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.checks.javadoc;
  
  import com.puppycrawl.tools.checkstyle.StatelessCheck;
  import com.puppycrawl.tools.checkstyle.api.DetailNode;
  import com.puppycrawl.tools.checkstyle.api.JavadocTokenTypes;
  import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
  import com.puppycrawl.tools.checkstyle.utils.JavadocUtil;
  import com.puppycrawl.tools.checkstyle.utils.TokenUtil;
  
  /**
   * <p>
   * Checks if the javadoc has
   * <a href="https://docs.oracle.com/en/java/javase/14/docs/specs/javadoc/doc-comment-spec.html#leading-asterisks">
   * leading asterisks</a> on each line.
   * </p>
   * <p>
   * The check does not require asterisks on the first line, nor on the last line if it is blank.
   * All other lines in a Javadoc should start with {@code *}, including blank lines and code blocks.
   * </p>
   * <ul>
   * <li>
   * Property {@code violateExecutionOnNonTightHtml} - Control when to print violations if the
   * Javadoc being examined by this check violates the tight html rules defined at
   * <a href="https://checkstyle.org/writingjavadocchecks.html#Tight-HTML_rules">Tight-HTML Rules</a>.
   * Type is {@code boolean}.
   * Default value is {@code false}.
   * </li>
   * </ul>
   * <p>
   * To configure the check:
   * </p>
   * <pre>
   * &lt;module name="JavadocMissingLeadingAsterisk"/&gt;
   * </pre>
   * <p>
   * Example:
   * </p>
   * <pre>
   * &#47;**
   *  * Valid Java-style comment.
   *  *
   *  * &lt;pre&gt;
   *  *   int value = 0;
   *  * &lt;/pre&gt;
   *  *&#47;
   * class JavaStyle {} // ok
   *
   * &#47;** Valid Scala-style comment.
   *   * Some description here.
   *   **&#47;
   * class ScalaStyle {} // ok
   *
   * &#47;** **
   *  * Asterisks on first and last lines are optional.
   *  * *&#47;
   * class Asterisks {} // ok
   *
   * &#47;** No asterisks are required for single-line comments. *&#47;
   * class SingleLine {} // ok
   *
   * &#47;** // violation on next blank line, javadoc has lines without leading asterisk.
   *
   *  *&#47;
   * class BlankLine {}
   *
   * &#47;** Wrapped
   *     single-line comment *&#47; // violation, javadoc has lines without leading asterisk.
   * class Wrapped {}
   *
   * &#47;**
   *  * &lt;pre&gt;
   *     int value; // violation, javadoc has lines without leading asterisk.
   *  * &lt;/pre&gt;
   *  *&#47;
   * class Code {}
   * </pre>
   * <p>
   * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
   * </p>
   * <p>
   * Violation Message Keys:
   * </p>
   * <ul>
   * <li>
   * {@code javadoc.missed.html.close}
   * </li>
   * <li>
   * {@code javadoc.missing.asterisk}
   * </li>
   * <li>
   * {@code javadoc.parse.rule.error}
   * </li>
   * <li>
   * {@code javadoc.wrong.singleton.html.tag}
   * </li>
   * </ul>
   *
   * @since 8.38
   */
  @StatelessCheck
  public class JavadocMissingLeadingAsteriskCheck extends AbstractJavadocCheck {
  
      /**
       * A key is pointing to the warning message text in "messages.properties"
       * file.
       */
      public static final String MSG_MISSING_ASTERISK = "javadoc.missing.asterisk";
  
      @Override
      public int[] getRequiredJavadocTokens() {
          return new int[] {
              JavadocTokenTypes.NEWLINE,
          };
      }
  
      @Override
      public int[] getAcceptableJavadocTokens() {
          return getRequiredJavadocTokens();
      }
  
      @Override
      public int[] getDefaultJavadocTokens() {
          return getRequiredJavadocTokens();
      }
  
      @Override
      public void visitJavadocToken(DetailNode detailNode) {
          DetailNode nextSibling = getNextNode(detailNode);
  
          // Till https://github.com/checkstyle/checkstyle/issues/9005
          // Due to bug in the Javadoc parser there may be phantom description nodes.
          while (TokenUtil.isOfType(nextSibling.getType(),
                  JavadocTokenTypes.DESCRIPTION, JavadocTokenTypes.WS)) {
              nextSibling = getNextNode(nextSibling);
          }
  
          if (!isLeadingAsterisk(nextSibling) && !isLastLine(nextSibling)) {
              log(nextSibling.getLineNumber(), MSG_MISSING_ASTERISK);
          }
      }
  
      /**
       * Gets next node in the ast (sibling or parent sibling for the last node).
       *
       * @param detailNode the node to process
       * @return next node.
       */
      private static DetailNode getNextNode(DetailNode detailNode) {
          DetailNode node = JavadocUtil.getFirstChild(detailNode);
          if (node == null) {
              node = JavadocUtil.getNextSibling(detailNode);
              if (node == null) {
                  DetailNode parent = detailNode;
                  do {
                      parent = parent.getParent();
                      node = JavadocUtil.getNextSibling(parent);
                  } while (node == null);
              }
          }
          return node;
      }
  
      /**
       * Checks whether the given node is a leading asterisk.
       *
       * @param detailNode the node to process
       * @return {@code true} if the node is {@link JavadocTokenTypes#LEADING_ASTERISK}
       */
      private static boolean isLeadingAsterisk(DetailNode detailNode) {
          return detailNode.getType() == JavadocTokenTypes.LEADING_ASTERISK;
      }
  
      /**
       * Checks whether this node is the end of a Javadoc comment,
       * optionally preceded by blank text.
       *
       * @param detailNode the node to process
       * @return {@code true} if the node is {@link JavadocTokenTypes#EOF}
       */
      private static boolean isLastLine(DetailNode detailNode) {
          final DetailNode node;
          if (detailNode.getType() == JavadocTokenTypes.TEXT
                  && CommonUtil.isBlank(detailNode.getText())) {
              node = getNextNode(detailNode);
          }
          else {
              node = detailNode;
          }
          return node.getType() == JavadocTokenTypes.EOF;
      }
  
  }
  