///////////////////////////////////////////////////////////////////////////////////////////////
// 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;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Optional;
import java.util.regex.Pattern;

import javax.annotation.Nullable;

import com.puppycrawl.tools.checkstyle.StatelessCheck;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.AuditEvent;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import com.puppycrawl.tools.checkstyle.utils.CommonUtil;

/**
 * <div>
 * Maintains a set of check suppressions from {@code @SuppressWarnings} annotations.
 * It allows to prevent Checkstyle from reporting violations from parts of code that were
 * annotated with {@code @SuppressWarnings} and using name of the check to be excluded.
 * It is possible to suppress all the checkstyle warnings with the argument {@code "all"}.
 * You can also use a {@code checkstyle:} prefix to prevent compiler
 * from processing these annotations.
 * You can also define aliases for check names that need to be suppressed.
 * </div>
 *
 * @since 5.7
 */
@StatelessCheck
public class SuppressWarningsHolder extends AbstractCheck {

    /**
     * Optional prefix for warning suppressions that are only intended to be
     * recognized by checkstyle. For instance, to suppress {@code
     * FallThroughCheck} only in checkstyle (and not in javac), use the
     * suppression {@code "checkstyle:fallthrough"} or {@code "checkstyle:FallThrough"}.
     * To suppress the warning in both tools, just use {@code "fallthrough"}.
     */
    private static final String CHECKSTYLE_PREFIX = "checkstyle:";

    /** Java.lang namespace prefix, which is stripped from SuppressWarnings. */
    private static final String JAVA_LANG_PREFIX = "java.lang.";

    /** Suffix to be removed from subclasses of Check. */
    private static final String CHECK_SUFFIX = "check";

    /** Special warning id for matching all the warnings. */
    private static final String ALL_WARNING_MATCHING_ID = "all";

    /** A map from check source names to suppression aliases. */
    private static final Map<String, String> CHECK_ALIAS_MAP = new HashMap<>();

    /**
     * A thread-local holder for the list of suppression entries for the last file parsed.
     */
    private static final ThreadLocal<List<Entry>> ENTRIES =
            ThreadLocal.withInitial(ArrayList::new);

    /**
     * Compiled pattern used to match whitespace in text block content.
     */
    private static final Pattern WHITESPACE = Pattern.compile("\\s+");

    /**
     * Compiled pattern used to match preceding newline in text block content.
     */
    private static final Pattern NEWLINE = Pattern.compile("\\n");

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

    /**
     * Returns the default alias for the source name of a check, which is the
     * source name in lower case with any dotted prefix or "Check"/"check" suffix removed.
     *
     * @param sourceName the source name of the check (generally the class name)
     * @return the default alias for the given check
     */
    public static String getDefaultAlias(String sourceName) {
        int endIndex = sourceName.length();
        final String sourceNameLower = sourceName.toLowerCase(Locale.ENGLISH);
        if (sourceNameLower.endsWith(CHECK_SUFFIX)) {
            endIndex -= CHECK_SUFFIX.length();
        }
        final int startIndex = sourceNameLower.lastIndexOf('.') + 1;
        return sourceNameLower.substring(startIndex, endIndex);
    }

    /**
     * Returns the alias of simple check name for a check, The alias is
     * for the form of CheckNameCheck or CheckName.
     *
     * @param sourceName the source name of the check (generally the class name)
     * @return the alias of the simple check name for the given check
     */
    @Nullable
    private static String getSimpleNameAlias(String sourceName) {
        final String checkName = CommonUtil.baseClassName(sourceName);
        final String checkNameSuffix = "Check";
        // check alias for the CheckNameCheck
        String checkAlias = CHECK_ALIAS_MAP.get(checkName);
        if (checkAlias == null && checkName.endsWith(checkNameSuffix)) {
            final int checkStartIndex = checkName.length() - checkNameSuffix.length();
            final String checkNameWithoutSuffix = checkName.substring(0, checkStartIndex);
            // check alias for the CheckName
            checkAlias = CHECK_ALIAS_MAP.get(checkNameWithoutSuffix);
        }

        return checkAlias;
    }

    /**
     * Returns the alias for the source name of a check. If an alias has been
     * explicitly registered via {@link #setAliasList(String...)}, that
     * alias is returned; otherwise, the default alias is used.
     *
     * @param sourceName the source name of the check (generally the class name)
     * @return the current alias for the given check
     */
    public static String getAlias(String sourceName) {
        String checkAlias = CHECK_ALIAS_MAP.get(sourceName);
        if (checkAlias == null) {
            checkAlias = getSimpleNameAlias(sourceName);
        }
        if (checkAlias == null) {
            checkAlias = getDefaultAlias(sourceName);
        }
        return checkAlias;
    }

