///////////////////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
// Copyright (C) 2001-2026 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.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Optional;
import java.util.Set;

import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.DetailNode;
import com.puppycrawl.tools.checkstyle.api.FullIdent;
import com.puppycrawl.tools.checkstyle.api.JavadocCommentsTokenTypes;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import com.puppycrawl.tools.checkstyle.checks.naming.AccessModifierOption;
import com.puppycrawl.tools.checkstyle.utils.AnnotationUtil;
import com.puppycrawl.tools.checkstyle.utils.CheckUtil;
import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
import com.puppycrawl.tools.checkstyle.utils.JavadocUtil;
import com.puppycrawl.tools.checkstyle.utils.UnmodifiableCollectionUtil;

/**
 * <div>
 * Checks the Javadoc of a method or constructor.
 * </div>
 *
 * <p>
 * Violates parameters and type parameters for which no param tags are present can
 * be suppressed by defining property {@code allowMissingParamTags}.
 * </p>
 *
 * <p>
 * Violates methods which return non-void but for which no return tag is present can
 * be suppressed by defining property {@code allowMissingReturnTag}.
 * </p>
 *
 * <p>
 * Violates exceptions which are declared to be thrown (by {@code throws} in the method
 * signature or by {@code throw new} in the method body), but for which no throws tag is
 * present by activation of property {@code validateThrows}.
 * Note that {@code throw new} is not checked in the following places:
 * </p>
 * <ul>
 * <li>
 * Inside a try block (with catch). It is not possible to determine if the thrown
 * exception can be caught by the catch block as there is no knowledge of the
 * inheritance hierarchy, so the try block is ignored entirely. However, catch
 * and finally blocks, as well as try blocks without catch, are still checked.
 * </li>
 * <li>
 * Local classes, anonymous classes and lambda expressions. It is not known when the
 * throw statements inside such classes are going to be evaluated, so they are ignored.
 * </li>
 * </ul>
 *
 * <p>
 * ATTENTION: Checkstyle does not have information about hierarchy of exception types
 * so usage of base class is considered as separate exception type.
 * As workaround, you need to specify both types in javadoc (parent and exact type).
 * </p>
 *
 * <p>
 * Javadoc is not required on a method that is tagged with the {@code @Override}
 * annotation. However, under Java 5 it is not possible to mark a method required
 * for an interface (this was <i>corrected</i> under Java 6). Hence, Checkstyle
 * supports using the convention of using a single {@code {@inheritDoc}} tag
 * instead of all the other tags.
 * </p>
 *
 * <p>
 * Note that only inheritable items will allow the {@code {@inheritDoc}}
 * tag to be used in place of comments. Static methods at all visibilities,
 * private non-static methods and constructors are not inheritable.
 * </p>
 *
 * <p>
 * For example, if the following method is implementing a method required by
 * an interface, then the Javadoc could be done as:
 * </p>
 * {@snippet lang="text" :
 * /** {@inheritDoc} * /
 * public int checkReturnTag(final int aTagIndex,
 *                           JavadocTag[] aTags,
 *                           int aLineNo)
 * }
 *
 * @since 3.0
 */
@FileStatefulCheck
public class JavadocMethodCheck extends AbstractJavadocCheck {

    /**
     * A key is pointing to the warning message text in "messages.properties" file.
     */
    public static final String MSG_CLASS_INFO = "javadoc.classInfo";

    /**
     * A key is pointing to the warning message text in "messages.properties" file.
     */
    public static final String MSG_UNUSED_TAG_GENERAL = "javadoc.unusedTagGeneral";

    /**
     * A key is pointing to the warning message text in "messages.properties" file.
     */
    public static final String MSG_INVALID_INHERIT_DOC = "javadoc.invalidInheritDoc";

    /**
     * A key is pointing to the warning message text in "messages.properties" file.
     */
    public static final String MSG_UNUSED_TAG = "javadoc.unusedTag";

    /**
     * A key is pointing to the warning message text in "messages.properties" file.
     */
    public static final String MSG_EXPECTED_TAG = "javadoc.expectedTag";

    /**
     * A key is pointing to the warning message text in "messages.properties" file.
     */
    public static final String MSG_RETURN_EXPECTED = "javadoc.return.expected";

