/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  package org.mycore.iview2.services;
  
  import java.awt.Graphics2D;
  import java.awt.image.BufferedImage;
  import java.io.IOException;
  import java.nio.file.FileSystem;
  import java.nio.file.Path;
  import java.util.Optional;
  import java.util.regex.Pattern;
  
  import javax.imageio.ImageReader;
  
  import org.mycore.datamodel.niofs.MCRPath;
  import org.mycore.imagetiler.MCRImage;
  import org.mycore.imagetiler.MCRTiledPictureProps;
  import org.mycore.media.services.MCRThumbnailGenerator;
  
  public class MCRImageThumbnailGenerator implements MCRThumbnailGenerator {
  
      private static final Pattern MATCHING_MIMETYPE = Pattern.compile("^image\\/.*");
  
      @Override
      public boolean matchesFileType(String mimeType, MCRPath path) {
          return MATCHING_MIMETYPE.matcher(mimeType).matches();
      }
  
      @Override
      public Optional<BufferedImage> getThumbnail(MCRPath path, int size) throws IOException {
          Path iviewFile = MCRImage.getTiledFile(MCRIView2Tools.getTileDir(), path.getOwner(),
              path.getOwnerRelativePath());
          MCRTiledPictureProps iviewFileProps = getIviewFileProps(iviewFile);
          final double width = iviewFileProps.getWidth();
          final double height = iviewFileProps.getHeight();
          final int newWidth = width > height ? (int) Math.ceil(size * width / height) : size;
          final int newHeight = width > height ? size : (int) Math.ceil(size * height / width);
  
          // this value determines the zoom level!
          final double scale = newWidth / width;
  
          // We always want to use the the best needed zoom level!
          int sourceZoomLevel = (int) Math.min(
              Math.max(0, Math.ceil(iviewFileProps.getZoomlevel() - Math.log(scale) / Math.log(1.0 / 2.0))),
              iviewFileProps.getZoomlevel());
  
          // scale is the real scale which is needed! zoomLevelScale is the scale of the nearest zoom level!
          double zoomLevelScale = Math.min(1.0, Math.pow(0.5, iviewFileProps.getZoomlevel() - sourceZoomLevel));
  
          // this is the scale which is needed from the nearest zoom level to the required size of image
          double drawScale = (newWidth / (width * zoomLevelScale));
  
          try (FileSystem zipFileSystem = MCRIView2Tools.getFileSystem(iviewFile)) {
              Path rootPath = zipFileSystem.getPath("/");
              ImageReader imageReader = MCRIView2Tools.getTileImageReader();
              BufferedImage testTile = MCRIView2Tools.readTile(rootPath, imageReader, sourceZoomLevel, 0, 0);
              BufferedImage targetImage = getTargetImage(newWidth, newHeight, testTile);
              Graphics2D graphics = targetImage.createGraphics();
              graphics.scale(drawScale, drawScale);
              for (int x = 0; x < Math.ceil(width * zoomLevelScale / 256); x++) {
                  for (int y = 0; y < Math.ceil(height * zoomLevelScale / 256); y++) {
                      BufferedImage tile = MCRIView2Tools.readTile(rootPath, imageReader, sourceZoomLevel, x, y);
                      graphics.drawImage(tile, x * 256, y * 256, null);
                  }
              }
              return Optional.of(targetImage);
          }
      }
  
      private MCRTiledPictureProps getIviewFileProps(Path tiledFile) throws IOException {
          MCRTiledPictureProps tiledPictureProps = null;
          try (FileSystem fileSystem = MCRIView2Tools.getFileSystem(tiledFile)) {
              tiledPictureProps = MCRTiledPictureProps.getInstanceFromDirectory(fileSystem.getPath("/"));
          } catch (IOException e) {
              throw new IOException("Could not provide image information!", e);
          }
          return tiledPictureProps;
      }
  
      private BufferedImage getTargetImage(int width, int height, BufferedImage firstTile) {
          return new BufferedImage(width, height, firstTile.getType());
      }
  }