/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.cocoon.template.instruction;

import java.util.Stack;

import org.apache.cocoon.components.expression.ExpressionContext;
import org.apache.cocoon.template.environment.ErrorHolder;
import org.apache.cocoon.template.environment.ExecutionContext;
import org.apache.cocoon.template.environment.ParsingContext;
import org.apache.cocoon.template.expression.JXTExpression;
import org.apache.cocoon.template.script.event.Event;
import org.apache.cocoon.template.script.event.StartElement;
import org.apache.cocoon.xml.XMLConsumer;
import org.xml.sax.Attributes;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;

/**
 * @version SVN $Id$
 */
public class If extends Instruction {
    private final JXTExpression test;

    public If(ParsingContext parsingContext, StartElement raw, Attributes attrs, Stack stack) 
        throws SAXException {

        super(raw);

        Locator locator = getLocation();
        String test = attrs.getValue("test");
        if (test != null) {
            this.test = parsingContext.getStringTemplateParser().compileExpr(test, "if: \"test\": ", locator);
            // Why is test lenient?
            this.test.setLenient(Boolean.TRUE);
        } else {
            throw new SAXParseException("if: \"test\" is required", locator, null);
        }
    }

    public Event execute(final XMLConsumer consumer,
                         ExpressionContext expressionContext, ExecutionContext executionContext,
                         MacroContext macroContext, Event startEvent, Event endEvent) 
        throws SAXException {

        Object val;
        try {
            val = this.test.getValue(expressionContext);
        } catch (Exception e) {
            throw new SAXParseException(e.getMessage(), getLocation(), e);
        } catch (Error err) {
            throw new SAXParseException(err.getMessage(), getLocation(),
                                        new ErrorHolder(err));
        }
        boolean result = false;
        if (val instanceof Boolean) {
            result = ((Boolean) val).booleanValue();
        } else {
            result = (val != null);
        }
        if (!result) {
            return getEndInstruction().getNext();
        }
        return getNext();
    }
}