/* AlgorithmParameters.java --- Algorithm Parameters Implementation Class
   Copyright (C) 1999, 2003, 2004  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.

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along with GNU Classpath; 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
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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
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terms of your choice, provided that you also meet, for each linked
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this exception to your version of the library, but you are not
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package java.security;

import gnu.java.security.Engine;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidParameterSpecException;

/**
 * <code>AlgorithmParameters</code> is an Algorithm Parameters class which
 * provides an interface through which the user can manage the parameters of an
 * Algorithm.
 *
 * @author Mark Benvenuto
 * @since 1.2
 * @see AlgorithmParameterSpec
 * @see java.security.spec.DSAParameterSpec
 * @see KeyPairGenerator
 */
public class AlgorithmParameters
{
  /** Service name for algorithm parameters. */
  private static final String ALGORITHM_PARAMETERS = "AlgorithmParameters";

  private AlgorithmParametersSpi paramSpi;
  private Provider provider;
  private String algorithm;

  /**
   * Constructs a new instance of <code>AlgorithmParameters</code>.
   * 
   * @param paramSpi
   *          the engine to use.
   * @param provider
   *          the provider to use.
   * @param algorithm
   *          the algorithm to use.
   */
  protected AlgorithmParameters(AlgorithmParametersSpi paramSpi,
                                Provider provider, String algorithm)
  {
    this.paramSpi = paramSpi;
    this.provider = provider;
    this.algorithm = algorithm;
  }

  /** @return A string with the name of the algorithm used. */
  public final String getAlgorithm()
  {
    return algorithm;
  }

  /**
   * Returns a new instance of <code>AlgorithmParameters</code> representing
   * the specified algorithm parameters.
   * <p>
   * The returned <code>AlgorithmParameters</code> must still be initialized
   * with an <code>init()</code> method.
   * 
   * @param algorithm the algorithm to use.
   * @return the new instance repesenting the desired algorithm.
   * @throws NoSuchAlgorithmException if the algorithm is not implemented by any
   *           provider.
   * @throws IllegalArgumentException if <code>algorithm</code> is
   *           <code>null</code> or is an empty string.
   */
  public static AlgorithmParameters getInstance(String algorithm)
      throws NoSuchAlgorithmException
  {
    Provider[] p = Security.getProviders();
    NoSuchAlgorithmException lastException = null;
    for (int i = 0; i < p.length; i++)
      try
        {
          return getInstance(algorithm, p[i]);
        }
      catch (NoSuchAlgorithmException x)
        {
          lastException = x;
        }
    if (lastException != null)
      throw lastException;
    throw new NoSuchAlgorithmException(algorithm);
  }

  /**
   * Returns a new instance of <code>AlgorithmParameters</code> representing
   * the specified algorithm parameters from a named provider.
   * <p>
   * The returned <code>AlgorithmParameters</code> must still be intialized
   * with an <code>init()</code> method.
   * </p>
   * 
   * @param algorithm the algorithm to use.
   * @param provider the name of the {@link Provider} to use.
   * @return the new instance repesenting the desired algorithm.
   * @throws NoSuchAlgorithmException if the algorithm is not implemented by the
   *           named provider.
   * @throws NoSuchProviderException if the named provider was not found.
   * @throws IllegalArgumentException if either <code>algorithm</code> or
   *           <code>provider</code> is <code>null</code> or empty.
   */
  public static AlgorithmParameters getInstance(String algorithm,
                                                String provider)
      throws NoSuchAlgorithmException, NoSuchProviderException
  {
    if (provider == null)
      throw new IllegalArgumentException("provider MUST NOT be null");
    provider = provider.trim();
    if (provider.length() == 0)
      throw new IllegalArgumentException("provider MUST NOT be empty");
    Provider p = Security.getProvider(provider);
    if (p == null)
      throw new NoSuchProviderException(provider);
    return getInstance(algorithm, p);
  }

