RamCache.kt

import rx.Single

class RamCache<in K, V>(val factory: (K) -> Single<V>): (K) -> Single<V> {
    private val cache: MutableMap<K, V> = mutableMapOf()
    private val requests: MutableMap<K, Single<V>> = mutableMapOf()

    fun clear() {
        cache.clear()
        requests.clear()
    }

    override fun invoke(key: K): Single<V> {
        val c = cache[key]
        return if (c != null)
            Single.just(c)
        else {
            if (requests[key] != null) {
                requests[key]!!
            } else {
                factory(key)
                        .apply {
                            requests[key] = this
                        }
                        .doOnSuccess {
                            cache[key] = it
                            requests.remove(key)
                        }
                        .doOnError {
                            requests.remove(key)
                        }
                        .doOnUnsubscribe {
                            requests.remove(key)
                        }
            }
        }
    }
}