/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.handler.codec.http.websocketx;

import io.netty.util.concurrent.FastThreadLocal;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Base64;
import java.util.concurrent.ThreadLocalRandom;

/**
 * A utility class mainly for use by web sockets
 */
final class WebSocketUtil {

    private static final FastThreadLocal<MessageDigest> MD5 = new FastThreadLocal<MessageDigest>() {
        @Override
        protected MessageDigest initialValue() throws Exception {
            try {
                //Try to get a MessageDigest that uses MD5
                return MessageDigest.getInstance("MD5");
            } catch (NoSuchAlgorithmException e) {
                //This shouldn't happen! How old is the computer?
                throw new InternalError("MD5 not supported on this platform - Outdated?");
            }
        }
    };

    private static final FastThreadLocal<MessageDigest> SHA1 = new FastThreadLocal<MessageDigest>() {
        @Override
        protected MessageDigest initialValue() throws Exception {
            try {
                //Try to get a MessageDigest that uses SHA1
                return MessageDigest.getInstance("SHA1");
            } catch (NoSuchAlgorithmException e) {
                //This shouldn't happen! How old is the computer?
                throw new InternalError("SHA-1 not supported on this platform - Outdated?");
            }
        }
    };

    /**
     * Performs a MD5 hash on the specified data
     *
     * @param data The data to hash
     * @return The hashed data
     */
    static byte[] md5(byte[] data) {
        // TODO(normanmaurer): Create md5 method that not need MessageDigest.
        return digest(MD5, data);
    }

    /**
     * Performs a SHA-1 hash on the specified data
     *
     * @param data The data to hash
     * @return The hashed data
     */
    static byte[] sha1(byte[] data) {
        // TODO(normanmaurer): Create sha1 method that not need MessageDigest.
        return digest(SHA1, data);
    }

    private static byte[] digest(FastThreadLocal<MessageDigest> digestFastThreadLocal, byte[] data) {
        MessageDigest digest = digestFastThreadLocal.get();
        digest.reset();
        return digest.digest(data);
    }

    /**
     * Performs base64 encoding on the specified data
     *
     * @param data The data to encode
     * @return An encoded string containing the data
     */
    static String base64(byte[] data) {
        return Base64.getEncoder().encodeToString(data);
    }
    /**
     * Creates an arbitrary number of random bytes
     *
     * @param size the number of random bytes to create
     * @return An array of random bytes
     */
    static byte[] randomBytes(int size) {
        byte[] bytes = new byte[size];
        ThreadLocalRandom.current().nextBytes(bytes);
        return bytes;
    }

    /**
     * A private constructor to ensure that instances of this class cannot be made
     */
    private WebSocketUtil() {
        // Unused
    }
}
