///////////////////////////////////////////////////////////////////////////////////////////////
   // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
   // Copyright (C) 2001-2025 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 java.util.ArrayList;
  import java.util.Arrays;
  import java.util.BitSet;
  import java.util.List;
  import java.util.Optional;
  import java.util.regex.Pattern;
  import java.util.stream.Stream;
  
  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;
  
  /**
   * <div>
   * Checks that
   * <a href="https://www.oracle.com/technical-resources/articles/java/javadoc-tool.html#firstsentence">
   * Javadoc summary sentence</a> does not contain phrases that are not recommended to use.
   * Summaries that contain only the {@code {@inheritDoc}} tag are skipped.
   * Summaries that contain a non-empty {@code {@return}} are allowed.
   * Check also violate Javadoc that does not contain first sentence, though with {@code {@return}} a
   * period is not required as the Javadoc tool adds it.
   * </div>
   *
   * <p>
   * Note: For defining a summary, both the first sentence and the @summary tag approaches
   * are supported.
   * </p>
   *
   * <ul>
   * <li>
   * Property {@code forbiddenSummaryFragments} - Specify the regexp for forbidden summary fragments.
   * Type is {@code java.util.regex.Pattern}.
   * Default value is {@code "^$"}.
   * </li>
   * <li>
   * Property {@code period} - Specify the period symbol. Used to check the first sentence ends with a
   * period. Periods that are not followed by a whitespace character are ignored (eg. the period in
   * v1.0). Because some periods include whitespace built into the character, if this is set to a
   * non-default value any period will end the sentence, whether it is followed by whitespace or not.
   * Type is {@code java.lang.String}.
   * Default value is {@code "."}.
   * </li>
   * <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>
   * 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.parse.rule.error}
   * </li>
   * <li>
   * {@code javadoc.unclosedHtml}
   * </li>
   * <li>
   * {@code javadoc.wrong.singleton.html.tag}
   * </li>
   * <li>
   * {@code summary.first.sentence}
   * </li>
   * <li>
  * {@code summary.javaDoc}
  * </li>
  * <li>
  * {@code summary.javaDoc.missing}
  * </li>
  * <li>
  * {@code summary.javaDoc.missing.period}
  * </li>
  * </ul>
  *
  * @since 6.0
  */
 @StatelessCheck
 public class SummaryJavadocCheck extends AbstractJavadocCheck {
 
     /**
      * A key is pointing to the warning message text in "messages.properties"
      * file.
      */
     public static final String MSG_SUMMARY_FIRST_SENTENCE = "summary.first.sentence";
 
     /**
      * A key is pointing to the warning message text in "messages.properties"
      * file.
      */
     public static final String MSG_SUMMARY_JAVADOC = "summary.javaDoc";
 
     /**
      * A key is pointing to the warning message text in "messages.properties"
      * file.
      */
     public static final String MSG_SUMMARY_JAVADOC_MISSING = "summary.javaDoc.missing";
 
     /**
      * A key is pointing to the warning message text in "messages.properties" file.
      */
     public static final String MSG_SUMMARY_MISSING_PERIOD = "summary.javaDoc.missing.period";
 
     /**
      * This regexp is used to convert multiline javadoc to single-line without stars.
      */
     private static final Pattern JAVADOC_MULTILINE_TO_SINGLELINE_PATTERN =
             Pattern.compile("\n +(\\*)|^ +(\\*)");
 
     /**
      * This regexp is used to remove html tags, whitespace, and asterisks from a string.
      */
     private static final Pattern HTML_ELEMENTS =
             Pattern.compile("<[^>]*>");
 
     /** Default period literal. */
     private static final String DEFAULT_PERIOD = ".";
 
     /** Summary tag text. */
     private static final String SUMMARY_TEXT = "@summary";
 
     /** Return tag text. */
     private static final String RETURN_TEXT = "@return";
 
     /** Set of allowed Tokens tags in summary java doc. */
     private static final BitSet ALLOWED_TYPES = TokenUtil.asBitSet(
                     JavadocTokenTypes.WS,
                     JavadocTokenTypes.DESCRIPTION,
                     JavadocTokenTypes.TEXT);
 
     /**
      * Specify the regexp for forbidden summary fragments.
      */
     private Pattern forbiddenSummaryFragments = CommonUtil.createPattern("^$");
 
     /**
      * Specify the period symbol. Used to check the first sentence ends with a period. Periods that
      * are not followed by a whitespace character are ignored (eg. the period in v1.0). Because some
      * periods include whitespace built into the character, if this is set to a non-default value
      * any period will end the sentence, whether it is followed by whitespace or not.
      */
     private String period = DEFAULT_PERIOD;
 
