package org.codehaus.plexus.digest;

 /*

  * Copyright 2001-2007 The Codehaus.

  *

  * 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.

  */

 import org.codehaus.plexus.util.FileUtils;

 import org.codehaus.plexus.util.StringUtils;

 import java.io.File;

 import java.io.FileNotFoundException;

 import java.io.IOException;

 /**

  * ChecksumFile 

  *

  * @author <a href="mailto:joakim@erdfelt.com">Joakim Erdfelt</a>

  * @version $Id$

  * 

  * @plexus.component role="org.codehaus.plexus.digest.ChecksumFile"

  */

 public class ChecksumFile

 {

     /**

      * @plexus.requirement role-hint="sha1"

      */

     private Digester digestSha1;

     /**

      * @plexus.requirement role-hint="md5";

      */

     private Digester digestMd5;

     /**

      * <p>

      * Given a checksum file, check to see if the file it represents is valid according to the checksum.

      * </p>

      * 

      * <dl>

      *   <lh>Terminology:</lh>

      *   <dt>Checksum File</dt>

      *   <dd>The file that contains the previously calculated checksum value for the reference file.

      *       This is a text file with the extension ".sha1" or ".md5", and contains a single entry

      *       consisting of an optional reference filename, and a checksum string.

      *   </dd>

      *   <dt>Reference File</dt>

      *   <dd>The file that is being referenced in the checksum file.</dd>

      * </dl>

      * 

      * <p>

      * NOTE: Only supports single file checksums of type MD5 or SHA1.

      * </p>

      * 

      * @param checksumFile the checksum file (must end in ".sha1" or ".md5")

      * @return true if the checksum is valid for the file it represents.

      * @throws DigesterException if there is a digester problem during the check of the reference file. 

      * @throws FileNotFoundException if the checksumFile itself or the file it refers to is not found.

      * @throws IOException if the reading of the checksumFile or the file it refers to fails.

      */

     public boolean isValidChecksum( File checksumFile ) throws DigesterException, FileNotFoundException, IOException

     {

         if ( !checksumFile.exists() )

         {

             throw new FileNotFoundException( "Unable to find checksum file " + checksumFile.getAbsolutePath() );

         }

         if ( !checksumFile.isFile() )

         {

             throw new IOException( "Unable to load checksum from non-file " + checksumFile.getAbsolutePath() );

         }

         String path = checksumFile.getAbsolutePath();

         Digester digester = null;

         if ( path.endsWith( digestMd5.getFilenameExtension() ) )

         {

             digester = digestMd5;

         }

         else if ( path.endsWith( digestSha1.getFilenameExtension() ) )

         {

             digester = digestSha1;

         }

         // TODO: Add more digester implementations here.

         if ( digester == null )

         {

             throw new DigesterException( "Unable to determine digester type from filename " + path );

         }

         File referenceFile = new File( path.substring( 0, path.length() - digester.getFilenameExtension().length() ) );

         String rawChecksum = FileUtils.fileRead( checksumFile, "UTF-8" );

         String expectedChecksum = DigestUtils.cleanChecksum( rawChecksum, digester, referenceFile.getName() );

         String actualChecksum = digester.calc( referenceFile );

         return StringUtils.equalsIgnoreCase( expectedChecksum, actualChecksum );

     }

     /**

      * Creates a checksum file of the provided referenceFile.

      * 

      * @param referenceFile the file to checksum.

      * @param digester the digester to use.

      * @return the checksum File that was created.

      * @throws DigesterException if there was a problem calculating the checksum of the referenceFile. 

      * @throws IOException if there was a problem either reading the referenceFile, or writing the checksum file.

      */

     public File createChecksum( File referenceFile, Digester digester ) throws DigesterException, IOException

     {

         File checksumFile = new File( referenceFile.getAbsolutePath() + digester.getFilenameExtension() );

         String checksum = digester.calc( referenceFile );

         FileUtils.fileWrite( checksumFile.getAbsolutePath(), "UTF-8", checksum + "  " + referenceFile.getName() );

         return checksumFile;

     }

 }