package li.earth.urchin.twic.collections;

import java.util.ListIterator;
import java.util.NoSuchElementException;

public class GeneralBigListIterator<E> implements BigListIterator<E> {
	
	private static final boolean FORWARD = true;
	private static final boolean BACKWARD = false;
	
	private final BigList<E> list;
	private long index; // index of following element
	private boolean directionSet;
	private boolean direction;
	
	public GeneralBigListIterator(BigList<E> list, long index) {
		if ((index < 0L) || (index > list.bigSize())) throw new IndexOutOfBoundsException(Long.toString(index));
		this.list = list;
		this.index = index;
	}
	
	public boolean hasNext() {
		return index < list.bigSize();
	}
	
	public boolean hasPrevious() {
		return index > 0;
	}
	
	public long nextBigIndex() {
		return index;
	}
	
	public int nextIndex() {
		return AbstractBigList.narrow(nextBigIndex());
	}
	
	public long previousBigIndex() {
		return index - 1L;
	}
	
	public int previousIndex() {
		return AbstractBigList.narrow(previousBigIndex());
	}
	
	public E next() {
		if (!hasNext()) throw new NoSuchElementException();
		E obj = list.get(index);
		++index;
		directionSet = true;
		direction = FORWARD;
		return obj;
	}
	
	public E previous() {
		if (!hasPrevious()) throw new NoSuchElementException();
		E obj = list.get(index - 1L);
		--index;
		directionSet = true;
		direction = BACKWARD;
		return obj;
	}
	
	public void add(E obj) {
		list.add(index, obj);
		++index;
		directionSet = false;
	}
	
	public void remove() {
		if (!directionSet) throw new IllegalStateException();
		if (direction == FORWARD) --index;
		list.remove(index);
		directionSet = false;
	}
	
	public void set(E obj) {
		if (!directionSet) throw new IllegalStateException();
		long index = this.index;
		if (direction == FORWARD) --index;
		list.set(index, obj);
	}
	
}