///////////////////////////////////////////////////////////////////////////////////////////////
// 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 java.util.regex.MatchResult;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import com.puppycrawl.tools.checkstyle.StatelessCheck;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.FileContents;
import com.puppycrawl.tools.checkstyle.api.FullIdent;
import com.puppycrawl.tools.checkstyle.api.TextBlock;
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.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>
 * <div class="wrapper"><pre class="prettyprint"><code class="language-java">
 * &#47;** {&#64;inheritDoc} *&#47;
 * public int checkReturnTag(final int aTagIndex,
 *                           JavadocTag[] aTags,
 *                           int aLineNo)
 * </code></pre></div>
 *
 * @since 3.0
 */
@StatelessCheck
public class JavadocMethodCheck extends AbstractCheck {

    /**
     * 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 = ">";

    /** Compiled regexp to match Javadoc tags that take an argument. */
    private static final Pattern MATCH_JAVADOC_ARG = CommonUtil.createPattern(
            "^\\s*(?>\\*|\\/\\*\\*)?\\s*@(throws|exception|param)\\s+(\\S+)\\s+\\S*");
    /** Compiled regexp to match Javadoc tags with argument but with missing description. */
    private static final Pattern MATCH_JAVADOC_ARG_MISSING_DESCRIPTION =
        CommonUtil.createPattern("^\\s*(?>\\*|\\/\\*\\*)?\\s*@(throws|exception|param)\\s+"
            + "(\\S[^*]*)(?:(\\s+|\\*\\/))?");

    /** Compiled regexp to look for a continuation of the comment. */
    private static final Pattern MATCH_JAVADOC_MULTILINE_CONT =
            CommonUtil.createPattern("(\\*\\/|@|[^\\s\\*])");

    /** Multiline finished at end of comment. */
    private static final String END_JAVADOC = "*/";
    /** Multiline finished at next Javadoc. */
    private static final String NEXT_TAG = "@";

    /** Compiled regexp to match Javadoc tags with no argument. */
    private static final Pattern MATCH_JAVADOC_NOARG =
            CommonUtil.createPattern("^\\s*(?>\\*|\\/\\*\\*)?\\s*@(return|see)\\s+\\S");
    /** Compiled regexp to match Javadoc tags with no argument allowing inline return tag. */
    private static final Pattern MATCH_JAVADOC_NOARG_INLINE_RETURN =
            CommonUtil.createPattern("^\\s*(?>\\*|\\/\\*\\*)?\\s*\\{?@(return|see)\\s+\\S");
    /** Compiled regexp to match first part of multilineJavadoc tags. */
    private static final Pattern MATCH_JAVADOC_NOARG_MULTILINE_START =
            CommonUtil.createPattern("^\\s*(?>\\*|\\/\\*\\*)?\\s*@(return|see)\\s*$");
    /** Compiled regexp to match Javadoc tags with no argument and {}. */
    private static final Pattern MATCH_JAVADOC_NOARG_CURLY =
            CommonUtil.createPattern("\\{\\s*@(inheritDoc)\\s*\\}");

    /**
     * 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");

    /**
     * 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;
    }

    @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) {
        processAST(ast);
    }

    /**
     * Called to process an AST when visiting it.
     *
     * @param ast the AST to process. Guaranteed to not be PACKAGE_DEF or
     *             IMPORT tokens.
     */
    // suppress deprecation until https://github.com/checkstyle/checkstyle/issues/11166
    @SuppressWarnings("deprecation")
    private void processAST(DetailAST ast) {
        if (shouldCheck(ast)) {
            final FileContents contents = getFileContents();
            final TextBlock textBlock = contents.getJavadocBefore(ast.getLineNo());

            if (textBlock != null) {
                checkComment(ast, textBlock);
            }
        }
    }

    /**
     * Whether we should check this node.
     *
     * @param ast a given node.
     * @return whether we should check a given node.
     */
    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);
    }