     /**
      * Setter to specify the regexp for forbidden summary fragments.
      *
      * @param pattern a pattern.
      * @since 6.0
      */
     public void setForbiddenSummaryFragments(Pattern pattern) {
         forbiddenSummaryFragments = pattern;
     }
 
     /**
      * Setter to specify the period symbol. Used to check the first sentence ends with a period.
      * Periods that are not followed by a whitespace character are ignored (eg. the period in v1.0).
      * Because some periods include whitespace built into the character, if this is set to a
      * non-default value any period will end the sentence, whether it is followed by whitespace or
      * not.
      *
      * @param period period's value.
      * @since 6.2
      */
     public void setPeriod(String period) {
         this.period = period;
     }
 
     @Override
     public int[] getDefaultJavadocTokens() {
         return new int[] {
             JavadocTokenTypes.JAVADOC,
         };
     }
 
     @Override
     public int[] getRequiredJavadocTokens() {
         return getAcceptableJavadocTokens();
     }
 
     @Override
     public void visitJavadocToken(DetailNode ast) {
         final Optional<DetailNode> inlineTagNode = getInlineTagNode(ast);
         boolean shouldValidateUntaggedSummary = true;
         if (inlineTagNode.isPresent()) {
             final DetailNode node = inlineTagNode.get();
             if (isSummaryTag(node) && isDefinedFirst(node)) {
                 shouldValidateUntaggedSummary = false;
                 validateSummaryTag(node);
             }
             else if (isInlineReturnTag(node)) {
                 shouldValidateUntaggedSummary = false;
                 validateInlineReturnTag(node);
             }
         }
         if (shouldValidateUntaggedSummary && !startsWithInheritDoc(ast)) {
             validateUntaggedSummary(ast);
         }
     }
 
     /**
      * Checks the javadoc text for {@code period} at end and forbidden fragments.
      *
      * @param ast the javadoc text node
      */
     private void validateUntaggedSummary(DetailNode ast) {
         final String summaryDoc = getSummarySentence(ast);
         if (summaryDoc.isEmpty()) {
             log(ast.getLineNumber(), MSG_SUMMARY_JAVADOC_MISSING);
         }
         else if (!period.isEmpty()) {
             if (summaryDoc.contains(period)) {
                 final Optional<String> firstSentence = getFirstSentence(ast, period);
 
                 if (firstSentence.isPresent()) {
                     if (containsForbiddenFragment(firstSentence.get())) {
                         log(ast.getLineNumber(), MSG_SUMMARY_JAVADOC);
                     }
                 }
                 else {
                     log(ast.getLineNumber(), MSG_SUMMARY_FIRST_SENTENCE);
                 }
             }
             else {
                 log(ast.getLineNumber(), MSG_SUMMARY_FIRST_SENTENCE);
             }
         }
     }
 
     /**
      * Gets the node for the inline tag if present.
      *
      * @param javadoc javadoc root node.
      * @return the node for the inline tag if present.
      */
     private static Optional<DetailNode> getInlineTagNode(DetailNode javadoc) {
         return Arrays.stream(javadoc.getChildren())
             .filter(SummaryJavadocCheck::isInlineTagPresent)
             .findFirst()
             .map(SummaryJavadocCheck::getInlineTagNodeForAst);
     }
 
     /**
      * Whether the {@code {@summary}} tag is defined first in the javadoc.
      *
      * @param inlineSummaryTag node of type {@link JavadocTokenTypes#JAVADOC_INLINE_TAG}
      * @return {@code true} if the {@code {@summary}} tag is defined first in the javadoc
      */
     private static boolean isDefinedFirst(DetailNode inlineSummaryTag) {
         boolean isDefinedFirst = true;
         DetailNode currentAst = inlineSummaryTag;
         while (currentAst != null && isDefinedFirst) {
             isDefinedFirst = switch (currentAst.getType()) {
                 case JavadocTokenTypes.TEXT -> currentAst.getText().isBlank();
                 case JavadocTokenTypes.HTML_ELEMENT -> !isTextPresentInsideHtmlTag(currentAst);
                 default -> isDefinedFirst;
             };
             currentAst = JavadocUtil.getPreviousSibling(currentAst);
         }
         return isDefinedFirst;
     }
 
