package jif.extension;

import java.util.ArrayList;
import java.util.List;

import jif.translate.ToJavaExt;
import jif.types.*;
import jif.types.label.Label;
import jif.visit.LabelChecker;
import polyglot.ast.*;
import polyglot.types.*;

/** The Jif extension of the <code>LocalAssign</code> node. 
 */
public class JifLocalAssignExt extends JifAssignExt
{
    public JifLocalAssignExt(ToJavaExt toJava) {
        super(toJava);
    }

    public Node labelCheckLHS(LabelChecker lc)
    throws SemanticException
    {
        final Assign assign = (Assign) node();
        Local lve = (Local) assign.left();

        JifTypeSystem ts = lc.jifTypeSystem();
        JifContext A = lc.jifContext();
        A = (JifContext) lve.del().enterScope(A);

        List throwTypes = new ArrayList(assign.del().throwTypes(ts));

        final LocalInstance li = lve.localInstance();

        Label L = ts.labelOfLocal(li, A.pc());

        Expr rhs = (Expr) lc.context(A).labelCheck(assign.right());
        PathMap Xr = rhsPathMap(lc.context(A), rhs, throwTypes);
        PathMap X;

        if (assign.operator() != Assign.ASSIGN) {
            PathMap Xv = ts.pathMap();
            Xv = Xv.N(A.pc());
            Xv = Xv.NV(lc.upperBound(L, A.pc()));

            if (assign.throwsArithmeticException()) {
                Type arithExc = ts.ArithmeticException();
                checkAndRemoveThrowType(throwTypes, arithExc);
                X = Xv.join(Xr).exc(Xr.NV(), arithExc);
            }
            else {
                X = Xv.join(Xr);
            }
        }
        else {
            X = Xr;
        }

        lc.constrain(new NamedLabel("rhs.nv", 
                                    "label of successful evaluation of right hand of assignment", 
                                    X.NV()), 
                    LabelConstraint.LEQ, 
                    new NamedLabel("label of var " + li.name(), L),
                    A.labelEnv(),
                    lve.position(),
                    new ConstraintMessage() {
            public String msg() {
                return "Label of right hand side not less " + 
                "restrictive than the label for local variable " + 
                li.name();
            }
            public String detailMsg() { 
                return "More information is revealed by the successful " +
                "evaluation of the right hand side of the " +
                "assignment than is allowed to flow to " +
                "the local variable " + li.name() + ".";
            }
            public String technicalMsg() {
                return "Invalid assignment: path NV of rhs is " +
                "not less restrictive than the declared label " +
                "of the local variable <" + li.name() + ">.";
            }

        }
        );

        Expr lhs = (Expr) updatePathMap(lve, X);
        checkThrowTypes(throwTypes);
        return (Assign) updatePathMap(assign.right(rhs).left(lhs), X);
    }

    protected PathMap rhsPathMap(LabelChecker lc, Expr rhs, List throwTypes) {
        return getPathMap(rhs);
    }
}
