io.datakernel.datastream.processor.StreamMapper Maven / Gradle / Ivy

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/*
 * Copyright (C) 2015 SoftIndex LLC.
 *
 * 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.datakernel.datastream.processor;

import io.datakernel.datastream.*;
import io.datakernel.promise.Promise;

import java.util.function.Function;

/**
 * Provides you apply function before sending data to the destination. It is a {@link StreamMapper}
 * which receives specified type and streams set of function's result  to the destination .
 *
 * @param  type of input data
 * @param  type of output data
 */
public final class StreamMapper implements StreamTransformer {
	private final Function function;
	private final Input input;
	private final Output output;

	// region creators
	private StreamMapper(Function function) {
		this.function = function;
		this.input = new Input();
		this.output = new Output();
	}

	public static  StreamMapper create(Function function) {
		return new StreamMapper<>(function);
	}

	@Override
	public StreamConsumer getInput() {
		return input;
	}

	@Override
	public StreamSupplier getOutput() {
		return output;
	}
	// endregion

	protected final class Input extends AbstractStreamConsumer {
		@Override
		protected Promise onEndOfStream() {
			return output.sendEndOfStream();
		}

		@Override
		protected void onError(Throwable e) {
			output.close(e);
		}
	}

	protected final class Output extends AbstractStreamSupplier {
		@Override
		protected void onSuspended() {
			input.getSupplier().suspend();
		}

		@Override
		protected void onError(Throwable e) {
			input.close(e);
		}

		@SuppressWarnings("unchecked")
		@Override
		protected void onProduce(StreamDataAcceptor dataAcceptor) {
			input.getSupplier().resume(
					function == Function.identity() ?
							(StreamDataAcceptor) dataAcceptor :
							item -> dataAcceptor.accept(function.apply(item)));
		}
	}
}