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