    /**
     * Registers an alias for the source name of a check.
     *
     * @param sourceName the source name of the check (generally the class name)
     * @param checkAlias the alias used in {@link SuppressWarnings} annotations
     */
    private static void registerAlias(String sourceName, String checkAlias) {
        CHECK_ALIAS_MAP.put(sourceName, checkAlias);
    }

    /**
     * Setter to specify aliases for check names that can be used in code
     * within {@code SuppressWarnings} in a format of comma separated attribute=value entries.
     * The attribute is the fully qualified name of the Check and value is its alias.
     *
     * @param aliasList comma-separated alias assignments
     * @throws IllegalArgumentException when alias item does not have '='
     * @since 5.7
     */
    public void setAliasList(String... aliasList) {
        for (String sourceAlias : aliasList) {
            final int index = sourceAlias.indexOf('=');
            if (index > 0) {
                registerAlias(sourceAlias.substring(0, index), sourceAlias
                    .substring(index + 1));
            }
            else if (!sourceAlias.isEmpty()) {
                throw new IllegalArgumentException(
                    "'=' expected in alias list item: " + sourceAlias);
            }
        }
    }

    /**
     * Checks for a suppression of a check with the given source name and
     * location in the last file processed.
     *
     * @param event audit event.
     * @return whether the check with the given name is suppressed at the given source location
     */
    public static boolean isSuppressed(AuditEvent event) {
        final List<Entry> entries = ENTRIES.get();
        final String sourceName = event.getSourceName();
        final String checkAlias = getAlias(sourceName);
        final int line = event.getLine();
        final int column = event.getColumn();
        boolean suppressed = false;
        for (Entry entry : entries) {
            final boolean afterStart = isSuppressedAfterEventStart(line, column, entry);
            final boolean beforeEnd = isSuppressedBeforeEventEnd(line, column, entry);
            final String checkName = entry.checkName();
            final boolean nameMatches =
                ALL_WARNING_MATCHING_ID.equals(checkName)
                    || checkName.equalsIgnoreCase(checkAlias)
                    || getDefaultAlias(checkName).equalsIgnoreCase(checkAlias)
                    || getDefaultAlias(sourceName).equalsIgnoreCase(checkName);
            if (afterStart && beforeEnd
                    && (nameMatches || checkName.equals(event.getModuleId()))) {
                suppressed = true;
                break;
            }
        }
        return suppressed;
    }

    /**
     * Checks whether suppression entry position is after the audit event occurrence position
     * in the source file.
     *
     * @param line the line number in the source file where the event occurred.
     * @param column the column number in the source file where the event occurred.
     * @param entry suppression entry.
     * @return true if suppression entry position is after the audit event occurrence position
     *         in the source file.
     */
    private static boolean isSuppressedAfterEventStart(int line, int column, Entry entry) {
        return entry.firstLine() < line
            || entry.firstLine() == line
            && (column == 0 || entry.firstColumn() <= column);
    }

    /**
     * Checks whether suppression entry position is before the audit event occurrence position
     * in the source file.
     *
     * @param line the line number in the source file where the event occurred.
     * @param column the column number in the source file where the event occurred.
     * @param entry suppression entry.
     * @return true if suppression entry position is before the audit event occurrence position
     *         in the source file.
     */
    private static boolean isSuppressedBeforeEventEnd(int line, int column, Entry entry) {
        return entry.lastLine() > line
            || entry.lastLine() == line && entry
                .lastColumn() >= column;
    }

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

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

    @Override
    public int[] getRequiredTokens() {
        return new int[] {TokenTypes.ANNOTATION};
    }

    @Override
    public void beginTree(DetailAST rootAST) {
        ENTRIES.get().clear();
    }

