package org.apache.maven.index.packer;
   
   /*
    * 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.ByteArrayInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.charset.StandardCharsets;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  
  /**
   * A util class to calculate various digests on Strings. Useful for some simple password management.
   * 
   * @author cstamas
   */
  public class DigesterUtils
  {
      /**
       * Calculates a digest for a String user the requested algorithm.
       * 
       * @param alg
       * @param is
       * @return
       * @throws NoSuchAlgorithmException
       */
      private static String getDigest( String alg, InputStream is )
          throws NoSuchAlgorithmException
      {
          String result;
  
          try
          {
              try
              {
                  byte[] buffer = new byte[1024];
  
                  MessageDigest md = MessageDigest.getInstance( alg );
  
                  int numRead;
  
                  do
                  {
                      numRead = is.read( buffer );
  
                      if ( numRead > 0 )
                      {
                          md.update( buffer, 0, numRead );
                      }
                  }
                  while ( numRead != -1 );
  
                  result = new String( encodeHex( md.digest() ) );
              }
              finally
              {
                  is.close();
              }
          }
          catch ( IOException e )
          {
              // hrm
              result = null;
          }
  
          return result;
      }
  
      // SHA1
  
      /**
       * Calculates a SHA1 digest for a string.
       * 
       * @param content
       * @return
       */
      public static String getSha1Digest( String content )
      {
          try
         {
             InputStream fis = new ByteArrayInputStream( content.getBytes( StandardCharsets.UTF_8 ) );
 
             return getDigest( "SHA1", fis );
         }
         catch ( NoSuchAlgorithmException e )
         {
             // will not happen
             return null;
         }
     }
 
     /**
      * Calculates a SHA1 digest for a stream.
      * 
      * @param is
      * @return
      */
     public static String getSha1Digest( InputStream is )
     {
         try
         {
             return getDigest( "SHA1", is );
         }
         catch ( NoSuchAlgorithmException e )
         {
             // will not happen
             return null;
         }
     }
 
     /**
      * Calculates a SHA1 digest for a file.
      * 
      * @param file
      * @return
      */
     public static String getSha1Digest( File file )
         throws IOException
     {
         try ( FileInputStream fis = new FileInputStream( file ) )
         {
             return getDigest( "SHA1", fis );
         }
         catch ( NoSuchAlgorithmException | FileNotFoundException e )
         {
             // will not happen
             return null;
         }
     }
 
     // MD5
 
     /**
      * Calculates a SHA1 digest for a string.
      * 
      * @param content
      * @return
      */
     public static String getMd5Digest( String content )
     {
         try
         {
             InputStream fis = new ByteArrayInputStream( content.getBytes( StandardCharsets.UTF_8 ) );
 
             return getDigest( "MD5", fis );
         }
         catch ( NoSuchAlgorithmException e )
         {
             // will not happen
             return null;
         }
     }
 
     /**
      * Calculates a SHA1 digest for a stream.
      * 
      * @param is
      * @return
      */
     public static String getMd5Digest( InputStream is )
     {
         try
         {
             return getDigest( "MD5", is );
         }
         catch ( NoSuchAlgorithmException e )
         {
             // will not happen
             return null;
         }
     }
 
     /**
      * Calculates a SHA1 digest for a file.
      * 
      * @param file
      * @return
      */
     public static String getMd5Digest( File file )
         throws IOException
     {
 
         try ( InputStream fis = new FileInputStream( file ) )
         {
             return getDigest( "MD5", fis );
         }
         catch ( NoSuchAlgorithmException | FileNotFoundException e )
         {
             // will not happen
             return null;
         }
     }
 
     // --
 
     private static final char[] DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e',
         'f' };
 
     /**
      * Blatantly copied from commons-codec version 1.3
      * 
      * @param data
      * @return
      */
     public static char[] encodeHex( byte[] data )
     {
         int l = data.length;
 
         char[] out = new char[l << 1];
 
         // two characters form the hex value.
         for ( int i = 0, j = 0; i < l; i++ )
         {
             out[j++] = DIGITS[( 0xF0 & data[i] ) >>> 4];
             out[j++] = DIGITS[0x0F & data[i]];
         }
 
         return out;
     }
 
 }