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/*
 * JBoss, Home of Professional Open Source
 * Copyright 2009, Red Hat Middleware LLC, and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * 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.jboss.shrinkwrap.api.asset;

import java.io.InputStream;

/**
 * ClassAsset
 * 
 * Implementation of a {@link Asset} backed by a loaded {@link Class}
 *
 * @author Aslak Knutsen
 *
 */
public class ClassAsset implements Asset {
    /**
     * Delimiter for paths while looking for resources
     */
    private static final char DELIMITER_RESOURCE_PATH = '/';

    /**
     * Delimiter for paths in fully-qualified class names
     */
    private static final char DELIMITER_CLASS_NAME_PATH = '.';

    /**
     * The filename extension appended to classes
     */
    private static final String EXTENSION_CLASS = ".class";

    private final Class clazz;

    /**
     * Load any class as a resource.
     *
     * @param clazz
     *            The class to load
     * @throws IllegalArgumentException
     *             Class can not be null
     */
    public ClassAsset(final Class clazz) {
        // Precondition check
        if (clazz == null) {
            throw new IllegalArgumentException("Class must be specified");
        }

        this.clazz = clazz;
    }

    /**
     * Converts the Class name into a Resource URL and uses the ClassloaderResource for loading the Class.
     */
    @Override
    public InputStream openStream() {
        /*
         * https://jira.jboss.org/jira/browse/TMPARCH-19 If class is loaded by the Bootstrap ClassLoader, getClassLoader
         * will return null. Use Thread Current Context ClassLoader instead.
         */
        ClassLoader classLoader = clazz.getClassLoader();
        if (classLoader == null) {
            classLoader = ClassLoader.getSystemClassLoader();
        }
        return new ClassLoaderAsset(getResourceNameOfClass(clazz), classLoader).openStream();
    }

    /**
     * Returns the loaded class.
     *
     */
    public Class getSource() {
        return clazz;
    }

    /**
     * Returns the name of the class such that it may be accessed via ClassLoader.getResource()
     *
     * @param clazz
     *            The class
     * @throws IllegalArgumentException
     *             If the class was not specified
     */
    private String getResourceNameOfClass(final Class clazz) throws IllegalArgumentException {
        // Build the name
        final String fqn = clazz.getName();
        final String nameAsResourcePath = fqn.replace(DELIMITER_CLASS_NAME_PATH, DELIMITER_RESOURCE_PATH);
        final String resourceName = nameAsResourcePath + EXTENSION_CLASS;

        // Return
        return resourceName;
    }
}