/* Authenticator.java -- Abstract class for obtaining authentication info
   Copyright (C) 1998, 2000, 2003 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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permission to link this library with independent modules to produce an
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package java.net;

/**
  * This abstract class provides a model for obtaining authentication
  * information (in the form of a username and password) required by
  * some network operations (such as hitting a password protected
  * web site).
  * <p>
  * To make use of this feature, a programmer must create a subclass 
  * that knows how to obtain the necessary info.  An example
  * would be a class that popped up a dialog box to prompt the user.  
  * After creating an instance of that subclass, the static 
  * <code>setDefault</code> method of this class is called to set up 
  * that instance as the object to use on subsequent calls to obtain 
  * authorization.
  *
  * @since 1.2
  *
  * @author Aaron M. Renn (arenn@urbanophile.com)
  * @status Believed to be JDK 1.4 complete
  */
public abstract class Authenticator
{
  /*
   * Class Variables
   */

  /**
    * This is the default Authenticator object to use for password requests
    */
  private static Authenticator defaultAuthenticator;

  /*
   * Instance Variables
   */

  /**
    * The hostname of the site requesting authentication
    */
  private String host;

  /**
    * InternetAddress of the site requesting authentication
    */
  private InetAddress addr;

  /**
    * The port number of the site requesting authentication
    */
  private int port;

  /**
    * The protocol name of the site requesting authentication
    */
  private String protocol;

  /**
    * The prompt to display to the user when requesting authentication info
    */
  private String prompt;

  /**
    * The authentication scheme in use
    */
  private String scheme;

  /*
   * Class Methods
   */

  /**
    * This method sets the default <code>Authenticator</code> object (an 
    * instance of a subclass of <code>Authenticator</code>) to use when 
    * prompting the user for
    * information.  Note that this method checks to see if the caller is
    * allowed to set this value (the "setDefaultAuthenticator" permission)
    * and throws a <code>SecurityException</code> if it is not.
    *
    * @param defAuth The new default <code>Authenticator</code> object to use
    *
    * @exception SecurityException If the caller does not have permission 
    * to perform this operation
    */ 
  public static void setDefault(Authenticator defAuth)
  {
    SecurityManager sm = System.getSecurityManager();
    if (sm != null)
      sm.checkPermission(new NetPermission("setDefaultAuthenticator"));

    defaultAuthenticator = defAuth;
  } 

  /**
    * This method is called whenever a username and password for a given
    * network operation is required.  First, a security check is made to see
    * if the caller has the "requestPasswordAuthentication"
    * permission.  If not, the method thows an exception.  If there is no
    * default <code>Authenticator</code> object, the method then returns 
    * <code>null</code>.  Otherwise, the default authenticators's instance 
    * variables are initialized and it's <code>getPasswordAuthentication</code>
    * method is called to get the actual authentication information to return.
    *
    * @param addr The address requesting authentication
    * @param port The port requesting authentication
    * @param protocol The protocol requesting authentication
    * @param prompt The prompt to display to the user when requesting 
    *        authentication info
    * @param scheme The authentication scheme in use
    * 
    * @return A <code>PasswordAuthentication</code> object with the user's 
    *         authentication info.
    *
    * @exception SecurityException If the caller does not have permission to 
    *         perform this operation
    */ 
  public static PasswordAuthentication 
    requestPasswordAuthentication(InetAddress addr, int port, String protocol,
      String prompt, String scheme) 
    throws SecurityException
  {
    return(requestPasswordAuthentication (null, addr, port, protocol,
  					prompt, scheme));
  }

  /**
    * This method is called whenever a username and password for a given
    * network operation is required.  First, a security check is made to see
    * if the caller has the "requestPasswordAuthentication"
    * permission.  If not, the method thows an exception.  If there is no
    * default <code>Authenticator</code> object, the method then returns
    * <code>null</code>.  Otherwise, the default authenticators's instance
    * variables are initialized and it's <code>getPasswordAuthentication</code>
    * method is called to get the actual authentication information to return.
    * This method is the preferred one as it can be used with hostname
    * when addr is unknown.
    *
    * @param host The hostname requesting authentication
    * @param addr The address requesting authentication
    * @param port The port requesting authentication
    * @param protocol The protocol requesting authentication
    * @param prompt The prompt to display to the user when requesting 
    *        authentication info
    * @param scheme The authentication scheme in use
    *
    * @return A <code>PasswordAuthentication</code> object with the user's 
    *         authentication info.
    *
    * @exception SecurityException If the caller does not have permission to 
    *         perform this operation
    *
    * @since 1.4
    */
  public static PasswordAuthentication
    requestPasswordAuthentication(String host, InetAddress addr, int port,
        String protocol, String prompt, String scheme)
    throws SecurityException
  {
    SecurityManager sm = System.getSecurityManager();
    if (sm != null)
      sm.checkPermission(new NetPermission("requestPasswordAuthentication"));

    if (defaultAuthenticator == null)
      return(null);

    defaultAuthenticator.host = host;
    defaultAuthenticator.addr = addr;
    defaultAuthenticator.port = port;
    defaultAuthenticator.protocol = protocol;
    defaultAuthenticator.prompt = prompt;
    defaultAuthenticator.scheme = scheme;

    return(defaultAuthenticator.getPasswordAuthentication());
  }

  /*
   * Constructors
   */

  /**
    * Default, no-argument constructor for subclasses to call.
    */
  public Authenticator()
  {
  }

  /*
   * Instance Methods
   */

  /**
    * This method returns the address of the site that is requesting
    * authentication.
    *
    * @return The requesting site's address
    */
  protected final InetAddress getRequestingSite()
  {
    return(addr);
  }

  /**
   * Returns the hostname of the host or proxy requesting authorization,
   * or <code>null</code> if not available.
   *
   * @return The name of the host requesting authentication, or
   * </code>null</code> if it is not available.
   *
   * @since 1.4
   */
  protected final String getRequestingHost()
  {
    return(host);
  }

  /**
    * This method returns the port of the site that is requesting 
    * authentication.
    *
    * @return The requesting port
    */
  protected final int getRequestingPort()
  {
    return(port);
  }

  /**
    * This method returns the requesting protocol of the operation that is
    * requesting authentication
    *
    * @return The requesting protocol
    */
  protected final String getRequestingProtocol()
  {
    return(protocol);
  }

  /**
    * Returns the prompt that should be used when requesting authentication 
    * information from the user
    * 
    * @return The user prompt
    */
  protected final String getRequestingPrompt()
  {
    return(prompt);
  }

  /**
    * This method returns the authentication scheme in use
    *
    * @return The authentication scheme
    */
  protected final String getRequestingScheme()
  {
    return(scheme);
  }

  /**
    * This method is called whenever a request for authentication is made.  It
    * can call the other getXXX methods to determine the information relevant
    * to this request.  Subclasses should override this method, which returns
    * <code>null</code> by default.
    *
    * @return The <code>PasswordAuthentication</code> information
    */
  protected PasswordAuthentication getPasswordAuthentication()
  {
    return(null);
  }

} // class Authenticator