001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2025 the original author or authors.
004//
005// This library is free software; you can redistribute it and/or
006// modify it under the terms of the GNU Lesser General Public
007// License as published by the Free Software Foundation; either
008// version 2.1 of the License, or (at your option) any later version.
009//
010// This library is distributed in the hope that it will be useful,
011// but WITHOUT ANY WARRANTY; without even the implied warranty of
012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013// Lesser General Public License for more details.
014//
015// You should have received a copy of the GNU Lesser General Public
016// License along with this library; if not, write to the Free Software
017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
018///////////////////////////////////////////////////////////////////////////////////////////////
019
020package com.puppycrawl.tools.checkstyle.checks.coding;
021
022import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
023import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
024import com.puppycrawl.tools.checkstyle.api.DetailAST;
025import com.puppycrawl.tools.checkstyle.api.TokenTypes;
026
027/**
028 * <div>
029 * Restricts nested if-else blocks to a specified depth.
030 * </div>
031 *
032 * @since 3.2
033 */
034@FileStatefulCheck
035public final class NestedIfDepthCheck extends AbstractCheck {
036
037    /**
038     * A key is pointing to the warning message text in "messages.properties"
039     * file.
040     */
041    public static final String MSG_KEY = "nested.if.depth";
042
043    /** Specify maximum allowed nesting depth. */
044    private int max = 1;
045    /** Current nesting depth. */
046    private int depth;
047
048    /**
049     * Setter to specify maximum allowed nesting depth.
050     *
051     * @param max maximum allowed nesting depth.
052     * @since 3.2
053     */
054    public void setMax(int max) {
055        this.max = max;
056    }
057
058    @Override
059    public int[] getDefaultTokens() {
060        return getRequiredTokens();
061    }
062
063    @Override
064    public int[] getAcceptableTokens() {
065        return getRequiredTokens();
066    }
067
068    @Override
069    public int[] getRequiredTokens() {
070        return new int[] {TokenTypes.LITERAL_IF};
071    }
072
073    @Override
074    public void visitToken(DetailAST literalIf) {
075        if (!isElseIf(literalIf)) {
076            if (depth > max) {
077                log(literalIf, MSG_KEY, depth, max);
078            }
079            ++depth;
080        }
081    }
082
083    @Override
084    public void leaveToken(DetailAST literalIf) {
085        if (!isElseIf(literalIf)) {
086            --depth;
087        }
088    }
089
090    /**
091     * Returns whether a token represents an ELSE as part of an ELSE / IF set.
092     *
093     * @param ast the token to check
094     * @return whether it is
095     */
096    private static boolean isElseIf(DetailAST ast) {
097        final DetailAST parentAST = ast.getParent();
098
099        return isElse(parentAST) || isElseWithCurlyBraces(parentAST);
100    }
101
102    /**
103     * Returns whether a token represents an ELSE.
104     *
105     * @param ast the token to check
106     * @return whether the token represents an ELSE
107     */
108    private static boolean isElse(DetailAST ast) {
109        return ast.getType() == TokenTypes.LITERAL_ELSE;
110    }
111
112    /**
113     * Returns whether a token represents an SLIST as part of an ELSE
114     * statement.
115     *
116     * @param ast the token to check
117     * @return whether the toke does represent an SLIST as part of an ELSE
118     */
119    private static boolean isElseWithCurlyBraces(DetailAST ast) {
120        return ast.getChildCount() == 2 && isElse(ast.getParent());
121    }
122}