/*
 * 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.forms.formmodel;

import org.apache.cocoon.forms.FormsException;
import org.apache.cocoon.forms.formmodel.library.Library;
import org.apache.cocoon.forms.util.DomHelper;

import org.w3c.dom.Element;

/**
 * @version $Id$
 */
public class ImportDefinitionBuilder extends AbstractWidgetDefinitionBuilder {

    public static final String PREFIX_ATTRIBUTE = "prefix";
    public static final String URI_ATTRIBUTE = "uri";

    /**
     * Imports a new library
     */
    public WidgetDefinition buildWidgetDefinition(Element widgetElement, WidgetDefinitionBuilderContext context)
    throws Exception {
        if (context.getLocalLibrary() == null) {
            throw new FormsException("Import statement seen and context is empty.",
                                     DomHelper.getLocationObject(widgetElement));
        }

        Library lib = context.getLocalLibrary();
        String prefix = DomHelper.getAttribute(widgetElement, PREFIX_ATTRIBUTE);
        String uri = DomHelper.getAttribute(widgetElement, URI_ATTRIBUTE);

        if (!lib.includeAs(prefix, uri)) {
            throw new FormsException("Import statement did not succeed (probably used ':' in the prefix?).",
                                     DomHelper.getLocationObject(widgetElement));
        }

        return null;
    }
}