    /**
     * A key is pointing to the warning message text in "messages.properties" file.
     */
    public static final String MSG_DUPLICATE_TAG = "javadoc.duplicateTag";

    /** Html element start symbol. */
    private static final String ELEMENT_START = "<";

    /** Html element end symbol. */
    private static final String ELEMENT_END = ">";

    /** Javadoc tags collected from the current Javadoc tree. */
    private final List<JavadocTag> javadocTags = new ArrayList<>();

    /**
     * Control whether to allow inline return tags.
     */
    private boolean allowInlineReturn;

    /** Specify the access modifiers where Javadoc comments are checked. */
    private AccessModifierOption[] accessModifiers = {
        AccessModifierOption.PUBLIC,
        AccessModifierOption.PROTECTED,
        AccessModifierOption.PACKAGE,
        AccessModifierOption.PRIVATE,
    };

    /**
     * Control whether to validate {@code throws} tags.
     */
    private boolean validateThrows;

    /**
     * Control whether to ignore violations when a method has parameters but does
     * not have matching {@code param} tags in the javadoc.
     */
    private boolean allowMissingParamTags;

    /**
     * Control whether to ignore violations when a method returns non-void type
     * and does not have a {@code return} tag in the javadoc.
     */
    private boolean allowMissingReturnTag;

    /** Specify annotations that allow missed documentation. */
    private Set<String> allowedAnnotations = Set.of("Override");

    /** Java AST node whose attached Javadoc is currently being processed. */
    private DetailAST currentAst;

    /**
     * Creates a new {@code JavadocMethodCheck} instance.
     */
    public JavadocMethodCheck() {
        // no code by default
    }

    /**
     * Setter to control whether to allow inline return tags.
     *
     * @param value a {@code boolean} value
     * @since 10.23.0
     */
    public void setAllowInlineReturn(boolean value) {
        allowInlineReturn = value;
    }

    /**
     * Setter to control whether to validate {@code throws} tags.
     *
     * @param value user's value.
     * @since 6.0
     */
    public void setValidateThrows(boolean value) {
        validateThrows = value;
    }

    /**
     * Setter to specify annotations that allow missed documentation.
     *
     * @param userAnnotations user's value.
     * @since 6.0
     */
    public void setAllowedAnnotations(String... userAnnotations) {
        allowedAnnotations = Set.of(userAnnotations);
    }

    /**
     * Setter to specify the access modifiers where Javadoc comments are checked.
     *
     * @param accessModifiers access modifiers.
     * @since 8.42
     */
    public void setAccessModifiers(AccessModifierOption... accessModifiers) {
        this.accessModifiers =
            UnmodifiableCollectionUtil.copyOfArray(accessModifiers, accessModifiers.length);
    }

    /**
     * Setter to control whether to ignore violations when a method has parameters
     * but does not have matching {@code param} tags in the javadoc.
     *
     * @param flag a {@code Boolean} value
     * @since 3.1
     */
    public void setAllowMissingParamTags(boolean flag) {
        allowMissingParamTags = flag;
    }

    /**
     * Setter to control whether to ignore violations when a method returns non-void type
     * and does not have a {@code return} tag in the javadoc.
     *
     * @param flag a {@code Boolean} value
     * @since 3.1
     */
    public void setAllowMissingReturnTag(boolean flag) {
        allowMissingReturnTag = flag;
    }

    /**
     * Setter to 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/writing-javadoc-checks.html#Tight-HTML_rules">
     *     Tight-HTML Rules</a>.
     *
     * @param shouldReportViolation value to which the field shall be set to
     * @since 8.3
     * @propertySince 13.7.0
     */
    @Override
    public void setViolateExecutionOnNonTightHtml(boolean shouldReportViolation) {
        super.setViolateExecutionOnNonTightHtml(shouldReportViolation);
    }

    @Override
    public final int[] getRequiredTokens() {
        return CommonUtil.EMPTY_INT_ARRAY;
    }

    @Override
    public int[] getDefaultTokens() {
        return getAcceptableTokens();
    }

    @Override
    public int[] getAcceptableTokens() {
        return new int[] {
            TokenTypes.METHOD_DEF,
            TokenTypes.CTOR_DEF,
            TokenTypes.ANNOTATION_FIELD_DEF,
            TokenTypes.COMPACT_CTOR_DEF,
        };
    }

