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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.Sequence;

import javax.annotation.concurrent.Immutable;

@Immutable
public abstract class SequenceCursor
        implements Cursor
{
    public static  Cursor of(Sequence sequence)
    {
        return StandardCursor.of(new SequenceSource(sequence));
    }

    @Immutable
    private static class SequenceSource
            implements StandardCursor.Source
    {
        private final Sequence sequence;

        private SequenceSource(Sequence sequence)
        {
            this.sequence = sequence;
        }

        @Override
        public boolean atEnd()
        {
            return sequence.isEmpty();
        }

        @Override
        public T currentValue()
        {
            return sequence.getHead();
        }

        @Override
        public StandardCursor.Source advance()
        {
            return new SequenceSource(sequence.getTail());
        }
    }
}