     /**
      * Whether some text is present inside the HTML element or tag.
      *
      * @param node DetailNode of type {@link JavadocTokenTypes#HTML_TAG}
      *             or {@link JavadocTokenTypes#HTML_ELEMENT}
      * @return {@code true} if some text is present inside the HTML element or tag
      */
     public static boolean isTextPresentInsideHtmlTag(DetailNode node) {
         DetailNode nestedChild = JavadocUtil.getFirstChild(node);
         if (node.getType() == JavadocTokenTypes.HTML_ELEMENT) {
             nestedChild = JavadocUtil.getFirstChild(nestedChild);
         }
         boolean isTextPresentInsideHtmlTag = false;
         while (nestedChild != null && !isTextPresentInsideHtmlTag) {
             isTextPresentInsideHtmlTag = switch (nestedChild.getType()) {
                 case JavadocTokenTypes.TEXT -> !nestedChild.getText().isBlank();
                 case JavadocTokenTypes.HTML_TAG, JavadocTokenTypes.HTML_ELEMENT ->
                     isTextPresentInsideHtmlTag(nestedChild);
                 default -> isTextPresentInsideHtmlTag;
             };
             nestedChild = JavadocUtil.getNextSibling(nestedChild);
         }
         return isTextPresentInsideHtmlTag;
     }
 
     /**
      * Checks if the inline tag node is present.
      *
      * @param ast ast node to check.
      * @return true, if the inline tag node is present.
      */
     private static boolean isInlineTagPresent(DetailNode ast) {
         return getInlineTagNodeForAst(ast) != null;
     }
 
     /**
      * Returns an inline javadoc tag node that is within a html tag.
      *
      * @param ast html tag node.
      * @return inline summary javadoc tag node or null if no node is found.
      */
     private static DetailNode getInlineTagNodeForAst(DetailNode ast) {
         DetailNode node = ast;
         DetailNode result = null;
         // node can never be null as this method is called when there is a HTML_ELEMENT
         if (node.getType() == JavadocTokenTypes.JAVADOC_INLINE_TAG) {
             result = node;
         }
         else if (node.getType() == JavadocTokenTypes.HTML_TAG) {
             // HTML_TAG always has more than 2 children.
             node = node.getChildren()[1];
             result = getInlineTagNodeForAst(node);
         }
         else if (node.getType() == JavadocTokenTypes.HTML_ELEMENT
                 // Condition for SINGLETON html element which cannot contain summary node
                 && node.getChildren()[0].getChildren().length > 1) {
             // Html elements have one tested tag before actual content inside it
             node = node.getChildren()[0].getChildren()[1];
             result = getInlineTagNodeForAst(node);
         }
         return result;
     }
 
     /**
      * Checks if the javadoc inline tag is {@code {@summary}} tag.
      *
      * @param javadocInlineTag node of type {@link JavadocTokenTypes#JAVADOC_INLINE_TAG}
      * @return {@code true} if inline tag is summary tag.
      */
     private static boolean isSummaryTag(DetailNode javadocInlineTag) {
         return isInlineTagWithName(javadocInlineTag, SUMMARY_TEXT);
     }
 
     /**
      * Checks if the first tag inside ast is {@code {@return}} tag.
      *
      * @param javadocInlineTag node of type {@link JavadocTokenTypes#JAVADOC_INLINE_TAG}
      * @return {@code true} if first tag is return tag.
      */
     private static boolean isInlineReturnTag(DetailNode javadocInlineTag) {
         return isInlineTagWithName(javadocInlineTag, RETURN_TEXT);
     }
 
     /**
      * Checks if the first tag inside ast is a tag with the given name.
      *
      * @param javadocInlineTag node of type {@link JavadocTokenTypes#JAVADOC_INLINE_TAG}
      * @param name name of inline tag.
      *
      * @return {@code true} if first tag is a tag with the given name.
      */
     private static boolean isInlineTagWithName(DetailNode javadocInlineTag, String name) {
         final DetailNode[] child = javadocInlineTag.getChildren();
 
         // Checking size of ast is not required, since ast contains
         // children of Inline Tag, as at least 2 children will be present which are
         // RCURLY and LCURLY.
         return name.equals(child[1].getText());
     }
 
