/*
 * 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.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.handler.codec.base64.Base64;
import io.netty.util.CharsetUtil;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

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

    /**
     * Performs a MD5 hash on the specified data
     *
     * @param data The data to hash
     * @return The hashed data
     */
    static byte[] md5(byte[] data) {
        try {
            //Try to get a MessageDigest that uses MD5
            MessageDigest md = MessageDigest.getInstance("MD5");
            //Hash the data
            return md.digest(data);
        } catch (NoSuchAlgorithmException e) {
            //This shouldn't happen! How old is the computer?
            throw new InternalError("MD5 not supported on this platform - Outdated?");
        }
    }

    /**
     * Performs a SHA-1 hash on the specified data
     *
     * @param data The data to hash
     * @return The hashed data
     */
    static byte[] sha1(byte[] data) {
        try {
            //Attempt to get a MessageDigest that uses SHA1
            MessageDigest md = MessageDigest.getInstance("SHA1");
            //Hash the data
            return md.digest(data);
        } catch (NoSuchAlgorithmException e) {
            //Alright, you might have an old system.
            throw new InternalError("SHA-1 is not supported on this platform - Outdated?");
        }
    }

    /**
     * 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) {
        ByteBuf encodedData = Unpooled.wrappedBuffer(data);
        ByteBuf encoded = Base64.encode(encodedData);
        String encodedString = encoded.toString(CharsetUtil.UTF_8);
        encoded.release();
        return encodedString;
    }

    /**
     * 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];

        for (int index = 0; index < size; index++) {
            bytes[index] = (byte) randomNumber(0, 255);
        }

        return bytes;
    }

    /**
     * Generates a pseudo-random number
     *
     * @param minimum The minimum allowable value
     * @param maximum The maximum allowable value
     * @return A pseudo-random number
     */
    static int randomNumber(int minimum, int maximum) {
        return (int) (Math.random() * maximum + minimum);
    }

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