    @Override
    public final void visitToken(DetailAST ast) {
        if (shouldCheck(ast)) {
            final DetailAST blockCommentNode = JavadocUtil.getAttachedJavadocComment(ast);
            if (blockCommentNode != null) {
                currentAst = ast;
                super.visitToken(blockCommentNode);
            }
        }
    }

    @Override
    public void beginJavadocTree(DetailNode rootAst) {
        javadocTags.clear();
    }

    @Override
    public void finishJavadocTree(DetailNode rootAst) {
        checkCollectedTags();
    }

    @Override
    public int[] getDefaultJavadocTokens() {
        return getRequiredJavadocTokens();
    }

    @Override
    public int[] getRequiredJavadocTokens() {
        return new int[] {
            JavadocCommentsTokenTypes.PARAM_BLOCK_TAG,
            JavadocCommentsTokenTypes.RETURN_BLOCK_TAG,
            JavadocCommentsTokenTypes.RETURN_INLINE_TAG,
            JavadocCommentsTokenTypes.THROWS_BLOCK_TAG,
            JavadocCommentsTokenTypes.EXCEPTION_BLOCK_TAG,
            JavadocCommentsTokenTypes.INHERIT_DOC_INLINE_TAG,
        };
    }

    @Override
    public void visitJavadocToken(DetailNode ast) {
        switch (ast.getType()) {
            case JavadocCommentsTokenTypes.RETURN_BLOCK_TAG -> collectReturn(ast);
            case JavadocCommentsTokenTypes.RETURN_INLINE_TAG -> {
                if (allowInlineReturn) {
                    collectReturn(ast);
                }
            }
            case JavadocCommentsTokenTypes.INHERIT_DOC_INLINE_TAG -> collectInheritDoc();
            case JavadocCommentsTokenTypes.PARAM_BLOCK_TAG -> collectParam(ast);
            case JavadocCommentsTokenTypes.THROWS_BLOCK_TAG -> collectThrows(ast, "throws");
            case JavadocCommentsTokenTypes.EXCEPTION_BLOCK_TAG -> collectThrows(ast, "exception");
            default -> throw new IllegalArgumentException("Unknown javadoc token type " + ast);
        }
    }

    /**
     * Collects a return tag if it has a description.
     *
     * @param ast the return tag node
     */
    private void collectReturn(DetailNode ast) {
        if (JavadocUtil.findFirstToken(ast, JavadocCommentsTokenTypes.DESCRIPTION) != null) {
            javadocTags.add(new JavadocTag(ast.getLineNumber(), ast.getColumnNumber(), "return"));
        }
    }

    /**
     * Collects an inheritDoc tag.
     */
    private void collectInheritDoc() {
        javadocTags.add(new JavadocTag(0, 0, "inheritDoc"));
    }

    /**
     * Collects a param tag.
     *
     * @param ast the param tag node
     */
    private void collectParam(DetailNode ast) {
        final DetailNode parameterName = JavadocUtil.findFirstToken(
                ast, JavadocCommentsTokenTypes.PARAMETER_NAME);
        if (parameterName != null) {
            javadocTags.add(new JavadocTag(ast.getLineNumber(), ast.getColumnNumber(),
                    "param", parameterName.getText()));
        }
    }

    /**
     * Collects a throws or exception tag.
     *
     * @param ast the throws or exception tag node
     * @param tagName the tag name
     */
    private void collectThrows(DetailNode ast, String tagName) {
        final DetailNode identifier = JavadocUtil.findFirstToken(
                ast, JavadocCommentsTokenTypes.IDENTIFIER);
        if (identifier != null) {
            javadocTags.add(new JavadocTag(0, 0,
                    tagName, identifier.getText()));
        }
    }