     /**
      * Checks the inline summary (if present) for {@code period} at end and forbidden fragments.
      *
      * @param inlineSummaryTag node of type {@link JavadocTokenTypes#JAVADOC_INLINE_TAG}
      */
     private void validateSummaryTag(DetailNode inlineSummaryTag) {
         final String inlineSummary = getContentOfInlineCustomTag(inlineSummaryTag);
         final String summaryVisible = getVisibleContent(inlineSummary);
         if (summaryVisible.isEmpty()) {
             log(inlineSummaryTag.getLineNumber(), MSG_SUMMARY_JAVADOC_MISSING);
         }
         else if (!period.isEmpty()) {
             final boolean isPeriodNotAtEnd =
                     summaryVisible.lastIndexOf(period) != summaryVisible.length() - 1;
             if (isPeriodNotAtEnd) {
                 log(inlineSummaryTag.getLineNumber(), MSG_SUMMARY_MISSING_PERIOD);
             }
             else if (containsForbiddenFragment(inlineSummary)) {
                 log(inlineSummaryTag.getLineNumber(), MSG_SUMMARY_JAVADOC);
             }
         }
     }
 
     /**
      * Checks the inline return for forbidden fragments.
      *
      * @param inlineReturnTag node of type {@link JavadocTokenTypes#JAVADOC_INLINE_TAG}
      */
     private void validateInlineReturnTag(DetailNode inlineReturnTag) {
         final String inlineReturn = getContentOfInlineCustomTag(inlineReturnTag);
         final String returnVisible = getVisibleContent(inlineReturn);
         if (returnVisible.isEmpty()) {
             log(inlineReturnTag.getLineNumber(), MSG_SUMMARY_JAVADOC_MISSING);
         }
         else if (containsForbiddenFragment(inlineReturn)) {
             log(inlineReturnTag.getLineNumber(), MSG_SUMMARY_JAVADOC);
         }
     }
 
     /**
      * Gets the content of inline custom tag.
      *
      * @param inlineTag inline tag node.
      * @return String consisting of the content of inline custom tag.
      */
     public static String getContentOfInlineCustomTag(DetailNode inlineTag) {
         final DetailNode[] childrenOfInlineTag = inlineTag.getChildren();
         final StringBuilder customTagContent = new StringBuilder(256);
         final int indexOfContentOfSummaryTag = 3;
         if (childrenOfInlineTag.length != indexOfContentOfSummaryTag) {
             DetailNode currentNode = childrenOfInlineTag[indexOfContentOfSummaryTag];
             while (currentNode.getType() != JavadocTokenTypes.JAVADOC_INLINE_TAG_END) {
                 extractInlineTagContent(currentNode, customTagContent);
                 currentNode = JavadocUtil.getNextSibling(currentNode);
             }
         }
         return customTagContent.toString();
     }
 
     /**
      * Extracts the content of inline custom tag recursively.
      *
      * @param node DetailNode
      * @param customTagContent content of custom tag
      */
     private static void extractInlineTagContent(DetailNode node,
         StringBuilder customTagContent) {
         final DetailNode[] children = node.getChildren();
         if (children.length == 0) {
             customTagContent.append(node.getText());
         }
         else {
             for (DetailNode child : children) {
                 if (child.getType() != JavadocTokenTypes.LEADING_ASTERISK) {
                     extractInlineTagContent(child, customTagContent);
                 }
             }
         }
     }
 
     /**
      * Gets the string that is visible to user in javadoc.
      *
      * @param summary entire content of summary javadoc.
      * @return string that is visible to user in javadoc.
      */
     private static String getVisibleContent(String summary) {
         final String visibleSummary = HTML_ELEMENTS.matcher(summary).replaceAll("");
         return visibleSummary.trim();
     }
 
     /**
      * Tests if first sentence contains forbidden summary fragment.
      *
      * @param firstSentence string with first sentence.
      * @return {@code true} if first sentence contains forbidden summary fragment.
      */
     private boolean containsForbiddenFragment(String firstSentence) {
         final String javadocText = JAVADOC_MULTILINE_TO_SINGLELINE_PATTERN
                 .matcher(firstSentence).replaceAll(" ");
         return forbiddenSummaryFragments.matcher(trimExcessWhitespaces(javadocText)).find();
     }
 
     /**
      * Trims the given {@code text} of duplicate whitespaces.
      *
      * @param text the text to transform.
      * @return the finalized form of the text.
      */
     private static String trimExcessWhitespaces(String text) {
         final StringBuilder result = new StringBuilder(256);
         boolean previousWhitespace = true;
 
         for (char letter : text.toCharArray()) {
             final char print;
             if (Character.isWhitespace(letter)) {
                 if (previousWhitespace) {
                     continue;
                 }
 
                 previousWhitespace = true;
                 print = ' ';
             }
             else {
                 previousWhitespace = false;
                 print = letter;
             }
 
