001///////////////////////////////////////////////////////////////////////////////////////////////
002// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
003// Copyright (C) 2001-2026 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     * Creates a new {@code NestedIfDepthCheck} instance.
050     */
051    public NestedIfDepthCheck() {
052        // no code by default
053    }
054
055    /**
056     * Setter to specify maximum allowed nesting depth.
057     *
058     * @param max maximum allowed nesting depth.
059     * @since 3.2
060     */
061    public void setMax(int max) {
062        this.max = max;
063    }
064
065    @Override
066    public int[] getDefaultTokens() {
067        return getRequiredTokens();
068    }
069
070    @Override
071    public int[] getAcceptableTokens() {
072        return getRequiredTokens();
073    }
074
075    @Override
076    public int[] getRequiredTokens() {
077        return new int[] {TokenTypes.LITERAL_IF};
078    }
079
080    @Override
081    public void visitToken(DetailAST literalIf) {
082        if (!isElseIf(literalIf)) {
083            if (depth > max) {
084                log(literalIf, MSG_KEY, depth, max);
085            }
086            ++depth;
087        }
088    }
089
090    @Override
091    public void leaveToken(DetailAST literalIf) {
092        if (!isElseIf(literalIf)) {
093            --depth;
094        }
095    }
096
097    /**
098     * Returns whether a token represents an ELSE as part of an ELSE / IF set.
099     *
100     * @param ast the token to check
101     * @return whether it is
102     */
103    private static boolean isElseIf(DetailAST ast) {
104        final DetailAST parentAST = ast.getParent();
105
106        return isElse(parentAST) || isElseWithCurlyBraces(parentAST);
107    }
108
109    /**
110     * Returns whether a token represents an ELSE.
111     *
112     * @param ast the token to check
113     * @return whether the token represents an ELSE
114     */
115    private static boolean isElse(DetailAST ast) {
116        return ast.getType() == TokenTypes.LITERAL_ELSE;
117    }
118
119    /**
120     * Returns whether a token represents an SLIST as part of an ELSE
121     * statement.
122     *
123     * @param ast the token to check
124     * @return whether the toke does represent an SLIST as part of an ELSE
125     */
126    private static boolean isElseWithCurlyBraces(DetailAST ast) {
127        return ast.getChildCount() == 2 && isElse(ast.getParent());
128    }
129
130}