    /**
     * Checks collected Javadoc tags against the current AST node.
     */
    private void checkCollectedTags() {
        final List<JavadocTag> tagsToCheck = new ArrayList<>(javadocTags);
        if (!hasShortCircuitTag(currentAst, tagsToCheck)) {
            if (currentAst.getType() == TokenTypes.ANNOTATION_FIELD_DEF) {
                checkReturnTag(tagsToCheck, currentAst.getLineNo(), true);
            }
            else {
                boolean hasInheritDocTag = false;
                final Iterator<JavadocTag> iterator = tagsToCheck.iterator();
                while (!hasInheritDocTag && iterator.hasNext()) {
                    hasInheritDocTag = iterator.next().isInheritDocTag();
                }
                final boolean reportExpectedTags = !hasInheritDocTag
                        && !AnnotationUtil.containsAnnotation(currentAst, allowedAnnotations);
                if (currentAst.getType() == TokenTypes.COMPACT_CTOR_DEF) {
                    checkRecordParamTags(tagsToCheck, currentAst, reportExpectedTags);
                }
                else {
                    checkParamTags(tagsToCheck, currentAst, reportExpectedTags);
                }
                final List<ExceptionInfo> thrown =
                        combineExceptionInfo(getThrows(currentAst), getThrowed(currentAst));
                checkThrowsTags(tagsToCheck, thrown, reportExpectedTags);
                if (CheckUtil.isNonVoidMethod(currentAst)) {
                    checkReturnTag(tagsToCheck, currentAst.getLineNo(), reportExpectedTags);
                }
            }
        }
        tagsToCheck.stream()
                .filter(javadocTag -> !javadocTag.isInheritDocTag())
                .forEach(javadocTag -> log(javadocTag.getLineNo(), MSG_UNUSED_TAG_GENERAL));
    }

    /**
     * Checks whether the given declaration should be validated.
     *
     * <p>The declaration is checked only when both its own access modifier and the
     * access modifier of the surrounding type match the configured
     * {@code accessModifiers}.</p>
     *
     * @param ast the method, constructor, annotation field, or compact constructor
     *        AST node to check
     * @return {@code true} if the declaration is inside the configured access scope
     */
    private boolean shouldCheck(final DetailAST ast) {
        final Optional<AccessModifierOption> surroundingAccessModifier = CheckUtil
                .getSurroundingAccessModifier(ast);
        final AccessModifierOption accessModifier = CheckUtil
                .getAccessModifierFromModifiersToken(ast);
        return surroundingAccessModifier.isPresent() && Arrays.stream(accessModifiers)
                        .anyMatch(modifier -> modifier == surroundingAccessModifier.get())
                && Arrays.stream(accessModifiers).anyMatch(modifier -> modifier == accessModifier);
    }

    /**
     * Retrieves the list of record components from a given record definition.
     *
     * @param recordDef the AST node representing the record definition
     * @return a list of AST nodes representing the record components
     */
    private static List<DetailAST> getRecordComponents(final DetailAST recordDef) {
        final List<DetailAST> components = new ArrayList<>();
        final DetailAST recordDecl = recordDef.findFirstToken(TokenTypes.RECORD_COMPONENTS);

        DetailAST child = recordDecl.getFirstChild();
        while (child != null) {
            if (child.getType() == TokenTypes.RECORD_COMPONENT_DEF) {
                components.add(child.findFirstToken(TokenTypes.IDENT));
            }
            child = child.getNextSibling();
        }
        return components;
    }

    /**
     * Finds the nearest ancestor record definition node for the given AST node.
     *
     * @param ast the AST node to start searching from
     * @return the nearest {@code RECORD_DEF} AST node, or {@code null} if not found
     */
    private static DetailAST getRecordDef(DetailAST ast) {
        DetailAST current = ast;
        while (current.getType() != TokenTypes.RECORD_DEF) {
            current = current.getParent();
        }
        return current;
    }

    /**
     * Validates whether the Javadoc has a short circuit tag. Currently, this is
     * the inheritTag. Any violations are logged.
     *
     * @param ast the construct being checked
     * @param tags the list of Javadoc tags associated with the construct
     * @return true if the construct has a short circuit tag.
     */
    private boolean hasShortCircuitTag(final DetailAST ast, final List<JavadocTag> tags) {
        boolean result = true;
        // Check if it contains {@inheritDoc} tag
        if (tags.size() == 1
                && tags.getFirst().isInheritDocTag()) {
            // Invalid if private, a constructor, or a static method
            if (!JavadocTagInfo.INHERIT_DOC.isValidOn(ast)) {
                log(ast, MSG_INVALID_INHERIT_DOC);
            }
        }
        else {
            result = false;
        }
        return result;
    }

