//
//  ========================================================================
//  Copyright (c) 1995-2020 Mort Bay Consulting Pty Ltd and others.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.websocket.common;

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.util.Base64;

/**
 * Logic for working with the <code>Sec-WebSocket-Key</code> and <code>Sec-WebSocket-Accept</code> headers.
 * <p>
 * This is kept separate from Connection objects to facilitate difference in behavior between client and server, as well as making testing easier.
 */
public class AcceptHash
{
    /**
     * Globally Unique Identifier for use in WebSocket handshake within <code>Sec-WebSocket-Accept</code> and <code>Sec-WebSocket-Key</code> http headers.
     * <p>
     * See <a href="https://tools.ietf.org/html/rfc6455#section-1.3">Opening Handshake (Section 1.3)</a>
     */
    private static final byte[] MAGIC = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11".getBytes(StandardCharsets.ISO_8859_1);

    /**
     * Concatenate the provided key with the Magic GUID and return the Base64 encoded form.
     *
     * @param key the key to hash
     * @return the <code>Sec-WebSocket-Accept</code> header response (per opening handshake spec)
     */
    public static String hashKey(String key)
    {
        try
        {
            MessageDigest md = MessageDigest.getInstance("SHA1");
            md.update(key.getBytes(StandardCharsets.UTF_8));
            md.update(MAGIC);
            return Base64.getEncoder().encodeToString(md.digest());
        }
        catch (Exception e)
        {
            throw new RuntimeException(e);
        }
    }
}
