/*
    * Copyright (c) 2016 ingenieux Labs
    *
    * 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 br.com.ingenieux.mojo.beanstalk.bundle;
  
  import com.amazonaws.auth.AWSCredentials;
  
  import org.apache.commons.codec.binary.Hex;
  
  import java.text.SimpleDateFormat;
  import java.util.Date;
  import java.util.SimpleTimeZone;
  
  import javax.crypto.Mac;
  import javax.crypto.spec.SecretKeySpec;
  
  /**
   * Created by aldrin on 04/01/16.
   */
  public class RequestSignerBase {
    public static final SimpleDateFormat DATE_TIME_FORMAT = new SimpleDateFormat("yyyyMMdd'T'HHmmss");
  
    public static final SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("yyyyMMdd");
  
    protected static final String AWS_ALGORITHM = "HMAC-SHA256";
  
    protected static final String TERMINATOR = "aws4_request";
  
    protected static final String SCHEME = "AWS4";
  
    static {
      SimpleTimeZone timezone = new SimpleTimeZone(0, "UTC");
  
      DATE_TIME_FORMAT.setTimeZone(timezone);
      DATE_FORMAT.setTimeZone(timezone);
    }
  
    final AWSCredentials awsCredentials;
  
    final String region;
  
    final String service;
  
    final Date date;
  
    final String strDate;
  
    final String strDateTime;
  
    protected RequestSignerBase(AWSCredentials awsCredentials, String region, String service, Date date) {
      this.awsCredentials = awsCredentials;
      this.region = region;
      this.service = service;
      this.date = date;
      this.strDate = DATE_FORMAT.format(date);
      this.strDateTime = DATE_TIME_FORMAT.format(date);
    }
  
    protected byte[] deriveKey() {
      String secret = RequestSigner.SCHEME.concat(awsCredentials.getAWSSecretKey());
      byte[] kSecret = secret.getBytes();
      byte[] kDate = hash(kSecret, strDate);
      byte[] kRegion = hash(kDate, region);
      byte[] kService = hash(kRegion, service);
      byte[] key = hash(kService, RequestSigner.TERMINATOR);
      return key;
    }
  
    protected byte[] hash(byte[] kSecret, String obj) {
      try {
        SecretKeySpec keySpec = new SecretKeySpec(kSecret, "HmacSHA256");
  
        Mac mac = Mac.getInstance("HmacSHA256");
  
        mac.init(keySpec);
  
        return mac.doFinal(obj.getBytes("UTF-8"));
      } catch (Exception exc) {
        throw new RuntimeException(exc);
      }
    }
  
    protected String hexEncode(String obj) {
      return Hex.encodeHexString(obj.getBytes());
    }
  }