/**
    * This file Copyright (c) 2003-2018 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.module.files;
  
  import info.magnolia.jcr.util.NodeTypes;
  import info.magnolia.jcr.util.NodeUtil;
  import info.magnolia.jcr.util.PropertyUtil;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.security.DigestInputStream;
  import java.security.DigestOutputStream;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  
  import javax.jcr.Node;
  import javax.jcr.RepositoryException;
  import javax.jcr.Session;
  
  import org.apache.commons.codec.binary.Hex;
  import org.apache.commons.io.IOUtils;
  import org.apache.commons.lang3.StringUtils;
  
  /**
   * A FileExtractorOperation which checks extracted files against an MD5 checksum
   * stored in the repository. If the checksum does not exist or is identical to the
   * file being extracted, the file is extracted and potentially overwrites the
   * existing one. If not, which means the file was modified by the user,
   * the operation is cancelled.
   *
   * TODO : what to do with removed files ? should probably be the responsibility of a different Task.
   */
  class MD5CheckingFileExtractorOperation extends BasicFileExtractorOperation {
      private final FileExtractionLogger log;
      private final Session session;
  
      MD5CheckingFileExtractorOperation(FileExtractionLogger log, Session session, String resourcePath, String absoluteTargetPath) {
          super(resourcePath, absoluteTargetPath);
          this.log = log;
          this.session = session;
      }
  
      @Override
      protected InputStream checkInput() throws IOException {
          return wrap(super.checkInput());
      }
  
      // TODO : behaviour: overwrite, log, backup, .. ?
      @Override
      protected File checkOutput() throws IOException {
          final File out = super.checkOutput();
  
          if (out.exists()) {
              // check md5 of the existing file
              final InputStream stream = new FileInputStream(out);
              try {
                  final String existingFileMD5 = calculateMD5(stream);
                  final String repoMD5 = PropertyUtil.getString(getOrCreateNode(), "md5");
  
                  // check repository md5
                  if (StringUtils.isNotBlank(repoMD5)) {
                      if (existingFileMD5.equals(repoMD5)) {
                          // resourcePath was found, with correct md5 in repo : repoMD5
                          return out;
                      }
                     log.error("Can't extract " + resourcePath + " as this file was probably modified locally: expected MD5 [" + repoMD5 + "] but current MD5 is [" + existingFileMD5 + "].");
                     return null;
                 }
             } finally {
                 IOUtils.closeQuietly(stream);
             }
             // resourcePath was found, but no md5 found in repo ...
         } else {
             // resourcePath does not exist yet, extracting ...
         }
         return out;
     }
 
     @Override
     protected OutputStream openOutput(File outFile) throws IOException {
         final OutputStream outputStream = super.openOutput(outFile);
         final MessageDigest md5 = getMessageDigest();
         return new DigestOutputStream(outputStream, md5);
     }
 
     @Override
     protected void copyAndClose(InputStream in, OutputStream out) throws IOException {
         super.copyAndClose(in, out);
 
         final DigestInputStream md5Stream = (DigestInputStream) in;
         final String newMD5 = retrieveMD5(md5Stream);
 
         try {
             getOrCreateNode().setProperty("md5", newMD5);
         } catch (RepositoryException e) {
             throw new RuntimeException(e); // TODO
         }
         //TODO save .. ?
     }
 
     protected Node getOrCreateNode() {
         try {
             final String repoPath = getRepositoryPath(resourcePath);
             final Node node;
             if (!session.nodeExists(repoPath)) {
                 node = NodeUtil.createPath(session.getRootNode(), repoPath, NodeTypes.Content.NAME);
             } else {
                 node = session.getNode(repoPath);
             }
             return node;
         } catch (RepositoryException e) {
             throw new RuntimeException(e); // TODO
         }
     }
 
     /**
      * Returns the path to the node that has the property with this resource's MD5.
      * TODO : implement properly + test
      */
     protected String getRepositoryPath(String resourcePath) {
         return "/server/install" + resourcePath;
     }
 
     /**
      * Completely reads an InputStream and returns its MD5.
      * TODO : should we close it?
      */
     protected String calculateMD5(InputStream stream) throws IOException {
         final DigestInputStream md5Stream = wrap(stream);
         byte[] buffer = new byte[1024];
         while (md5Stream.read(buffer) != -1) {
         }
 
         return retrieveMD5(md5Stream);
     }
 
     protected DigestInputStream wrap(InputStream stream) {
         final MessageDigest md5 = getMessageDigest();
         return new DigestInputStream(stream, md5);
     }
 
     protected String retrieveMD5(DigestInputStream md5Stream) {
         final byte[] digInBytes = md5Stream.getMessageDigest().digest();
         return String.valueOf(Hex.encodeHex(digInBytes));
     }
 
     protected MessageDigest getMessageDigest() {
         try {
             return MessageDigest.getInstance("MD5");
         } catch (NoSuchAlgorithmException e) {
             throw new RuntimeException("Can't check files with md5: " + e.getMessage(), e);
         }
     }
 }