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.maybe;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;

Maps the upstream success value into some other value.
Type parameters:
<T> – the upstream value type
<R> – the downstream value type/**
 * Maps the upstream success value into some other value.
 *
 * @param <T> the upstream value type
 * @param <R> the downstream value type
 */
public final class MaybeMap<T, R> extends AbstractMaybeWithUpstream<T, R> {

    final Function<? super T, ? extends R> mapper;

    public MaybeMap(MaybeSource<T> source, Function<? super T, ? extends R> mapper) {
        super(source);
        this.mapper = mapper;
    }

    @Override
    protected void subscribeActual(MaybeObserver<? super R> observer) {
        source.subscribe(new MapMaybeObserver<T, R>(observer, mapper));
    }

    static final class MapMaybeObserver<T, R> implements MaybeObserver<T>, Disposable {

        final MaybeObserver<? super R> downstream;

        final Function<? super T, ? extends R> mapper;

        Disposable upstream;

        MapMaybeObserver(MaybeObserver<? super R> actual, Function<? super T, ? extends R> mapper) {
            this.downstream = actual;
            this.mapper = mapper;
        }

        @Override
        public void dispose() {
            Disposable d = this.upstream;
            this.upstream = DisposableHelper.DISPOSED;
            d.dispose();
        }

        @Override
        public boolean isDisposed() {
            return upstream.isDisposed();
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.validate(this.upstream, d)) {
                this.upstream = d;

                downstream.onSubscribe(this);
            }
        }

        @Override
        public void onSuccess(T value) {
            R v;

            try {
                v = ObjectHelper.requireNonNull(mapper.apply(value), "The mapper returned a null item");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                downstream.onError(ex);
                return;
            }

            downstream.onSuccess(v);
        }

        @Override
        public void onError(Throwable e) {
            downstream.onError(e);
        }

        @Override
        public void onComplete() {
            downstream.onComplete();
        }
    }
}