/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF 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 org.apache.maven.shared.repository.utils;

 import java.io.File;

 import java.io.FileInputStream;

 import java.io.IOException;

 import java.io.InputStream;

 import java.security.MessageDigest;

 import java.security.NoSuchAlgorithmException;

 import java.util.regex.Matcher;

 import java.util.regex.Pattern;

 import org.codehaus.plexus.util.IOUtil;

 /**

  * Create a digest for a file. Stolen from repository-utils - once released, use that instead.

  *

  * @author <a href="mailto:brett@apache.org">Brett Porter</a>

  * @todo [jdcasey] This needs unit tests.

  */

 public final class DigestUtils

 {

     private static final int CHECKSUM_BUFFER_SIZE = 16384;

     private static final int BYTE_MASK = 0xFF;

     private DigestUtils()

     {

     }

     public static String createChecksum( File file, String algorithm )

         throws IOException, NoSuchAlgorithmException

     {

         MessageDigest digest = MessageDigest.getInstance( algorithm );

         InputStream fis = new FileInputStream( file );

         try

         {

             byte[] buffer = new byte[CHECKSUM_BUFFER_SIZE];

             int numRead;

             do

             {

                 numRead = fis.read( buffer );

                 if ( numRead > 0 )

                 {

                     digest.update( buffer, 0, numRead );

                 }

             }

             while ( numRead != -1 );

         }

         finally

         {

             IOUtil.close( fis );

         }

         return byteArrayToHexStr( digest.digest() );

     }

     public boolean verifyChecksum( File file, String checksum, String algorithm )

         throws NoSuchAlgorithmException, IOException

     {

         boolean result = true;

         String trimmedChecksum = checksum.replace( '\n', ' ' ).trim();

         // Free-BSD / openssl

         Matcher m = Pattern.compile( algorithm.replaceAll( "-", "" ) + "\\s*\\((.*?)\\)\\s*=\\s*([a-zA-Z0-9]+)" )

             .matcher( trimmedChecksum );

         if ( m.matches() )

         {

             String filename = m.group( 1 );

             if ( !filename.equals( file.getName() ) )

             {

                 // TODO: provide better warning

                 result = false;

             }

             trimmedChecksum = m.group( 2 );

         }

         else

         {

             // GNU tools

             m = Pattern.compile( "([a-zA-Z0-9]+)\\s\\*?(.+)" ).matcher( trimmedChecksum );

             if ( m.matches() )

             {

                 String filename = m.group( 2 );

                 if ( !filename.equals( file.getName() ) )

                 {

                     // TODO: provide better warning

                     result = false;

                 }

                 trimmedChecksum = m.group( 1 );

             }

         }

         if ( result )

         {

             //Create checksum for jar file

             String sum = createChecksum( file, algorithm );

             result = trimmedChecksum.toUpperCase().equals( sum.toUpperCase() );

         }

         return result;

     }

     /**

      * Convert an incoming array of bytes into a string that represents each of

      * the bytes as two hex characters.

      *

      * @param data

      */

     private static String byteArrayToHexStr( byte[] data )

     {

         String output = "";

         for ( int cnt = 0; cnt < data.length; cnt++ )

         {

             //Deposit a byte into the 8 lsb of an int.

             int tempInt = data[cnt] & BYTE_MASK;

             //Get hex representation of the int as a string.

             String tempStr = Integer.toHexString( tempInt );

             //Append a leading 0 if necessary so that each hex string will contain 2 characters.

             if ( tempStr.length() == 1 )

             {

                 tempStr = "0" + tempStr;

             }

             //Concatenate the two characters to the output string.

             output = output + tempStr;

         }

         return output.toUpperCase();

     }

 }