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package java.security;

import java.io.*;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.InvalidParameterSpecException;
import java.util.Objects;

/**
 * This class is used as an opaque representation of cryptographic parameters.
 *
 * <p>An {@code AlgorithmParameters} object for managing the parameters
 * for a particular algorithm can be obtained by
 * calling one of the {@code getInstance} factory methods
 * (static methods that return instances of a given class).
 *
 * <p>Once an {@code AlgorithmParameters} object is obtained, it must be
 * initialized via a call to {@code init}, using an appropriate parameter
 * specification or parameter encoding.
 *
 * <p>A transparent parameter specification is obtained from an
 * {@code AlgorithmParameters} object via a call to
 * {@code getParameterSpec}, and a byte encoding of the parameters is
 * obtained via a call to {@code getEncoded}.
 *
 * <p> Every implementation of the Java platform is required to support the
 * following standard {@code AlgorithmParameters} algorithms:
 * <ul>
 * <li>{@code AES}</li>
 * <li>{@code DES}</li>
 * <li>{@code DESede}</li>
 * <li>{@code DiffieHellman}</li>
 * <li>{@code DSA}</li>
 * </ul>
 * These algorithms are described in the <a href=
 * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms">
 * AlgorithmParameters section</a> of the
 * Java Security Standard Algorithm Names Specification.
 * Consult the release documentation for your implementation to see if any
 * other algorithms are supported.
 *
 * @author Jan Luehe
 *
 *
 * @see java.security.spec.AlgorithmParameterSpec
 * @see java.security.spec.DSAParameterSpec
 * @see KeyPairGenerator
 *
 * @since 1.2
 */

public class AlgorithmParameters {

 // The provider
 private Provider provider;

 // The provider implementation (delegate)
 private AlgorithmParametersSpi paramSpi;

 // The algorithm
 private String algorithm;

 // Has this object been initialized?
 private boolean initialized = false;

 /**
 * Creates an AlgorithmParameters object.
 *
 * @param paramSpi the delegate
 * @param provider the provider
 * @param algorithm the algorithm
 */
 protected AlgorithmParameters(AlgorithmParametersSpi paramSpi,
 Provider provider, String algorithm)
 {
 this.paramSpi = paramSpi;
 this.provider = provider;
 this.algorithm = algorithm;
 }

 /**
 * Returns the name of the algorithm associated with this parameter object.
 *
 * @return the algorithm name.
 */
 public final String getAlgorithm() {
 return this.algorithm;
 }

 /**
 * Returns a parameter object for the specified algorithm.
 *
 * <p> This method traverses the list of registered security Providers,
 * starting with the most preferred Provider.
 * A new AlgorithmParameters object encapsulating the
 * AlgorithmParametersSpi implementation from the first
 * Provider that supports the specified algorithm is returned.
 *
 * <p> Note that the list of registered providers may be retrieved via
 * the {@link Security#getProviders() Security.getProviders()} method.
 *
 * <p> The returned parameter object must be initialized via a call to
 * {@code init}, using an appropriate parameter specification or
 * parameter encoding.
 *
 * @implNote
 * The JDK Reference Implementation additionally uses the
 * {@code jdk.security.provider.preferred}
 * {@link Security#getProperty(String) Security} property to determine
 * the preferred provider order for the specified algorithm. This
 * may be different than the order of providers returned by
 * {@link Security#getProviders() Security.getProviders()}.
 *
 * @param algorithm the name of the algorithm requested.
 * See the AlgorithmParameters section in the <a href=
 * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms">
 * Java Security Standard Algorithm Names Specification</a>
 * for information about standard algorithm names.
 *
 * @return the new parameter object
 *
 * @throws NoSuchAlgorithmException if no {@code Provider} supports an
 * {@code AlgorithmParametersSpi} implementation for the
 * specified algorithm
 *
 * @throws NullPointerException if {@code algorithm} is {@code null}
 *
 * @see Provider
 */
 public static AlgorithmParameters getInstance(String algorithm)
 throws NoSuchAlgorithmException {
 Objects.requireNonNull(algorithm, "null algorithm name");
 try {
 Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters",
 (String)null);
 return new AlgorithmParameters((AlgorithmParametersSpi)objs[0],
 (Provider)objs[1],
 algorithm);
 } catch(NoSuchProviderException e) {
 throw new NoSuchAlgorithmException(algorithm + " not found");
 }
 }

