package org.spongycastle.crypto.params;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Date;
import java.util.Enumeration;
import java.util.Hashtable;

import org.spongycastle.crypto.CipherParameters;
import org.spongycastle.crypto.digests.SkeinDigest;
import org.spongycastle.crypto.digests.SkeinEngine;
import org.spongycastle.crypto.macs.SkeinMac;
import org.spongycastle.util.Integers;

/**
 * Parameters for the Skein hash function - a series of byte[] strings identified by integer tags.
 * <p/>
 * Parameterised Skein can be used for:
 * <ul>
 * <li>MAC generation, by providing a {@link SkeinParameters.Builder#setKey(byte[]) key}.</li>
 * <li>Randomised hashing, by providing a {@link SkeinParameters.Builder#setNonce(byte[]) nonce}.</li>
 * <li>A hash function for digital signatures, associating a
 * {@link SkeinParameters.Builder#setPublicKey(byte[]) public key} with the message digest.</li>
 * <li>A key derivation function, by providing a
 * {@link SkeinParameters.Builder#setKeyIdentifier(byte[]) key identifier}.</li>
 * <li>Personalised hashing, by providing a
 * {@link SkeinParameters.Builder#setPersonalisation(Date, String, String) recommended format} or
 * {@link SkeinParameters.Builder#setPersonalisation(byte[]) arbitrary} personalisation string.</li>
 * </ul>
 *
 * @see SkeinEngine
 * @see SkeinDigest
 * @see SkeinMac
 */
public class SkeinParameters
    implements CipherParameters
{
    /**
     * The parameter type for a secret key, supporting MAC or KDF functions: {@value
     * #PARAM_TYPE_KEY}.
     */
    public static final int PARAM_TYPE_KEY = 0;

    /**
     * The parameter type for the Skein configuration block: {@value #PARAM_TYPE_CONFIG}.
     */
    public static final int PARAM_TYPE_CONFIG = 4;

    /**
     * The parameter type for a personalisation string: {@value #PARAM_TYPE_PERSONALISATION}.
     */
    public static final int PARAM_TYPE_PERSONALISATION = 8;

    /**
     * The parameter type for a public key: {@value #PARAM_TYPE_PUBLIC_KEY}.
     */
    public static final int PARAM_TYPE_PUBLIC_KEY = 12;

    /**
     * The parameter type for a key identifier string: {@value #PARAM_TYPE_KEY_IDENTIFIER}.
     */
    public static final int PARAM_TYPE_KEY_IDENTIFIER = 16;

    /**
     * The parameter type for a nonce: {@value #PARAM_TYPE_NONCE}.
     */
    public static final int PARAM_TYPE_NONCE = 20;

    /**
     * The parameter type for the message: {@value #PARAM_TYPE_MESSAGE}.
     */
    public static final int PARAM_TYPE_MESSAGE = 48;

    /**
     * The parameter type for the output transformation: {@value #PARAM_TYPE_OUTPUT}.
     */
    public static final int PARAM_TYPE_OUTPUT = 63;

    private Hashtable parameters;

    public SkeinParameters()
    {
        this(new Hashtable());
    }

    private SkeinParameters(final Hashtable parameters)
    {
        this.parameters = parameters;
    }

    /**
     * Obtains a map of type (Integer) to value (byte[]) for the parameters tracked in this object.
     */
    public Hashtable getParameters()
    {
        return parameters;
    }

    /**
     * Obtains the value of the {@link #PARAM_TYPE_KEY key parameter}, or <code>null</code> if not
     * set.
     */
    public byte[] getKey()
    {
        return (byte[])parameters.get(Integers.valueOf(PARAM_TYPE_KEY));
    }

    /**
     * Obtains the value of the {@link #PARAM_TYPE_PERSONALISATION personalisation parameter}, or
     * <code>null</code> if not set.
     */
    public byte[] getPersonalisation()
    {
        return (byte[])parameters.get(Integers.valueOf(PARAM_TYPE_PERSONALISATION));
    }

    /**
     * Obtains the value of the {@link #PARAM_TYPE_PUBLIC_KEY public key parameter}, or
     * <code>null</code> if not set.
     */
    public byte[] getPublicKey()
    {
        return (byte[])parameters.get(Integers.valueOf(PARAM_TYPE_PUBLIC_KEY));
    }

