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/*
 * Copyright (c) 2016-2022 VMware Inc. or its affiliates, All Rights Reserved.
 *
 * 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
 *
 *   https://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 reactor.core.publisher;

import java.util.Objects;
import java.util.function.Function;

import org.reactivestreams.Subscription;
import reactor.core.CorePublisher;
import reactor.core.CoreSubscriber;
import reactor.core.Fuseable;
import reactor.util.annotation.Nullable;

/**
 * Maps the values of the source publisher one-on-one via a mapper function.
 *
 * @param  the source value type
 * @param  the result value type
 *
 * @see Reactive-Streams-Commons
 */
final class FluxMap extends InternalFluxOperator {

	final Function mapper;

	/**
	 * Constructs a FluxMap instance with the given source and mapper.
	 *
	 * @param source the source Publisher instance
	 * @param mapper the mapper function
	 *
	 * @throws NullPointerException if either {@code source} or {@code mapper} is null.
	 */
	FluxMap(Flux source,
			Function mapper) {
		super(source);
		this.mapper = Objects.requireNonNull(mapper, "mapper");
	}

	@Override
	@SuppressWarnings("unchecked")
	public CoreSubscriber subscribeOrReturn(CoreSubscriber actual) {
		if (actual instanceof Fuseable.ConditionalSubscriber) {
			Fuseable.ConditionalSubscriber cs =
					(Fuseable.ConditionalSubscriber) actual;
			return new MapConditionalSubscriber<>(cs, mapper);
		}
		return new MapSubscriber<>(actual, mapper);
	}

	@Override
	public Object scanUnsafe(Attr key) {
		if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;
		return super.scanUnsafe(key);
	}

	static final class MapSubscriber
			implements InnerOperator {

		final CoreSubscriber        actual;
		final Function mapper;

		boolean done;

		Subscription s;

		MapSubscriber(CoreSubscriber actual,
				Function mapper) {
			this.actual = actual;
			this.mapper = mapper;
		}

		@Override
		public void onSubscribe(Subscription s) {
			if (Operators.validate(this.s, s)) {
				this.s = s;

				actual.onSubscribe(this);
			}
		}

		@Override
		public void onNext(T t) {
			if (done) {
				Operators.onNextDropped(t, actual.currentContext());
				return;
			}

			R v;

			try {
				v = mapper.apply(t);
				if (v == null) {
					throw new NullPointerException("The mapper [" + mapper.getClass().getName() + "] returned a null value.");
				}
			}
			catch (Throwable e) {
				Throwable e_ = Operators.onNextError(t, e, actual.currentContext(), s);
				if (e_ != null) {
					onError(e_);
				}
				else {
					s.request(1);
				}
				return;
			}

			actual.onNext(v);
		}

		@Override
		public void onError(Throwable t) {
			if (done) {
				Operators.onErrorDropped(t, actual.currentContext());
				return;
			}

			done = true;

			actual.onError(t);
		}

		@Override
		public void onComplete() {
			if (done) {
				return;
			}
			done = true;

			actual.onComplete();
		}

		@Override
		@Nullable
		public Object scanUnsafe(Attr key) {
			if (key == Attr.PARENT) return s;
			if (key == Attr.TERMINATED) return done;
			if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;

			return InnerOperator.super.scanUnsafe(key);
		}

		@Override
		public CoreSubscriber actual() {
			return actual;
		}

		@Override
		public void request(long n) {
			s.request(n);
		}

		@Override
		public void cancel() {
			s.cancel();
		}
	}

	static final class MapConditionalSubscriber
			implements Fuseable.ConditionalSubscriber, InnerOperator {

		final Fuseable.ConditionalSubscriber actual;
		final Function          mapper;

		boolean done;

		Subscription s;

		MapConditionalSubscriber(Fuseable.ConditionalSubscriber actual,
				Function mapper) {
			this.actual = actual;
			this.mapper = mapper;
		}

		@Override
		public void onSubscribe(Subscription s) {
			if (Operators.validate(this.s, s)) {
				this.s = s;

				actual.onSubscribe(this);
			}
		}

		@Override
		public void onNext(T t) {
			if (done) {
				Operators.onNextDropped(t, actual.currentContext());
				return;
			}

			R v;

			try {
				v = mapper.apply(t);
				if (v == null) {
					throw new NullPointerException("The mapper [" + mapper.getClass().getName() + "] returned a null value.");
				}
			}
			catch (Throwable e) {
				Throwable e_ = Operators.onNextError(t, e, actual.currentContext(), s);
				if (e_ != null) {
					onError(e_);
				}
				else {
					s.request(1);
				}
				return;
			}

			actual.onNext(v);
		}

		@Override
		public boolean tryOnNext(T t) {
			if (done) {
				Operators.onNextDropped(t, actual.currentContext());
				return true;
			}

			R v;

			try {
				v = mapper.apply(t);
				if (v == null) {
					throw new NullPointerException("The mapper [" + mapper.getClass().getName() + "] returned a null value.");
				}
				return actual.tryOnNext(v);
			}
			catch (Throwable e) {
				Throwable e_ = Operators.onNextError(t, e, actual.currentContext(), s);
				if (e_ != null) {
					done = true;
					actual.onError(e_);
					return true;
				}
				else {
					return false;
				}
			}
		}

		@Override
		public void onError(Throwable t) {
			if (done) {
				Operators.onErrorDropped(t, actual.currentContext());
				return;
			}

			done = true;

			actual.onError(t);
		}

		@Override
		public void onComplete() {
			if (done) {
				return;
			}
			done = true;

			actual.onComplete();
		}

		@Override
		@Nullable
		public Object scanUnsafe(Attr key) {
			if (key == Attr.PARENT) return s;
			if (key == Attr.TERMINATED) return done;
			if (key == Attr.RUN_STYLE) return Attr.RunStyle.SYNC;

			return InnerOperator.super.scanUnsafe(key);
		}

		@Override
		public CoreSubscriber actual() {
			return actual;
		}

		@Override
		public void request(long n) {
			s.request(n);
		}

		@Override
		public void cancel() {
			s.cancel();
		}
	}

}