 /**
 * Returns a parameter object for the specified algorithm.
 *
 * <p> A new AlgorithmParameters object encapsulating the
 * AlgorithmParametersSpi implementation from the specified provider
 * is returned. The specified provider must be registered
 * in the security provider list.
 *
 * <p> Note that the list of registered providers may be retrieved via
 * the {@link Security#getProviders() Security.getProviders()} method.
 *
 * <p>The returned parameter object must be initialized via a call to
 * {@code init}, using an appropriate parameter specification or
 * parameter encoding.
 *
 * @param algorithm the name of the algorithm requested.
 * See the AlgorithmParameters section in the <a href=
 * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms">
 * Java Security Standard Algorithm Names Specification</a>
 * for information about standard algorithm names.
 *
 * @param provider the name of the provider.
 *
 * @return the new parameter object
 *
 * @throws IllegalArgumentException if the provider name is {@code null}
 * or empty
 *
 * @throws NoSuchAlgorithmException if an {@code AlgorithmParametersSpi}
 * implementation for the specified algorithm is not
 * available from the specified provider
 *
 * @throws NoSuchProviderException if the specified provider is not
 * registered in the security provider list
 *
 * @throws NullPointerException if {@code algorithm} is {@code null}
 *
 * @see Provider
 */
 public static AlgorithmParameters getInstance(String algorithm,
 String provider)
 throws NoSuchAlgorithmException, NoSuchProviderException
 {
 Objects.requireNonNull(algorithm, "null algorithm name");
 if (provider == null || provider.length() == 0)
 throw new IllegalArgumentException("missing provider");
 Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters",
 provider);
 return new AlgorithmParameters((AlgorithmParametersSpi)objs[0],
 (Provider)objs[1],
 algorithm);
 }

 /**
 * Returns a parameter object for the specified algorithm.
 *
 * <p> A new AlgorithmParameters object encapsulating the
 * AlgorithmParametersSpi implementation from the specified Provider
 * object is returned. Note that the specified Provider object
 * does not have to be registered in the provider list.
 *
 * <p>The returned parameter object must be initialized via a call to
 * {@code init}, using an appropriate parameter specification or
 * parameter encoding.
 *
 * @param algorithm the name of the algorithm requested.
 * See the AlgorithmParameters section in the <a href=
 * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms">
 * Java Security Standard Algorithm Names Specification</a>
 * for information about standard algorithm names.
 *
 * @param provider the name of the provider.
 *
 * @return the new parameter object
 *
 * @throws IllegalArgumentException if the provider is {@code null}
 *
 * @throws NoSuchAlgorithmException if an
 * {@code AlgorithmParameterGeneratorSpi}
 * implementation for the specified algorithm is not available
 * from the specified {@code Provider} object
 *
 * @throws NullPointerException if {@code algorithm} is {@code null}
 *
 * @see Provider
 *
 * @since 1.4
 */
 public static AlgorithmParameters getInstance(String algorithm,
 Provider provider)
 throws NoSuchAlgorithmException
 {
 Objects.requireNonNull(algorithm, "null algorithm name");
 if (provider == null)
 throw new IllegalArgumentException("missing provider");
 Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters",
 provider);
 return new AlgorithmParameters((AlgorithmParametersSpi)objs[0],
 (Provider)objs[1],
 algorithm);
 }

