() implies predicate
        callsInPlace(block, InvocationKind.AT_MOST_ONCE)
    }

vitusortner

/**
 * Applies [transform] to values from the [Observable] and forwards values with non-null results.
 */
inline fun <T : Any, S : Any> Observable<T>.mapNotNull(
    crossinline transform: (T) -> S?
): Observable<S> {
    return this
        .flatMap {
            val result = transform(it)
            if (result == null) {

vitusortner

fun <T> Observable<T>.delaySucceeding(interval: Long, timeUnit: TimeUnit): Observable<T> {
    return Observable.merge(
        this.take(1),
        this.skip(1).delayEach(interval, timeUnit)
    )
}

private fun <T> Observable<T>.delayEach(interval: Long, timeUnit: TimeUnit): Observable<T> {
    return Observable.zip(
        this,