    /**
     * Computes the parameter nodes for a method.
     *
     * @param ast the method node.
     * @return the list of parameter nodes for ast.
     */
    private static List<DetailAST> getParameters(DetailAST ast) {
        final DetailAST params = ast.findFirstToken(TokenTypes.PARAMETERS);
        final List<DetailAST> returnValue = new ArrayList<>();

        DetailAST child = params.getFirstChild();
        while (child != null) {
            final DetailAST ident = child.findFirstToken(TokenTypes.IDENT);
            if (ident != null) {
                returnValue.add(ident);
            }
            child = child.getNextSibling();
        }
        return returnValue;
    }

    /**
     * Computes the exception nodes for a method.
     *
     * @param ast the method node.
     * @return the list of exception nodes for ast.
     */
    private static List<ExceptionInfo> getThrows(DetailAST ast) {
        final List<ExceptionInfo> returnValue = new ArrayList<>();
        final DetailAST throwsAST = ast
                .findFirstToken(TokenTypes.LITERAL_THROWS);
        if (throwsAST != null) {
            DetailAST child = throwsAST.getFirstChild();
            while (child != null) {
                if (child.getType() == TokenTypes.IDENT
                        || child.getType() == TokenTypes.DOT) {
                    returnValue.add(getExceptionInfo(child));
                }
                child = child.getNextSibling();
            }
        }
        return returnValue;
    }

    /**
     * Get ExceptionInfo for all exceptions that throws in method code by 'throw new'.
     *
     * @param methodAst method DetailAST object where to find exceptions
     * @return list of ExceptionInfo
     */
    private static List<ExceptionInfo> getThrowed(DetailAST methodAst) {
        final List<ExceptionInfo> returnValue = new ArrayList<>();
        final List<DetailAST> throwLiterals = findTokensInAstByType(methodAst,
                    TokenTypes.LITERAL_THROW);
        for (DetailAST throwAst : throwLiterals) {
            if (!isInIgnoreBlock(methodAst, throwAst)) {
                final DetailAST newAst = throwAst.getFirstChild().getFirstChild();
                if (newAst.getType() == TokenTypes.LITERAL_NEW) {
                    final DetailAST child = newAst.getFirstChild();
                    returnValue.add(getExceptionInfo(child));
                }
            }
        }
        return returnValue;
    }

    /**
     * Get ExceptionInfo instance.
     *
     * @param ast DetailAST object where to find exceptions node;
     * @return ExceptionInfo
     */
    private static ExceptionInfo getExceptionInfo(DetailAST ast) {
        final FullIdent ident = FullIdent.createFullIdent(ast);
        final DetailAST firstClassNameNode = getFirstClassNameNode(ast);
        return new ExceptionInfo(firstClassNameNode,
                new ClassInfo(new Token(ident)));
    }

    /**
     * Get node where class name of exception starts.
     *
     * @param ast DetailAST object where to find exceptions node;
     * @return exception node where class name starts
     */
    private static DetailAST getFirstClassNameNode(DetailAST ast) {
        DetailAST startNode = ast;
        while (startNode.getType() == TokenTypes.DOT) {
            startNode = startNode.getFirstChild();
        }
        return startNode;
    }

    /**
     * Checks if a 'throw' usage is contained within a block that should be ignored.
     * Such blocks consist of try (with catch) blocks, local classes, anonymous classes,
     * and lambda expressions. Note that a try block without catch is not considered.
     *
     * @param methodBodyAst DetailAST node representing the method body
     * @param throwAst DetailAST node representing the 'throw' literal
     * @return true if throwAst is inside a block that should be ignored
     */
    private static boolean isInIgnoreBlock(DetailAST methodBodyAst, DetailAST throwAst) {
        DetailAST ancestor = throwAst;
        while (ancestor != methodBodyAst) {
            if (ancestor.getType() == TokenTypes.LAMBDA
                    || ancestor.getType() == TokenTypes.OBJBLOCK
                    || ancestor.findFirstToken(TokenTypes.LITERAL_CATCH) != null) {
                // throw is inside a lambda expression/anonymous class/local class,
                // or throw is inside a try block, and there is a catch block
                break;
            }
            if (ancestor.getType() == TokenTypes.LITERAL_CATCH
                    || ancestor.getType() == TokenTypes.LITERAL_FINALLY) {
                // if the throw is inside a catch or finally block,
                // skip the immediate ancestor (try token)
                ancestor = ancestor.getParent();
            }
            ancestor = ancestor.getParent();
        }
        return ancestor != methodBodyAst;
    }

