Add filterSome and filterNone extensions for Flowable, Maybe and Sing…

…le. (#12)

koptional-rxjava2-extensions/src/main/kotlin/com/gojuno/koptional/rxjava2/rxjava2.kt

@@ -3,9 +3,15 @@ package com.gojuno.koptional.rxjava2
 import com.gojuno.koptional.None
 import com.gojuno.koptional.Optional
 import com.gojuno.koptional.Some
+import io.reactivex.Flowable
+import io.reactivex.Maybe
 import io.reactivex.Observable
+import io.reactivex.Single
 
 private inline fun <reified R : Any> Observable<*>.ofType(): Observable<R> = ofType(R::class.java)
+private inline fun <reified R : Any> Flowable<*>.ofType(): Flowable<R> = ofType(R::class.java)
+private inline fun <reified R : Any> Maybe<*>.ofType(): Maybe<R> = ofType(R::class.java)
+private inline fun <reified R : Any> Single<*>.ofType(): Maybe<R> = filter { it is R }.cast(R::class.java)
 
 /**
  * Filters items emitted by an ObservableSource by only emitting those that are `Some`.
@@ -21,6 +27,48 @@ private inline fun <reified R : Any> Observable<*>.ofType(): Observable<R> = ofT
  */
 fun <T : Any> Observable<Optional<T>>.filterSome(): Observable<T> = ofType<Some<T>>().map { it.value }
 
+/**
+ * Filters items emitted by a Publisher by only emitting those that are `Some`.
+ * <p>
+ * <img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/filter.png" alt="">
+ * <dl>
+ *  <dt><b>Scheduler:</b></dt>
+ *  <dd>{@code filter} does not operate by default on a particular {@link Scheduler}.</dd>
+ * </dl>
+ *
+ * @return an Flowable that emits `Some.value` of those items emitted by the source Publisher that are `Some`.
+ * @see <a href="http://reactivex.io/documentation/operators/filter.html">ReactiveX operators documentation: Filter</a>
+ */
+fun <T : Any> Flowable<Optional<T>>.filterSome(): Flowable<T> = ofType<Some<T>>().map { it.value }
+
+/**
+ * Filters items emitted by an MaybeSource by only emitting those that are `Some`.
+ * <p>
+ * <img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/filter.png" alt="">
+ * <dl>
+ *  <dt><b>Scheduler:</b></dt>
+ *  <dd>{@code filter} does not operate by default on a particular {@link Scheduler}.</dd>
+ * </dl>
+ *
+ * @return an Maybe that emits `Some.value` of those items emitted by the source MaybeSource that are `Some`.
+ * @see <a href="http://reactivex.io/documentation/operators/filter.html">ReactiveX operators documentation: Filter</a>
+ */
+fun <T : Any> Maybe<Optional<T>>.filterSome(): Maybe<T> = ofType<Some<T>>().map { it.value }
+
+/**
+ * Filters items emitted by an SingleSource by only emitting those that are `Some`.
+ * <p>
+ * <img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/filter.png" alt="">
+ * <dl>
+ *  <dt><b>Scheduler:</b></dt>
+ *  <dd>{@code filter} does not operate by default on a particular {@link Scheduler}.</dd>
+ * </dl>
+ *
+ * @return an Maybe that emits `Some.value` of those items emitted by the source SingleSource that are `Some`.
+ * @see <a href="http://reactivex.io/documentation/operators/filter.html">ReactiveX operators documentation: Filter</a>
+ */
+fun <T : Any> Single<Optional<T>>.filterSome(): Maybe<T> = ofType<Some<T>>().map { it.value }
+
 /**
  * Filters items emitted by an ObservableSource by only emitting those that are `None`.
  * <p>
@@ -34,3 +82,45 @@ fun <T : Any> Observable<Optional<T>>.filterSome(): Observable<T> = ofType<Some<
  * @see <a href="http://reactivex.io/documentation/operators/filter.html">ReactiveX operators documentation: Filter</a>
  */
 fun <T : Any> Observable<Optional<T>>.filterNone(): Observable<Unit> = ofType<None>().map { Unit }
+
+/**
+ * Filters items emitted by an Publisher by only emitting those that are `None`.
+ * <p>
+ * <img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/filter.png" alt="">
+ * <dl>
+ *  <dt><b>Scheduler:</b></dt>
+ *  <dd>{@code filter} does not operate by default on a particular {@link Scheduler}.</dd>
+ * </dl>
+ *
+ * @return an Flowable that emits `Unit` for each item emitted by the source Publisher that is `None`.
+ * @see <a href="http://reactivex.io/documentation/operators/filter.html">ReactiveX operators documentation: Filter</a>
+ */
+fun <T : Any> Flowable<Optional<T>>.filterNone(): Flowable<Unit> = ofType<None>().map { Unit }
+
+/**
+ * Filters items emitted by an MaybeSource by only emitting those that are `None`.
+ * <p>
+ * <img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/filter.png" alt="">
+ * <dl>
+ *  <dt><b>Scheduler:</b></dt>
+ *  <dd>{@code filter} does not operate by default on a particular {@link Scheduler}.</dd>
+ * </dl>
+ *
+ * @return an Maybe that emits `Unit` for each item emitted by the source MaybeSource that is `None`.
+ * @see <a href="http://reactivex.io/documentation/operators/filter.html">ReactiveX operators documentation: Filter</a>
+ */
+fun <T : Any> Maybe<Optional<T>>.filterNone(): Maybe<Unit> = ofType<None>().map { Unit }
+
+/**
+ * Filters items emitted by an SingleSource by only emitting those that are `None`.
+ * <p>
+ * <img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/filter.png" alt="">
+ * <dl>
+ *  <dt><b>Scheduler:</b></dt>
+ *  <dd>{@code filter} does not operate by default on a particular {@link Scheduler}.</dd>
+ * </dl>
+ *
+ * @return an Maybe that emits `Unit` for each item emitted by the source SingleSource that is `None`.
+ * @see <a href="http://reactivex.io/documentation/operators/filter.html">ReactiveX operators documentation: Filter</a>
+ */
+fun <T : Any> Single<Optional<T>>.filterNone(): Maybe<Unit> = ofType<None>().map { Unit }