/*
* 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.stream.processor;
import com.google.common.base.Function;
import io.datakernel.eventloop.Eventloop;
import io.datakernel.stream.StreamConsumer;
import java.util.Comparator;
import static com.google.common.base.Preconditions.checkNotNull;
/**
* Merges sorted by keys streams and streams its sorted union. It is simple
* {@link AbstractStreamReducer} which do nothing with data and only streams it
* sorted by keys.
*
* @param <K> type of key for mapping
* @param <T> type of output data
*/
public final class StreamMerger<K, T> extends AbstractStreamReducer<K, T, Void> {
private final Function<T, K> keyFunction;
private final StreamReducers.Reducer<K, T, T, Void> reducer;
// region creators
private StreamMerger(Eventloop eventloop, Function<T, K> keyFunction, Comparator<K> keyComparator,
boolean deduplicate) {
super(eventloop, keyComparator);
this.keyFunction = checkNotNull(keyFunction);
this.reducer = deduplicate ? StreamReducers.<K, T>mergeDeduplicateReducer() : StreamReducers.<K, T>mergeSortReducer();
}
/**
* Returns new instance of StreamMerger
*
* @param eventloop eventloop in which runs reducer
* @param keyComparator comparator for compare keys
* @param keyFunction function for counting key
* @param deduplicate if it is true it means that in result will be not objects with same key
* @param <K> type of key for mapping
* @param <T> type of output data
*/
public static <K, T> StreamMerger<K, T> create(Eventloop eventloop, Function<T, K> keyFunction,
Comparator<K> keyComparator,
boolean deduplicate) {
return new StreamMerger<K, T>(eventloop, keyFunction, keyComparator, deduplicate);
}
// endregion
/**
* Adds new consumer to StreamMerger
*
* @return this consumer
*/
public StreamConsumer<T> newInput() {
return super.newInput(keyFunction, reducer);
}
}