/*
 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
 *
 * 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.jbpm.compiler.xml.compiler.rules;

import org.drools.drl.ast.descr.AndDescr;
import org.drools.drl.ast.descr.AttributeDescr;
import org.drools.drl.ast.descr.PackageDescr;
import org.drools.drl.ast.descr.RuleDescr;
import org.jbpm.compiler.xml.Handler;
import org.jbpm.compiler.xml.Parser;
import org.jbpm.compiler.xml.core.BaseAbstractHandler;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;

public class RuleHandler extends BaseAbstractHandler
        implements
        Handler {
    public RuleHandler() {
    }

    public Object start(final String uri,
            final String localName,
            final Attributes attrs,
            final Parser parser) throws SAXException {
        parser.startElementBuilder(localName,
                attrs);

        final String ruleName = attrs.getValue("name");
        emptyAttributeCheck(localName,
                "name",
                ruleName,
                parser);

        return new RuleDescr(ruleName.trim());
    }

    public Object end(final String uri,
            final String localName,
            final Parser parser) throws SAXException {
        final Element element = parser.endElementBuilder();

        final RuleDescr ruleDescr = (RuleDescr) parser.getCurrent();

        final AndDescr lhs = ruleDescr.getLhs();

        if (lhs == null) {
            throw new SAXParseException("<rule> requires a LHS",
                    parser.getLocator());
        }

        NodeList list = element.getElementsByTagName("rhs");
        if (list.getLength() == 0) {
            throw new SAXParseException("<rule> requires a <rh> child element",
                    parser.getLocator());
        }

        ruleDescr.setConsequence(((org.w3c.dom.Text) list.item(0).getChildNodes().item(0)).getWholeText());

        NodeList attributes = element.getElementsByTagName("rule-attribute");
        for (int i = 0, length = attributes.getLength(); i < length; i++) {
            final String name = ((Element) attributes.item(i)).getAttribute("name");
            emptyAttributeCheck("rule-attribute",
                    "name",
                    name,
                    parser);

            final String value = ((Element) attributes.item(i)).getAttribute("value");

            ruleDescr.addAttribute(new AttributeDescr(name,
                    value));
        }

        ((PackageDescr) parser.getData()).addRule(ruleDescr);

        return ruleDescr;
    }

    public Class generateNodeFor() {
        return RuleDescr.class;
    }
}
