001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2024 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 * <ul>
032 * <li>
033 * Property {@code max} - Specify maximum allowed nesting depth.
034 * Type is {@code int}.
035 * Default value is {@code 1}.
036 * </li>
037 * </ul>
038 *
039 * <p>
040 * Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
041 * </p>
042 *
043 * <p>
044 * Violation Message Keys:
045 * </p>
046 * <ul>
047 * <li>
048 * {@code nested.if.depth}
049 * </li>
050 * </ul>
051 *
052 * @since 3.2
053 */
054@FileStatefulCheck
055public final class NestedIfDepthCheck extends AbstractCheck {
056
057    /**
058     * A key is pointing to the warning message text in "messages.properties"
059     * file.
060     */
061    public static final String MSG_KEY = "nested.if.depth";
062
063    /** Specify maximum allowed nesting depth. */
064    private int max = 1;
065    /** Current nesting depth. */
066    private int depth;
067
068    /**
069     * Setter to specify maximum allowed nesting depth.
070     *
071     * @param max maximum allowed nesting depth.
072     * @since 3.2
073     */
074    public void setMax(int max) {
075        this.max = max;
076    }
077
078    @Override
079    public int[] getDefaultTokens() {
080        return getRequiredTokens();
081    }
082
083    @Override
084    public int[] getAcceptableTokens() {
085        return getRequiredTokens();
086    }
087
088    @Override
089    public int[] getRequiredTokens() {
090        return new int[] {TokenTypes.LITERAL_IF};
091    }
092
093    @Override
094    public void visitToken(DetailAST literalIf) {
095        if (!isElseIf(literalIf)) {
096            if (depth > max) {
097                log(literalIf, MSG_KEY, depth, max);
098            }
099            ++depth;
100        }
101    }
102
103    @Override
104    public void leaveToken(DetailAST literalIf) {
105        if (!isElseIf(literalIf)) {
106            --depth;
107        }
108    }
109
110    /**
111     * Returns whether a token represents an ELSE as part of an ELSE / IF set.
112     *
113     * @param ast the token to check
114     * @return whether it is
115     */
116    private static boolean isElseIf(DetailAST ast) {
117        final DetailAST parentAST = ast.getParent();
118
119        return isElse(parentAST) || isElseWithCurlyBraces(parentAST);
120    }
121
122    /**
123     * Returns whether a token represents an ELSE.
124     *
125     * @param ast the token to check
126     * @return whether the token represents an ELSE
127     */
128    private static boolean isElse(DetailAST ast) {
129        return ast.getType() == TokenTypes.LITERAL_ELSE;
130    }
131
132    /**
133     * Returns whether a token represents an SLIST as part of an ELSE
134     * statement.
135     *
136     * @param ast the token to check
137     * @return whether the toke does represent an SLIST as part of an ELSE
138     */
139    private static boolean isElseWithCurlyBraces(DetailAST ast) {
140        return ast.getChildCount() == 2 && isElse(ast.getParent());
141    }
142}