/*
    * Copyright (c) 2002-2026 Gargoyle Software Inc.
    *
    * 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
    * https://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.htmlunit.attachment;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.file.Files;
  import java.nio.file.LinkOption;
  import java.nio.file.Path;
  
  import org.apache.commons.io.FileUtils;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.htmlunit.Page;
  import org.htmlunit.WebResponse;
  import org.htmlunit.util.StringUtils;
  
  /**
   * Implementation of an {@link AttachmentHandler} that mimics how browsers handle attachments, specifically
   * <ul>
   * <li>download file into a default folder when attachment response is detected</li>
   * <li>infer filename from octet stream response and use that when saving file</li>
   * <li>if a file already exists, append number to it.
   * Keep incrementing numbers until you find a slot that is free (that's how Chrome handles duplicate filenames).</li>
   * </ul>
   *
   * @author Marek Andreansky
   * @author Ronald Brill
   */
  public class DownloadingAttachmentHandler implements AttachmentHandler {
  
      private static final Log LOG = LogFactory.getLog(DownloadingAttachmentHandler.class);
  
      private final Path downloadFolder_;
  
      /**
       * Creates a new DownloadingAttachmentHandler that stores all downloaded files in the
       * provided directory. The directory must exist and be writable.
       *
       * @param downloadFolder the path to the folder for storing all downloaded files
       * @throws IOException if the folder does not exist or the folder is not writable
       */
      public DownloadingAttachmentHandler(final Path downloadFolder) throws IOException {
          downloadFolder_ = downloadFolder;
          if (Files.notExists(downloadFolder)) {
              throw new IOException("The provided download folder '"
                          + downloadFolder + "' does not exist");
          }
          if (!Files.isWritable(downloadFolder)) {
              throw new IOException("Can't write to the download folder '"
                          + downloadFolder + "'");
          }
      }
  
      /**
       * Creates a new DownloadingAttachmentHandler that stores all downloaded files in the
       * 'temp'-dir (System.getProperty("java.io.tmpdir")).
       *
       * @throws IOException if the folder does not exist or the folder is not writable
       */
      public DownloadingAttachmentHandler() throws IOException {
          this(Path.of(System.getProperty("java.io.tmpdir")));
      }
  
      /**
       * {@inheritDoc}
       */
      @Override
      public void handleAttachment(final Page page, final String attachmentFilename) {
          final Path destination = determineDestionationFile(page, attachmentFilename);
  
          final WebResponse webResponse = page.getWebResponse();
          try (InputStream contentAsStream = webResponse.getContentAsStream()) {
              FileUtils.copyToFile(contentAsStream, destination.toFile());
          }
          catch (final Exception e) {
              LOG.error("Failed to write attachment response content to '"
                              + destination.toAbsolutePath() + "'");
              return;
          }
  
          webResponse.cleanUp();
      }
  
      private Path determineDestionationFile(final Page page, final String attachmentFilename) {
          String fileName = attachmentFilename;
  
         if (StringUtils.isBlank(fileName)) {
             final String file = page.getWebResponse().getWebRequest().getUrl().getFile();
             fileName = file.substring(file.lastIndexOf('/') + 1);
         }
 
         if (StringUtils.isBlank(fileName)) {
             fileName = "download";
         }
 
         Path newPath = downloadFolder_.resolve(fileName);
         int count = 1;
         while (Files.exists(newPath, LinkOption.NOFOLLOW_LINKS)) {
             final String newFileName;
             final int pos = fileName.lastIndexOf('.');
             if (pos == -1) {
                 newFileName = fileName + "(" + count + ")";
             }
             else {
                 newFileName = fileName.substring(0, pos)
                                         + "(" + count + ")"
                                         + fileName.substring(pos);
             }
 
             newPath = downloadFolder_.resolve(newFileName);
             count++;
         }
 
         return newPath.toAbsolutePath();
     }
 }