/* HttpURLConnection.java -- HTTP connection to web server
   Copyright (C) 1998 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
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */


package java.net;

import java.io.IOException;
import java.io.InputStream;
import java.io.PushbackInputStream;
import java.security.Permission;

/**
  * This class provides a common abstract implementation for those 
  * URL connection classes that will connect using the HTTP protocol.
  * In addition to the functionality provided by the URLConnection
  * class, it defines constants for HTTP return code values and
  * methods for setting the HTTP request method and determining whether
  * or not to follow redirects. 
  *
  * @version 0.5
  *
  * @author Aaron M. Renn (arenn@urbanophile.com)
  */
public abstract class HttpURLConnection extends URLConnection
{

/*************************************************************************/

/*
 * Class Variables
 */

// HTTP return codes

/**
  * Indicates that the client may continue with its request.  This value
  * is specified as part of RFC 2068 but was not included in Sun's JDK, so
  * beware of using this value
  */
static final int HTTP_CONTINUE = 100;

/**
  * Indicates that the server received and is willing to comply with a 
  * request to switch protocols initiated by the client.  This value is
  * specified as part of RFC 2068 but was not included in Sun's JDK as of
  * release 1.2, so beware of using this value.
  */
static final int HTTP_SWITCHING_PROTOCOLS = 101;

/**
  * Indicates the request succeeded
  */
public static final int HTTP_OK = 200;

/**
  * The requested resource has been created.
  */
public static final int HTTP_CREATED = 201;

/**
  * The request has been accepted for processing but has not completed.
  * There is no guarantee that the requested action will actually ever
  * be completed succesfully, but everything is ok so far.
  */
public static final int HTTP_ACCEPTED = 202;

/**
  * The meta-information returned in the header is not the actual data
  * from the original server, but may be from a local or other copy. 
  * Normally this still indicates a successful completion.
  */
public static final int HTTP_NOT_AUTHORITATIVE = 203;

/**
  * The server performed the request, but there is no data to send
  * back.  This indicates that the user's display should not be changed.
  */
public static final int HTTP_NO_CONTENT = 204;

/**
  * The server performed the request, but there is no data to sent back,
  * however, the user's display should be "reset" to clear out any form
  * fields entered.
  */
public static final int HTTP_RESET = 205;

/**
  * The server completed the partial GET request for the resource.
  */
public static final int HTTP_PARTIAL = 206;

/**
  * There is a list of choices available for the requested resource
  */
public static final int HTTP_MULT_CHOICE = 300;

/**
  * The resource has been permanently moved to a new location.
  */
public static final int HTTP_MOVED_PERM = 301;

/**
  * The resource requested has been temporarily moved to a new location.
  */
public static final int HTTP_MOVED_TEMP = 302;

/**
  * The response to the request issued is available at another location
  */
public static final int HTTP_SEE_OTHER = 303;

/**
  * The document has not been modified since the criteria specified in
  * a conditional GET
  */
public static final int HTTP_NOT_MODIFIED = 304;

/**
  * The requested resource needs to be accessed through a proxy.
  */
public static final int HTTP_USE_PROXY = 305;

/**
  * The request was misformed or could not be understood.
  */
public static final int HTTP_BAD_REQUEST = 400;

/**
  * The request made requires user authorization.  Try again with
  * a correct authentication header.
  */
public static final int HTTP_UNAUTHORIZED = 401;

/**
  * Code reserved for future use - I hope way in the future
  */
public static final int HTTP_PAYMENT_REQUIRED = 402;

/**
  * There is no permission to access the requested resource
  */
public static final int HTTP_FORBIDDEN = 403;

/**
  * The requested resource was not found
  */
public static final int HTTP_NOT_FOUND = 404;

/**
  * The specified request method is not allowed for this resource
  */
public static final int HTTP_BAD_METHOD = 405;

/**
  * Based on the input headers sent, the resource returned in response
  * to the request would not be acceptable to the client.
  */
public static final int HTTP_NOT_ACCEPTABLE = 406;

/**
  * The client must authenticate with a proxy prior to attempting this
  * request.
  */
public static final int HTTP_PROXY_AUTH = 407;

/**
  * The request timed out.
  */
public static final int HTTP_CLIENT_TIMEOUT = 408;

/**
  * There is a conflict between the current state of the resource and the
  * requested action.
  */
public static final int HTTP_CONFLICT = 409;

/**
  * The requested resource is no longer available.  This ususally indicates
  * a permanent condition.
  */
public static final int HTTP_GONE = 410;

/**
  * A Content-Length header is required for this request, but was not
  * supplied
  */
public static final int HTTP_LENGTH_REQUIRED = 411;

/**
  * A client specified pre-condition was not met on the server.
  */
public static final int HTTP_PRECON_FAILED = 412;

/**
  * The request sent was too large for the server to handle
  */
public static final int HTTP_ENTITY_TOO_LARGE = 413;

/**
  * The name of the resource specified was too long
  */
public static final int HTTP_REQ_TOO_LONG = 414;

/**
  * The request is in a format not supported by the requested resource
  */
public static final int HTTP_UNSUPPORTED_TYPE = 415;

/**
  * This error code indicates that some sort of server error occurred
  */
public static final int HTTP_SERVER_ERROR = 500;

/**
  * The server encountered an unexpected error (such as a CGI script crash)
  * that prevents the request from being fulfilled
  */
public static final int HTTP_INTERNAL_ERROR = 500;

