/*
 *  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.tools.ant.taskdefs.optional.javah;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.ProjectComponent;
import org.apache.tools.ant.util.ClasspathUtils;
import org.apache.tools.ant.util.JavaEnvUtils;

/**
 * Creates the JavahAdapter based on the user choice and
 * potentially the VM vendor.
 *
 * @since Ant 1.6.3
 */
public class JavahAdapterFactory {

    /**
     * Determines the default choice of adapter based on the VM
     * vendor.
     *
     * @return the default choice of adapter based on the VM
     * vendor
     */
    public static String getDefault() {
        if (JavaEnvUtils.isKaffe()) {
            return Kaffeh.IMPLEMENTATION_NAME;
        }
        return SunJavah.IMPLEMENTATION_NAME;
    }

    /**
     * Creates the JavahAdapter based on the user choice and
     * potentially the VM vendor.
     *
     * @param choice the user choice (if any).
     * @param log a ProjectComponent instance used to access Ant's
     * logging system.
     * @return The adapter to use.
     * @throws BuildException if there is an error.
     */
    public static JavahAdapter getAdapter(String choice,
                                          ProjectComponent log)
        throws BuildException {
        if ((JavaEnvUtils.isKaffe() && choice == null)
            || Kaffeh.IMPLEMENTATION_NAME.equals(choice)) {
            return new Kaffeh();
        } else if (SunJavah.IMPLEMENTATION_NAME.equals(choice)) {
            return new SunJavah();
        } else if (choice != null) {
            return resolveClassName(choice);
        }

        // This default has been good enough until Ant 1.6.3, so stick
        // with it
        return new SunJavah();
    }

    /**
     * Tries to resolve the given classname into a javah adapter.
     * Throws a fit if it can't.
     *
     * @param className The fully qualified classname to be created.
     * @throws BuildException This is the fit that is thrown if className
     * isn't an instance of JavahAdapter.
     */
    private static JavahAdapter resolveClassName(String className)
            throws BuildException {
        return (JavahAdapter) ClasspathUtils.newInstance(className,
                JavahAdapterFactory.class.getClassLoader(), JavahAdapter.class);
    }
}