package gnu.crypto.sig;

// ----------------------------------------------------------------------------
// $Id: SignatureFactory.java,v 1.5 2005/10/06 04:24:18 rsdio Exp $
//
// Copyright (C) 2001, 2002, 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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// library, you may extend this exception to your version of the
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// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------

import gnu.crypto.Registry;
import gnu.crypto.sig.dss.DSSSignature;
import gnu.crypto.sig.rsa.RSAPSSSignature;
import gnu.crypto.sig.rsa.RSAPKCS1V1_5Signature;

import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

/**
 * <p>A Factory to instantiate signature-with-appendix handlers.</p>
 *
 * @version $Revision: 1.5 $
 */
public class SignatureFactory {

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

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

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

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

   /**
    * <p>Returns an instance of a signature-with-appendix scheme given its name.</p>
    *
    * @param ssa the case-insensitive signature-with-appendix scheme name.
    * @return an instance of the scheme, or <code>null</code> if none found.
    */
   public static final ISignature getInstance(String ssa) {
      if (ssa == null) {
         return null;
      }

      ssa = ssa.trim();
      ISignature result = null;
      if (ssa.equalsIgnoreCase(Registry.DSA_SIG) || ssa.equals(Registry.DSS_SIG)) {
         result = new DSSSignature();
      } else if (ssa.equalsIgnoreCase(Registry.RSA_PSS_SIG)) {
         result = new RSAPSSSignature();
      } else if (ssa.equalsIgnoreCase(Registry.RSA_PKCS1_V1_5_SIG)) {
         result = new RSAPKCS1V1_5Signature();
      }

      return result;
   }

   /**
    * <p>Returns a {@link Set} of signature-with-appendix scheme names supported
    * by this <i>Factory</i>.</p>
    *
    * @return a {@link Set} of signature-with-appendix scheme names (Strings).
    */
   public static final Set getNames() {
      HashSet hs = new HashSet();
      hs.add(Registry.DSS_SIG);
      hs.add(Registry.RSA_PSS_SIG);
      hs.add(Registry.RSA_PKCS1_V1_5_SIG);

      return Collections.unmodifiableSet(hs);
   }

   // Instance methods
   // -------------------------------------------------------------------------
}
