/*
    * Copyright (C) 2014 Laurent Goujon <lgoujon@twitter.com> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  
  package org.eclipse.jgit.util;
  
  import java.lang.reflect.Constructor;
  import java.lang.reflect.InvocationTargetException;
  import java.net.URL;
  
  import org.ietf.jgss.GSSManager;
  
  /**
   * Factory to detect which GSSManager implementation should be used.
   *
   * @since 3.4
   */
  public abstract class GSSManagerFactory {
  	/**
  	 * Auto-detects the GSSManager factory to use based on system.
  	 *
  	 * @return detected GSSManager factory
  	 */
  	public static GSSManagerFactory detect() {
  		return (SunGSSManagerFactory.isSupported()) ? new SunGSSManagerFactory()
  				: new DefaultGSSManagerFactory();
  	}
  
  	/**
  	 * Returns a GSS Manager instance for the provided url
  	 *
  	 * @param url
  	 *            the repository url
  	 * @return a GSSManager instance
  	 */
  	public abstract GSSManager newInstance(URL url);
  
  	/**
  	 * DefaultGSSManagerFactory uses @link {@link GSSManager#getInstance()} but
  	 * you might need to set
  	 * <code>javax.security.auth.useSubjectCredsOnly</code> system property to
  	 * <code>false</code> for authentication to work.
  	 */
  	private static class DefaultGSSManagerFactory extends GSSManagerFactory {
  		private static final GSSManager INSTANCE = GSSManager.getInstance();
  
  		@Override
  		public GSSManager newInstance(URL url) {
  			return INSTANCE;
  		}
  	}
  
  	private static class SunGSSManagerFactory extends GSSManagerFactory {
  		private static boolean IS_SUPPORTED;
  		private static Constructor<?> HTTP_CALLER_INFO_CONSTRUCTOR;
  		private static Constructor<?> HTTP_CALLER_CONSTRUCTOR;
  
  		private static Constructor<?> GSS_MANAGER_IMPL_CONSTRUCTOR;
  
  		static {
  			try {
  				init();
  				IS_SUPPORTED = true;
  			} catch (Exception e) {
  				IS_SUPPORTED = false;
  			}
  		}
  
  		private static void init() throws ClassNotFoundException,
  				NoSuchMethodException {
  			Class<?> httpCallerInfoClazz = Class
  					.forName("sun.net.www.protocol.http.HttpCallerInfo"); //$NON-NLS-1$
  			HTTP_CALLER_INFO_CONSTRUCTOR = httpCallerInfoClazz
  					.getConstructor(URL.class);
  
  			Class<?> httpCallerClazz = Class
  					.forName("sun.security.jgss.HttpCaller"); //$NON-NLS-1$
  			HTTP_CALLER_CONSTRUCTOR = httpCallerClazz
  					.getConstructor(httpCallerInfoClazz);
  
  			Class<?> gssCallerClazz = Class
  					.forName("sun.security.jgss.GSSCaller"); //$NON-NLS-1$
  			Class<?> gssManagerImplClazz = Class
  					.forName("sun.security.jgss.GSSManagerImpl"); //$NON-NLS-1$
  			GSS_MANAGER_IMPL_CONSTRUCTOR = gssManagerImplClazz
  					.getConstructor(gssCallerClazz);
  
  		}
  
  		/**
  		 * Detects if SunGSSManagerProvider is supported by the system
  		 *
  		 * @return true if it is supported
 		 */
 		public static boolean isSupported() {
 			return IS_SUPPORTED;
 		}
 
 		@Override
 		public GSSManager newInstance(URL url) {
 			try {
 				Object httpCallerInfo = HTTP_CALLER_INFO_CONSTRUCTOR
 						.newInstance(url);
 				Object httpCaller = HTTP_CALLER_CONSTRUCTOR
 						.newInstance(httpCallerInfo);
 
 				return (GSSManager) GSS_MANAGER_IMPL_CONSTRUCTOR
 						.newInstance(httpCaller);
 			} catch (InstantiationException | IllegalAccessException
 					| IllegalArgumentException | InvocationTargetException e) {
 				throw new Error(e);
 			}
 		}
 	}
 }