/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.classic.util;

import java.util.Iterator;
import java.util.ServiceLoader;

import ch.qos.logback.core.util.Loader;

/**
 * @author Ceki G&uuml;c&uuml;
 */
public class EnvUtil {

    /*
     * Used to replace the ClassLoader that the ServiceLoader uses for unit testing. We need this to mock the resources
     * the ServiceLoader attempts to load from /META-INF/services thus keeping the projects src/test/resources clean
     * (see src/test/resources/README.txt).
     */
    static ClassLoader testServiceLoaderClassLoader = null;

    static public boolean isGroovyAvailable() {
        ClassLoader classLoader = Loader.getClassLoaderOfClass(EnvUtil.class);
        try {
            Class<?> bindingClass = classLoader.loadClass("groovy.lang.Binding");
            return (bindingClass != null);
        } catch (ClassNotFoundException e) {
            return false;
        }
    }

    private static ClassLoader getServiceLoaderClassLoader() {
        return testServiceLoaderClassLoader == null ? Loader.getClassLoaderOfClass(EnvUtil.class) : testServiceLoaderClassLoader;
    }

    public static <T> T loadFromServiceLoader(Class<T> c) {
        ServiceLoader<T> loader = ServiceLoader.load(c, getServiceLoaderClassLoader());
        Iterator<T> it = loader.iterator();
        if (it.hasNext())
            return it.next();
        return null;
    }

}
