/*
 * 微信公众平台(JAVA) SDK
 *
 * Copyright (c) 2014, Ansitech Network Technology Co.,Ltd All rights reserved.
 * 
 * http://www.weixin4j.org/
 *
 * Licensed 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 org.weixin4j.util;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * SHA1算法
 *
 * @author yangqisheng
 * @since 0.0.1
 */
public final class SHA1 {

    private static final char[] HEX_DIGITS = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};

    /**
     * Takes the raw bytes from the digest and formats them correct.
     *
     * @param bytes the raw bytes from the digest.
     * @return the formatted bytes.
     */
    private static String getFormattedText(byte[] bytes) {
        int len = bytes.length;
        StringBuilder buf = new StringBuilder(len * 2);
        // 把密文转换成十六进制的字符串形式
        for (int j = 0; j < len; j++) {
            buf.append(HEX_DIGITS[(bytes[j] >> 4) & 0x0f]);
            buf.append(HEX_DIGITS[bytes[j] & 0x0f]);
        }
        return buf.toString();
    }

    public static String encode(String str) {
        if (str == null) {
            return null;
        }
        try {
            MessageDigest messageDigest = MessageDigest.getInstance("SHA1");
            messageDigest.update(str.getBytes());
            return getFormattedText(messageDigest.digest());
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    }
}
