Copyright (c) 2016-present, RxJava Contributors.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is
distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
the License for the specific language governing permissions and limitations under the License.
/**
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
 * the License for the specific language governing permissions and limitations under the License.
 */

package io.reactivex.internal.operators.single;

import java.util.*;
import java.util.concurrent.Callable;

import org.reactivestreams.Publisher;

import io.reactivex.*;
import io.reactivex.Observable;
import io.reactivex.functions.Function;

Helper utility class to support Single with inner classes.
/**
 * Helper utility class to support Single with inner classes.
 */
public final class SingleInternalHelper {

    
Utility class. /** Utility class. */
    private SingleInternalHelper() {
        throw new IllegalStateException("No instances!");
    }

    enum NoSuchElementCallable implements Callable<NoSuchElementException> {
        INSTANCE;

        @Override
        public NoSuchElementException call() throws Exception {
            return new NoSuchElementException();
        }
    }

    public static <T> Callable<NoSuchElementException> emptyThrower() {
        return NoSuchElementCallable.INSTANCE;
    }

    @SuppressWarnings("rawtypes")
    enum ToFlowable implements Function<SingleSource, Publisher> {
        INSTANCE;
        @SuppressWarnings("unchecked")
        @Override
        public Publisher apply(SingleSource v) {
            return new SingleToFlowable(v);
        }
    }

    @SuppressWarnings({ "rawtypes", "unchecked" })
    public static <T> Function<SingleSource<? extends T>, Publisher<? extends T>> toFlowable() {
        return (Function)ToFlowable.INSTANCE;
    }

    static final class ToFlowableIterator<T> implements Iterator<Flowable<T>> {
        private final Iterator<? extends SingleSource<? extends T>> sit;

        ToFlowableIterator(Iterator<? extends SingleSource<? extends T>> sit) {
            this.sit = sit;
        }

        @Override
        public boolean hasNext() {
            return sit.hasNext();
        }

        @Override
        public Flowable<T> next() {
            return new SingleToFlowable<T>(sit.next());
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }
    }

    static final class ToFlowableIterable<T> implements Iterable<Flowable<T>> {

        private final Iterable<? extends SingleSource<? extends T>> sources;

        ToFlowableIterable(Iterable<? extends SingleSource<? extends T>> sources) {
            this.sources = sources;
        }

        @Override
        public Iterator<Flowable<T>> iterator() {
            return new ToFlowableIterator<T>(sources.iterator());
        }
    }

    public static <T> Iterable<? extends Flowable<T>> iterableToFlowable(final Iterable<? extends SingleSource<? extends T>> sources) {
        return new ToFlowableIterable<T>(sources);
    }

    @SuppressWarnings("rawtypes")
    enum ToObservable implements Function<SingleSource, Observable> {
        INSTANCE;
        @SuppressWarnings("unchecked")
        @Override
        public Observable apply(SingleSource v) {
            return new SingleToObservable(v);
        }
    }

    @SuppressWarnings({ "rawtypes", "unchecked" })
    public static <T> Function<SingleSource<? extends T>, Observable<? extends T>> toObservable() {
        return (Function)ToObservable.INSTANCE;
    }
}