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package org.javimmutable.collections.iterators;

import org.javimmutable.collections.SplitIterator;
import org.javimmutable.collections.SplitableIterator;

import javax.annotation.Nonnull;
import java.util.Spliterator;
import java.util.function.Consumer;

public abstract class AbstractSplitableIterator
    implements SplitableIterator
{
    /**
     * Returns a Spliterator with the specified characteristics that use this
     * Iterator to visit all elements.  Advancing the Spliterator also advances
     * this Iterator so the two cannot be used at the same time.
     */
    @Nonnull
    @Override
    public Spliterator spliterator(int characteristics)
    {
        return new SpliteratorImpl<>(characteristics, this);
    }

    private static class SpliteratorImpl
        implements Spliterator
    {
        private final int characteristics;
        @Nonnull
        private SplitableIterator iterator;

        private SpliteratorImpl(int characteristics,
                                @Nonnull SplitableIterator iterator)
        {
            this.characteristics = characteristics;
            this.iterator = iterator;
        }

        @Override
        public boolean tryAdvance(Consumer action)
        {
            if (iterator.hasNext()) {
                action.accept(iterator.next());
                return true;
            }
            return false;
        }

        @Override
        public Spliterator trySplit()
        {
            if (iterator.isSplitAllowed()) {
                final SplitIterator split = iterator.splitIterator();
                iterator = split.getRight();
                return new SpliteratorImpl<>(characteristics, split.getLeft());
            }
            return null;
        }

        @Override
        public long estimateSize()
        {
            return Long.MAX_VALUE;
        }

        @Override
        public int characteristics()
        {
            return characteristics;
        }
    }
}