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// Burton Computer Corporation
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package org.javimmutable.collections.cursors;

import org.javimmutable.collections.Cursor;
import org.javimmutable.collections.Tuple2;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;

/**
 * Provides static factory method to create a cursor to combines corresponding values from
 * other cursors into Tuples.
 */
@Immutable
public final class ZipCursor
{
    private ZipCursor()
    {
    }

    public static  Cursor> of(final Cursor cursor1,
                                                     final Cursor cursor2)
    {
        return new AbstractStartCursor>()
        {
            @Nonnull
            @Override
            public Cursor> next()
            {
                return ZipCursor.next(cursor1.next(), cursor2.next());
            }
        };
    }

    private static  Cursor> next(final Cursor cursor1,
                                                        final Cursor cursor2)
    {
        if (!(cursor1.hasValue() && cursor2.hasValue())) {
            return EmptyStartedCursor.of();
        }

        return new AbstractStartedCursor>()
        {
            @Nonnull
            @Override
            public Cursor> next()
            {
                return ZipCursor.next(cursor1.next(), cursor2.next());
            }

            @Override
            public Tuple2 getValue()
            {
                return new Tuple2<>(cursor1.getValue(), cursor2.getValue());
            }
        };
    }
}