    /**
     * Combine ExceptionInfo collections together by matching names.
     *
     * @param first the first collection of ExceptionInfo
     * @param second the second collection of ExceptionInfo
     * @return combined list of ExceptionInfo
     */
    private static List<ExceptionInfo> combineExceptionInfo(Collection<ExceptionInfo> first,
                                                            Iterable<ExceptionInfo> second) {
        final List<ExceptionInfo> result = new ArrayList<>(first);
        for (ExceptionInfo exceptionInfo : second) {
            if (result.stream().noneMatch(item -> isExceptionInfoSame(item, exceptionInfo))) {
                result.add(exceptionInfo);
            }
        }
        return result;
    }

    /**
     * Finds node of specified type among root children, siblings, siblings children
     * on any deep level.
     *
     * @param root    DetailAST
     * @param astType value of TokenType
     * @return {@link List} of {@link DetailAST} nodes which matches the predicate.
     */
    public static List<DetailAST> findTokensInAstByType(DetailAST root, int astType) {
        final List<DetailAST> result = new ArrayList<>();
        // iterative preorder depth-first search
        DetailAST curNode = root;
        do {
            // process curNode
            if (curNode.getType() == astType) {
                result.add(curNode);
            }
            // process children (if any)
            if (curNode.hasChildren()) {
                curNode = curNode.getFirstChild();
                continue;
            }
            // backtrack to parent if last child, stopping at root
            while (curNode.getNextSibling() == null) {
                curNode = curNode.getParent();
            }
            // explore siblings if not root
            if (curNode != root) {
                curNode = curNode.getNextSibling();
            }
        } while (curNode != root);
        return result;
    }

    /**
     * Checks if all record components in a compact constructor have
     * corresponding {@code @param} tags.
     * Reports missing or extra {@code @param} tags in the Javadoc.
     *
     * @param tags the list of Javadoc tags
     * @param compactDef the compact constructor AST node
     * @param reportExpectedTags whether to report missing {@code @param} tags
     */
    private void checkRecordParamTags(final List<JavadocTag> tags,
        final DetailAST compactDef, boolean reportExpectedTags) {

        final DetailAST parent = getRecordDef(compactDef);
        final List<DetailAST> params = getRecordComponents(parent);

        for (JavadocTag tag : tags) {
            if (!tag.isParamTag()) {
                continue;
            }

            if (isDuplicateParamTag(tags, tag)) {
                log(tag.getLineNo(), tag.getColumnNo(), MSG_DUPLICATE_TAG,
                        JavadocTagInfo.PARAM.getText());
            }
            else {
                final String arg1 = tag.getFirstArg();
                final boolean found = removeMatchingParam(params, arg1);

                if (!found) {
                    log(tag.getLineNo(), tag.getColumnNo(), MSG_UNUSED_TAG,
                            JavadocTagInfo.PARAM.getText(), arg1);
                }
            }
        }
        tags.removeIf(JavadocTag::isParamTag);

        if (!allowMissingParamTags && reportExpectedTags) {
            for (DetailAST param : params) {
                log(compactDef, MSG_EXPECTED_TAG,
                    JavadocTagInfo.PARAM.getText(), param.getText());
            }
        }
    }

    /**
     * Checks a set of tags for matching parameters.
     *
     * @param tags the tags to check
     * @param parent the node which takes the parameters
     * @param reportExpectedTags whether we should report if do not find expected tag
     */
    private void checkParamTags(final List<JavadocTag> tags,
            final DetailAST parent, boolean reportExpectedTags) {
        final List<DetailAST> params = getParameters(parent);
        final List<DetailAST> typeParams = CheckUtil
                .getTypeParameters(parent);

        // Loop over the tags, checking to see they exist in the params.
        for (JavadocTag tag : tags) {
            if (!tag.isParamTag()) {
                continue;
            }

            if (isDuplicateParamTag(tags, tag)) {
                log(tag.getLineNo(), tag.getColumnNo(), MSG_DUPLICATE_TAG,
                        JavadocTagInfo.PARAM.getText());
            }
            else {
                final String arg1 = tag.getFirstArg();
                boolean found = removeMatchingParam(params, arg1);

                if (arg1.endsWith(ELEMENT_END)) {
                    found = searchMatchingTypeParameter(typeParams,
                            arg1.substring(1, arg1.length() - 1));
                }

