import edu.neu.ccs.demeterf.ID;
import edu.neu.ccs.demeterf.Traversal;
import edu.neu.ccs.demeterf.control.EdgeControl;
import edu.neu.ccs.demeterf.control.Edge;
import edu.neu.ccs.demeter.Ident;


public class Eval extends ID{
    static Env<Value> empty = Env.<Value>empty();
    Traversal trav;

    static Value doEval(Exp e, ClassList c){
        Eval eval = new ConstrEval(c);
        EdgeControl ctrl = EdgeControl.create(new Edge(IfExp.class, "thn"),
                                              new Edge(IfExp.class, "els"),
                                              /*[*/new Edge(Assign.class, "sym"),
                                              /*]*/new Edge(RevDef.class, "rest"));
        ctrl.addBuiltIns(Ident.class,UserT.class,SymExp.class,SymMethExp.class);
        eval.trav = new Traversal(eval, ctrl);
        return eval.eval(e, empty);
    }
    Value eval(Object e, Env<Value> env){ return trav.traverse(e, env); }
    ValueList eval(AssignList a, Env<Value> env){ return trav.traverse(a, env); }/*[*/
    ValueList combine(EmptyList e){ return new ValueEmpty(); }
    ValueList combine(ConsList c, Value f, ValueList r){ return r.push(f); }/*]*/
}

class LitEval extends Eval{
    Value combine(IntLit lit, int i){ return new IntV(i); }
    Value combine(BoolLit lit, boolean b){ return new BoolV(b); }
}

class ExpEval extends LitEval{
    Value combine(AddExp e, IntV l, IntV r){ return l.add(r); }
    Value combine(MultExp e, IntV l, IntV r){ return l.mult(r); }
    Value combine(NegExp e, IntV l){ return new IntV(-l.val); }
    Value combine(LessExp e, IntV l, IntV r){ return l.less(r); }
    Value combine(AndExp e, BoolV l, BoolV r){ return l.and(r); }

    Value combine(IfExp f, BoolV c, Exp t, Exp e, Env<Value> env){
        return eval((c.val?t:e), env);
    }
}

class ConstrEval extends MethodEval{
    ConDescList constr;
    ConstrEval(ClassList c){ super(c); constr = Methods.conEnv(c); }

    Value combine(NewExp n, UserT t, ValueList args, Env<Value> env){
        ConDesc c = constr.find(t);
        ValueList vl = eval(c.body, empty.push(c.flds.env())
                                         .push(args.env())),
                  obj = vl.pop(args.length());
        if(obj.hasNull())throw new RunErr("Uninitialized Fields!");
        return new ObjV(t, obj);
    }
    ValueList combine(Assign a, AddrExp f, Value v, Env<Value> env){
        return ValueList.from(env.replace(v, f.addr));
    }
    ValueList combine(AssignCons c, ValueList f, ValueEmpty r){ return f; }
    ValueList combine(AssignCons c, ValueList f, ValueCons r){ return f.merge(r); }
} 

class MethodEval extends ExpEval{
    ClassMethList mthds;
    MethodEval(ClassList c){ mthds = Methods.methEnv(c); }
 
    Value combine(CallExp c, ObjV v, SymMethExp m, ValueList args, Env<Value> env){
        MethDesc meth = mthds.findMethod(v.type, m.id);
        Env<Value> nenv = empty.push(v.fields.env())
                               .push(v).push(args.env());
        return eval(meth.body, nenv);
    }
    Value combine(AddrExp a, int addr, Env<Value> env){ return env.get(addr); }
    Value combine(RevDef rd, Value v, RevDefRest rst, Env<Value> env)
      { return eval(rst.rest, env.push(v)); }
    Value combine(Return r, Value v){ return v; }
}