             result.append(print);
         }
 
         return result.toString();
     }
 
     /**
      * Checks if the node starts with an {&#64;inheritDoc}.
      *
      * @param root the root node to examine.
      * @return {@code true} if the javadoc starts with an {&#64;inheritDoc}.
      */
     private static boolean startsWithInheritDoc(DetailNode root) {
         boolean found = false;
 
         for (DetailNode child : root.getChildren()) {
             if (child.getType() == JavadocTokenTypes.JAVADOC_INLINE_TAG
                     && child.getChildren()[1].getType() == JavadocTokenTypes.INHERIT_DOC_LITERAL) {
                 found = true;
             }
             if ((child.getType() == JavadocTokenTypes.TEXT
                     || child.getType() == JavadocTokenTypes.HTML_ELEMENT)
                     && !CommonUtil.isBlank(child.getText())) {
                 break;
             }
         }
 
         return found;
     }
 
     /**
      * Finds and returns summary sentence.
      *
      * @param ast javadoc root node.
      * @return violation string.
      */
     private static String getSummarySentence(DetailNode ast) {
         final StringBuilder result = new StringBuilder(256);
         for (DetailNode child : ast.getChildren()) {
             if (child.getType() != JavadocTokenTypes.EOF
                     && ALLOWED_TYPES.get(child.getType())) {
                 result.append(child.getText());
             }
             else {
                 final String summary = result.toString();
                 if (child.getType() == JavadocTokenTypes.HTML_ELEMENT
                         && CommonUtil.isBlank(summary)) {
                     result.append(getStringInsideTag(summary,
                             child.getChildren()[0].getChildren()[0]));
                 }
             }
         }
         return result.toString().trim();
     }
 
     /**
      * Get concatenated string within text of html tags.
      *
      * @param result javadoc string
      * @param detailNode javadoc tag node
      * @return java doc tag content appended in result
      */
     private static String getStringInsideTag(String result, DetailNode detailNode) {
         final StringBuilder contents = new StringBuilder(result);
         DetailNode tempNode = detailNode;
         while (tempNode != null) {
             if (tempNode.getType() == JavadocTokenTypes.TEXT) {
                 contents.append(tempNode.getText());
             }
             tempNode = JavadocUtil.getNextSibling(tempNode);
         }
         return contents.toString();
     }
 
     /**
      * Finds the first sentence.
      *
      * @param ast The Javadoc root node.
      * @param period The configured period symbol.
      * @return An Optional containing the first sentence
      *     up to and excluding the period, or an empty
      *     Optional if no ending was found.
      */
     private static Optional<String> getFirstSentence(DetailNode ast, String period) {
         final List<String> sentenceParts = new ArrayList<>();
         Optional<String> result = Optional.empty();
         for (String text : (Iterable<String>) streamTextParts(ast)::iterator) {
             final Optional<String> sentenceEnding = findSentenceEnding(text, period);
 
             if (sentenceEnding.isPresent()) {
                 sentenceParts.add(sentenceEnding.get());
                 result = Optional.of(String.join("", sentenceParts));
                 break;
             }
             sentenceParts.add(text);
         }
         return result;
     }
 
     /**
      * Streams through all the text under the given node.
      *
      * @param node The Javadoc node to examine.
      * @return All the text in all nodes that have no child nodes.
      */
     private static Stream<String> streamTextParts(DetailNode node) {
         final Stream<String> stream;
         if (node.getChildren().length == 0) {
             stream = Stream.of(node.getText());
         }
         else {
             stream = Stream.of(node.getChildren())
                 .flatMap(SummaryJavadocCheck::streamTextParts);
         }
         return stream;
     }
 
     /**
      * Finds the end of a sentence. The end of sentence detection here could be replaced in the
      * future by Java's built-in BreakIterator class.
      *
      * @param text The string to search.
      * @param period The period character to find.
      * @return An Optional containing the string up to and excluding the period,
      *     or empty Optional if no ending was found.
      */
     private static Optional<String> findSentenceEnding(String text, String period) {
         int periodIndex = text.indexOf(period);
         Optional<String> result = Optional.empty();
         while (periodIndex >= 0) {
             final int afterPeriodIndex = periodIndex + period.length();
 
             // Handle western period separately as it is only the end of a sentence if followed
             // by whitespace. Other period characters often include whitespace in the character.
             if (!DEFAULT_PERIOD.equals(period)
                 || afterPeriodIndex >= text.length()
                 || Character.isWhitespace(text.charAt(afterPeriodIndex))) {
                 final String resultStr = text.substring(0, periodIndex);
                 result = Optional.of(resultStr);
                 break;
             }
             periodIndex = text.indexOf(period, afterPeriodIndex);
         }
         return result;
     }
 }