                // Handle extra JavadocTag
                if (!found) {
                    log(tag.getLineNo(), tag.getColumnNo(), MSG_UNUSED_TAG,
                            JavadocTagInfo.PARAM.getText(), arg1);
                }
            }
        }
        tags.removeIf(JavadocTag::isParamTag);

        // Now dump out all type parameters/parameters without tags :- unless
        // the user has chosen to suppress these problems
        if (!allowMissingParamTags && reportExpectedTags) {
            for (DetailAST param : params) {
                log(param, MSG_EXPECTED_TAG,
                    JavadocTagInfo.PARAM.getText(), param.getText());
            }

            for (DetailAST typeParam : typeParams) {
                log(typeParam, MSG_EXPECTED_TAG,
                    JavadocTagInfo.PARAM.getText(),
                    ELEMENT_START + typeParam.findFirstToken(TokenTypes.IDENT).getText()
                    + ELEMENT_END);
            }
        }
    }

    /**
     * Checks if the {@code @param} tag duplicates an earlier {@code @param} tag.
     *
     * @param tags all tags to check
     * @param tag the tag to check
     * @return true if there is an earlier {@code @param} tag with the same argument
     */
    private static boolean isDuplicateParamTag(List<JavadocTag> tags, JavadocTag tag) {
        final int tagIndex = tags.indexOf(tag);
        boolean result = false;
        for (int tagPosition = 0; tagPosition < tagIndex; tagPosition++) {
            final JavadocTag currentTag = tags.get(tagPosition);
            if (currentTag.isParamTag()
                    && currentTag.getFirstArg().equals(tag.getFirstArg())) {
                result = true;
            }
        }
        return result;
    }

    /**
     * Returns true if required type found in type parameters.
     *
     * @param typeParams
     *            collection of type parameters
     * @param requiredTypeName
     *            name of required type
     * @return true if required type found in type parameters.
     */
    private static boolean searchMatchingTypeParameter(Iterable<DetailAST> typeParams,
            String requiredTypeName) {
        // Loop looking for matching type param
        final Iterator<DetailAST> typeParamsIt = typeParams.iterator();
        boolean found = false;
        while (typeParamsIt.hasNext()) {
            final DetailAST typeParam = typeParamsIt.next();
            if (typeParam.findFirstToken(TokenTypes.IDENT).getText()
                    .equals(requiredTypeName)) {
                found = true;
                typeParamsIt.remove();
                break;
            }
        }
        return found;
    }

    /**
     * Remove parameter from params collection by name.
     *
     * @param params collection of DetailAST parameters
     * @param paramName name of parameter
     * @return true if parameter found and removed
     */
    private static boolean removeMatchingParam(Iterable<DetailAST> params, String paramName) {
        boolean found = false;
        final Iterator<DetailAST> paramIt = params.iterator();
        while (paramIt.hasNext()) {
            final DetailAST param = paramIt.next();
            if (param.getText().equals(paramName)) {
                found = true;
                paramIt.remove();
                break;
            }
        }
        return found;
    }

    /**
     * Checks for only one return tag. All return tags will be removed from the supplied list.
     *
     * @param tags the tags to check
     * @param lineNo the line number of the expected tag
     * @param reportExpectedTags whether we should report if do not find expected tag
     */
    private void checkReturnTag(List<JavadocTag> tags, int lineNo,
        boolean reportExpectedTags) {
        // Loop over tags finding return tags. After the first one, report a violation
        boolean found = false;
        final ListIterator<JavadocTag> it = tags.listIterator();
        while (it.hasNext()) {
            final JavadocTag javadocTag = it.next();
            if (javadocTag.isReturnTag()) {
                if (found) {
                    log(javadocTag.getLineNo(), javadocTag.getColumnNo(),
                            MSG_DUPLICATE_TAG,
                            JavadocTagInfo.RETURN.getText());
                }
                found = true;
                it.remove();
            }
        }

        // Handle there being no @return tags :- unless
        // the user has chosen to suppress these problems
        if (!found && !allowMissingReturnTag && reportExpectedTags) {
            log(lineNo, MSG_RETURN_EXPECTED);
        }
    }