/**
  * The server does not support the requested functionality.  This code
  * is specified in RFC 2068, but is not in Sun's JDK 1.2  Beware of using
  * this variable.
  */
static final int HTTP_NOT_IMPLEMENTED = 501;

/**
  * The proxy encountered a bad response from the server it was proxy-ing for
  */
public static final int HTTP_BAD_GATEWAY = 502;

/**
  * The HTTP service is not availalble, such as because it is overloaded
  * and does not want additional requests.
  */
public static final int HTTP_UNAVAILABLE = 503;

/**
  * The proxy timed out getting a reply from the remote server it was
  * proxy-ing for.
  */
public static final int HTTP_GATEWAY_TIMEOUT = 504;

/**
  * This server does not support the protocol version requested.
  */
public static final int HTTP_VERSION = 505;

// Non-HTTP response static variables

/**
  * Flag to indicate whether or not redirects should be automatically
  * followed.
  */
private static boolean follow_redirects = true;

/**
  * This is a list of valid request methods, separated by "|" characters.
  */
private static String valid_methods = "|GET|POST|HEAD|OPTIONS|PUT|DELETE|TRACE|";

/*************************************************************************/

/*
 * Instance Variables
 */

/**
  * The requested method in use for this connection.
  */
protected String method = "GET"; // GET is the default method

/**
  * The response code received from the server
  */
protected int responseCode = -1;

/**
  * The response message string received from the server.
  */
protected String responseMessage = null;

/*************************************************************************/

/*
 * Class Methods
 */

/**
  * Sets a flag indicating whether or not to automatically follow HTTP
  * redirects.  If not otherwise set, this value defaults to true.  Note
  * that this value cannot be set by applets.
  *
  * @param follow true if redirects should be followed, false otherwise
  */
public static void
setFollowRedirects(boolean follow)
{
  follow_redirects = follow;
}
  
/*************************************************************************/

/**
  * Returns a boolean indicating whether or not HTTP redirects will 
  * automatically be followed or not.
  *
  * @return true if redirects will be followed, false otherwise
  */
public static boolean
getFollowRedirects()
{
  return(follow_redirects);
}

/*************************************************************************/

/*
 * Constructors
 */

/**
  * Create an HttpURLConnection for the specified URL
  *
  * @param url The URL to create this connection for.
  */
protected
HttpURLConnection(URL url)
{
  super(url);
}

/*************************************************************************/

/*
 * Instance Methods
 */

/**
  * Sets the HTTP request method for this object.  Allowable methods are:
  * GET, POST, HEAD, OPTIONS, PUT, DELETE, and TRACE.  Note that not all
  * protocol implementations will necessarily support all of these
  * request methods.  The default value is GET.
  *
  * @param method The request method to use
  *
  * @exception ProtocolException If the requested method isn't valid or cannot be used
  */
public synchronized void
setRequestMethod(String method) throws ProtocolException
{
  if (valid_methods.indexOf("|" + method.toUpperCase() + "|") == -1)
    throw new ProtocolException(method.toUpperCase());

  this.method = method;
}

/*************************************************************************/

/**
  * The request method currently in use for this connection.
  *
  * @return The request method
  */
public String
getRequestMethod()
{
  return(method);
}

/*************************************************************************/

/**
  * Returns the numeric response code received from the server, or -1 if
  * no response code has yet been received, or the response code could not
  * be determined.  Note that all valid response codes have class variables
  * defined for them in this class.
  *
  * @return The response code
  *
  * @IOException If an error occurs
  */
public int
getResponseCode() throws IOException
{
  return(responseCode);
}

/*************************************************************************/

/**
  * Returns the response message (everything after the response code in the
  * reply string received from the server) or null if no connection has been
  * made or no response message could be determined from the server output
  *
  * @return The response message
  *
  * @exception IOException If an error occurs
  */
public String
getResponseMessage() throws IOException
{
  return(responseMessage);
}

/*************************************************************************/

/**
  * This method allows the caller to retrieve any data that might have
  * been sent despite the fact that an error occurred.  For example, the
  * HTML page sent along with a 404 File Not Found error.  If the socket
  * is not connected, or if no error occurred or no data was returned,
  * this method returns <code>null</code>.
  *
  * @return An <code>InputStream</code> for reading error data.
  */
public InputStream
getErrorStream()
{
  if (!connected)
    return(null);

  int code;
  try
    {
      code = getResponseCode();
    }
  catch(IOException e)
    {
      code = -1;
    }

  if (code == -1)
    return(null);

  if (((code/100) != 4) || ((code/100) != 5))
    return(null);

  try
    {
      PushbackInputStream pbis = new PushbackInputStream(getInputStream());

     int i = pbis.read();
     if (i == -1)
       return(null);
 
     pbis.unread(i);
     return(pbis);
    }
  catch(IOException e)
    {
      return(null);
    }
}

/*************************************************************************/

/**
  * This method returns a <code>Permission</code> object that represents
  * the permission needed in order to access this URL.
  *
  * @param The needed permissions for accessing this URL.
  */
public Permission
getPermission() throws IOException
{
  URL url = getURL();
  String host = url.getHost();
  int port = url.getPort();
  if (port == -1)
    port = 80;

  host = host + ":" + port;

  return(new SocketPermission(host, "connect"));
}

/*************************************************************************/

/**
  * Closes the connection to the server.
  */
public abstract void
disconnect();

/*************************************************************************/

/**
  * Returns a boolean indicating whether or not this connection is going
  * through a proxy
  *
  * @return true if through a proxy, false otherwise
  */
public abstract boolean
usingProxy();

} // class HttpURLConnection