    /**
     * Checks the Javadoc for a method.
     *
     * @param ast the token for the method
     * @param comment the Javadoc comment
     */
    private void checkComment(DetailAST ast, TextBlock comment) {
        final List<JavadocTag> tags = getMethodTags(comment);

        if (!hasShortCircuitTag(ast, tags)) {
            if (ast.getType() == TokenTypes.ANNOTATION_FIELD_DEF) {
                checkReturnTag(tags, ast.getLineNo(), true);
            }
            else {
                final Iterator<JavadocTag> it = tags.iterator();
                // Check for inheritDoc
                boolean hasInheritDocTag = false;
                while (!hasInheritDocTag && it.hasNext()) {
                    hasInheritDocTag = it.next().isInheritDocTag();
                }
                final boolean reportExpectedTags = !hasInheritDocTag
                    && !AnnotationUtil.containsAnnotation(ast, allowedAnnotations);

                // COMPACT_CTOR_DEF has no parameters
                if (ast.getType() == TokenTypes.COMPACT_CTOR_DEF) {
                    checkRecordParamTags(tags, ast, reportExpectedTags);
                }
                else {
                    checkParamTags(tags, ast, reportExpectedTags);
                }
                final List<ExceptionInfo> throwed =
                    combineExceptionInfo(getThrows(ast), getThrowed(ast));
                checkThrowsTags(tags, throwed, reportExpectedTags);
                if (CheckUtil.isNonVoidMethod(ast)) {
                    checkReturnTag(tags, ast.getLineNo(), reportExpectedTags);
                }
            }
        }
        tags.stream().filter(javadocTag -> !javadocTag.isSeeOrInheritDocTag())
            .forEach(javadocTag -> log(javadocTag.getLineNo(), MSG_UNUSED_TAG_GENERAL));
    }

    /**
     * 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;
    }

    /**
     * Returns the tags in a javadoc comment. Only finds throws, exception,
     * param, return and see tags.
     *
     * @param comment the Javadoc comment
     * @return the tags found
     */
    private List<JavadocTag> getMethodTags(TextBlock comment) {
        Pattern matchJavadocNoArg = MATCH_JAVADOC_NOARG;
        if (allowInlineReturn) {
            matchJavadocNoArg = MATCH_JAVADOC_NOARG_INLINE_RETURN;
        }
        final String[] lines = comment.getText();
        final List<JavadocTag> tags = new ArrayList<>();
        int currentLine = comment.getStartLineNo() - 1;
        final int startColumnNumber = comment.getStartColNo();

        for (int i = 0; i < lines.length; i++) {
            currentLine++;
            final Matcher javadocArgMatcher =
                MATCH_JAVADOC_ARG.matcher(lines[i]);
            final Matcher javadocArgMissingDescriptionMatcher =
                MATCH_JAVADOC_ARG_MISSING_DESCRIPTION.matcher(lines[i]);
            final Matcher javadocNoargMatcher =
                matchJavadocNoArg.matcher(lines[i]);
            final Matcher noargCurlyMatcher =
                MATCH_JAVADOC_NOARG_CURLY.matcher(lines[i]);
            final Matcher noargMultilineStart =
                MATCH_JAVADOC_NOARG_MULTILINE_START.matcher(lines[i]);

