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/*
 * Copyright 2017 Chunlei Wang
 *
 * 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 com.github.codedrinker.fm.utils;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.util.Formatter;

public class Signature {
    public static String decode(String payload, String secret) {
        try {
            SecretKeySpec key = new SecretKeySpec(secret.getBytes("UTF-8"), "HmacSHA1");
            Mac mac = Mac.getInstance("HmacSHA1");
            mac.init(key);
            String decodeSignature = String.format("sha1=%s", toHexString(mac.doFinal(payload.getBytes("UTF-8"))));
            return decodeSignature;
        } catch (Exception e) {
        }
        return null;
    }

    private static String toHexString(byte[] bytes) {
        Formatter formatter = new Formatter();
        for (byte b : bytes) {
            formatter.format("%02x", b);
        }
        return formatter.toString();
    }
}