/*
 * The contents of this file are subject to the Mozilla Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code is TransforMiiX XSLT processor.
 *
 * The Initial Developer of the Original Code is The MITRE Corporation.
 * Portions created by MITRE are Copyright (C) 1999 The MITRE Corporation.
 *
 * Portions created by Keith Visco as a Non MITRE employee,
 * (C) 1999 Keith Visco. All Rights Reserved.
 *
 * Contributor(s):
 * Keith Visco, kvisco@ziplink.net
 *   -- original author.
 *
 * Marc Schefer, schefer@xo3.com
 *   -- fixed a bug regarding Or expressions
 *      - If the left hand was false, the right hand expression
 *        was not getting checked.
 *
 */


/**
 * Represents a BooleanExpr, a binary expression that
 * performs a boolean operation between it's lvalue and rvalue.
**/

#include "Expr.h"

/**
 * Creates a new BooleanExpr using the given operator
**/
BooleanExpr::BooleanExpr(Expr* leftExpr, Expr* rightExpr, short op) {
    this->op = op;
    this->leftExpr = leftExpr;
    this->rightExpr = rightExpr;
} //-- BooleanExpr

BooleanExpr::~BooleanExpr() {
    delete leftExpr;
    delete rightExpr;
} //-- ~BooleanExpr

/**
 * Evaluates this Expr based on the given context node and processor state
 * @param context the context node for evaluation of this Expr
 * @param ps the ContextState containing the stack information needed
 * for evaluation
 * @return the result of the evaluation
**/
ExprResult* BooleanExpr::evaluate(Node* context, ContextState* cs) {


    MBool lval = MB_FALSE;
    ExprResult* exprRes = 0;
    if ( leftExpr ) {
        exprRes = leftExpr->evaluate(context, cs);
        if ( exprRes ) lval = exprRes->booleanValue();
        delete exprRes;
    }


    //-- check left expression for early decision
    if (( op == OR ) && (lval)) return new BooleanResult(MB_TRUE);
    else if ((op == AND) && (!lval)) return new BooleanResult(MB_FALSE);

    MBool rval = MB_FALSE;
    if ( rightExpr ) {
        exprRes = rightExpr->evaluate(context, cs);
        if ( exprRes ) rval = exprRes->booleanValue();
        delete exprRes;
    }
    //-- just use rval, since we already checked lval
    return new BooleanResult(rval);

} //-- evaluate

/**
 * Returns the String representation of this Expr.
 * @param dest the String to use when creating the String
 * representation. The String representation will be appended to
 * any data in the destination String, to allow cascading calls to
 * other #toString() methods for Expressions.
 * @return the String representation of this Expr.
**/
void BooleanExpr::toString(String& str) {

    if ( leftExpr ) leftExpr->toString(str);
    else str.append("null");

    switch ( op ) {
        case OR:
            str.append(" or ");
            break;
        default:
            str.append(" and ");
            break;
    }
    if ( rightExpr ) rightExpr->toString(str);
    else str.append("null");

} //-- toString