    @Override
    public void visitToken(DetailAST ast) {
        // check whether annotation is SuppressWarnings
        // expected children: AT ( IDENT | DOT ) LPAREN <values> RPAREN
        String identifier = getIdentifier(getNthChild(ast, 1));
        if (identifier.startsWith(JAVA_LANG_PREFIX)) {
            identifier = identifier.substring(JAVA_LANG_PREFIX.length());
        }
        if ("SuppressWarnings".equals(identifier)) {
            getAnnotationTarget(ast).ifPresent(targetAST -> {
                addSuppressions(getAllAnnotationValues(ast), targetAST);
            });
        }
    }

    /**
     * Method to populate list of suppression entries.
     *
     * @param values
     *            - list of check names
     * @param targetAST
     *            - annotation target
     */
    private static void addSuppressions(List<String> values, DetailAST targetAST) {
        // get text range of target
        final int firstLine = targetAST.getLineNo();
        final int firstColumn = targetAST.getColumnNo();
        final DetailAST nextAST = targetAST.getNextSibling();
        final int lastLine;
        final int lastColumn;
        if (nextAST == null) {
            lastLine = Integer.MAX_VALUE;
            lastColumn = Integer.MAX_VALUE;
        }
        else {
            lastLine = nextAST.getLineNo();
            lastColumn = nextAST.getColumnNo();
        }

        final List<Entry> entries = ENTRIES.get();
        for (String value : values) {
            // strip off the checkstyle-only prefix if present
            final String checkName = removeCheckstylePrefixIfExists(value);
            entries.add(new Entry(checkName, firstLine, firstColumn,
                    lastLine, lastColumn));
        }
    }

    /**
     * Method removes checkstyle prefix (checkstyle:) from check name if exists.
     *
     * @param checkName
     *            - name of the check
     * @return check name without prefix
     */
    private static String removeCheckstylePrefixIfExists(String checkName) {
        String result = checkName;
        if (checkName.startsWith(CHECKSTYLE_PREFIX)) {
            result = checkName.substring(CHECKSTYLE_PREFIX.length());
        }
        return result;
    }

    /**
     * Get all annotation values.
     *
     * @param ast annotation token
     * @return list values
     * @throws IllegalArgumentException if there is an unknown annotation value type.
     */
    private static List<String> getAllAnnotationValues(DetailAST ast) {
        // get values of annotation
        List<String> values = List.of();
        final DetailAST lparenAST = ast.findFirstToken(TokenTypes.LPAREN);
        if (lparenAST != null) {
            final DetailAST nextAST = lparenAST.getNextSibling();
            final int nextType = nextAST.getType();
            switch (nextType) {
                case TokenTypes.EXPR, TokenTypes.ANNOTATION_ARRAY_INIT ->
                    values = getAnnotationValues(nextAST);
                case TokenTypes.ANNOTATION_MEMBER_VALUE_PAIR ->
                    // expected children: IDENT ASSIGN ( EXPR |
                    // ANNOTATION_ARRAY_INIT )
                    values = getAnnotationValues(getNthChild(nextAST, 2));
                case TokenTypes.RPAREN -> {
                    // no value present (not valid Java)
                }
                default ->
                    // unknown annotation value type (new syntax?)
                    throw new IllegalArgumentException("Unexpected AST: " + nextAST);
            }
        }
        return values;
    }

    /**
     * Get target of annotation.
     *
     * @param ast the AST node to get the child of
     * @return get target of annotation
     * @throws IllegalArgumentException if there is an unexpected container type.
     */
    private static Optional<DetailAST> getAnnotationTarget(DetailAST ast) {
        DetailAST current = ast.getParent();
        while (current.getType() == TokenTypes.ANNOTATION_ARRAY_INIT) {
            current = current.getParent();
        }
        return switch (current.getType()) {
            case TokenTypes.MODIFIERS, TokenTypes.ANNOTATIONS, TokenTypes.ANNOTATION,
                 TokenTypes.ANNOTATION_MEMBER_VALUE_PAIR -> Optional.of(current.getParent());
            case TokenTypes.LITERAL_DEFAULT -> Optional.empty();
            default -> throw new IllegalArgumentException("Unexpected container AST: " + current);
        };
    }

