package org.eclipse.aether.util;
   
   /*
    * 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.
   */
  
  import java.io.BufferedReader;
  import java.io.ByteArrayInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.nio.charset.StandardCharsets;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  import java.util.Collection;
  import java.util.LinkedHashMap;
  import java.util.Map;
  
  /**
   * A utility class to assist in the verification and generation of checksums.
   */
  public final class ChecksumUtils
  {
  
      private ChecksumUtils()
      {
          // hide constructor
      }
  
      /**
       * Extracts the checksum from the specified file.
       * 
       * @param checksumFile The path to the checksum file, must not be {@code null}.
       * @return The checksum stored in the file, never {@code null}.
       * @throws IOException If the checksum does not exist or could not be read for other reasons.
       * @deprecated Use SPI FileProcessor to read and write checksum files.
       */
      @Deprecated
      public static String read( File checksumFile )
          throws IOException
      {
          String checksum = "";
          try ( BufferedReader br = new BufferedReader( new InputStreamReader(
                  new FileInputStream( checksumFile ), StandardCharsets.UTF_8 ), 512 ) )
          {
              while ( true )
              {
                  String line = br.readLine();
                  if ( line == null )
                  {
                      break;
                  }
                  line = line.trim();
                  if ( line.length() > 0 )
                  {
                      checksum = line;
                      break;
                  }
              }
          }
  
          if ( checksum.matches( ".+= [0-9A-Fa-f]+" ) )
          {
              int lastSpacePos = checksum.lastIndexOf( ' ' );
              checksum = checksum.substring( lastSpacePos + 1 );
          }
          else
          {
              int spacePos = checksum.indexOf( ' ' );
  
              if ( spacePos != -1 )
              {
                  checksum = checksum.substring( 0, spacePos );
              }
          }
  
          return checksum;
      }
  
      /**
       * Calculates checksums for the specified file.
       * 
      * @param dataFile The file for which to calculate checksums, must not be {@code null}.
      * @param algos The names of checksum algorithms (cf. {@link MessageDigest#getInstance(String)} to use, must not be
      *            {@code null}.
      * @return The calculated checksums, indexed by algorithm name, or the exception that occurred while trying to
      *         calculate it, never {@code null}.
      * @throws IOException If the data file could not be read.
      * @deprecated Use SPI checksum selector instead.
      */
     @Deprecated
     public static Map<String, Object> calc( File dataFile, Collection<String> algos )
                     throws IOException
     {
        return calc( new FileInputStream( dataFile ), algos );
     }
 
     /**
      * @deprecated Use SPI checksum selector instead.
      */
     @Deprecated
     public static Map<String, Object> calc( byte[] dataBytes, Collection<String> algos )
                     throws IOException
     {
         return calc( new ByteArrayInputStream( dataBytes ), algos );
     }
 
     private static Map<String, Object> calc( InputStream data, Collection<String> algos )
         throws IOException
     {
         Map<String, Object> results = new LinkedHashMap<>();
 
         Map<String, MessageDigest> digests = new LinkedHashMap<>();
         for ( String algo : algos )
         {
             try
             {
                 digests.put( algo, MessageDigest.getInstance( algo ) );
             }
             catch ( NoSuchAlgorithmException e )
             {
                 results.put( algo, e );
             }
         }
 
         try ( InputStream in = data )
         {
             for ( byte[] buffer = new byte[ 32 * 1024 ];; )
             {
                 int read = in.read( buffer );
                 if ( read < 0 )
                 {
                     break;
                 }
                 for ( MessageDigest digest : digests.values() )
                 {
                     digest.update( buffer, 0, read );
                 }
             }
         }
 
         for ( Map.Entry<String, MessageDigest> entry : digests.entrySet() )
         {
             byte[] bytes = entry.getValue().digest();
 
             results.put( entry.getKey(), toHexString( bytes ) );
         }
 
         return results;
     }
     
 
     /**
      * Creates a hexadecimal representation of the specified bytes. Each byte is converted into a two-digit hex number
      * and appended to the result with no separator between consecutive bytes.
      * 
      * @param bytes The bytes to represent in hex notation, may be be {@code null}.
      * @return The hexadecimal representation of the input or {@code null} if the input was {@code null}.
      */
     @SuppressWarnings( "checkstyle:magicnumber" )
     public static String toHexString( byte[] bytes )
     {
         if ( bytes == null )
         {
             return null;
         }
 
         StringBuilder buffer = new StringBuilder( bytes.length * 2 );
 
         for ( byte aByte : bytes )
         {
             int b = aByte & 0xFF;
             if ( b < 0x10 )
             {
                 buffer.append( '0' );
             }
             buffer.append( Integer.toHexString( b ) );
         }
 
         return buffer.toString();
     }
 
     /**
      * Creates a byte array out of hexadecimal representation of the specified bytes. If input string is {@code null},
      * {@code null} is returned. Input value must have even length (due hex encoding = 2 chars one byte).
      *
      * @param hexString The hexString to convert to byte array, may be {@code null}.
      * @return The byte array of the input or {@code null} if the input was {@code null}.
      * @since 1.8.0
      */
     @SuppressWarnings( "checkstyle:magicnumber" )
     public static byte[] fromHexString( String hexString )
     {
         if ( hexString == null )
         {
             return null;
         }
         if ( hexString.isEmpty() )
         {
             return new byte[] {};
         }
         int len = hexString.length();
         if ( len % 2 != 0 )
         {
             throw new IllegalArgumentException( "hexString length not even" );
         }
         byte[] data = new byte[ len / 2 ];
         for ( int i = 0; i < len; i += 2 )
         {
             data[ i / 2 ] = (byte) ( ( Character.digit( hexString.charAt( i ), 16 ) << 4 )
                 + Character.digit( hexString.charAt( i + 1 ), 16 ) );
         }
         return data;
     }
 
 }