package listFW.visitor;

import listFW.*;

public class Invert implements IListAlgo {

    private IListFactory _fact;

    public Invert(IListFactory f) {
        _fact = f;
    }

    public Object emptyCase(IEmptyList host, Object nu) {
        return host;
    }

    public Object nonEmptyCase(INEList host, Object nu) {
        IList accRev = _fact.makeNEList(host.getFirst(),
                                  _fact.makeEmptyList());
        return host.getRest ().execute(new IListAlgo() {

            public Object emptyCase(IEmptyList h, Object acc) {
                // TO DO
                return acc;
            }

            public Object nonEmptyCase(INEList h, Object acc) {
                //TO DO
                return h.getRest().execute (this,
                                  _fact.makeNEList(h.getFirst(), (IList)acc));
            }
        }  // end of anonymous local inner class
        , accRev);  // accumulated reverse passed to the helper as input.
    }
}