            if (javadocArgMatcher.find()) {
                final int col = calculateTagColumn(javadocArgMatcher, i, startColumnNumber);
                tags.add(new JavadocTag(currentLine, col, javadocArgMatcher.group(1),
                        javadocArgMatcher.group(2)));
            }
            else if (javadocArgMissingDescriptionMatcher.find()) {
                final int col = calculateTagColumn(javadocArgMissingDescriptionMatcher, i,
                    startColumnNumber);
                tags.add(new JavadocTag(currentLine, col,
                    javadocArgMissingDescriptionMatcher.group(1),
                    javadocArgMissingDescriptionMatcher.group(2)));
            }
            else if (javadocNoargMatcher.find()) {
                final int col = calculateTagColumn(javadocNoargMatcher, i, startColumnNumber);
                tags.add(new JavadocTag(currentLine, col, javadocNoargMatcher.group(1)));
            }
            else if (noargCurlyMatcher.find()) {
                tags.add(new JavadocTag(currentLine, 0, noargCurlyMatcher.group(1)));
            }
            else if (noargMultilineStart.find()) {
                tags.addAll(getMultilineNoArgTags(noargMultilineStart, lines, i, currentLine));
            }
        }
        return tags;
    }

    /**
     * Calculates column number using Javadoc tag matcher.
     *
     * @param javadocTagMatchResult found javadoc tag match result
     * @param lineNumber line number of Javadoc tag in comment
     * @param startColumnNumber column number of Javadoc comment beginning
     * @return column number
     */
    private static int calculateTagColumn(MatchResult javadocTagMatchResult,
            int lineNumber, int startColumnNumber) {
        int col = javadocTagMatchResult.start(1) - 1;
        if (lineNumber == 0) {
            col += startColumnNumber;
        }
        return col;
    }

    /**
     * Gets multiline Javadoc tags with no arguments.
     *
     * @param noargMultilineStart javadoc tag Matcher
     * @param lines comment text lines
     * @param lineIndex line number that contains the javadoc tag
     * @param tagLine javadoc tag line number in file
     * @return javadoc tags with no arguments
     */
    private static List<JavadocTag> getMultilineNoArgTags(final Matcher noargMultilineStart,
            final String[] lines, final int lineIndex, final int tagLine) {
        int remIndex = lineIndex;
        Matcher multilineCont;

        do {
            remIndex++;
            multilineCont = MATCH_JAVADOC_MULTILINE_CONT.matcher(lines[remIndex]);
        } while (!multilineCont.find());

        final List<JavadocTag> tags = new ArrayList<>();
        final String lFin = multilineCont.group(1);
        if (!NEXT_TAG.equals(lFin)
            && !END_JAVADOC.equals(lFin)) {
            final String param1 = noargMultilineStart.group(1);
            final int col = noargMultilineStart.start(1) - 1;

            tags.add(new JavadocTag(tagLine, col, param1));
        }

        return tags;
    }

    /**
     * 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);

        final ListIterator<JavadocTag> tagIt = tags.listIterator();
        while (tagIt.hasNext()) {
            final JavadocTag tag = tagIt.next();

            if (!tag.isParamTag()) {
                continue;
            }

            tagIt.remove();

            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);
            }
        }

        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.
        final ListIterator<JavadocTag> tagIt = tags.listIterator();
        while (tagIt.hasNext()) {
            final JavadocTag tag = tagIt.next();

            if (!tag.isParamTag()) {
                continue;
            }

            tagIt.remove();

            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);
            }
        }

        // 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);
            }
        }
    }

    /**
     * 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.getText());
                });
        }
    }

    /**
     * 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().getText(),
                    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().getText(),
                                    info2.getName().getText());
    }

    /**
     * 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}.
     */
    private static class ClassInfo {

        /** {@code FullIdent} associated with this class. */
        private final Token name;

        /**
         * Creates new instance of class information object.
         *
         * @param className token which represents class name.
         * @throws IllegalArgumentException when className is nulls
         */
        /* package */ ClassInfo(final Token className) {
            name = className;
        }

        /**
         * Gets class name.
         *
         * @return class name
         */
        /* package */ final Token getName() {
            return name;
        }

    }

    /**
     * Represents text element with location in the text.
     */
    private static final class Token {

        /** Token's text. */
        private final String text;

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

        /**
         * Gets text of the token.
         *
         * @return text of the token
         */
        /* package */ String getText() {
            return text;
        }

    }

    /** 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.getName();
        }

    }

}