/*
 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
 */
/*
 * 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.qetest.xslwrapper;

import java.util.Properties;

/**
 * Factory static class for creating TransformWrappers.
 *
 * Includes a 'wrapperMapper' functionality to simplify specifying the 'flavor'
 * of a wrapper to create. This is optional, but will allow a user to specify
 * newWrapper("trax.file") and get back an instance of an
 * org.apache.qetest.xslwrapper.TraxFileWrapper.
 */
public class TransformWrapperFactory {

    /**
     * Currently known list of implemented wrappers.
     * <ul>
     * <p>Allows specification of a simple name for each wrapper, so clients 
     * don't necessarily have to know the FQCN or fully qualified class name of
     * their wrapper.</p>
     * </ul>
     */
    protected final static Properties wrapperMapper = new Properties();

    /**
     * Static initializer for wrapperMapper. Attempts to load
     * TransformWrapperFactory.properties into our wrapperMapper.
     */
    static {
        // Add a default trax flavor, since it's widely used
        // This should be overwritten below if the properties
        //  file can be loaded.
        wrapperMapper.put("trax.systemId", "org.apache.qetest.xslwrapper.TraxSystemIdWrapper");
        wrapperMapper.put("trax.file", "org.apache.qetest.xslwrapper.TraxFileWrapper");
        wrapperMapper.put("trax.stream", "org.apache.qetest.xslwrapper.TraxStreamWrapper");
        wrapperMapper.put("trax.dom", "org.apache.qetest.xslwrapper.TraxDOMWrapper");
        wrapperMapper.put("trax.sax", "org.apache.qetest.xslwrapper.TraxSAXWrapper");
        wrapperMapper.put("trax.localPath", "org.apache.qetest.xslwrapper.TraxLocalPathWrapper");
        wrapperMapper.put("trax.systemId3", "org.apache.qetest.xslwrapper.TraxSystemId3Wrapper");
    }

    /**
     * Accessor for our wrapperMapper.
     * @return Properties block of wrapper implementations
     * that we implicitly know about; may be null if we have none
     */
    public static final Properties getDescriptions() {
        return wrapperMapper;
    }

    /**
     * Return an instance of a TransformWrapper of requested flavor.
     *
     * This static factory method creates TransformWrappers for the user. Our
     * 'wrapperMapper' functionality allows users to either specify short names
     * listed in TransformWrapperFactory.properties (which are mapped to the
     * appropriate FQCN's) or to directly supply the FQCN of a wrapper to
     * create.
     *
     * @param flavor to create, either a wrapperMapped one or FQCN
     *
     * @return instance of a wrapper; will throw an IllegalArgumentException if
     * we cannot find the asked-for wrapper class anywhere
     */
    public static final TransformWrapper newWrapper(String flavor) {
        // Attempt to lookup the flavor: if found, use the
        //  value we got, otherwise default to the same value
        String className = wrapperMapper.getProperty(flavor, flavor);

        try {
            // Allow people to use bare classnames in popular packages
            Class clazz = Class.forName(className);
            return (TransformWrapper) clazz.newInstance();
        } catch (ClassNotFoundException | IllegalAccessException | InstantiationException e) {
            throw new IllegalArgumentException("newWrapper(" + flavor + ") threw: " + e.toString());
        }
    }
}