code: ///////////////////////////////////////////////////////////////////////////////////////////////
  // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
  // Copyright (C) 2001-2023 the original author or authors.
  //
  // This library is free software; you can redistribute it and/or
  // modify it under the terms of the GNU Lesser General Public
  // License as published by the Free Software Foundation; either
  // version 2.1 of the License, or (at your option) any later version.
  //
  // This library 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
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle.gui;
  
  import java.io.File;
  import java.io.IOException;
  import java.nio.charset.StandardCharsets;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Locale;
  
  import com.puppycrawl.tools.checkstyle.JavaParser;
  import com.puppycrawl.tools.checkstyle.api.CheckstyleException;
  import com.puppycrawl.tools.checkstyle.api.DetailAST;
  import com.puppycrawl.tools.checkstyle.api.FileText;
  
  /**
   * Model for checkstyle frame.
   */
  public class MainFrameModel {
  
      /**
       * Parsing modes which available in GUI.
       */
      public enum ParseMode {
  
          /** Only Java tokens without comments. */
          PLAIN_JAVA("Plain Java"),
  
          /** Java tokens and comment nodes (singleline comments and block comments). */
          JAVA_WITH_COMMENTS("Java with comments"),
  
          /**
           * Java tokens, comments and Javadoc comments nodes
           * (which are parsed from block comments).
           */
          JAVA_WITH_JAVADOC_AND_COMMENTS("Java with comments and Javadocs");
  
          /**
           * Mode's short description.
           */
          private final String description;
  
          /**
           * Provides description.
           *
           * @param descr description
           */
          ParseMode(String descr) {
              description = descr;
          }
  
          @Override
          public String toString() {
              return description;
          }
  
      }
  
      /** Parse tree model. */
      private final ParseTreeTableModel parseTreeTableModel;
  
      /** Lines to position map. */
      private List<Integer> linesToPosition = new ArrayList<>();
  
      /** Current mode. */
      private ParseMode parseMode = ParseMode.PLAIN_JAVA;
  
      /** The file which is being parsed. */
      private File currentFile;
  
      /** Text for a frame's text area. */
      private String text;
  
      /** Title for the main frame. */
      private String title = "Checkstyle GUI";
  
      /** Whether the reload action is enabled. */
      private boolean reloadActionEnabled;
  
      /** Instantiate the model. */
      public MainFrameModel() {
          parseTreeTableModel = new ParseTreeTableModel(null);
      }
  
      /**
       * Set current parse mode.
       *
       * @param mode ParseMode enum.
       */
      public void setParseMode(ParseMode mode) {
          parseMode = mode;
      }
  
      /**
       * Get parse tree table model.
       *
       * @return parse tree table model.
       */
      public ParseTreeTableModel getParseTreeTableModel() {
          return parseTreeTableModel;
      }
  
      /**
       * Get text to display in a text area.
       *
       * @return text to display in a text area.
       */
      public String getText() {
          return text;
      }
  
      /**
       * Returns title for the main frame.
       *
       * @return title for the main frame.
       */
      public String getTitle() {
          return title;
      }
  
      /**
       * Returns true if the reload action is enabled, false otherwise.
       *
       * @return true if the reload action is enabled.
       */
      public boolean isReloadActionEnabled() {
          return reloadActionEnabled;
      }
  
      /**
       * Whether a file chooser should accept the file as a source file.
       *
       * @param file the file to check.
       * @return true if the file should be accepted.
       */
      public static boolean shouldAcceptFile(File file) {
          return file.isDirectory() || file.getName().endsWith(".java");
      }
  
      /**
       * Get the directory of the last loaded file.
       *
       * @return directory of the last loaded file.
       */
      public File getLastDirectory() {
          File lastDirectory = null;
          if (currentFile != null) {
              lastDirectory = currentFile.getParentFile();
          }
          return lastDirectory;
      }
  
      /**
       * Get current file.
       *
       * @return current file.
       */
      public File getCurrentFile() {
          return currentFile;
      }
  
      /**
       * Get lines to position map.
       * It returns unmodifiable collection to
       * prevent additional overhead of copying
       * and possible state modifications.
       *
       * @return lines to position map.
       */
      public List<Integer> getLinesToPosition() {
          return new ArrayList<>(linesToPosition);
      }
  
      /**
       * Open file and load the file.
       *
       * @param file the file to open.
       * @throws CheckstyleException if the file can not be parsed.
       * @throws IllegalArgumentException if parseMode is unknown
       */
      public void openFile(File file) throws CheckstyleException {
          if (file != null) {
              try {
                  currentFile = file;
                  title = "Checkstyle GUI : " + file.getName();
                  reloadActionEnabled = true;
                  final DetailAST parseTree;
  
                  if (parseMode == ParseMode.PLAIN_JAVA) {
                      parseTree = JavaParser.parseFile(file, JavaParser.Options.WITHOUT_COMMENTS);
                  }
                  else if (parseMode == ParseMode.JAVA_WITH_COMMENTS
                          || parseMode == ParseMode.JAVA_WITH_JAVADOC_AND_COMMENTS) {
                      parseTree = JavaParser.parseFile(file, JavaParser.Options.WITH_COMMENTS);
                  }
                  else {
                      throw new IllegalArgumentException("Unknown mode: " + parseMode);
                  }
  
                  parseTreeTableModel.setParseTree(parseTree);
                  parseTreeTableModel.setParseMode(parseMode);
                  final String[] sourceLines = getFileText(file).toLinesArray();
  
                  final List<Integer> linesToPositionTemp = new ArrayList<>(sourceLines.length + 1);
                  // starts line counting at 1
                  linesToPositionTemp.add(0);
  
                  final StringBuilder sb = new StringBuilder(1024);
                  // insert the contents of the file to the text area
                  for (final String element : sourceLines) {
                      linesToPositionTemp.add(sb.length());
                      sb.append(element).append(System.lineSeparator());
                  }
                  linesToPosition = linesToPositionTemp;
                  text = sb.toString();
              }
              catch (IOException ex) {
                  final String exceptionMsg = String.format(Locale.ROOT,
                      "%s occurred while opening file %s.",
                      ex.getClass().getSimpleName(), file.getPath());
                  throw new CheckstyleException(exceptionMsg, ex);
              }
          }
      }
  
      /**
       * Get FileText from a file.
       *
       * @param file the file to get the FileText from.
       * @return the FileText.
       * @throws IOException if the file could not be read.
       */
      private static FileText getFileText(File file) throws IOException {
          return new FileText(file.getAbsoluteFile(),
                  System.getProperty("file.encoding", StandardCharsets.UTF_8.name()));
      }
  
  }
  