    /**
     * Checks a set of tags for matching throws.
     *
     * @param tags the tags to check
     * @param throwsList the throws to check
     * @param reportExpectedTags whether we should report if do not find expected tag
     */
    private void checkThrowsTags(List<JavadocTag> tags,
            List<ExceptionInfo> throwsList, boolean reportExpectedTags) {
        // Loop over the tags, checking to see they exist in the throws.
        final ListIterator<JavadocTag> tagIt = tags.listIterator();
        while (tagIt.hasNext()) {
            final JavadocTag tag = tagIt.next();

            if (!tag.isThrowsTag()) {
                continue;
            }
            tagIt.remove();

            // Loop looking for matching throw
            processThrows(throwsList, tag.getFirstArg());
        }
        // Now dump out all throws without tags :- unless
        // the user has chosen to suppress these problems
        if (validateThrows && reportExpectedTags) {
            throwsList.stream().filter(exceptionInfo -> !exceptionInfo.isFound())
                .forEach(exceptionInfo -> {
                    final Token token = exceptionInfo.getName();
                    log(exceptionInfo.getAst(),
                        MSG_EXPECTED_TAG,
                        JavadocTagInfo.THROWS.getText(), token.text());
                });
        }
    }

    /**
     * Verifies that documented exception is in throws.
     *
     * @param throwsIterable collection of throws
     * @param documentedClassName documented exception class name
     */
    private static void processThrows(Iterable<ExceptionInfo> throwsIterable,
                                      String documentedClassName) {
        for (ExceptionInfo exceptionInfo : throwsIterable) {
            if (isClassNamesSame(exceptionInfo.getName().text(),
                    documentedClassName)) {
                exceptionInfo.setFound();
                break;
            }
        }
    }

    /**
     * Check that ExceptionInfo objects are same by name.
     *
     * @param info1 ExceptionInfo object
     * @param info2 ExceptionInfo object
     * @return true is ExceptionInfo object have the same name
     */
    private static boolean isExceptionInfoSame(ExceptionInfo info1, ExceptionInfo info2) {
        return isClassNamesSame(info1.getName().text(),
                                    info2.getName().text());
    }

    /**
     * Check that class names are same by short name of class. If some class name is fully
     * qualified it is cut to short name.
     *
     * @param class1 class name
     * @param class2 class name
     * @return true is ExceptionInfo object have the same name
     */
    private static boolean isClassNamesSame(String class1, String class2) {
        final String class1ShortName = class1
                .substring(class1.lastIndexOf('.') + 1);
        final String class2ShortName = class2
                .substring(class2.lastIndexOf('.') + 1);
        return class1ShortName.equals(class2ShortName);
    }

    /**
     * Contains class's {@code Token}.
     *
     * @param name {@code FullIdent} associated with this class.
     */
    private record ClassInfo(Token name) {
    }

    /**
     * Represents text element with location in the text.
     *
     * @param text Token's text.
     */
    private record Token(String text) {

        /**
         * Converts FullIdent to Token.
         *
         * @param fullIdent full ident to convert.
         */
        private Token(FullIdent fullIdent) {
            this(fullIdent.getText());
        }
    }

    /** Stores useful information about declared exception. */
    private static final class ExceptionInfo {

        /** AST node representing this exception. */
        private final DetailAST ast;

        /** Class information associated with this exception. */
        private final ClassInfo classInfo;
        /** Does the exception have throws tag associated with. */
        private boolean found;

        /**
         * Creates new instance for {@code FullIdent}.
         *
         * @param ast AST node representing this exception
         * @param classInfo class info
         */
        private ExceptionInfo(DetailAST ast, ClassInfo classInfo) {
            this.ast = ast;
            this.classInfo = classInfo;
        }

        /**
         * Gets the AST node representing this exception.
         *
         * @return the AST node representing this exception
         */
        private DetailAST getAst() {
            return ast;
        }

        /** Mark that the exception has associated throws tag. */
        private void setFound() {
            found = true;
        }

        /**
         * Checks that the exception has throws tag associated with it.
         *
         * @return whether the exception has throws tag associated with
         */
        private boolean isFound() {
            return found;
        }

        /**
         * Gets exception name.
         *
         * @return exception's name
         */
        private Token getName() {
            return classInfo.name();
        }

    }

}