  /**
   * Returns a new instance of <code>AlgorithmParameters</code> representing
   * the specified algorithm parameters from the specified {@link Provider}.
   * <p>
   * The returned <code>AlgorithmParameters</code> must still be intialized
   * with an <code>init()</code> method.
   * 
   * @param algorithm the algorithm to use.
   * @param provider the {@link Provider} to use.
   * @return the new instance repesenting the desired algorithm.
   * @throws NoSuchAlgorithmException if the algorithm is not implemented by the
   *           {@link Provider}.
   * @throws IllegalArgumentException if either <code>algorithm</code> or
   *           <code>provider</code> is <code>null</code>, or if
   *           <code>algorithm</code> is an empty string.
   * @since 1.4
   */
  public static AlgorithmParameters getInstance(String algorithm,
                                                Provider provider)
      throws NoSuchAlgorithmException
  {
    StringBuilder sb = new StringBuilder("AlgorithmParameters for algorithm [")
        .append(algorithm).append("] from provider[")
        .append(provider).append("] could not be created");
    Throwable cause;
    try
      {
        Object spi = Engine.getInstance(ALGORITHM_PARAMETERS, algorithm, provider);
        return new AlgorithmParameters((AlgorithmParametersSpi) spi,
                                       provider,
                                       algorithm);
      }
    catch (InvocationTargetException x)
      {
        cause = x.getCause();
        if (cause instanceof NoSuchAlgorithmException)
          throw (NoSuchAlgorithmException) cause;
        if (cause == null)
          cause = x;
      }
    catch (ClassCastException x)
      {
        cause = x;
      }
    NoSuchAlgorithmException x = new NoSuchAlgorithmException(sb.toString());
    x.initCause(cause);
    throw x;
  }

  /** @return the provider of this parameter object. */
  public final Provider getProvider()
  {
    return provider;
  }

  /**
   * Initializes the engine with the specified {@link AlgorithmParameterSpec}.
   * 
   * @param paramSpec
   *          A {@link AlgorithmParameterSpec} to use.
   * @throws InvalidParameterSpecException
   *           if <code>paramSpec</code> is invalid.
   */
  public final void init(AlgorithmParameterSpec paramSpec)
    throws InvalidParameterSpecException
  {
    paramSpi.engineInit(paramSpec);
  }

  /**
   * Initializes the engine with the specified parameters stored in the byte
   * array and decodes them according to the ASN.1 specification. If the ASN.1
   * specification exists then it succeeds otherwise an {@link IOException} is
   * thrown.
   * 
   * @param params
   *          the parameters to use.
   * @throws IOException
   *           if a decoding error occurs.
   */
  public final void init(byte[]params) throws IOException
  {
    paramSpi.engineInit(params);
  }

  /**
   * Initializes the engine with the specified parameters stored in the byte
   * array and decodes them according to the specified decoding specification.
   * If <code>format</code> is <code>null</code>, then this method decodes the
   * byte array using the ASN.1 specification if it exists, otherwise it throws
   * an {@link IOException}.
   * 
   * @param params
   *          the parameters to use.
   * @param format
   *          the name of decoding format to use.
   * @throws IOException
   *           if a decoding error occurs.
   */
  public final void init(byte[]params, String format) throws IOException
  {
    paramSpi.engineInit(params, format);
  }

  /**
   * Returns a new instance of <code>AlgorithmParameters</code> as a
   * designated parameter specification {@link Class}.
   * 
   * @param paramSpec
   *          the {@link Class} to use.
   * @return the parameter specification.
   * @throws InvalidParameterSpecException
   *           if <code>paramSpec</code> is invalid.
   */
  public final <T extends AlgorithmParameterSpec>
  T getParameterSpec(Class<T> paramSpec)
    throws InvalidParameterSpecException
  {
    return paramSpi.engineGetParameterSpec(paramSpec);
  }

  /**
   * Returns the parameters in the default encoding format. The primary encoding
   * format is ASN.1 if it exists for the specified type.
   * 
   * @return byte array representing the parameters.
   */
  public final byte[] getEncoded() throws IOException
  {
    return paramSpi.engineGetEncoded();
  }

  /**
   * Returns the parameters in the specified encoding format. If
   * <code>format</code> is <code>null</code> then the ASN.1 encoding
   * format is used if it exists for the specified type.
   * 
   * @param format
   *          the name of the encoding format to use.
   * @return the parameters encoded using the specified encoding scheme.
   * @throws IOException
   *           if an encoding exception occurs, or if this parameter object has
   *           not been initialized.
   */
  public final byte[] getEncoded(String format) throws IOException
  {
    return paramSpi.engineGetEncoded(format);
  }

  /**
   * Returns a string representation of the encoded form.
   * 
   * @return a string representation of the encoded form.
   */
  public final String toString()
  {
    return paramSpi.engineToString();
  }
}