SeqValue.java

package moulder.values;

import moulder.Value;

import java.util.*;

/**
 * A value that sequentially generates the items it was supplied with
 *
 * @param <T> the resulting values type
 * @author jawher
 */
public class SeqValue<T> implements Value<T> {
    private Iterator<T> values;

    public SeqValue(Iterator<T> values) {
        super();
        this.values = values;
    }

    public SeqValue(Iterable<T> values) {
        this.values = values.iterator();
    }

    public SeqValue(T... values) {
        this.values = Arrays.asList(values).iterator();
    }

    public T get() {
        return values.hasNext() ? values.next() : null;
    }

    public SeqValue<T> cycle() {
        return new SeqValue<T>(new CyclingIterator<T>(values));
    }

    private static final class CyclingIterator<S> implements Iterator<S> {
        private Iterator<S> it;
        private final boolean itHasValues;
        private final List<S> values = new ArrayList<S>();
        private boolean cycled = false;

        public CyclingIterator(Iterator<S> it) {
            this.it = it;
            itHasValues = it.hasNext();
        }

        public boolean hasNext() {
            return itHasValues;
        }

        public S next() {
            if (!itHasValues) {
                throw new NoSuchElementException();
            }
            if (it.hasNext()) {
                S res = it.next();
                if (!cycled) {
                    values.add(res);
                }
                return res;
            } else {
                cycled = true;
                it = values.iterator();
                return next();
            }
        }

        public void remove() {

        }

    }

    public SeqValue<T> repeatLast() {
        return new SeqValue<T>(new RepeatLastIterator<T>(values));
    }

    private static final class RepeatLastIterator<S> implements Iterator<S> {
        private Iterator<S> it;
        private final boolean itHasValues;
        private S last;

        public RepeatLastIterator(Iterator<S> it) {
            this.it = it;
            itHasValues = it.hasNext();
        }

        public boolean hasNext() {
            return itHasValues;
        }

        public S next() {
            if (!itHasValues) {
                throw new NoSuchElementException();
            }
            if (it.hasNext()) {
                last = it.next();
            }
            return last;
        }

        public void remove() {

        }

    }
}