    /**
     * Returns the n'th child of an AST node.
     *
     * @param ast the AST node to get the child of
     * @param index the index of the child to get
     * @return the n'th child of the given AST node, or {@code null} if none
     */
    private static DetailAST getNthChild(DetailAST ast, int index) {
        DetailAST child = ast.getFirstChild();
        for (int childIndex = 0; childIndex < index && child != null; childIndex++) {
            child = child.getNextSibling();
        }
        return child;
    }

    /**
     * Returns the Java identifier represented by an AST.
     *
     * @param ast an AST node for an IDENT or DOT
     * @return the Java identifier represented by the given AST subtree
     * @throws IllegalArgumentException if the AST is invalid
     */
    private static String getIdentifier(DetailAST ast) {
        if (ast == null) {
            throw new IllegalArgumentException("Identifier AST expected, but get null.");
        }
        final String identifier;
        if (ast.getType() == TokenTypes.IDENT) {
            identifier = ast.getText();
        }
        else {
            identifier = getIdentifier(ast.getFirstChild()) + "."
                + getIdentifier(ast.getLastChild());
        }
        return identifier;
    }

    /**
     * Returns the literal string expression represented by an AST.
     *
     * @param ast an AST node for an EXPR
     * @return the Java string represented by the given AST expression
     *         or empty string if expression is too complex
     * @throws IllegalArgumentException if the AST is invalid
     */
    private static String getStringExpr(DetailAST ast) {
        final DetailAST firstChild = ast.getFirstChild();

        return switch (firstChild.getType()) {
            case TokenTypes.STRING_LITERAL -> {
                // NOTE: escaped characters are not unescaped
                final String quotedText = firstChild.getText();
                yield quotedText.substring(1, quotedText.length() - 1);
            }
            case TokenTypes.IDENT -> firstChild.getText();
            case TokenTypes.DOT -> firstChild.getLastChild().getText();
            case TokenTypes.TEXT_BLOCK_LITERAL_BEGIN -> {
                final String textBlockContent = firstChild.getFirstChild().getText();
                yield getContentWithoutPrecedingWhitespace(textBlockContent);
            }
            default ->
                // annotations with complex expressions cannot suppress warnings
                "";
        };
    }

    /**
     * Returns the annotation values represented by an AST.
     *
     * @param ast an AST node for an EXPR or ANNOTATION_ARRAY_INIT
     * @return the list of Java string represented by the given AST for an
     *         expression or annotation array initializer
     * @throws IllegalArgumentException if the AST is invalid
     */
    private static List<String> getAnnotationValues(DetailAST ast) {
        return switch (ast.getType()) {
            case TokenTypes.EXPR -> List.of(getStringExpr(ast));
            case TokenTypes.ANNOTATION_ARRAY_INIT -> findAllExpressionsInChildren(ast);
            default -> throw new IllegalArgumentException(
                    "Expression or annotation array initializer AST expected: " + ast);
        };
    }

    /**
     * Method looks at children and returns list of expressions in strings.
     *
     * @param parent ast, that contains children
     * @return list of expressions in strings
     */
    private static List<String> findAllExpressionsInChildren(DetailAST parent) {
        final List<String> valueList = new ArrayList<>();
        DetailAST childAST = parent.getFirstChild();
        while (childAST != null) {
            if (childAST.getType() == TokenTypes.EXPR) {
                valueList.add(getStringExpr(childAST));
            }
            childAST = childAST.getNextSibling();
        }
        return valueList;
    }

    /**
     * Remove preceding newline and whitespace from the content of a text block.
     *
     * @param textBlockContent the actual text in a text block.
     * @return content of text block with preceding whitespace and newline removed.
     */
    private static String getContentWithoutPrecedingWhitespace(String textBlockContent) {
        final String contentWithNoPrecedingNewline =
            NEWLINE.matcher(textBlockContent).replaceAll("");
        return WHITESPACE.matcher(contentWithNoPrecedingNewline).replaceAll("");
    }

    @Override
    public void destroy() {
        super.destroy();
        ENTRIES.remove();
    }

    /**
     * Records a particular suppression for a region of a file.
     *
     * @param checkName   the source name of the suppressed check
     * @param firstLine   the first line of the suppression region
     * @param firstColumn the first column of the suppression region
     * @param lastLine    the last line of the suppression region
     * @param lastColumn  the last column of the suppression region
     */
    private record Entry(String checkName, int firstLine,
                         int firstColumn, int lastLine, int lastColumn) {

    }

}