/**
 * Copyright Microsoft Corporation
 * 
 * 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.microsoft.windowsazure.services.blob.implementation;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

import com.sun.jersey.core.util.Base64;

public class HmacSHA256Sign {
    private final String accessKey;

    public HmacSHA256Sign(String accessKey) {
        this.accessKey = accessKey;
    }

    public String sign(String stringToSign) {
        try {
            // Encoding the Signature
            // Signature=Base64(HMAC-SHA256(UTF8(StringToSign)))

            Mac hmac = Mac.getInstance("hmacSHA256");
            hmac.init(new SecretKeySpec(Base64.decode(accessKey), "hmacSHA256"));
            byte[] digest = hmac.doFinal(stringToSign.getBytes("UTF-8"));
            return new String(Base64.encode(digest), "UTF-8");
        } catch (Exception e) {
            throw new IllegalArgumentException("accessKey", e);
        }
    }
}
