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package org.aksw.commons.collections.utils;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import com.google.common.collect.AbstractIterator;

public class StreamUtils {

    public static  Stream> mapToBatch(Stream stream, long batchSize) {

        Iterator baseIt = stream.iterator();

        Iterator> it = new AbstractIterator>() {
            @Override
            protected List computeNext() {
                List items = new ArrayList<>((int)batchSize);
                for(int i = 0; baseIt.hasNext() && i < batchSize; ++i) {
                    T item = baseIt.next();
                    items.add(item);
                }

                List r = items.isEmpty()
                        ? endOfData()
                        : items;

                return r;
            }
        };

        Iterable> tmp = () -> it;
        Stream> result = StreamUtils.stream(tmp);
        result.onClose(() -> stream.close());
        return result;
    }

    public static  Stream stream(Iterator it) {
        Iterable i = () -> it;
        return stream(i);
    }

    public static  Stream stream(Iterable i) {
        Stream result = StreamSupport.stream(i.spliterator(), false);
        return result;
    }


    /**
     * Creates a new stream which upon reaching its end performs and action.
     * It concatenates the original stream with one having a single item
     * that is filtered out again. The action is run as- part of the filter.
     *
     * @param stream
     * @param runnable
     * @return
     */
    public static  Stream appendAction(Stream stream, Runnable runnable) {
        Stream result = Stream.concat(
                stream,
                Stream
                    .of((T)null)
                    .filter(x -> {
                        runnable.run();
                        return false;
                    })
                );
        return result;
    }

    // TODO Add to StreamUtils
    public static  Stream stream(BiConsumer> fn, S baseSolution) {
        List result = new ArrayList<>();

        fn.accept(baseSolution, (item) -> result.add(item));

        return result.stream();
    }

}