/* Extensions.java -- various static extension utilities.
   Copyright (C) 2003  Casey Marshall <rsdio@metastatic.org>

This file is a part of Jessie.

Jessie 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 of the License, or (at your
option) any later version.

Jessie 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 Jessie; if not, write to the

   Free Software Foundation, Inc.,
   59 Temple Place, Suite 330,
   Boston, MA  02111-1307
   USA

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under terms
of your choice, provided that you also meet, for each linked independent
module, the terms and conditions of the license of that module.  An
independent module is a module which is not derived from or based on
this library.  If you modify this library, you may extend this exception
to your version of the library, but you are not obligated to do so.  If
you do not wish to do so, delete this exception statement from your
version.  */


package org.metastatic.jessie.provider;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;

import org.metastatic.jessie.pki.X500Name;

final class Extensions
{

  // Constants.
  // -------------------------------------------------------------------------

  private static final Integer _512  = new Integer(512),
    _1024 = new Integer(1024), _2048 = new Integer(2048),
    _4096 = new Integer(4096);

  // Class methods only.
  private Extensions() { }

  // Class methods.
  // -------------------------------------------------------------------------

  static List getServerName(Extension ex)
  {
    LinkedList l = new LinkedList();
    byte[] buf = ex.getValue();
    int pos = 0;
    try
      {
        while (pos < buf.length)
          {
            if (buf[pos++] != 0)
              break;
            int len = (buf[pos++] & 0xFF) << 8;
            len |= buf[pos++] & 0xFF;
            l.add(new String(buf, pos, len, "UTF-8"));
            pos += len;
          }
      }
    catch (Exception x)
      {
      }
    return Collections.unmodifiableList(l);
  }

  static List getClientCertTypes(Extension ex) throws IOException
  {
    List l = new LinkedList();
    ByteArrayInputStream in = new ByteArrayInputStream(ex.getValue());
    final int len = in.read() & 0xFF;
    for (int i = 0; i < len; i++)
      {
        l.add(CertificateType.read(in));
      }
    return Collections.unmodifiableList(l);
  }

  static CertificateType getServerCertType(Extension ex) throws IOException
  {
    return CertificateType.read(new ByteArrayInputStream(ex.getValue()));
  }

  static Integer getMaxFragmentLength(Extension ex)
  {
    switch (ex.getValue()[0] & 0xFF)
      {
      case 1: return _512;
      case 2: return _1024;
      case 3: return _2048;
      case 4: return _4096;
      }
    throw new IllegalArgumentException();
  }

  static Object[] getTrustedCA(Extension ex)
  {
    byte[] buf = ex.getValue();
    int type = buf[0] & 0xFF;
    try
      {
        switch (type)
          {
          case 0:
            return new Object[] { new Integer(type), null };
          case 1:
          case 3:
            return new Object[] { new Integer(type),
                                  Util.trim(buf, 1, 20) };
          case 2:
            return new Object[] { new Integer(type),
                                  new X500Name(Util.trim(buf, 1, 20)) };
          }
      }
    catch (Exception x)
      {
      }
    throw new IllegalArgumentException();
  }

  static String getSRPUsername(Extension ex)
  {
    int len = ex.getValue()[0] & 0xFF;
    if (len > ex.getValue().length - 1)
      throw new IllegalArgumentException();
    try
      {
        return new String(ex.getValue(), 1, len, "UTF-8");
      }
    catch (UnsupportedEncodingException uee)
      {
        throw new Error(uee.toString());
      }
  }
}