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

 /**
 * Initializes this parameter object using the parameters
 * specified in {@code paramSpec}.
 *
 * @param paramSpec the parameter specification.
 *
 * @exception InvalidParameterSpecException if the given parameter
 * specification is inappropriate for the initialization of this parameter
 * object, or if this parameter object has already been initialized.
 */
 public final void init(AlgorithmParameterSpec paramSpec)
 throws InvalidParameterSpecException
 {
 if (this.initialized)
 throw new InvalidParameterSpecException("already initialized");
 paramSpi.engineInit(paramSpec);
 this.initialized = true;
 }

 /**
 * Imports the specified parameters and decodes them according to the
 * primary decoding format for parameters. The primary decoding
 * format for parameters is ASN.1, if an ASN.1 specification for this type
 * of parameters exists.
 *
 * @param params the encoded parameters.
 *
 * @exception IOException on decoding errors, or if this parameter object
 * has already been initialized.
 */
 public final void init(byte[] params) throws IOException {
 if (this.initialized)
 throw new IOException("already initialized");
 paramSpi.engineInit(params);
 this.initialized = true;
 }

 /**
 * Imports the parameters from {@code params} and decodes them
 * according to the specified decoding scheme.
 * If {@code format} is null, the
 * primary decoding format for parameters is used. The primary decoding
 * format is ASN.1, if an ASN.1 specification for these parameters
 * exists.
 *
 * @param params the encoded parameters.
 *
 * @param format the name of the decoding scheme.
 *
 * @exception IOException on decoding errors, or if this parameter object
 * has already been initialized.
 */
 public final void init(byte[] params, String format) throws IOException {
 if (this.initialized)
 throw new IOException("already initialized");
 paramSpi.engineInit(params, format);
 this.initialized = true;
 }

 /**
 * Returns a (transparent) specification of this parameter object.
 * {@code paramSpec} identifies the specification class in which
 * the parameters should be returned. It could, for example, be
 * {@code DSAParameterSpec.class}, to indicate that the
 * parameters should be returned in an instance of the
 * {@code DSAParameterSpec} class.
 *
 * @param <T> the type of the parameter specification to be returrned
 * @param paramSpec the specification class in which
 * the parameters should be returned.
 *
 * @return the parameter specification.
 *
 * @exception InvalidParameterSpecException if the requested parameter
 * specification is inappropriate for this parameter object, or if this
 * parameter object has not been initialized.
 */
 public final <T extends AlgorithmParameterSpec>
 T getParameterSpec(Class<T> paramSpec)
 throws InvalidParameterSpecException
 {
 if (this.initialized == false) {
 throw new InvalidParameterSpecException("not initialized");
 }
 return paramSpi.engineGetParameterSpec(paramSpec);
 }

 /**
 * Returns the parameters in their primary encoding format.
 * The primary encoding format for parameters is ASN.1, if an ASN.1
 * specification for this type of parameters exists.
 *
 * @return the parameters encoded using their primary encoding format.
 *
 * @exception IOException on encoding errors, or if this parameter object
 * has not been initialized.
 */
 public final byte[] getEncoded() throws IOException
 {
 if (this.initialized == false) {
 throw new IOException("not initialized");
 }
 return paramSpi.engineGetEncoded();
 }

 /**
 * Returns the parameters encoded in the specified scheme.
 * If {@code format} is null, the
 * primary encoding format for parameters is used. The primary encoding
 * format is ASN.1, if an ASN.1 specification for these parameters
 * exists.
 *
 * @param format the name of the encoding format.
 *
 * @return the parameters encoded using the specified encoding scheme.
 *
 * @exception IOException on encoding errors, or if this parameter object
 * has not been initialized.
 */
 public final byte[] getEncoded(String format) throws IOException
 {
 if (this.initialized == false) {
 throw new IOException("not initialized");
 }
 return paramSpi.engineGetEncoded(format);
 }

 /**
 * Returns a formatted string describing the parameters.
 *
 * @return a formatted string describing the parameters, or null if this
 * parameter object has not been initialized.
 */
 public final String toString() {
 if (this.initialized == false) {
 return null;
 }
 return paramSpi.engineToString();
 }
}