    /**
     * Obtains the value of the {@link #PARAM_TYPE_KEY_IDENTIFIER key identifier parameter}, or
     * <code>null</code> if not set.
     */
    public byte[] getKeyIdentifier()
    {
        return (byte[])parameters.get(Integers.valueOf(PARAM_TYPE_KEY_IDENTIFIER));
    }

    /**
     * Obtains the value of the {@link #PARAM_TYPE_NONCE nonce parameter}, or <code>null</code> if
     * not set.
     */
    public byte[] getNonce()
    {
        return (byte[])parameters.get(Integers.valueOf(PARAM_TYPE_NONCE));
    }

    /**
     * A builder for {@link SkeinParameters}.
     */
    public static class Builder
    {
        private Hashtable parameters = new Hashtable();

        public Builder()
        {
        }

        public Builder(Hashtable paramsMap)
        {
            Enumeration keys = paramsMap.keys();
            while (keys.hasMoreElements())
            {
                Integer key = (Integer)keys.nextElement();
                parameters.put(key, paramsMap.get(key));
            }
        }

        public Builder(SkeinParameters params)
        {
            Enumeration keys = params.parameters.keys();
            while (keys.hasMoreElements())
            {
                Integer key = (Integer)keys.nextElement();
                parameters.put(key, params.parameters.get(key));
            }
        }

        /**
         * Sets a parameters to apply to the Skein hash function.<br>
         * Parameter types must be in the range 0,5..62, and cannot use the value {@value
         * SkeinParameters#PARAM_TYPE_MESSAGE} (reserved for message body).
         * <p/>
         * Parameters with type < {@value SkeinParameters#PARAM_TYPE_MESSAGE} are processed before
         * the message content, parameters with type > {@value SkeinParameters#PARAM_TYPE_MESSAGE}
         * are processed after the message and prior to output.
         *
         * @param type  the type of the parameter, in the range 5..62.
         * @param value the byte sequence of the parameter.
         * @return
         */
        public Builder set(int type, byte[] value)
        {
            if (value == null)
            {
                throw new IllegalArgumentException("Parameter value must not be null.");
            }
            if ((type != PARAM_TYPE_KEY)
                && (type <= PARAM_TYPE_CONFIG || type >= PARAM_TYPE_OUTPUT || type == PARAM_TYPE_MESSAGE))
            {
                throw new IllegalArgumentException("Parameter types must be in the range 0,5..47,49..62.");
            }
            if (type == PARAM_TYPE_CONFIG)
            {
                throw new IllegalArgumentException("Parameter type " + PARAM_TYPE_CONFIG
                    + " is reserved for internal use.");
            }
            this.parameters.put(Integers.valueOf(type), value);
            return this;
        }

        /**
         * Sets the {@link SkeinParameters#PARAM_TYPE_KEY} parameter.
         */
        public Builder setKey(byte[] key)
        {
            return set(PARAM_TYPE_KEY, key);
        }

        /**
         * Sets the {@link SkeinParameters#PARAM_TYPE_PERSONALISATION} parameter.
         */
        public Builder setPersonalisation(byte[] personalisation)
        {
            return set(PARAM_TYPE_PERSONALISATION, personalisation);
        }

        /**
         * Sets the {@link SkeinParameters#PARAM_TYPE_KEY_IDENTIFIER} parameter.
         */
        public Builder setPublicKey(byte[] publicKey)
        {
            return set(PARAM_TYPE_PUBLIC_KEY, publicKey);
        }

        /**
         * Sets the {@link SkeinParameters#PARAM_TYPE_KEY_IDENTIFIER} parameter.
         */
        public Builder setKeyIdentifier(byte[] keyIdentifier)
        {
            return set(PARAM_TYPE_KEY_IDENTIFIER, keyIdentifier);
        }

        /**
         * Sets the {@link SkeinParameters#PARAM_TYPE_NONCE} parameter.
         */
        public Builder setNonce(byte[] nonce)
        {
            return set(PARAM_TYPE_NONCE, nonce);
        }

        /**
         * Constructs a new {@link SkeinParameters} instance with the parameters provided to this
         * builder.
         */
        public SkeinParameters build()
        {
            return new SkeinParameters(parameters);
        }
    }
}
