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package org.javimmutable.collections.iterators;

import org.javimmutable.collections.Indexed;
import org.javimmutable.collections.SplitIterator;
import org.javimmutable.collections.indexed.IndexedHelper;

import javax.annotation.Nonnull;
import java.util.NoSuchElementException;

public class IndexedIterator
    extends AbstractSplitableIterator
{
    @Nonnull
    private final Indexed values;
    private final int limit;
    private int index;

    private IndexedIterator(@Nonnull Indexed values,
                            int index,
                            int limit)
    {
        this.values = values;
        this.limit = limit;
        this.index = index;
    }

    public static  IndexedIterator iterator(@Nonnull Indexed values)
    {
        return new IndexedIterator<>(values, -1, values.size() - 1);
    }

    public static IndexedIterator forRange(int low,
                                                    int high)
    {
        return iterator(IndexedHelper.range(low, high));
    }

    @Override
    public boolean hasNext()
    {
        return index < limit;
    }

    @Override
    public T next()
    {
        if (index >= limit) {
            throw new NoSuchElementException();
        }
        index += 1;
        return values.get(index);
    }

    @Override
    public boolean isSplitAllowed()
    {
        return (limit - index) > 1;
    }

    @Nonnull
    @Override
    public SplitIterator splitIterator()
    {
        final int splitIndex = index + (limit - index) / 2;
        if (splitIndex == index) {
            throw new UnsupportedOperationException();
        }
        return new SplitIterator<>(new IndexedIterator<>(values, index, splitIndex),
                                   new IndexedIterator<>(values, splitIndex, limit));
    }
}