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package com.github.andyshao.util.stream;

import com.github.andyshao.util.CollectionOperation;

import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.BaseStream;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

/**
 * 
 * 
 * Title:

 * Descript:

 * Copyright: Copryright(c) May 27, 2019

 * Encoding: UNIX UTF-8
 * 
 * @author Andy.Shao
 *
 */
public final class StreamOperation {
	/**
	 * all of matched
	 * @param stream {@link Stream}
	 * @param predicate {@link Predicate}
	 * @return {@link Pair}
	 * @param  data type
	 */
	public static  Pair, Boolean> allOfMatched(Stream stream, Predicate predicate) {
		List ls = stream.filter(predicate)
			.collect(Collectors.toList());
		return CollectionOperation.isEmptyOrNull(ls) ? Pair.of(ls, false) : Pair.of(ls, true);
	}

	/**
	 * any match
	 * @param stream {@link Stream}
	 * @param predicate {@link Predicate}
	 * @return {@link Pair}
	 * @param  data type
	 */
	public static  Pair anyMatch(Stream stream, Predicate predicate) {
		Optional op = stream.filter(predicate)
			.findAny();
		return op.isPresent() ? Pair.of(op.get(), true) : Pair.of(null, false);
	}

	/**
	 * distinct
	 * @param stream {@link Stream}
	 * @param keyExtractor key extractor
	 * @return {@link Stream}
	 * @param  data type
	 */
	public static  Stream distinct(Stream stream, Function keyExtractor) {
		return stream.filter(distinctByKey(keyExtractor));
	}

	/**
	 * distinct by key
	 * @param keyExtractor key extractor
	 * @return {@link Predicate}
	 * @param  data type
	 */
	public static  Predicate distinctByKey(Function keyExtractor) {
		Map seen = new ConcurrentHashMap<>();
		return t -> seen.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
	}

	/**
	 * first match
	 * @param stream {@link Stream}
	 * @param predicate {@link Predicate}
	 * @return {@link Pair}
	 * @param  data type
	 */
	public static  Pair firstMatch(Stream stream, Predicate predicate) {
		Optional op = stream.filter(predicate)
			.findFirst();
		return op.isPresent() ? Pair.of(op.get(), true) : Pair.of(null, false);
	}

	/**
	 * value of
	 * @param stream {@link BaseStream}
	 * @return {@link Stream}
	 * @param  data type
	 * @param  {@link BaseStream} type
	 */
	public static > Stream valueOf(BaseStream stream) {
		return valueOf(stream, false);
	}

	/**
	 * value of
	 * @param stream {@link BaseStream}
	 * @param parallel is parallel mode
	 * @return {@link Stream}
	 * @param  data type
	 * @param  {@link BaseStream} type
	 */
	public static > Stream valueOf(BaseStream stream, boolean parallel) {
		return StreamSupport.stream(stream.spliterator(), parallel);
	}
	
	private StreamOperation() {}
}