package gnu.crypto.key;

// ----------------------------------------------------------------------------
// $Id: KeyPairCodecFactory.java,v 1.2 2005/10/06 04:24:16 rsdio Exp $
//
// Copyright (C) 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto 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 Crypto 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 this program; see the file COPYING.  If not, write to the
//
//    Free Software Foundation Inc.,
//    51 Franklin Street, Fifth Floor,
//    Boston, MA 02110-1301
//    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
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// 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.
// ----------------------------------------------------------------------------

import gnu.crypto.Registry;
import gnu.crypto.key.dh.DHKeyPairRawCodec;
import gnu.crypto.key.dh.GnuDHPrivateKey;
import gnu.crypto.key.dh.GnuDHPublicKey;
import gnu.crypto.key.dss.DSSKeyPairRawCodec;
import gnu.crypto.key.dss.DSSPrivateKey;
import gnu.crypto.key.dss.DSSPublicKey;
import gnu.crypto.key.rsa.GnuRSAPrivateKey;
import gnu.crypto.key.rsa.GnuRSAPublicKey;
import gnu.crypto.key.rsa.RSAKeyPairRawCodec;
import gnu.crypto.key.srp6.SRPKeyPairRawCodec;
import gnu.crypto.key.srp6.SRPPrivateKey;
import gnu.crypto.key.srp6.SRPPublicKey;

import java.util.Set;
import java.security.Key;
import java.security.PrivateKey;
import java.security.PublicKey;

/**
 * <p>A <i>Factory</i> class to instantiate key encoder/decoder instances.</p>
 *
 * @version $Revision: 1.2 $
 */
public class KeyPairCodecFactory {

   // Constants and variables
   // -------------------------------------------------------------------------

   // Constructor(s)
   // -------------------------------------------------------------------------

   /** Trivial constructor to enforce Singleton pattern. */
   private KeyPairCodecFactory() {
      super();
   }

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

   /**
    * <p>Returns an instance of a keypair codec given its name.</p>
    *
    * @param name the case-insensitive key codec name.
    * @return an instance of the keypair codec, or <code>null</code> if none
    * found.
    */
   public static IKeyPairCodec getInstance(String name) {
      if (name == null) {
         return null;
      }

      name = name.trim();
      IKeyPairCodec result = null;
      if (name.equalsIgnoreCase(Registry.DSA_KPG) || name.equals(Registry.DSS_KPG)) {
         result = new DSSKeyPairRawCodec();
      } else if (name.equalsIgnoreCase(Registry.RSA_KPG)) {
         result = new RSAKeyPairRawCodec();
      } else if (name.equalsIgnoreCase(Registry.DH_KPG)) {
         result = new DHKeyPairRawCodec();
      } else if (name.equalsIgnoreCase(Registry.SRP_KPG)) {
         result = new SRPKeyPairRawCodec();
      }

      return result;
   }

   /**
    * <p>Returns an instance of a keypair codec given a byte array that is
    * assumed to contain a previously encoded key (public or private).</p>
    *
    * @param buffer a byte array containing a previously encoded key.
    * @return an instance of the keypair codec, or <code>null</code> if none
    * found.
    */
   public static IKeyPairCodec getInstance(byte[] buffer) {
      if (buffer == null) {
         return null;
      }
      // our codecs prefix the stream with a 4-byte magic
      if (buffer.length < 5) {
         return null;
      }
      // the first byte is always 0x47
      if (buffer[0] != 0x47) {
         return null;
      }
      // so far we only have RAW codecs
      if (buffer[1] != Registry.RAW_ENCODING_ID) {
         return null;
      }
      IKeyPairCodec result = null;
      switch (buffer[2]) {
      case 0x44: result = new DSSKeyPairRawCodec(); break;
      case 0x52: result = new RSAKeyPairRawCodec(); break;
      case 0x48: result = new DHKeyPairRawCodec();  break;
      case 0x53: result = new SRPKeyPairRawCodec();  break;
      }

      return result;
   }

   /**
    * <p>Returns an instance of a keypair codec given a key.</p>
    *
    * @param key the key to encode.
    * @return an instance of the keypair codec, or <code>null</code> if none
    * found.
    */
   public static IKeyPairCodec getInstance(Key key) {
      if (key == null) {
         return null;
      }

      IKeyPairCodec result = null;
      if (key instanceof PublicKey) {
         if (key instanceof DSSPublicKey) {
            result = new DSSKeyPairRawCodec();
         } else if (key instanceof GnuRSAPublicKey) {
            result = new RSAKeyPairRawCodec();
         } else if (key instanceof GnuDHPublicKey) {
            result = new DHKeyPairRawCodec();
         } else if (key instanceof SRPPublicKey) {
            result = new SRPKeyPairRawCodec();
         }
      } else if (key instanceof PrivateKey) {
         if (key instanceof DSSPrivateKey) {
            result = new DSSKeyPairRawCodec();
         } else if (key instanceof GnuRSAPrivateKey) {
            result = new RSAKeyPairRawCodec();
         } else if (key instanceof GnuDHPrivateKey) {
            result = new DHKeyPairRawCodec();
         } else if (key instanceof SRPPrivateKey) {
            result = new SRPKeyPairRawCodec();
         }
      }

      return result;
   }

   /**
    * <p>Returns a {@link Set} of keypair codec names supported by this
    * <i>Factory</i>.</p>
    *
    * @return a {@link Set} of keypair codec names (Strings).
    */
   public static final Set getNames() {
      return KeyPairGeneratorFactory.getNames();
   }
}
