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/*
 * Copyright (C) 2009 JavaRosa
 *
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package org.javarosa.xpath.expr;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

import org.javarosa.core.model.condition.EvaluationContext;
import org.javarosa.core.model.instance.DataInstance;
import org.javarosa.core.util.externalizable.DeserializationException;
import org.javarosa.core.util.externalizable.ExtUtil;
import org.javarosa.core.util.externalizable.PrototypeFactory;

public class XPathArithExpr extends XPathBinaryOpExpr {
    public static final int ADD = 0;
    public static final int SUBTRACT = 1;
    public static final int MULTIPLY = 2;
    public static final int DIVIDE = 3;
    public static final int MODULO = 4;

    public int op;

    public XPathArithExpr () { } //for deserialization

    public XPathArithExpr (int op, XPathExpression a, XPathExpression b) {
        super(a, b);
        this.op = op;
    }

    public Object eval (DataInstance model, EvaluationContext evalContext) {
        double aval = XPathFuncExpr.toNumeric(a.eval(model, evalContext)).doubleValue();
        double bval = XPathFuncExpr.toNumeric(b.eval(model, evalContext)).doubleValue();

        double result = 0;
        switch (op) {
        case ADD: result = aval + bval; break;
        case SUBTRACT: result = aval - bval; break;
        case MULTIPLY: result = aval * bval; break;
        case DIVIDE: result = aval / bval; break;
        case MODULO: result = aval % bval; break;
        }
        return new Double(result);
    }

    public String toString () {
        String sOp = null;

        switch (op) {
        case ADD: sOp = "+"; break;
        case SUBTRACT: sOp = "-"; break;
        case MULTIPLY: sOp = "*"; break;
        case DIVIDE: sOp = "/"; break;
        case MODULO: sOp = "%"; break;
        }

        return super.toString(sOp);
    }

    public boolean equals (Object o) {
        if (o instanceof XPathArithExpr) {
            XPathArithExpr x = (XPathArithExpr)o;
            return super.equals(o) && op == x.op;
        } else {
            return false;
        }
    }

    public void readExternal(DataInputStream in, PrototypeFactory pf) throws IOException, DeserializationException {
        op = ExtUtil.readInt(in);
        super.readExternal(in, pf);
    }

    public void writeExternal(DataOutputStream out) throws IOException {
        ExtUtil.writeNumeric(out, op);
        super.writeExternal(out);
    }
}